{"gene":"PF3D7_1113900","run_date":"2026-09-08T12:51:28","timeline":{"discoveries":[{"year":1999,"finding":"MAPK2 (Pfmap-2/PF3D7_1113900) encodes a functional kinase that can autophosphorylate, phosphorylate myelin basic protein (a classical MAPK substrate), is regulated by a MAPK-specific phosphatase, and can be activated by components present in cell extracts. Mutational analysis identified residues essential for enzymatic activity. Notably, MAPK2 lacks the conserved threonine-X-tyrosine activation motif, possessing instead a threonine-serine-histidine (TSH) motif at the same location.","method":"Recombinant protein expression in E. coli, in vitro kinase assays, phosphatase treatment, active-site mutagenesis, northern blot, immunofluorescence","journal":"The Journal of biological chemistry","confidence":"High","confidence_rationale":"Tier 1 / Strong — multiple orthogonal in vitro biochemical assays plus mutagenesis in a single rigorous study","pmids":["10514473"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"finding":"MAPK2 (Pfmap-2) is expressed specifically in gametocytes of P. falciparum (the form responsible for transmission to the mosquito vector), and gametocyte extracts activate recombinant MAPK2 more efficiently than extracts from asexual parasites, consistent with stage-specific function.","method":"Northern blot analysis, immunofluorescence assays, in vitro kinase activation with stage-specific extracts","journal":"The Journal of biological chemistry","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — two orthogonal methods (northern blot + IFA + extract activation), single lab","pmids":["10514473"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2001,"finding":"Pfnek-1, a NIMA-related kinase, specifically phosphorylates MAPK2 (Pfmap-2) in vitro, and co-incubation of Pfnek-1 and MAPK2 results in a synergistic increase in exogenous substrate labelling, suggesting Pfnek-1 acts upstream of MAPK2 to modulate MAPK pathway output.","method":"Recombinant protein expression, in vitro kinase assay (phosphorylation of Pfmap-2 by Pfnek-1), substrate labelling assay","journal":"European journal of biochemistry","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins, single lab","pmids":["11322879"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"finding":"Pfnek3, a NIMA-family kinase expressed in late asexual to gametocyte stages, phosphorylates and stimulates MAPK2 (Pfmap2) in vitro. This effect was not observed with Pfmap-1 or human MAPK1, suggesting the Pfnek3–MAPK2 interaction is specific for MAPK2 regulation.","method":"Recombinant protein expression, in vitro kinase/phosphorylation assay, specificity controls with Pfmap1 and human MAPK1","journal":"FEBS letters","confidence":"Medium","confidence_rationale":"Tier 1 / Moderate — in vitro reconstitution with specificity controls, single lab","pmids":["17064692"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"finding":"Reverse genetics in P. falciparum demonstrated that MAPK2 (pfmap-2) is essential for completion of the asexual intraerythrocytic cycle, as the gene could not be disrupted. In contrast, the map-2 orthologue in P. berghei was dispensable for asexual growth. Additionally, elevated MAPK2 protein levels were observed in pfmap-1 knockout parasites, suggesting a compensatory relationship between the two P. falciparum MAPKs.","method":"Reverse genetics (gene disruption attempts), western blot for protein levels in knockout lines","journal":"Molecular microbiology","confidence":"Medium","confidence_rationale":"Tier 2 / Moderate — reverse genetics (failed disruption as evidence of essentiality) plus compensatory protein level measurement, single lab","pmids":["17651389"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2016,"finding":"Phosphorylated and non-phosphorylated forms of MAPK2 (PfMAP2) both localize to the nucleus of P. falciparum asexual erythrocytic stages, with the phosphorylated form more prevalent at all stages. MAPK2 protein is expressed at highest levels during the early trophozoite (ring form) stage and is significantly reduced in mature trophozoite and schizont stages.","method":"Immunofluorescence microscopy, immunoelectron microscopy, western blot using TSH motif-specific antibody","journal":"BioMed research international","confidence":"Low","confidence_rationale":"Tier 3 / Weak — localization by IFA/IEM with no direct functional consequence established, single lab, single study","pmids":["27525262"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"finding":"Using DiCre-mediated conditional excision, MAPK2 (PfMAP-2) was shown to be dispensable for P. falciparum asexual growth, sexual commitment, and gametocytogenesis, but is required for male gametogenesis — specifically for initiating axonemal beating, while DNA replication and axoneme formation occur normally in its absence. Double null mutants of PfMAP-2 and PfMAP-1 showed no defect in asexual proliferation.","method":"Conditional gene excision (DiCre system), phenotypic analysis of gametogenesis (DNA replication, axoneme formation, flagellar motility assays)","journal":"Scientific reports","confidence":"High","confidence_rationale":"Tier 2 / Strong — conditional knockout with multiple orthogonal phenotypic readouts, replicates and extends earlier P. berghei findings with consistent results","pmids":["32681115"],"is_preprint":false,"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"finding":"Transcriptomic analysis of PbPP6-knockout P. berghei parasites revealed over 11-fold downregulation of nek3, described as a regulator of MAPK2 within the PKG-Ca2+ signaling cascade, suggesting MAPK2 functions downstream of PKG-Ca2+ signaling during male gametogenesis.","method":"Transcriptomic analysis of pbpp6 knockout parasites","journal":"PLoS pathogens","confidence":"Low","confidence_rationale":"Tier 4 / Weak — pathway placement inferred from transcriptomics of a different gene's knockout; no direct experiment on MAPK2 itself","pmids":["40623036"],"is_preprint":false,"attribution":[{"species":"Plasmodium berghei","strain":""}]}],"current_model":"MAPK2 (PF3D7_1113900/Pfmap-2) is an atypical MAPK-family kinase bearing a TSH rather than TXY activation motif; it is catalytically active (autophosphorylation, MBP phosphorylation), is regulated by MAPK-specific phosphatases and by upstream NIMA-family kinases Pfnek-1 and Pfnek3 that directly phosphorylate and stimulate it in vitro; it localizes to the nucleus of asexual blood-stage parasites; it is dispensable for asexual proliferation, sexual commitment, and gametocytogenesis in P. falciparum, but is essential for male gametogenesis — specifically for initiating flagellar/axonemal beating — and is proposed to act within a PKG-Ca2+ signaling cascade during this process."},"narrative":{"mechanistic_narrative":"MAPK2 (PF3D7_1113900/Pfmap-2) is an atypical MAP kinase-family enzyme of Plasmodium falciparum that functions in stage-specific signaling, most critically during sexual development [PMID:10514473, PMID:32681115]. It is a catalytically active kinase that autophosphorylates and phosphorylates myelin basic protein, and its activity is reversed by a MAPK-specific phosphatase; unusually, it lacks the canonical threonine-X-tyrosine activation motif and instead carries a threonine-serine-histidine (TSH) motif at the equivalent position [PMID:10514473]. Its activation state is set by upstream NIMA-related kinases: Pfnek-1 and Pfnek3 each directly phosphorylate and stimulate MAPK2 in vitro, with Pfnek3 acting specifically on MAPK2 and not on Pfmap-1 or human MAPK1 [PMID:11322879, PMID:17064692]. Conditional excision established that MAPK2 is dispensable for asexual proliferation, sexual commitment, and gametocytogenesis, but is required for male gametogenesis — specifically to initiate axonemal beating, while DNA replication and axoneme assembly proceed normally in its absence [PMID:32681115]. The narrative of essentiality diverges by approach: earlier gene-disruption attempts in P. falciparum implied MAPK2 was required for the asexual cycle and pointed to a compensatory relationship with Pfmap-1 [PMID:17651389], whereas conditional-excision and double-null analysis showed no asexual defect [PMID:32681115].","teleology":[{"year":1999,"claim":"Establishing whether Pfmap-2 encodes a genuine kinase and how it relates to canonical MAPKs was the first requirement; the study showed it is an active, regulatable kinase but with a divergent activation motif, defining it as an atypical MAPK.","evidence":"Recombinant expression in E. coli with in vitro autophosphorylation and MBP kinase assays, phosphatase treatment, and active-site mutagenesis","pmids":["10514473"],"confidence":"High","gaps":["The physiological substrate(s) beyond MBP were not identified","The functional significance of the TSH-versus-TXY motif for regulation was not resolved"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":1999,"claim":"Whether MAPK2 acts constitutively or in a stage-restricted manner was addressed by showing gametocyte-specific expression and preferential activation by gametocyte extracts, pointing toward a role in transmission stages.","evidence":"Northern blot, immunofluorescence, and in vitro activation with stage-specific parasite extracts","pmids":["10514473"],"confidence":"Medium","gaps":["The activating component in gametocyte extracts was not identified","Stage-specific expression alone did not establish a gametocyte function"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2001,"claim":"The question of what regulates MAPK2 upstream was first answered by identifying Pfnek-1 as a NIMA-related kinase that phosphorylates MAPK2 and synergizes with it on substrate, placing a Nek kinase upstream of the MAPK2 pathway.","evidence":"In vitro kinase and substrate-labelling assays with recombinant Pfnek-1 and MAPK2","pmids":["11322879"],"confidence":"Medium","gaps":["Interaction shown only in vitro with recombinant proteins","Whether Pfnek-1 activates MAPK2 in the parasite was not tested"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2006,"claim":"Extending upstream regulation, Pfnek3 was shown to phosphorylate and stimulate MAPK2 specifically — not Pfmap-1 or human MAPK1 — establishing a dedicated Nek3-MAPK2 regulatory link.","evidence":"In vitro phosphorylation/stimulation assay with recombinant proteins and specificity controls","pmids":["17064692"],"confidence":"Medium","gaps":["Specificity demonstrated in vitro only","In vivo requirement for Pfnek3 in MAPK2 activation not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2007,"claim":"The requirement of MAPK2 for the asexual cycle was probed by reverse genetics; failed disruption in P. falciparum implied essentiality and revealed compensatory upregulation in pfmap-1 knockouts, while the P. berghei ortholog was dispensable — an early sign of species/approach divergence.","evidence":"Gene-disruption attempts and western blot of protein levels in knockout lines","pmids":["17651389"],"confidence":"Medium","gaps":["Failed disruption is indirect evidence of essentiality and was later contradicted by conditional excision","Mechanism of Pfmap-1/MAPK2 compensation not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""},{"species":"Plasmodium berghei","strain":""}]},{"year":2016,"claim":"Where MAPK2 acts within the asexual parasite was addressed by localizing both phospho- and non-phospho forms to the nucleus, with expression peaking at the ring/early trophozoite stage.","evidence":"Immunofluorescence, immunoelectron microscopy, and western blot with a TSH-motif-specific antibody","pmids":["27525262"],"confidence":"Low","gaps":["Localization established with no direct functional consequence","Nuclear substrates and the role of the phosphorylated form were not identified"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2020,"claim":"Conditional excision resolved the essentiality question and pinpointed the true function: MAPK2 is dispensable for asexual growth and gametocytogenesis but required to initiate axonemal beating during male gametogenesis, with axoneme formation and DNA replication intact.","evidence":"DiCre conditional excision with gametogenesis phenotyping (DNA replication, axoneme formation, flagellar motility) and PfMAP-2/PfMAP-1 double-null analysis","pmids":["32681115"],"confidence":"High","gaps":["The molecular targets of MAPK2 that trigger axonemal beating are unknown","How MAPK2 couples to the motility machinery was not defined"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]},{"year":2025,"claim":"Placing MAPK2 in a broader signaling context, transcriptomics of a PbPP6 knockout showed strong downregulation of nek3, positioning MAPK2 downstream of PKG-Ca2+ signaling during male gametogenesis.","evidence":"Transcriptomic analysis of pbpp6 knockout P. berghei","pmids":["40623036"],"confidence":"Low","gaps":["Pathway placement inferred from a different gene's knockout with no direct MAPK2 experiment","Direct connection between PKG-Ca2+ signaling and MAPK2 activation not tested"],"attribution":[{"species":"Plasmodium berghei","strain":""}]},{"year":null,"claim":"The physiological substrates of MAPK2 and the mechanism by which it triggers axonemal beating downstream of PKG-Ca2+ signaling remain undefined.","evidence":"","pmids":[],"confidence":"Low","gaps":["No in vivo substrate identified beyond the in vitro MBP model","Mechanistic link between MAPK2 activity and flagellar motility unknown","In vivo relevance of Nek1/Nek3-mediated activation not established"],"attribution":[{"species":"Plasmodium falciparum","strain":""}]}],"mechanism_profile":{"molecular_activity":[],"localization":[],"pathway":[],"complexes":[],"partners":["PFNEK-1 (NIMA-RELATED KINASE, PHOSPHORYLATES AND ACTIVATES MAPK2 IN VITRO)","PFNEK3 (NIMA-FAMILY KINASE, SPECIFICALLY PHOSPHORYLATES AND STIMULATES MAPK2 IN VITRO)","PFMAP-1 (COMPENSATORY RELATIONSHIP IN P. FALCIPARUM)"],"other_free_text":["Atypical MAPK bearing a TSH activation motif in place of the canonical TXY motif [#0]","Activity reversible by a MAPK-specific phosphatase [#0]","Expression peaks at the ring/early trophozoite stage and is gametocyte-enriched [#1, #5]","Essentiality in the asexual cycle differs by method: implied essential by failed gene disruption [#4] but dispensable by conditional excision [#6]","Proposed to act downstream of PKG-Ca2+ signaling during male gametogenesis, inferred from P. berghei transcriptomics (Low confidence) [#7]"]}},"prefetch_data":{},"corpus_meta":[{"pmid":"15479470","id":"PMC_15479470","title":"Protein kinases of the human malaria parasite Plasmodium falciparum: the kinome of a divergent eukaryote.","date":"2004","source":"BMC genomics","url":"https://pubmed.ncbi.nlm.nih.gov/15479470","citation_count":421,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"11322879","id":"PMC_11322879","title":"Pfnek-1, a NIMA-related kinase from the human malaria parasite Plasmodium falciparum Biochemical properties and possible involvement in MAPK regulation.","date":"2001","source":"European journal of biochemistry","url":"https://pubmed.ncbi.nlm.nih.gov/11322879","citation_count":94,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"10514473","id":"PMC_10514473","title":"An atypical mitogen-activated protein kinase (MAPK) homologue expressed in gametocytes of the human malaria parasite Plasmodium falciparum. Identification of a MAPK signature.","date":"1999","source":"The Journal of biological chemistry","url":"https://pubmed.ncbi.nlm.nih.gov/10514473","citation_count":92,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17651389","id":"PMC_17651389","title":"Functional characterization of both MAP kinases of the human malaria parasite Plasmodium falciparum by reverse genetics.","date":"2007","source":"Molecular microbiology","url":"https://pubmed.ncbi.nlm.nih.gov/17651389","citation_count":91,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"26934697","id":"PMC_26934697","title":"Biochemical Screening of Five Protein Kinases from Plasmodium falciparum against 14,000 Cell-Active Compounds.","date":"2016","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/26934697","citation_count":45,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MAPK2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"17064692","id":"PMC_17064692","title":"Pfnek3: an atypical activator of a MAP kinase in Plasmodium falciparum.","date":"2006","source":"FEBS letters","url":"https://pubmed.ncbi.nlm.nih.gov/17064692","citation_count":40,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"32681115","id":"PMC_32681115","title":"PfMAP-2 is essential for male gametogenesis in the malaria parasite Plasmodium falciparum.","date":"2020","source":"Scientific reports","url":"https://pubmed.ncbi.nlm.nih.gov/32681115","citation_count":35,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"23544094","id":"PMC_23544094","title":"Plasmodium berghei MAPK1 displays differential and dynamic subcellular localizations during liver stage development.","date":"2013","source":"PloS one","url":"https://pubmed.ncbi.nlm.nih.gov/23544094","citation_count":8,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MAPK2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"27525262","id":"PMC_27525262","title":"Phosphorylated and Nonphosphorylated PfMAP2 Are Localized in the Nucleus, Dependent on the Stage of Plasmodium falciparum Asexual Maturation.","date":"2016","source":"BioMed research international","url":"https://pubmed.ncbi.nlm.nih.gov/27525262","citation_count":5,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["curated_ref"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false},{"pmid":"40623036","id":"PMC_40623036","title":"Loss of serine/threonine protein phosphatase 6 severely impairs sexual stage development in malaria parasite Plasmodium berghei.","date":"2025","source":"PLoS pathogens","url":"https://pubmed.ncbi.nlm.nih.gov/40623036","citation_count":0,"is_preprint":false,"source_species":["Pf"],"role":"primary","match_terms":["MAPK2"],"competing_organism_flag":false,"competing_organism_match":"","competing_organism_only":false}],"cost":{"stage1":{"model":"claude-sonnet-4-6","input_tokens":8007,"output_tokens":2368,"usd":0.02977,"stage1_stop_reason":"end_turn"},"stage2":{"model":"claude-opus-4-8","input_tokens":7738,"output_tokens":3634,"usd":0.06477,"stage2_stop_reason":"end_turn"},"total_usd":0.09454,"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\": 1999,\n      \"finding\": \"MAPK2 (Pfmap-2/PF3D7_1113900) encodes a functional kinase that can autophosphorylate, phosphorylate myelin basic protein (a classical MAPK substrate), is regulated by a MAPK-specific phosphatase, and can be activated by components present in cell extracts. Mutational analysis identified residues essential for enzymatic activity. Notably, MAPK2 lacks the conserved threonine-X-tyrosine activation motif, possessing instead a threonine-serine-histidine (TSH) motif at the same location.\",\n      \"method\": \"Recombinant protein expression in E. coli, in vitro kinase assays, phosphatase treatment, active-site mutagenesis, northern blot, immunofluorescence\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 1 / Strong — multiple orthogonal in vitro biochemical assays plus mutagenesis in a single rigorous study\",\n      \"pmids\": [\"10514473\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"finding\": \"MAPK2 (Pfmap-2) is expressed specifically in gametocytes of P. falciparum (the form responsible for transmission to the mosquito vector), and gametocyte extracts activate recombinant MAPK2 more efficiently than extracts from asexual parasites, consistent with stage-specific function.\",\n      \"method\": \"Northern blot analysis, immunofluorescence assays, in vitro kinase activation with stage-specific extracts\",\n      \"journal\": \"The Journal of biological chemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — two orthogonal methods (northern blot + IFA + extract activation), single lab\",\n      \"pmids\": [\"10514473\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"finding\": \"Pfnek-1, a NIMA-related kinase, specifically phosphorylates MAPK2 (Pfmap-2) in vitro, and co-incubation of Pfnek-1 and MAPK2 results in a synergistic increase in exogenous substrate labelling, suggesting Pfnek-1 acts upstream of MAPK2 to modulate MAPK pathway output.\",\n      \"method\": \"Recombinant protein expression, in vitro kinase assay (phosphorylation of Pfmap-2 by Pfnek-1), substrate labelling assay\",\n      \"journal\": \"European journal of biochemistry\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with recombinant proteins, single lab\",\n      \"pmids\": [\"11322879\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"finding\": \"Pfnek3, a NIMA-family kinase expressed in late asexual to gametocyte stages, phosphorylates and stimulates MAPK2 (Pfmap2) in vitro. This effect was not observed with Pfmap-1 or human MAPK1, suggesting the Pfnek3–MAPK2 interaction is specific for MAPK2 regulation.\",\n      \"method\": \"Recombinant protein expression, in vitro kinase/phosphorylation assay, specificity controls with Pfmap1 and human MAPK1\",\n      \"journal\": \"FEBS letters\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 1 / Moderate — in vitro reconstitution with specificity controls, single lab\",\n      \"pmids\": [\"17064692\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"finding\": \"Reverse genetics in P. falciparum demonstrated that MAPK2 (pfmap-2) is essential for completion of the asexual intraerythrocytic cycle, as the gene could not be disrupted. In contrast, the map-2 orthologue in P. berghei was dispensable for asexual growth. Additionally, elevated MAPK2 protein levels were observed in pfmap-1 knockout parasites, suggesting a compensatory relationship between the two P. falciparum MAPKs.\",\n      \"method\": \"Reverse genetics (gene disruption attempts), western blot for protein levels in knockout lines\",\n      \"journal\": \"Molecular microbiology\",\n      \"confidence\": \"Medium\",\n      \"confidence_rationale\": \"Tier 2 / Moderate — reverse genetics (failed disruption as evidence of essentiality) plus compensatory protein level measurement, single lab\",\n      \"pmids\": [\"17651389\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"finding\": \"Phosphorylated and non-phosphorylated forms of MAPK2 (PfMAP2) both localize to the nucleus of P. falciparum asexual erythrocytic stages, with the phosphorylated form more prevalent at all stages. MAPK2 protein is expressed at highest levels during the early trophozoite (ring form) stage and is significantly reduced in mature trophozoite and schizont stages.\",\n      \"method\": \"Immunofluorescence microscopy, immunoelectron microscopy, western blot using TSH motif-specific antibody\",\n      \"journal\": \"BioMed research international\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 3 / Weak — localization by IFA/IEM with no direct functional consequence established, single lab, single study\",\n      \"pmids\": [\"27525262\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"finding\": \"Using DiCre-mediated conditional excision, MAPK2 (PfMAP-2) was shown to be dispensable for P. falciparum asexual growth, sexual commitment, and gametocytogenesis, but is required for male gametogenesis — specifically for initiating axonemal beating, while DNA replication and axoneme formation occur normally in its absence. Double null mutants of PfMAP-2 and PfMAP-1 showed no defect in asexual proliferation.\",\n      \"method\": \"Conditional gene excision (DiCre system), phenotypic analysis of gametogenesis (DNA replication, axoneme formation, flagellar motility assays)\",\n      \"journal\": \"Scientific reports\",\n      \"confidence\": \"High\",\n      \"confidence_rationale\": \"Tier 2 / Strong — conditional knockout with multiple orthogonal phenotypic readouts, replicates and extends earlier P. berghei findings with consistent results\",\n      \"pmids\": [\"32681115\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"finding\": \"Transcriptomic analysis of PbPP6-knockout P. berghei parasites revealed over 11-fold downregulation of nek3, described as a regulator of MAPK2 within the PKG-Ca2+ signaling cascade, suggesting MAPK2 functions downstream of PKG-Ca2+ signaling during male gametogenesis.\",\n      \"method\": \"Transcriptomic analysis of pbpp6 knockout parasites\",\n      \"journal\": \"PLoS pathogens\",\n      \"confidence\": \"Low\",\n      \"confidence_rationale\": \"Tier 4 / Weak — pathway placement inferred from transcriptomics of a different gene's knockout; no direct experiment on MAPK2 itself\",\n      \"pmids\": [\"40623036\"],\n      \"is_preprint\": false,\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    }\n  ],\n  \"current_model\": \"MAPK2 (PF3D7_1113900/Pfmap-2) is an atypical MAPK-family kinase bearing a TSH rather than TXY activation motif; it is catalytically active (autophosphorylation, MBP phosphorylation), is regulated by MAPK-specific phosphatases and by upstream NIMA-family kinases Pfnek-1 and Pfnek3 that directly phosphorylate and stimulate it in vitro; it localizes to the nucleus of asexual blood-stage parasites; it is dispensable for asexual proliferation, sexual commitment, and gametocytogenesis in P. falciparum, but is essential for male gametogenesis — specifically for initiating flagellar/axonemal beating — and is proposed to act within a PKG-Ca2+ signaling cascade during this process.\"\n}\n```","stage2_raw":"{\n  \"mechanistic_narrative\": \"MAPK2 (PF3D7_1113900/Pfmap-2) is an atypical MAP kinase-family enzyme of Plasmodium falciparum that functions in stage-specific signaling, most critically during sexual development [#0, #6]. It is a catalytically active kinase that autophosphorylates and phosphorylates myelin basic protein, and its activity is reversed by a MAPK-specific phosphatase; unusually, it lacks the canonical threonine-X-tyrosine activation motif and instead carries a threonine-serine-histidine (TSH) motif at the equivalent position [#0]. Its activation state is set by upstream NIMA-related kinases: Pfnek-1 and Pfnek3 each directly phosphorylate and stimulate MAPK2 in vitro, with Pfnek3 acting specifically on MAPK2 and not on Pfmap-1 or human MAPK1 [#2, #3]. Conditional excision established that MAPK2 is dispensable for asexual proliferation, sexual commitment, and gametocytogenesis, but is required for male gametogenesis — specifically to initiate axonemal beating, while DNA replication and axoneme assembly proceed normally in its absence [#6]. The narrative of essentiality diverges by approach: earlier gene-disruption attempts in P. falciparum implied MAPK2 was required for the asexual cycle and pointed to a compensatory relationship with Pfmap-1 [#4], whereas conditional-excision and double-null analysis showed no asexual defect [#6].\",\n  \"teleology\": [\n    {\n      \"year\": 1999,\n      \"claim\": \"Establishing whether Pfmap-2 encodes a genuine kinase and how it relates to canonical MAPKs was the first requirement; the study showed it is an active, regulatable kinase but with a divergent activation motif, defining it as an atypical MAPK.\",\n      \"evidence\": \"Recombinant expression in E. coli with in vitro autophosphorylation and MBP kinase assays, phosphatase treatment, and active-site mutagenesis\",\n      \"pmids\": [\"10514473\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The physiological substrate(s) beyond MBP were not identified\", \"The functional significance of the TSH-versus-TXY motif for regulation was not resolved\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 1999,\n      \"claim\": \"Whether MAPK2 acts constitutively or in a stage-restricted manner was addressed by showing gametocyte-specific expression and preferential activation by gametocyte extracts, pointing toward a role in transmission stages.\",\n      \"evidence\": \"Northern blot, immunofluorescence, and in vitro activation with stage-specific parasite extracts\",\n      \"pmids\": [\"10514473\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"The activating component in gametocyte extracts was not identified\", \"Stage-specific expression alone did not establish a gametocyte function\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2001,\n      \"claim\": \"The question of what regulates MAPK2 upstream was first answered by identifying Pfnek-1 as a NIMA-related kinase that phosphorylates MAPK2 and synergizes with it on substrate, placing a Nek kinase upstream of the MAPK2 pathway.\",\n      \"evidence\": \"In vitro kinase and substrate-labelling assays with recombinant Pfnek-1 and MAPK2\",\n      \"pmids\": [\"11322879\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Interaction shown only in vitro with recombinant proteins\", \"Whether Pfnek-1 activates MAPK2 in the parasite was not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2006,\n      \"claim\": \"Extending upstream regulation, Pfnek3 was shown to phosphorylate and stimulate MAPK2 specifically — not Pfmap-1 or human MAPK1 — establishing a dedicated Nek3-MAPK2 regulatory link.\",\n      \"evidence\": \"In vitro phosphorylation/stimulation assay with recombinant proteins and specificity controls\",\n      \"pmids\": [\"17064692\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Specificity demonstrated in vitro only\", \"In vivo requirement for Pfnek3 in MAPK2 activation not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2007,\n      \"claim\": \"The requirement of MAPK2 for the asexual cycle was probed by reverse genetics; failed disruption in P. falciparum implied essentiality and revealed compensatory upregulation in pfmap-1 knockouts, while the P. berghei ortholog was dispensable — an early sign of species/approach divergence.\",\n      \"evidence\": \"Gene-disruption attempts and western blot of protein levels in knockout lines\",\n      \"pmids\": [\"17651389\"],\n      \"confidence\": \"Medium\",\n      \"gaps\": [\"Failed disruption is indirect evidence of essentiality and was later contradicted by conditional excision\", \"Mechanism of Pfmap-1/MAPK2 compensation not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}, {\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2016,\n      \"claim\": \"Where MAPK2 acts within the asexual parasite was addressed by localizing both phospho- and non-phospho forms to the nucleus, with expression peaking at the ring/early trophozoite stage.\",\n      \"evidence\": \"Immunofluorescence, immunoelectron microscopy, and western blot with a TSH-motif-specific antibody\",\n      \"pmids\": [\"27525262\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Localization established with no direct functional consequence\", \"Nuclear substrates and the role of the phosphorylated form were not identified\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2020,\n      \"claim\": \"Conditional excision resolved the essentiality question and pinpointed the true function: MAPK2 is dispensable for asexual growth and gametocytogenesis but required to initiate axonemal beating during male gametogenesis, with axoneme formation and DNA replication intact.\",\n      \"evidence\": \"DiCre conditional excision with gametogenesis phenotyping (DNA replication, axoneme formation, flagellar motility) and PfMAP-2/PfMAP-1 double-null analysis\",\n      \"pmids\": [\"32681115\"],\n      \"confidence\": \"High\",\n      \"gaps\": [\"The molecular targets of MAPK2 that trigger axonemal beating are unknown\", \"How MAPK2 couples to the motility machinery was not defined\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": 2025,\n      \"claim\": \"Placing MAPK2 in a broader signaling context, transcriptomics of a PbPP6 knockout showed strong downregulation of nek3, positioning MAPK2 downstream of PKG-Ca2+ signaling during male gametogenesis.\",\n      \"evidence\": \"Transcriptomic analysis of pbpp6 knockout P. berghei\",\n      \"pmids\": [\"40623036\"],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"Pathway placement inferred from a different gene's knockout with no direct MAPK2 experiment\", \"Direct connection between PKG-Ca2+ signaling and MAPK2 activation not tested\"],\n      \"attribution\": [{\"species\": \"Plasmodium berghei\", \"strain\": \"\"}]\n    },\n    {\n      \"year\": null,\n      \"claim\": \"The physiological substrates of MAPK2 and the mechanism by which it triggers axonemal beating downstream of PKG-Ca2+ signaling remain undefined.\",\n      \"evidence\": \"\",\n      \"pmids\": [],\n      \"confidence\": \"Low\",\n      \"gaps\": [\"No in vivo substrate identified beyond the in vitro MBP model\", \"Mechanistic link between MAPK2 activity and flagellar motility unknown\", \"In vivo relevance of Nek1/Nek3-mediated activation not established\"],\n      \"attribution\": [{\"species\": \"Plasmodium falciparum\", \"strain\": \"\"}]\n    }\n  ],\n  \"mechanism_profile\": {\n    \"molecular_activity\": [\n      {\"term_id\": \"GO:0004707\", \"supporting_discovery_ids\": [0]},\n      {\"term_id\": \"GO:0004672\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0046872\", \"supporting_discovery_ids\": [0]}\n    ],\n    \"localization\": [\n      {\"term_id\": \"GO:0005634\", \"supporting_discovery_ids\": [5]}\n    ],\n    \"pathway\": [\n      {\"term_id\": \"GO:0000165\", \"supporting_discovery_ids\": [0, 2, 3]},\n      {\"term_id\": \"GO:0007140\", \"supporting_discovery_ids\": [6]},\n      {\"term_id\": \"GO:0036159\", \"supporting_discovery_ids\": [6]}\n    ],\n    \"complexes\": [],\n    \"partners\": [\n      \"Pfnek-1 (NIMA-related kinase, phosphorylates and activates MAPK2 in vitro)\",\n      \"Pfnek3 (NIMA-family kinase, specifically phosphorylates and stimulates MAPK2 in vitro)\",\n      \"Pfmap-1 (compensatory relationship in P. falciparum)\"\n    ],\n    \"other_free_text\": [\n      \"Atypical MAPK bearing a TSH activation motif in place of the canonical TXY motif [#0]\",\n      \"Activity reversible by a MAPK-specific phosphatase [#0]\",\n      \"Expression peaks at the ring/early trophozoite stage and is gametocyte-enriched [#1, #5]\",\n      \"Essentiality in the asexual cycle differs by method: implied essential by failed gene disruption [#4] but dispensable by conditional excision [#6]\",\n      \"Proposed to act downstream of PKG-Ca2+ signaling during male gametogenesis, inferred from P. berghei transcriptomics (Low confidence) [#7]\"\n    ]\n  }\n}","audit_flag":null,"strains":[{"strain":"Pf3D7","gene_id":"PF3D7_1113900","name":null,"product":"mitogen-activated protein kinase 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PbANKA","gene_id":"PBANKA_0933700","name":null,"product":"mitogen-activated protein kinase 2","uniprot_acc":null,"chromosome":null,"start_pos":null},{"strain":"PkH","gene_id":"PKNH_0911500","name":null,"product":"mitogen-activated protein kinase 2, putative","uniprot_acc":null,"chromosome":null,"start_pos":null}],"gene_symbol":"MAPK2","evaluation":null}