{"gene":"PF3D7_0717500","run_date":"2026-09-08T12:51:27","timeline":{"discoveries":[{"year":2004,"finding":"CDPK4 is essential for cell cycle progression in male gametocytes of P. berghei; genetic disruption of CDPK4 blocks sexual reproduction and mosquito transmission. Xanthurenic acid (XA) triggers a rapid cytosolic calcium rise in gametocytes, and CDPK4 acts as the molecular switch translating this calcium signal into cellular response regulating male gametocyte cell cycle progression.","method":"Gene disruption in P. berghei; bioluminescent calcium sensor imaging; gametocyte activation assays","journal":"Cell","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic knockout with defined cellular phenotype (cell cycle arrest, transmission block), validated by calcium sensor imaging, replicated in subsequent studies","pmids":["15137943"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2009,"finding":"PfCDPK4 kinase activity requires its catalytic lysine residue (mutation to alanine abolishes phosphorylation). PfCDPK4 phosphorylation is activated by increased Ca2+ concentration, decreased temperature, and elevated pH (mimicking mosquito bloodmeal conditions). Its activity in the parasite is regulated by phospholipase C. PfCDPK4 is localized to the gametocyte periphery. The Junction Domain (JD) plays a pivotal role in PfCDPK4 regulation, with mapped regions interacting with both the kinase domain and the calmodulin-like domain.","method":"Active-site mutagenesis (K→A); in vitro phosphorylation assay with [γ-32P]ATP; phosphatase treatment; immunofluorescence localization; phospholipase C inhibition assay","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Moderate — in vitro enzymatic assay with catalytic mutant, multiple biochemical methods (mutagenesis, domain mapping, localization), single lab","pmids":["19307175"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2009,"finding":"PfCDPK4 is a calcium-activated kinase; its phosphorylation activity is eliminated by mutation of its putative catalytic lysine. PfCDPK4 is overexpressed in day 15 gametocytes exposed to xanthurenic acid or human serum and shows activation under conditions mimicking the mosquito bloodmeal (lower temperature, higher pH, elevated Ca2+).","method":"Recombinant protein purification; [γ-32P]ATP labeling; phosphatase treatment; active-site mutagenesis; western blot expression analysis","journal":"Parasitology international","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro enzymatic assay with mutagenesis, single lab, partially overlapping with PMID:19307175","pmids":["19666141"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"finding":"Trifluoperazine non-competitively inhibits PfCDPK4 in the micromolar range by targeting its calmodulin-like domain, demonstrating that selective inhibition of PfCDPK4 can be achieved through this domain.","method":"In vitro enzyme inhibition assay with trifluoperazine and other calmodulin antagonists; kinetic analysis of inhibition mechanism","journal":"Protein and peptide letters","confidence":"Medium","confidence_rationale":"Tier 1 / Weak — in vitro biochemical assay with defined inhibitor mechanism, single lab, single method","pmids":["21787279"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2012,"finding":"Bumped kinase inhibitors (BKIs) block microgametocyte exflagellation and oocyst/sporozoite formation by inhibiting CDPK4; the small serine gatekeeper residue in the CDPK4 active site confers selectivity over mammalian kinases.","method":"In vitro exflagellation assay; mosquito feeding experiments; mammalian cell proliferation assay; in vivo mouse pharmacokinetics","journal":"The Journal of clinical investigation","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — functional inhibitor assay with transmission phenotype, but mechanism of action inferred rather than directly proved by genetic rescue at this stage","pmids":["22565309"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2013,"finding":"Chemical-genetic validation confirms that CDPK4 is the direct target of bumped kinase inhibitor compound 1294: P. falciparum parasites expressing a drug-resistant methionine gatekeeper mutant (S147M) at the CDPK4 active site show a shift in exflagellation EC50, and the small serine gatekeeper residue (S147) is responsible for BKI selectivity.","method":"Chemical-genetic validation: generation of P. falciparum S147M CDPK4 gatekeeper mutant parasites; exflagellation EC50 shift assay; pharmacokinetic analysis","journal":"The Journal of infectious diseases","confidence":"High","confidence_rationale":"Tier 1 / Moderate — chemical-genetic rescue (gatekeeper mutant EC50 shift) directly confirms target engagement, two orthogonal approaches (mutagenesis + cellular assay), single lab","pmids":["24123773"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2014,"finding":"Two structural features in the ATP-binding site of PfCDPK4 (including the small serine gatekeeper) can be exploited to obtain potent and selective inhibitors; pyrazolopyrimidine-based inhibitors of PfCDPK4 in vitro activity also block P. falciparum exflagellation without toxicity to human cells.","method":"In vitro PfCDPK4 kinase inhibition assay; P. falciparum exflagellation assay; cytotoxicity assay","journal":"European journal of medicinal chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — in vitro enzyme assay correlated with cellular phenotype (exflagellation block), single lab, two orthogonal readouts","pmids":["24531197"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2016,"finding":"In P. berghei, CDPK4 is required for sporozoite invasion of hepatocytes and sporozoite motility; sporozoites carrying a deletion of CDPK4 are defective in hepatocyte invasion. Unlike PKG inhibition, CDPK4 genetic deletion does not significantly decrease merosome numbers, indicating distinct roles for CDPK4 and PKG in liver stage egress.","method":"CDPK4 gene deletion in P. berghei; hepatocyte invasion assay; sporozoite motility assay; specific kinase inhibitors; merosome counting","journal":"Molecular microbiology","confidence":"High","confidence_rationale":"Tier 2 / Strong — clean genetic deletion with specific cellular phenotype (invasion defect), complemented with chemical inhibition, two orthogonal approaches","pmids":["27425827"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"finding":"In P. berghei, CDPK4 controls three cell cycle events during microgametogenesis: (1) a myristoylated isoform is activated by Ca2+ within 20 seconds of activation to initiate genome replication, acting via a SAPS-domain family protein involved in S-phase entry; (2) CDPK4 is required for mitotic spindle assembly, phosphorylating a microtubule-associated protein important for spindle formation; (3) a non-myristoylated isoform is essential for cytokinesis by activating flagellum motility, linked to phosphorylation of a flagellar protein.","method":"Analysis of isoform-specific mutants (myristoylation-site mutants); live imaging; phosphoproteomic analysis; identification of SAPS-domain protein as substrate; identification of microtubule-associated protein substrate; in vitro kinase assays","journal":"eLife","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — multiple isoform-specific genetic mutants with distinct cellular phenotypes, substrate identification, phosphoproteomics, multiple orthogonal methods in one study","pmids":["28481199"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"finding":"Phosphoproteomic analysis of P. berghei CDPK4 mutant gametocytes during the first minute of gametogenesis reveals distinct phosphoproteomic disruptions compared to SRPK1 mutants, consistent with CDPK4 controlling broad cell cycle phosphorylation events during male gametogenesis. CDPK4 mutants show disruptions in phosphorylation of proteins related to distinct cell cycle events.","method":"High-resolution time course phosphoproteomics of CDPK4 mutant vs. wild-type gametocytes; comparison with SRPK1 mutant phosphoproteome","journal":"Cell reports","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphoproteomic readout of genetic mutant, single lab, one primary method but high-resolution time course","pmids":["29141230"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"finding":"In P. berghei, a synthetic negative genetic interaction exists between a hypomorphic allele of PKG and CDPK4 in controlling erythrocyte invasion; CDPK4 becomes critical when PKG-dependent calcium signals are attenuated, phosphorylating proteins important for stability of the inner membrane complex (IMC), which anchors the acto-myosin motor required for motility and invasion. This PKG–CDPK4 epistatic interaction is conserved in P. falciparum.","method":"Genetic interaction screen (294 kinase interactions in P. berghei); hypomorphic PKG allele combined with CDPK4 deletion; epistasis analysis; phosphoproteomic identification of IMC substrates; conservation validated in P. falciparum","journal":"Nature communications","confidence":"High","confidence_rationale":"Tier 2 / Strong — epistasis screen with double-mutant analysis, phosphoproteomic substrate identification, conservation validated in two species, multiple orthogonal methods","pmids":["30315162"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"In P. berghei, CDPK4 is required for optimal sporozoite motility and hepatocyte invasion; increased cGMP cannot compensate for loss of CDPK4 during sporozoite invasion (unlike CDPK1 and CDPK5). Chemical inhibition of CDPK4 in liver stages implicates it in merosome formation and/or release.","method":"Gene deletion of P. berghei CDPK4; sporozoite motility assay; hepatocyte invasion assay; cGMP modulation epistasis; chemical inhibition of CDPK4 in liver stages; merosome counting","journal":"PLoS pathogens","confidence":"High","confidence_rationale":"Tier 2 / Moderate — genetic deletion with defined invasion phenotype, epistasis with cGMP pathway, complemented by chemical inhibition, single lab with multiple methods","pmids":["32866196"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2021,"finding":"P. falciparum CDPK4 gene deletion causes severe defects in male gametogenesis and exflagellation (but not blood-stage growth or gametocyte development). Phosphoproteomic comparison of wild-type and Pfcdpk4 deletion late gametocytes identifies CDPK4-dependent phosphorylation events linked to DNA replication, mRNA translation, and cell motility. In vitro kinase assays identify putative direct substrates; notably, EB1 (End Binding protein 1) is hypophosphorylated in Pfcdpk4 parasites.","method":"Targeted gene deletion in P. falciparum; exflagellation assay; mass spectrometry-based phosphoproteomics; in vitro kinase substrate assays","journal":"mBio","confidence":"High","confidence_rationale":"Tier 1-2 / Strong — clean genetic deletion in P. falciparum with defined male gametogenesis phenotype, phosphoproteomic substrate identification, in vitro kinase assays, multiple orthogonal methods","pmids":["34724830"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"finding":"In P. berghei male gametogenesis, CDPK4 is a non-canonical regulator of the bipartite microtubule-organising centre (MTOC) that coordinates mitosis with axoneme assembly; CDPK4 is required for the dynamic architecture of this MTOC.","method":"Ultrastructure expansion microscopy (U-ExM); Pan-ExM; 3D reconstruction; analysis of CDPK4 mutants","journal":"PLoS pathogens","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — expansion microscopy with CDPK4 mutant analysis, direct structural localization with functional consequence, single lab","pmids":["35077503"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2023,"finding":"PfCDPK4-dependent phosphorylation of EB1 (End Binding protein 1) was identified; EB1 is hypophosphorylated in Pfcdpk4 deletion gametocytes. EB1 loss-of-function (not CDPK4 itself) results in severe nuclear segregation defects in male gametogenesis, placing EB1 as a downstream effector of CDPK4 phosphorylation in male fertility.","method":"Comparative phosphoproteomics of Pfcdpk4 mutant gametocytes; EB1 gene deletion; male/female sterile genetic crosses; fluorescence microscopy","journal":"mBio","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — phosphoproteomic identification of CDPK4 substrate (EB1), functional validation of substrate by genetic deletion, single lab","pmids":["37535401"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"CDPK4 localizes to the cytoplasmic compartment (distinct from nuclear SRPK1 and MAP2) during P. berghei male gamete formation. Immunoprecipitation reveals CDPK4 interacts with key drivers of rapid DNA replication. Absence of CDPK4 results in severe defects in MTOC organisation and kinetochore segregation during endomitosis.","method":"Live-cell imaging (localization); immunoprecipitation (interacting partner identification); ultrastructure expansion microscopy; transmission electron microscopy of CDPK4 deletion mutants","journal":"Life science alliance","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — direct localization with functional consequence, Co-IP for interacting partners, morphological phenotype by EM in genetic mutant, single lab","pmids":["40127922"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2026,"finding":"In P. berghei, a signaling cascade initiated by CDPK4 upon male gametocyte activation leads to phosphorylation of male-specific early-phosphorylated IDR-rich proteins (MPDs); MPD2 is required for microgamete release and oocyst formation, placing MPD2 as a downstream effector in the CDPK4-initiated phosphorylation cascade during male gametogenesis.","method":"Phosphoproteomic identification of early-phosphorylated proteins; gene disruption of MPD2 in P. berghei; genetic complementation with tagged MPD2; live-cell imaging; oocyst counting","journal":"Frontiers in cellular and infection microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Weak — pathway placement of CDPK4 upstream of MPD2 by phosphoproteomics and genetic analysis, but CDPK4's direct phosphorylation of MPDs not biochemically confirmed; single lab","pmids":["42620507"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2010,"finding":"PvCDPK4 (Plasmodium vivax ortholog) is expressed at the mature schizont stage and localizes to the schizont by immunofluorescence; recombinant EF-hand domain is produced as a 34 kDa protein, and the protein has four EF-hand motifs for calcium binding.","method":"Molecular cloning; recombinant protein expression in E. coli; immunofluorescence assay by confocal microscopy","journal":"The Korean journal of parasitology","confidence":"Low","confidence_rationale":"Tier 3 / Weak — localization by immunofluorescence at schizont stage, single lab, no functional consequence demonstrated","pmids":["21234235"],"is_preprint":false,"attribution":[{"species":"Plasmodium vivax","strain":""}]}],"current_model":"PF3D7_0717500 (CDPK4) is a calcium-activated kinase with a small serine gatekeeper (S147) in its ATP-binding site and an auto-regulatory Junction Domain; it exists as at least two isoforms (myristoylated and non-myristoylated), is activated by xanthurenic acid-induced cytosolic Ca2+ rises in gametocytes, and sequentially controls genome replication (via a SAPS-domain effector), mitotic spindle assembly (phosphorylating a microtubule-associated protein), and flagellum-driven cytokinesis (phosphorylating flagellar proteins including EB1) during male gametogenesis in both P. berghei and P. falciparum; it also localizes to the cytoplasm where it interacts with DNA replication factors and regulates MTOC architecture, and acts epistatically downstream of PKG to phosphorylate inner membrane complex proteins required for acto-myosin motor function during erythrocyte invasion and sporozoite motility."},"narrative":{"mechanistic_narrative":"PF3D7_0717500 (CDPK4) is a calcium-activated serine/threonine protein kinase that serves as the molecular switch converting xanthurenic acid-induced cytosolic Ca2+ rises into the cell-cycle program of male gametogenesis, and it is essential for sexual reproduction and mosquito transmission [PMID:15137943, PMID:28481199]. Its catalytic activity requires an active-site lysine and is stimulated by the combination of elevated Ca2+, lower temperature, and higher pH that mimics the mosquito bloodmeal, and is regulated by phospholipase C and an autoregulatory Junction Domain that couples the kinase and calmodulin-like domains [PMID:19307175, PMID:19666141]. In P. berghei, distinct CDPK4 isoforms drive three sequential events after activation: a myristoylated isoform initiates rapid genome replication via a SAPS-domain effector, the kinase then promotes mitotic spindle assembly by phosphorylating a microtubule-associated protein, and a non-myristoylated isoform triggers flagellum-driven cytokinesis [PMID:28481199]. CDPK4 localizes to a cytoplasmic compartment where it interacts with drivers of DNA replication and governs the architecture of the bipartite microtubule-organising centre and kinetochore segregation during endomitosis [PMID:35077503, PMID:40127922]. Among its substrates, phosphorylation of EB1 is required downstream for nuclear segregation in male gametogenesis [PMID:34724830, PMID:37535401]. Beyond gametogenesis, CDPK4 acts epistatically with PKG-dependent signaling to phosphorylate inner membrane complex proteins that anchor the acto-myosin motor for erythrocyte invasion, and it is independently required for sporozoite motility and hepatocyte invasion [PMID:27425827, PMID:30315162, PMID:32866196]. Its small serine gatekeeper (S147) confers selectivity to bumped kinase inhibitors, validated by a gatekeeper-mutant EC50 shift, making CDPK4 a transmission-blocking drug target [PMID:22565309, PMID:24123773].","teleology":[{"year":2004,"claim":"Established that a calcium signal must be transduced into the male gametocyte cell-cycle program, identifying CDPK4 as the switch linking xanthurenic acid-triggered Ca2+ rise to sexual reproduction and transmission.","evidence":"Gene disruption in P. berghei with bioluminescent calcium sensor imaging and gametocyte activation assays","pmids":["15137943"],"confidence":"High","gaps":["Direct substrates transducing the signal not identified","Molecular basis of Ca2+ activation not resolved"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2009,"claim":"Defined the biochemical basis of CDPK4 activity, showing it is a calcium-activated kinase requiring an active-site lysine, tuned by bloodmeal-mimicking conditions and PLC, and autoregulated by its Junction Domain.","evidence":"Recombinant kinase assays with [γ-32P]ATP, active-site K→A mutagenesis, phosphatase treatment, domain mapping, immunofluorescence, and PLC inhibition in P. falciparum","pmids":["19307175","19666141"],"confidence":"High","gaps":["Physiological substrates not identified","Structural mechanism of Junction Domain regulation not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2011,"claim":"Demonstrated that the calmodulin-like domain is a druggable site, with trifluoperazine acting as a non-competitive inhibitor.","evidence":"In vitro enzyme inhibition kinetics with calmodulin antagonists in P. falciparum","pmids":["21787279"],"confidence":"Medium","gaps":["Cellular efficacy of CaM-domain inhibition not demonstrated","Single method, single lab"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2013,"claim":"Provided chemical-genetic proof that CDPK4 is the direct transmission-blocking target of bumped kinase inhibitors, and that the small serine gatekeeper (S147) confers their selectivity.","evidence":"S147M gatekeeper-mutant P. falciparum parasites showing exflagellation EC50 shift, complementing earlier BKI phenotype and structure-based inhibitor work","pmids":["22565309","24123773","24531197"],"confidence":"High","gaps":["Resistance liabilities of gatekeeper mutations not fully mapped","Off-target parasite kinases not exhaustively excluded"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2016,"claim":"Extended CDPK4 function beyond gametogenesis, showing it is required for sporozoite motility and hepatocyte invasion with a role distinct from PKG in liver-stage egress.","evidence":"CDPK4 gene deletion in P. berghei with invasion and motility assays, specific inhibitors, and merosome counting","pmids":["27425827"],"confidence":"High","gaps":["Substrates in sporozoites not identified","Mechanism linking CDPK4 to motility machinery in this stage unresolved"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2017,"claim":"Resolved how CDPK4 orchestrates the male cell cycle by showing two isoforms and staged substrate phosphorylation control genome replication, spindle assembly, and flagellar cytokinesis, and that CDPK4 governs broad early phosphorylation events distinct from SRPK1.","evidence":"Isoform-specific (myristoylation) mutants, live imaging, in vitro kinase assays, and high-resolution phosphoproteomic time courses in P. berghei","pmids":["28481199","29141230"],"confidence":"High","gaps":["Identity of the SAPS-domain and MAP substrates only partially characterized","How Ca2+ dynamics select between isoform activities unclear"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2018,"claim":"Placed CDPK4 in a signaling network with PKG, showing it becomes critical for erythrocyte invasion when PKG-dependent Ca2+ signals are attenuated by phosphorylating inner membrane complex proteins that anchor the acto-myosin motor.","evidence":"Kinase genetic-interaction screen with hypomorphic PKG allele, epistasis and phosphoproteomics in P. berghei, conservation validated in P. falciparum","pmids":["30315162"],"confidence":"High","gaps":["Direct IMC substrates not fully validated biochemically","Basis of functional redundancy with PKG unresolved"],"attribution":[{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Showed CDPK4's role in sporozoite invasion is non-redundant with the cGMP pathway, unlike CDPK1 and CDPK5, and implicated it in liver-stage merosome formation.","evidence":"P. berghei CDPK4 deletion with motility and invasion assays, cGMP-modulation epistasis, and chemical inhibition in liver stages","pmids":["32866196"],"confidence":"High","gaps":["Liver-stage substrates not identified","Mechanistic distinction from CDPK1/CDPK5 unexplained"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2021,"claim":"Confirmed in P. falciparum that CDPK4 deletion specifically disrupts male gametogenesis and identified CDPK4-dependent phosphosites in DNA replication, translation, and motility proteins, including hypophosphorylated EB1.","evidence":"Targeted gene deletion in P. falciparum with exflagellation assays, phosphoproteomics, and in vitro kinase substrate assays","pmids":["34724830"],"confidence":"High","gaps":["Direct versus indirect substrates not fully distinguished","Functional consequence of individual phosphosites not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2022,"claim":"Defined CDPK4 as a non-canonical regulator of the bipartite MTOC that coordinates mitosis with axoneme assembly during male gametogenesis.","evidence":"Ultrastructure expansion and Pan-ExM microscopy with 3D reconstruction of CDPK4 mutants in P. berghei","pmids":["35077503"],"confidence":"Medium","gaps":["Molecular targets at the MTOC not identified","Single lab, structural readout only"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2023,"claim":"Validated EB1 as a functionally important downstream effector of CDPK4, showing EB1 loss causes nuclear segregation defects in male gametogenesis.","evidence":"Comparative phosphoproteomics of Pfcdpk4 gametocytes, EB1 gene deletion, sterile genetic crosses, and microscopy in P. falciparum","pmids":["37535401"],"confidence":"Medium","gaps":["Direct CDPK4 phosphorylation of EB1 not biochemically confirmed here","Phosphosite requirement on EB1 not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Localized CDPK4 to a cytoplasmic compartment interacting with DNA-replication drivers and showed its loss disrupts MTOC organisation and kinetochore segregation during endomitosis.","evidence":"Live-cell imaging, immunoprecipitation, expansion microscopy, and transmission EM of CDPK4 deletion mutants in P. berghei","pmids":["40127922"],"confidence":"Medium","gaps":["Identity of interacting replication factors not fully defined","Co-IP interactions not reciprocally validated"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":2026,"claim":"Extended the CDPK4-initiated cascade to male-specific IDR-rich phosphoproteins, placing MPD2 as a downstream effector required for microgamete release and oocyst formation.","evidence":"Phosphoproteomics of early-phosphorylated proteins, MPD2 disruption and complementation, live imaging, and oocyst counting in P. berghei","pmids":["42620507"],"confidence":"Medium","gaps":["Direct CDPK4 phosphorylation of MPDs not biochemically confirmed","Pathway placement inferred, not enzymatically demonstrated"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":null,"claim":"How Ca2+ dynamics and isoform partitioning select among CDPK4's sequential roles, and the full complement of its direct in vivo substrates across gametogenesis, invasion, and liver stages, remain unresolved.","evidence":"","pmids":[],"confidence":"Medium","gaps":["No structure of full-length activated CDPK4","Direct substrate repertoire not comprehensively validated by in vitro kinase assays","Mechanism coupling myristoylation to isoform-specific function unknown"],"attribution":[{"species":"Plasmodium berghei","strain":""},{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["EB1 (END BINDING PROTEIN 1) — CDPK4-DEPENDENT PHOSPHOSUBSTRATE [#12, #14]","SAPS-DOMAIN FAMILY PROTEIN — S-PHASE ENTRY EFFECTOR [#8]","MICROTUBULE-ASSOCIATED PROTEIN (SPINDLE) — CDPK4 SUBSTRATE [#8]","INNER MEMBRANE COMPLEX PROTEINS — CDPK4 SUBSTRATES IN INVASION [#10]","MPD2 (MALE-SPECIFIC IDR-RICH PHOSPHOPROTEIN) — DOWNSTREAM EFFECTOR [#16]","PKG — EPISTATIC SIGNALING PARTNER IN ERYTHROCYTE INVASION [#10]","DNA REPLICATION DRIVERS — CDPK4 CO-IMMUNOPRECIPITATION PARTNERS [#15]"],"other_free_text":["Small serine gatekeeper S147 in the ATP-binding site confers bumped kinase inhibitor selectivity; S147M mutation shifts inhibitor EC50 [#4, #5, #6]","Exists as myristoylated and non-myristoylated isoforms with distinct cell-cycle roles [#8]","Junction Domain autoregulates the kinase by bridging kinase and calmodulin-like domains [#1]","Activated by combined elevated Ca2+, lower temperature, and higher pH mimicking mosquito bloodmeal; regulated by phospholipase C [#1, #2]","Essential for mosquito transmission and male gametogenesis but not blood-stage growth or gametocyte development [#0, #12]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"15137943","id":"PMC_15137943","title":"Calcium and a calcium-dependent protein kinase regulate gamete formation and mosquito transmission in a malaria parasite.","date":"2004","source":"Cell","url":"https://pubmed.ncbi.nlm.nih.gov/15137943","citation_count":368,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CDPK4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"22565309","id":"PMC_22565309","title":"Transmission of malaria to mosquitoes blocked by bumped kinase inhibitors.","date":"2012","source":"The Journal of clinical investigation","url":"https://pubmed.ncbi.nlm.nih.gov/22565309","citation_count":88,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calcium-dependent protein kinase 4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"24123773","id":"PMC_24123773","title":"A specific inhibitor of PfCDPK4 blocks malaria transmission: chemical-genetic validation.","date":"2013","source":"The Journal of infectious diseases","url":"https://pubmed.ncbi.nlm.nih.gov/24123773","citation_count":78,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CDPK4","calcium-dependent protein kinase 4","PfCDPK4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27425827","id":"PMC_27425827","title":"Invasion of hepatocytes by Plasmodium sporozoites requires cGMP-dependent protein kinase and calcium dependent protein kinase 4.","date":"2016","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/27425827","citation_count":62,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CDPK4","calcium-dependent protein kinase 4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"30315162","id":"PMC_30315162","title":"Epistasis studies reveal redundancy among calcium-dependent protein kinases in motility and invasion of malaria parasites.","date":"2018","source":"Nature communications","url":"https://pubmed.ncbi.nlm.nih.gov/30315162","citation_count":55,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["CDPK4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"35077503","id":"PMC_35077503","title":"Expansion microscopy of Plasmodium gametocytes reveals the molecular architecture of a bipartite microtubule organisation centre coordinating mitosis with axoneme assembly.","date":"2022","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/35077503","citation_count":53,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calcium-dependent protein kinase 4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"29141230","id":"PMC_29141230","title":"Sub-minute Phosphoregulation of Cell Cycle Systems during Plasmodium Gamete 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proteins reveal an intrinsically disordered protein required for microgamete release in Plasmodium berghei.","date":"2026","source":"Frontiers in cellular and infection microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/42620507","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["calcium-dependent protein kinase 4"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":16622,"output_tokens":5405,"usd":0.065471,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":12189,"output_tokens":5483,"usd":0.09901,"stage2_stop_reason":"end_turn"},"total_usd":0.164481,"stage1_batch_id":"msgbatch_01DisAaTypwmC8QwdMBuePHo","stage2_batch_id":"msgbatch_0184zxZTqxiEfdYYfPMfkqjb","note":"batch pricing = 50% of standard"},"stage1_raw":"```json\n{\n  \"discoveries\": [\n    {\n      \"year\": 2004,\n      \"finding\": \"CDPK4 is essential for cell cycle progression in male gametocytes of P. berghei; genetic disruption of CDPK4 blocks sexual reproduction and mosquito transmission. Xanthurenic acid (XA) triggers a rapid cytosolic calcium rise in gametocytes, and CDPK4 acts as the molecular switch translating this calcium signal into cellular response regulating male gametocyte cell cycle progression.\",\n      \"method\": \"Gene disruption in P. berghei; bioluminescent calcium sensor imaging; gametocyte activation assays\",\n      \"journal\": \"Cell\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic knockout with defined cellular phenotype (cell cycle arrest, transmission block), validated by calcium sensor imaging, replicated in subsequent studies\",\n      \"pmids\": [\"15137943\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PfCDPK4 kinase activity requires its catalytic lysine residue (mutation to alanine abolishes phosphorylation). PfCDPK4 phosphorylation is activated by increased Ca2+ concentration, decreased temperature, and elevated pH (mimicking mosquito bloodmeal conditions). Its activity in the parasite is regulated by phospholipase C. PfCDPK4 is localized to the gametocyte periphery. The Junction Domain (JD) plays a pivotal role in PfCDPK4 regulation, with mapped regions interacting with both the kinase domain and the calmodulin-like domain.\",\n      \"method\": \"Active-site mutagenesis (K→A); in vitro phosphorylation assay with [γ-32P]ATP; phosphatase treatment; immunofluorescence localization; phospholipase C inhibition assay\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro enzymatic assay with catalytic mutant, multiple biochemical methods (mutagenesis, domain mapping, localization), single lab\",\n      \"pmids\": [\"19307175\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"finding\": \"PfCDPK4 is a calcium-activated kinase; its phosphorylation activity is eliminated by mutation of its putative catalytic lysine. PfCDPK4 is overexpressed in day 15 gametocytes exposed to xanthurenic acid or human serum and shows activation under conditions mimicking the mosquito bloodmeal (lower temperature, higher pH, elevated Ca2+).\",\n      \"method\": \"Recombinant protein purification; [γ-32P]ATP labeling; phosphatase treatment; active-site mutagenesis; western blot expression analysis\",\n      \"journal\": \"Parasitology international\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro enzymatic assay with mutagenesis, single lab, partially overlapping with PMID:19307175\",\n      \"pmids\": [\"19666141\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"finding\": \"Trifluoperazine non-competitively inhibits PfCDPK4 in the micromolar range by targeting its calmodulin-like domain, demonstrating that selective inhibition of PfCDPK4 can be achieved through this domain.\",\n      \"method\": \"In vitro enzyme inhibition assay with trifluoperazine and other calmodulin antagonists; kinetic analysis of inhibition mechanism\",\n      \"journal\": \"Protein and peptide letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Weak — in vitro biochemical assay with defined inhibitor mechanism, single lab, single method\",\n      \"pmids\": [\"21787279\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2012,\n      \"finding\": \"Bumped kinase inhibitors (BKIs) block microgametocyte exflagellation and oocyst/sporozoite formation by inhibiting CDPK4; the small serine gatekeeper residue in the CDPK4 active site confers selectivity over mammalian kinases.\",\n      \"method\": \"In vitro exflagellation assay; mosquito feeding experiments; mammalian cell proliferation assay; in vivo mouse pharmacokinetics\",\n      \"journal\": \"The Journal of clinical investigation\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — functional inhibitor assay with transmission phenotype, but mechanism of action inferred rather than directly proved by genetic rescue at this stage\",\n      \"pmids\": [\"22565309\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"finding\": \"Chemical-genetic validation confirms that CDPK4 is the direct target of bumped kinase inhibitor compound 1294: P. falciparum parasites expressing a drug-resistant methionine gatekeeper mutant (S147M) at the CDPK4 active site show a shift in exflagellation EC50, and the small serine gatekeeper residue (S147) is responsible for BKI selectivity.\",\n      \"method\": \"Chemical-genetic validation: generation of P. falciparum S147M CDPK4 gatekeeper mutant parasites; exflagellation EC50 shift assay; pharmacokinetic analysis\",\n      \"journal\": \"The Journal of infectious diseases\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — chemical-genetic rescue (gatekeeper mutant EC50 shift) directly confirms target engagement, two orthogonal approaches (mutagenesis + cellular assay), single lab\",\n      \"pmids\": [\"24123773\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2014,\n      \"finding\": \"Two structural features in the ATP-binding site of PfCDPK4 (including the small serine gatekeeper) can be exploited to obtain potent and selective inhibitors; pyrazolopyrimidine-based inhibitors of PfCDPK4 in vitro activity also block P. falciparum exflagellation without toxicity to human cells.\",\n      \"method\": \"In vitro PfCDPK4 kinase inhibition assay; P. falciparum exflagellation assay; cytotoxicity assay\",\n      \"journal\": \"European journal of medicinal chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — in vitro enzyme assay correlated with cellular phenotype (exflagellation block), single lab, two orthogonal readouts\",\n      \"pmids\": [\"24531197\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"In P. berghei, CDPK4 is required for sporozoite invasion of hepatocytes and sporozoite motility; sporozoites carrying a deletion of CDPK4 are defective in hepatocyte invasion. Unlike PKG inhibition, CDPK4 genetic deletion does not significantly decrease merosome numbers, indicating distinct roles for CDPK4 and PKG in liver stage egress.\",\n      \"method\": \"CDPK4 gene deletion in P. berghei; hepatocyte invasion assay; sporozoite motility assay; specific kinase inhibitors; merosome counting\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — clean genetic deletion with specific cellular phenotype (invasion defect), complemented with chemical inhibition, two orthogonal approaches\",\n      \"pmids\": [\"27425827\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"In P. berghei, CDPK4 controls three cell cycle events during microgametogenesis: (1) a myristoylated isoform is activated by Ca2+ within 20 seconds of activation to initiate genome replication, acting via a SAPS-domain family protein involved in S-phase entry; (2) CDPK4 is required for mitotic spindle assembly, phosphorylating a microtubule-associated protein important for spindle formation; (3) a non-myristoylated isoform is essential for cytokinesis by activating flagellum motility, linked to phosphorylation of a flagellar protein.\",\n      \"method\": \"Analysis of isoform-specific mutants (myristoylation-site mutants); live imaging; phosphoproteomic analysis; identification of SAPS-domain protein as substrate; identification of microtubule-associated protein substrate; in vitro kinase assays\",\n      \"journal\": \"eLife\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — multiple isoform-specific genetic mutants with distinct cellular phenotypes, substrate identification, phosphoproteomics, multiple orthogonal methods in one study\",\n      \"pmids\": [\"28481199\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"finding\": \"Phosphoproteomic analysis of P. berghei CDPK4 mutant gametocytes during the first minute of gametogenesis reveals distinct phosphoproteomic disruptions compared to SRPK1 mutants, consistent with CDPK4 controlling broad cell cycle phosphorylation events during male gametogenesis. CDPK4 mutants show disruptions in phosphorylation of proteins related to distinct cell cycle events.\",\n      \"method\": \"High-resolution time course phosphoproteomics of CDPK4 mutant vs. wild-type gametocytes; comparison with SRPK1 mutant phosphoproteome\",\n      \"journal\": \"Cell reports\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphoproteomic readout of genetic mutant, single lab, one primary method but high-resolution time course\",\n      \"pmids\": [\"29141230\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"finding\": \"In P. berghei, a synthetic negative genetic interaction exists between a hypomorphic allele of PKG and CDPK4 in controlling erythrocyte invasion; CDPK4 becomes critical when PKG-dependent calcium signals are attenuated, phosphorylating proteins important for stability of the inner membrane complex (IMC), which anchors the acto-myosin motor required for motility and invasion. This PKG–CDPK4 epistatic interaction is conserved in P. falciparum.\",\n      \"method\": \"Genetic interaction screen (294 kinase interactions in P. berghei); hypomorphic PKG allele combined with CDPK4 deletion; epistasis analysis; phosphoproteomic identification of IMC substrates; conservation validated in P. falciparum\",\n      \"journal\": \"Nature communications\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — epistasis screen with double-mutant analysis, phosphoproteomic substrate identification, conservation validated in two species, multiple orthogonal methods\",\n      \"pmids\": [\"30315162\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"In P. berghei, CDPK4 is required for optimal sporozoite motility and hepatocyte invasion; increased cGMP cannot compensate for loss of CDPK4 during sporozoite invasion (unlike CDPK1 and CDPK5). Chemical inhibition of CDPK4 in liver stages implicates it in merosome formation and/or release.\",\n      \"method\": \"Gene deletion of P. berghei CDPK4; sporozoite motility assay; hepatocyte invasion assay; cGMP modulation epistasis; chemical inhibition of CDPK4 in liver stages; merosome counting\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — genetic deletion with defined invasion phenotype, epistasis with cGMP pathway, complemented by chemical inhibition, single lab with multiple methods\",\n      \"pmids\": [\"32866196\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"finding\": \"P. falciparum CDPK4 gene deletion causes severe defects in male gametogenesis and exflagellation (but not blood-stage growth or gametocyte development). Phosphoproteomic comparison of wild-type and Pfcdpk4 deletion late gametocytes identifies CDPK4-dependent phosphorylation events linked to DNA replication, mRNA translation, and cell motility. In vitro kinase assays identify putative direct substrates; notably, EB1 (End Binding protein 1) is hypophosphorylated in Pfcdpk4 parasites.\",\n      \"method\": \"Targeted gene deletion in P. falciparum; exflagellation assay; mass spectrometry-based phosphoproteomics; in vitro kinase substrate assays\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1-2 / Strong — clean genetic deletion in P. falciparum with defined male gametogenesis phenotype, phosphoproteomic substrate identification, in vitro kinase assays, multiple orthogonal methods\",\n      \"pmids\": [\"34724830\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"finding\": \"In P. berghei male gametogenesis, CDPK4 is a non-canonical regulator of the bipartite microtubule-organising centre (MTOC) that coordinates mitosis with axoneme assembly; CDPK4 is required for the dynamic architecture of this MTOC.\",\n      \"method\": \"Ultrastructure expansion microscopy (U-ExM); Pan-ExM; 3D reconstruction; analysis of CDPK4 mutants\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — expansion microscopy with CDPK4 mutant analysis, direct structural localization with functional consequence, single lab\",\n      \"pmids\": [\"35077503\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"finding\": \"PfCDPK4-dependent phosphorylation of EB1 (End Binding protein 1) was identified; EB1 is hypophosphorylated in Pfcdpk4 deletion gametocytes. EB1 loss-of-function (not CDPK4 itself) results in severe nuclear segregation defects in male gametogenesis, placing EB1 as a downstream effector of CDPK4 phosphorylation in male fertility.\",\n      \"method\": \"Comparative phosphoproteomics of Pfcdpk4 mutant gametocytes; EB1 gene deletion; male/female sterile genetic crosses; fluorescence microscopy\",\n      \"journal\": \"mBio\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — phosphoproteomic identification of CDPK4 substrate (EB1), functional validation of substrate by genetic deletion, single lab\",\n      \"pmids\": [\"37535401\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"CDPK4 localizes to the cytoplasmic compartment (distinct from nuclear SRPK1 and MAP2) during P. berghei male gamete formation. Immunoprecipitation reveals CDPK4 interacts with key drivers of rapid DNA replication. Absence of CDPK4 results in severe defects in MTOC organisation and kinetochore segregation during endomitosis.\",\n      \"method\": \"Live-cell imaging (localization); immunoprecipitation (interacting partner identification); ultrastructure expansion microscopy; transmission electron microscopy of CDPK4 deletion mutants\",\n      \"journal\": \"Life science alliance\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — direct localization with functional consequence, Co-IP for interacting partners, morphological phenotype by EM in genetic mutant, single lab\",\n      \"pmids\": [\"40127922\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"finding\": \"In P. berghei, a signaling cascade initiated by CDPK4 upon male gametocyte activation leads to phosphorylation of male-specific early-phosphorylated IDR-rich proteins (MPDs); MPD2 is required for microgamete release and oocyst formation, placing MPD2 as a downstream effector in the CDPK4-initiated phosphorylation cascade during male gametogenesis.\",\n      \"method\": \"Phosphoproteomic identification of early-phosphorylated proteins; gene disruption of MPD2 in P. berghei; genetic complementation with tagged MPD2; live-cell imaging; oocyst counting\",\n      \"journal\": \"Frontiers in cellular and infection microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Weak — pathway placement of CDPK4 upstream of MPD2 by phosphoproteomics and genetic analysis, but CDPK4's direct phosphorylation of MPDs not biochemically confirmed; single lab\",\n      \"pmids\": [\"42620507\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2010,\n      \"finding\": \"PvCDPK4 (Plasmodium vivax ortholog) is expressed at the mature schizont stage and localizes to the schizont by immunofluorescence; recombinant EF-hand domain is produced as a 34 kDa protein, and the protein has four EF-hand motifs for calcium binding.\",\n      \"method\": \"Molecular cloning; recombinant protein expression in E. coli; immunofluorescence assay by confocal microscopy\",\n      \"journal\": \"The Korean journal of parasitology\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — localization by immunofluorescence at schizont stage, single lab, no functional consequence demonstrated\",\n      \"pmids\": [\"21234235\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium vivax\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"PF3D7_0717500 (CDPK4) is a calcium-activated kinase with a small serine gatekeeper (S147) in its ATP-binding site and an auto-regulatory Junction Domain; it exists as at least two isoforms (myristoylated and non-myristoylated), is activated by xanthurenic acid-induced cytosolic Ca2+ rises in gametocytes, and sequentially controls genome replication (via a SAPS-domain effector), mitotic spindle assembly (phosphorylating a microtubule-associated protein), and flagellum-driven cytokinesis (phosphorylating flagellar proteins including EB1) during male gametogenesis in both P. berghei and P. falciparum; it also localizes to the cytoplasm where it interacts with DNA replication factors and regulates MTOC architecture, and acts epistatically downstream of PKG to phosphorylate inner membrane complex proteins required for acto-myosin motor function during erythrocyte invasion and sporozoite motility.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"PF3D7_0717500 (CDPK4) is a calcium-activated serine/threonine protein kinase that serves as the molecular switch converting xanthurenic acid-induced cytosolic Ca2+ rises into the cell-cycle program of male gametogenesis, and it is essential for sexual reproduction and mosquito transmission [#0, #8]. Its catalytic activity requires an active-site lysine and is stimulated by the combination of elevated Ca2+, lower temperature, and higher pH that mimics the mosquito bloodmeal, and is regulated by phospholipase C and an autoregulatory Junction Domain that couples the kinase and calmodulin-like domains [#1, #2]. In P. berghei, distinct CDPK4 isoforms drive three sequential events after activation: a myristoylated isoform initiates rapid genome replication via a SAPS-domain effector, the kinase then promotes mitotic spindle assembly by phosphorylating a microtubule-associated protein, and a non-myristoylated isoform triggers flagellum-driven cytokinesis [#8]. CDPK4 localizes to a cytoplasmic compartment where it interacts with drivers of DNA replication and governs the architecture of the bipartite microtubule-organising centre and kinetochore segregation during endomitosis [#13, #15]. Among its substrates, phosphorylation of EB1 is required downstream for nuclear segregation in male gametogenesis [#12, #14]. Beyond gametogenesis, CDPK4 acts epistatically with PKG-dependent signaling to phosphorylate inner membrane complex proteins that anchor the acto-myosin motor for erythrocyte invasion, and it is independently required for sporozoite motility and hepatocyte invasion [#7, #10, #11]. Its small serine gatekeeper (S147) confers selectivity to bumped kinase inhibitors, validated by a gatekeeper-mutant EC50 shift, making CDPK4 a transmission-blocking drug target [#4, #5].\",\n  \"teleology\": [\n    {\n      \"year\": 2004,\n      \"claim\": \"Established that a calcium signal must be transduced into the male gametocyte cell-cycle program, identifying CDPK4 as the switch linking xanthurenic acid-triggered Ca2+ rise to sexual reproduction and transmission.\",\n      \"evidence\": \"Gene disruption in P. berghei with bioluminescent calcium sensor imaging and gametocyte activation assays\",\n      \"pmids\": [\"15137943\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct substrates transducing the signal not identified\", \"Molecular basis of Ca2+ activation not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2009,\n      \"claim\": \"Defined the biochemical basis of CDPK4 activity, showing it is a calcium-activated kinase requiring an active-site lysine, tuned by bloodmeal-mimicking conditions and PLC, and autoregulated by its Junction Domain.\",\n      \"evidence\": \"Recombinant kinase assays with [γ-32P]ATP, active-site K→A mutagenesis, phosphatase treatment, domain mapping, immunofluorescence, and PLC inhibition in P. falciparum\",\n      \"pmids\": [\"19307175\", \"19666141\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Physiological substrates not identified\", \"Structural mechanism of Junction Domain regulation not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2011,\n      \"claim\": \"Demonstrated that the calmodulin-like domain is a druggable site, with trifluoperazine acting as a non-competitive inhibitor.\",\n      \"evidence\": \"In vitro enzyme inhibition kinetics with calmodulin antagonists in P. falciparum\",\n      \"pmids\": [\"21787279\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Cellular efficacy of CaM-domain inhibition not demonstrated\", \"Single method, single lab\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2013,\n      \"claim\": \"Provided chemical-genetic proof that CDPK4 is the direct transmission-blocking target of bumped kinase inhibitors, and that the small serine gatekeeper (S147) confers their selectivity.\",\n      \"evidence\": \"S147M gatekeeper-mutant P. falciparum parasites showing exflagellation EC50 shift, complementing earlier BKI phenotype and structure-based inhibitor work\",\n      \"pmids\": [\"22565309\", \"24123773\", \"24531197\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Resistance liabilities of gatekeeper mutations not fully mapped\", \"Off-target parasite kinases not exhaustively excluded\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Extended CDPK4 function beyond gametogenesis, showing it is required for sporozoite motility and hepatocyte invasion with a role distinct from PKG in liver-stage egress.\",\n      \"evidence\": \"CDPK4 gene deletion in P. berghei with invasion and motility assays, specific inhibitors, and merosome counting\",\n      \"pmids\": [\"27425827\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Substrates in sporozoites not identified\", \"Mechanism linking CDPK4 to motility machinery in this stage unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2017,\n      \"claim\": \"Resolved how CDPK4 orchestrates the male cell cycle by showing two isoforms and staged substrate phosphorylation control genome replication, spindle assembly, and flagellar cytokinesis, and that CDPK4 governs broad early phosphorylation events distinct from SRPK1.\",\n      \"evidence\": \"Isoform-specific (myristoylation) mutants, live imaging, in vitro kinase assays, and high-resolution phosphoproteomic time courses in P. berghei\",\n      \"pmids\": [\"28481199\", \"29141230\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Identity of the SAPS-domain and MAP substrates only partially characterized\", \"How Ca2+ dynamics select between isoform activities unclear\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2018,\n      \"claim\": \"Placed CDPK4 in a signaling network with PKG, showing it becomes critical for erythrocyte invasion when PKG-dependent Ca2+ signals are attenuated by phosphorylating inner membrane complex proteins that anchor the acto-myosin motor.\",\n      \"evidence\": \"Kinase genetic-interaction screen with hypomorphic PKG allele, epistasis and phosphoproteomics in P. berghei, conservation validated in P. falciparum\",\n      \"pmids\": [\"30315162\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct IMC substrates not fully validated biochemically\", \"Basis of functional redundancy with PKG unresolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Showed CDPK4's role in sporozoite invasion is non-redundant with the cGMP pathway, unlike CDPK1 and CDPK5, and implicated it in liver-stage merosome formation.\",\n      \"evidence\": \"P. berghei CDPK4 deletion with motility and invasion assays, cGMP-modulation epistasis, and chemical inhibition in liver stages\",\n      \"pmids\": [\"32866196\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Liver-stage substrates not identified\", \"Mechanistic distinction from CDPK1/CDPK5 unexplained\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2021,\n      \"claim\": \"Confirmed in P. falciparum that CDPK4 deletion specifically disrupts male gametogenesis and identified CDPK4-dependent phosphosites in DNA replication, translation, and motility proteins, including hypophosphorylated EB1.\",\n      \"evidence\": \"Targeted gene deletion in P. falciparum with exflagellation assays, phosphoproteomics, and in vitro kinase substrate assays\",\n      \"pmids\": [\"34724830\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"Direct versus indirect substrates not fully distinguished\", \"Functional consequence of individual phosphosites not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2022,\n      \"claim\": \"Defined CDPK4 as a non-canonical regulator of the bipartite MTOC that coordinates mitosis with axoneme assembly during male gametogenesis.\",\n      \"evidence\": \"Ultrastructure expansion and Pan-ExM microscopy with 3D reconstruction of CDPK4 mutants in P. berghei\",\n      \"pmids\": [\"35077503\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Molecular targets at the MTOC not identified\", \"Single lab, structural readout only\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2023,\n      \"claim\": \"Validated EB1 as a functionally important downstream effector of CDPK4, showing EB1 loss causes nuclear segregation defects in male gametogenesis.\",\n      \"evidence\": \"Comparative phosphoproteomics of Pfcdpk4 gametocytes, EB1 gene deletion, sterile genetic crosses, and microscopy in P. falciparum\",\n      \"pmids\": [\"37535401\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CDPK4 phosphorylation of EB1 not biochemically confirmed here\", \"Phosphosite requirement on EB1 not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Localized CDPK4 to a cytoplasmic compartment interacting with DNA-replication drivers and showed its loss disrupts MTOC organisation and kinetochore segregation during endomitosis.\",\n      \"evidence\": \"Live-cell imaging, immunoprecipitation, expansion microscopy, and transmission EM of CDPK4 deletion mutants in P. berghei\",\n      \"pmids\": [\"40127922\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Identity of interacting replication factors not fully defined\", \"Co-IP interactions not reciprocally validated\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2026,\n      \"claim\": \"Extended the CDPK4-initiated cascade to male-specific IDR-rich phosphoproteins, placing MPD2 as a downstream effector required for microgamete release and oocyst formation.\",\n      \"evidence\": \"Phosphoproteomics of early-phosphorylated proteins, MPD2 disruption and complementation, live imaging, and oocyst counting in P. berghei\",\n      \"pmids\": [\"42620507\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Direct CDPK4 phosphorylation of MPDs not biochemically confirmed\", \"Pathway placement inferred, not enzymatically demonstrated\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"How Ca2+ dynamics and isoform partitioning select among CDPK4's sequential roles, and the full complement of its direct in vivo substrates across gametogenesis, invasion, and liver stages, remain unresolved.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"No structure of full-length activated CDPK4\", \"Direct substrate repertoire not comprehensively validated by in vitro kinase assays\", \"Mechanism coupling myristoylation to isoform-specific function unknown\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}, {\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004683\", \"supporting_discovery_ids\": [1, 2, 8, 12]},\n      {\"term_id\": \"GO:0005509\", \"supporting_discovery_ids\": [3, 17]},\n      {\"term_id\": \"GO:0005524\", \"supporting_discovery_ids\": [5, 6]},\n      {\"term_id\": \"GO:0004672\", \"supporting_discovery_ids\": [1, 8, 14]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005737\", \"supporting_discovery_ids\": [15]},\n      {\"term_id\": \"GO:0005815\", \"supporting_discovery_ids\": [13, 15]},\n      {\"term_id\": \"GO:0009986\", \"supporting_discovery_ids\": [1]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0019953\", \"supporting_discovery_ids\": [0, 8]},\n      {\"term_id\": \"GO:0007140\", \"supporting_discovery_ids\": [8, 13, 15]},\n      {\"term_id\": \"GO:0006260\", \"supporting_discovery_ids\": [8, 12, 15]},\n      {\"term_id\": \"GO:0006935\", \"supporting_discovery_ids\": [7, 11]},\n      {\"term_id\": \"GO:0044409\", \"supporting_discovery_ids\": [7, 10, 11]},\n      {\"term_id\": \"GO:0019722\", \"supporting_discovery_ids\": [0, 1]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"EB1 (End Binding protein 1) — CDPK4-dependent phosphosubstrate [#12, #14]\",\n      \"SAPS-domain family protein — S-phase entry effector [#8]\",\n      \"microtubule-associated protein (spindle) — CDPK4 substrate [#8]\",\n      \"inner membrane complex proteins — CDPK4 substrates in invasion [#10]\",\n      \"MPD2 (male-specific IDR-rich phosphoprotein) — downstream effector [#16]\",\n      \"PKG — epistatic signaling partner in erythrocyte invasion [#10]\",\n      \"DNA replication drivers — CDPK4 co-immunoprecipitation partners [#15]\"\n    ],\n    \"other_free_text\": [\n      \"Small serine gatekeeper S147 in the ATP-binding site confers bumped kinase inhibitor selectivity; S147M mutation shifts inhibitor EC50 [#4, #5, #6]\",\n      \"Exists as myristoylated and non-myristoylated isoforms with distinct cell-cycle roles [#8]\",\n      \"Junction Domain autoregulates the kinase by bridging kinase and calmodulin-like domains [#1]\",\n      \"Activated by combined elevated Ca2+, lower temperature, and higher pH mimicking mosquito bloodmeal; regulated by phospholipase C [#1, #2]\",\n      \"Essential for mosquito transmission and male gametogenesis but not blood-stage growth or gametocyte development [#0, #12]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_0717500","name":null,"product":"calcium-dependent protein kinase 4","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0615200","name":null,"product":"calcium-dependent protein kinase 4","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0312500","name":null,"product":"calcium-dependent protein kinase 4, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"CDPK4","evaluation":null}