Affinage · Plasmodium

eIF2alpha

PF3D7_0728000 · eukaryotic translation initiation factor 2 subunit alpha

Annotated
2026-09-08
24 papers in source corpus 16 papers cited in narrative 16 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PF3D7_0728000 (eIF2alpha) is the central translational regulator of Plasmodium whose phosphorylation state gates global protein synthesis across the parasite life cycle and under stress (PMID:22355110, PMID:26735921). Its activity is controlled by phosphorylation of the regulatory serine 59, identified by site-specific mutagenesis as the residue modified by the kinase PK4; this modification arrests protein synthesis in schizonts and gametocytes and is essential for completion of the erythrocytic cycle (PMID:22355110). Multiple stage- and stress-specific kinases converge on eIF2alpha: PfeIK1/GCN2 phosphorylates it in response to amino acid (isoleucine) starvation in asexual parasites (PMID:19435497, PMID:23112171), and IK2 phosphorylates it in salivary gland sporozoites to drive translational latency, stalling mRNAs into granules and maintaining sporozoite infectivity until host injection (PMID:20584882). eIK1 and eIK2 respond to distinct amino acid-limiting conditions at temporally separated life cycle stages (PMID:36810637). Reversal of this modification is carried out by the PP2C/PPM-family phosphatase UIS2, which dephosphorylates eIF2alpha phosphoserine-59 and, unusually for a eukaryotic phosphatase, stably binds the phosphorylated substrate; loss of UIS2 raises eIF2alpha phosphorylation and blocks sporozoite transformation in the host (PMID:26735921). The phosphatase PfPPM2 similarly represses eIF2alpha phosphorylation and influences asexual division and sexual conversion (PMID:40410154). Beyond its developmental roles, eIF2alpha phosphorylation is a node of drug response: PK4-mediated phosphorylation of eIF2alpha drives artemisinin-induced latency and recrudescence (PMID:29241041), and the pathway is engaged by ER stress via PfGRP170-restrained PK4 activation (PMID:31087747). The direct molecular activity of eIF2alpha itself beyond serving as the serine-59 phosphoacceptor substrate has not been characterized in the available corpus.

Mechanistic history

Synthesis pass · year-by-year structured walk · 12 steps
  1. 2009 High

    Establishing which kinase phosphorylates eIF2alpha under nutrient stress was needed to connect the initiation factor to a defined signaling input; PfeIK1 was identified as the kinase for starvation-induced phosphorylation.

    Evidence In vitro kinase assay with recombinant PfeIK1 and eIF2alpha, plus pfeik1 gene disruption abolishing starvation-induced phosphorylation

    PMID:19435497

    Open questions at the time
    • Did not map the phosphorylated residue on eIF2alpha
    • Did not test whether other kinases redundantly phosphorylate eIF2alpha under starvation
  2. 2010 High

    Whether eIF2alpha phosphorylation controls a discrete developmental transition was open; IK2-mediated phosphorylation was shown to enforce sporozoite translational latency and preserve infectivity, with a phosphatase reversing it on host entry.

    Evidence IK2 knockout with phospho-eIF2alpha immunodetection, mRNA granule microscopy, and sporozoite infectivity assays

    PMID:20584882

    Open questions at the time
    • Identity of the reversing phosphatase not resolved in this study
    • Direct demonstration that IK2 phosphorylates eIF2alpha biochemically not shown
  3. 2012 High

    The regulatory residue and the erythrocytic-cycle requirement were unknown; serine 59 was defined as the PK4 phosphorylation site required to arrest protein synthesis in schizonts and gametocytes.

    Evidence PK4 knockout with developmental phenotype, site-specific mutagenesis of serine 59, and protein synthesis assays

    PMID:22355110

    Open questions at the time
    • Downstream mRNAs preferentially translated during arrest not identified
    • Interplay with other kinases at the same residue not delineated
  4. 2012 Medium

    Whether the eIF2alpha phosphorylation pathway itself confers survival during isoleucine starvation was tested; GCN2/eIK1 knockouts still hibernated and recovered, dissociating survival from this pathway.

    Evidence GCN2 kinase-knockout clones with viability, re-growth, and phosphorylation assays after isoleucine withdrawal

    PMID:23112171

    Open questions at the time
    • Negative result does not exclude a modulatory role
    • Alternative survival pathway not identified
  5. 2016 High

    The phosphatase reversing eIF2alpha phosphorylation and its mode of substrate engagement were unknown; UIS2 was shown to dephosphorylate phosphoserine-59 and to bind the phosphorylated substrate stably, controlling sporozoite transformation.

    Evidence Conditional uis2 knockout, phospho-eIF2alpha immunodetection, sporozoite morphology/infectivity assays, and UIS2–phospho-eIF2alpha binding assay

    PMID:26735921

    Open questions at the time
    • Structural basis of the stable interaction not resolved here
    • Whether UIS2 acts on eIF2alpha in blood stages not addressed
  6. 2017 High

    The mechanism of artemisinin-induced latency was unclear; PK4-mediated eIF2alpha phosphorylation was shown to drive translational repression and recrudescence, blockable by PK4 inhibition.

    Evidence PK4 dominant-negative overexpression, pharmacological PK4 inhibition, phospho-eIF2alpha immunodetection, and in vivo mouse recrudescence assays

    PMID:29241041

    Open questions at the time
    • How artemisinin activates PK4 upstream not defined
    • Reversal step out of drug-induced latency not characterized
  7. 2019 Medium

    An ER-stress input to eIF2alpha phosphorylation was sought; loss of the ER chaperone PfGRP170 activates PK4, placing eIF2alpha downstream of a chaperone-restrained ER stress response.

    Evidence Conditional PfGRP170 mutant with PK4-activation readout and PfGRP170–BiP co-immunoprecipitation

    PMID:31087747

    Open questions at the time
    • Direct effect on eIF2alpha phosphorylation levels quantified only indirectly
    • Mechanism linking GRP170 loss to PK4 activation unresolved
  8. 2019 Medium

    Whether eIF2alpha signaling mediates the adaptive response to halofuginone-induced proline stress was tested; the adaptive proline response was shown to be independent of PfeIK1 and eIF2alpha, despite drug-induced phosphorylation.

    Evidence Phospho-eIF2alpha immunodetection and pfeik1-knockout drug-tolerance (APR) assay

    PMID:30773881

    Open questions at the time
    • Negative result; other kinases driving the observed phosphorylation not identified
    • Functional consequence of the drug-induced phosphorylation unclear
  9. 2023 Medium

    The division of labor among eIF2alpha kinases across the life cycle was refined; eIK1 and eIK2 were shown to sense distinct amino acid-limiting conditions at temporally separated stages.

    Evidence Kinase-knockout mutant phenotypic screen under defined amino acid deprivation with life cycle stage analysis

    PMID:36810637

    Open questions at the time
    • Direct eIF2alpha phosphorylation measurements not detailed
    • How each kinase distinguishes specific amino acid limitations not defined
  10. 2023 Medium

    Additional regulators of the eIF2alpha stress response were sought; PfCYP19B was shown to act as a negative regulator of phospho-eIF2alpha, contributing to artemisinin resistance.

    Evidence PfCYP19B overexpression with phospho-eIF2alpha immunodetection and drug resistance assays

    PMID:36696458

    Open questions at the time
    • Whether PfCYP19B acts on a kinase or phosphatase unresolved
    • No direct interaction with eIF2alpha demonstrated
  11. 2025 Medium

    A second phosphatase restraining eIF2alpha phosphorylation was identified; PfPPM2 represses eIF2alpha phosphorylation and influences asexual division and sexual conversion.

    Evidence Conditional PfPPM2 loss-of-function with phospho-eIF2alpha immunodetection and growth/gametocyte conversion assays

    PMID:40410154

    Open questions at the time
    • Direct dephosphorylation of eIF2alpha by PfPPM2 in vitro not shown
    • Division of labor between PfPPM2 and UIS2 not resolved
  12. 2025 Low

    The structural basis of UIS2 recognition of phospho-eIF2alpha was modeled; a phosphatase-domain pocket distinct from human PP1alpha with cooperative binding patches was defined, and salubrinal was shown computationally to compete for it.

    Evidence Integrated structural modeling (AlphaFold, molecular dynamics, metadynamics), docking, free energy perturbation, and domain-binding analysis (preprint)

    PMID:40463039

    Open questions at the time
    • Primarily computational; no experimental structural validation reported
    • Predicted binding patches not tested by mutagenesis

Open questions

Synthesis pass · forward-looking unresolved questions
  • The intrinsic molecular activity of eIF2alpha within the initiation complex and the identity of mRNAs selectively regulated by its phosphorylation state remain undefined in this corpus.
  • No characterization of eIF2 ternary complex assembly for this protein
  • Selectively translated mRNAs during phospho-eIF2alpha arrest not mapped
  • Blood-stage phosphatase(s) versus sporozoite UIS2 roles not fully partitioned

Mechanism profile

Synthesis pass · controlled-vocabulary classification
Partners
EIK2 (KINASE, AMINO ACID SENSING) [#11]IK2 (KINASE, PHOSPHORYLATES EIF2ALPHA IN SPOROZOITES) [#1]PFCYP19B (NEGATIVE REGULATOR OF PHOSPHO-EIF2ALPHA) [#13]PFEIK1/GCN2/EIK1 (KINASE, STARVATION-INDUCED PHOSPHORYLATION) [#0, #3, #11]PFGRP170 (ER CHAPERONE RESTRAINING PK4 ACTIVATION UPSTREAM) [#9]PFPPM2 (PHOSPHATASE, REPRESSES EIF2ALPHA PHOSPHORYLATION) [#15]PK4 (KINASE, PHOSPHORYLATES EIF2ALPHA SER59) [#2, #5, #9]UIS2 (PP2C/PPM PHOSPHATASE, DEPHOSPHORYLATES AND STABLY BINDS PHOSPHO-EIF2ALPHA SER59) [#4, #14]

Evidence

Reading pass · 16 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2009 PfeIK1 (eIK1) phosphorylates P. falciparum eIF2alpha in vitro, and eIF2alpha phosphorylation in response to amino acid starvation is abolished in pfeik1-knockout asexual parasites, establishing PfeIK1 as the kinase responsible for starvation-induced eIF2alpha phosphorylation. In vitro kinase assay with recombinant PfeIK1 and recombinant PfeIF2alpha; reverse genetics (gene disruption of pfeik1) with phenotypic readout of eIF2alpha phosphorylation under starvation Malaria journal High 19435497
2010 The eIF2alpha kinase IK2 phosphorylates eIF2alpha in salivary gland sporozoites, leading to translation inhibition and accumulation of stalled mRNAs into granules; IK2 knockout sporozoites lack phosphorylated eIF2alpha and transform prematurely into liver stages, losing infectivity. An eIF2alpha phosphatase reverses this phosphorylation upon host injection. Genetic knockout of IK2; immunodetection of phosphorylated eIF2alpha; microscopic analysis of mRNA granules; sporozoite infectivity assays The Journal of experimental medicine High 20584882
2012 The kinase PK4 phosphorylates the regulatory serine 59 of P. falciparum eIF2alpha; this phosphorylation is essential for the completion of the erythrocytic cycle, arresting global protein synthesis in schizonts and gametocytes. Genetic knockout of PK4 with loss-of-function developmental phenotype; site-specific mutagenesis identifying serine 59 as the phosphorylation site; protein synthesis assays Proceedings of the National Academy of Sciences of the United States of America High 22355110
2012 Isoleucine starvation of intraerythrocytic P. falciparum results in GCN2 (eIK1)-mediated phosphorylation of eIF2alpha; however, GCN2 kinase-knockout clones can still hibernate and recover, indicating that the eIF2alpha phosphorylation pathway does not directly promote survival during isoleucine starvation. Kinase-knockout clones; parasite viability and re-growth assays after isoleucine withdrawal; phosphorylation assays Proceedings of the National Academy of Sciences of the United States of America Medium 23112171
2016 UIS2, a PP2C/PPM-family phosphatase, dephosphorylates eIF2alpha phosphoserine-59 in Plasmodium sporozoites; conditional knockout of uis2 leads to high eIF2alpha phosphorylation, crescent-shaped sporozoites that fail to transform in the mammalian host, and loss of infectivity. UIS2 stably binds phosphorylated eIF2alpha, unlike the transient interactions of most eukaryotic phosphatases. Conditional genetic knockout of uis2; immunodetection of phosphorylated eIF2alpha; sporozoite morphology and infectivity assays; co-immunoprecipitation/binding assay of UIS2 with phosphorylated eIF2alpha PLoS pathogens High 26735921
2017 Artemisinin treatment causes phosphorylation of eIF2alpha in P. falciparum, mediated by the kinase PK4, leading to global translation repression and latency induction; inhibiting PK4 (dominant-negative overexpression or pharmacological inhibition) blocks eIF2alpha phosphorylation, prevents parasite entry into latency, and abolishes recrudescence after artemisinin treatment in mice. PK4 dominant-negative overexpression; pharmacological PK4 inhibition; immunodetection of phosphorylated eIF2alpha; in vivo mouse infection recrudescence assays Cell host & microbe High 29241041
2006 15-Deoxyspergualin induces phosphorylation of eIF2alpha in P. falciparum through Hsp70 sequestration, resulting in stalled protein synthesis; however, this eIF2alpha-mediated protein synthesis inhibition occurs only at high micromolar concentrations, whereas the primary antimalarial mechanism is via apicoplast protein trafficking inhibition at submicromolar concentrations. Protein synthesis assays; immunodetection of phosphorylated eIF2alpha; drug dose-response experiments The Journal of biological chemistry Medium 17194705
2016 Addition of biliverdin to P. falciparum cultures alters the phosphorylation pattern of eIF2alpha, suggesting biliverdin-induced stress activates eIF2alpha kinases. Immunodetection of phosphorylated eIF2alpha in drug-treated parasite cultures Scientific reports Low 26915471
2016 Phosphorylation of eIF2alpha and attenuation of global protein synthesis occur during in vitro differentiation of P. berghei gametocytes to ookinetes under mosquito midgut-like oxidative stress conditions. Immunodetection of phosphorylated eIF2alpha; protein synthesis attenuation assay; reactive oxygen species detection; in vitro gametocyte-to-ookinete differentiation Biochemistry and cell biology Low 28177775
2019 Loss of function of the ER chaperone PfGRP170 activates the P. falciparum eIF2alpha kinase PK4, indicating that PfGRP170 normally suppresses PK4-mediated eIF2alpha phosphorylation as part of the ER stress response pathway. Conditional mutant generation; immunodetection of PK4 activation downstream of PfGRP170 loss; co-immunoprecipitation of PfGRP170 with BiP Cellular microbiology Medium 31087747
2019 Halofuginone treatment induces eIF2alpha phosphorylation in P. falciparum; however, the adaptive proline response (APR) caused by halofuginone is independent of PfeIK1 and eIF2alpha signaling, as demonstrated by a pfeik1-knockout parasite line showing unaltered APR. Immunodetection of phosphorylated eIF2alpha; pfeik1-knockout parasites; drug tolerance (APR) assay ACS infectious diseases Medium 30773881
2023 P. falciparum eIK1 and eIK2 (eIF2alpha kinases) are critical for sensing and responding to distinct amino acid-limiting conditions across the life cycle, as shown by phenotypic screening of kinase-knockout mutants under amino acid deprivation; this sensing pathway is temporally regulated at distinct life cycle stages. Kinase-knockout mutant phenotypic screen; amino acid deprivation assays; life cycle stage analysis Communications biology Medium 36810637
2023 Inhibition of P. falciparum glutamine synthetase (GS) reduces asparagine levels and induces eIF2alpha phosphorylation, leading to inhibition of protein synthesis and parasite death. GS inhibitor treatment (MSO, PPT); immunodetection of phosphorylated eIF2alpha; protein synthesis assay Nature communications Low 37452051
2023 P. falciparum cyclophilin 19B (PfCYP19B) acts as a negative regulator of the integrated stress response by modulating levels of phosphorylated eIF2alpha; overexpression of PfCYP19B reduces eIF2alpha-P and contributes to artemisinin resistance. Overexpression of PfCYP19B; immunodetection of phosphorylated eIF2alpha; drug resistance assays PLoS pathogens Medium 36696458
2025 The phosphatase UIS2 binds eIF2alpha phosphoserine-59 through its N-terminal and phosphatase domains via electrostatic interactions; integrated structural modeling (AlphaFold + molecular dynamics) defines a binding pocket in the phosphatase domain distinct from human PP1α, with six cooperative binding patches. Salubrinal competes with the phospho-eIF2alpha peptide for this pocket via hydrophobic and hydrogen-bonding interactions at three of these patches. Integrated structural modeling (AlphaFold, molecular dynamics, metadynamics simulations); molecular docking; free energy perturbation analysis; domain-binding assays bioRxivpreprint Low 40463039
2025 The phosphatase PfPPM2 represses eIF2alpha phosphorylation in P. falciparum, thereby regulating protein synthesis; loss of PfPPM2 function increases eIF2alpha phosphorylation and affects parasite asexual division and sexual conversion. Conditional loss-of-function of PfPPM2; immunodetection of phosphorylated eIF2alpha; parasite growth and gametocyte conversion assays Nature communications Medium 40410154

Source papers

Stage 0 corpus · 24 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 Plasmodium falciparum responds to amino acid starvation by entering into a hibernatory state. Proceedings of the National Academy of Sciences of the United States of America 125 23112171
2010 The Plasmodium eukaryotic initiation factor-2alpha kinase IK2 controls the latency of sporozoites in the mosquito salivary glands. The Journal of experimental medicine 109 20584882
2017 Inhibiting the Plasmodium eIF2α Kinase PK4 Prevents Artemisinin-Induced Latency. Cell host & microbe 105 29241041
2012 PK4, a eukaryotic initiation factor 2α(eIF2α) kinase, is essential for the development of the erythrocytic cycle of Plasmodium. Proceedings of the National Academy of Sciences of the United States of America 80 22355110
2016 Plasmodium falciparum: multifaceted resistance to artemisinins. Malaria journal 79 26955948
2009 PfeIK1, a eukaryotic initiation factor 2alpha kinase of the human malaria parasite Plasmodium falciparum, regulates stress-response to amino-acid starvation. Malaria journal 77 19435497
2011 The Puf-family RNA-binding protein Puf2 controls sporozoite conversion to liver stages in the malaria parasite. PloS one 59 21673790
2014 Translational regulation during stage transitions in malaria parasites. Annals of the New York Academy of Sciences 50 25387887
1997 Molecular cloning, characterization and localization of PfPK4, an eIF-2alpha kinase-related enzyme from the malarial parasite Plasmodium falciparum. The Biochemical journal 47 9371731
2016 UIS2: A Unique Phosphatase Required for the Development of Plasmodium Liver Stages. PLoS pathogens 38 26735921
2006 15-deoxyspergualin primarily targets the trafficking of apicoplast proteins in Plasmodium falciparum. The Journal of biological chemistry 38 17194705
2019 The endoplasmic reticulum chaperone PfGRP170 is essential for asexual development and is linked to stress response in malaria parasites. Cellular microbiology 23 31087747
2016 Biliverdin targets enolase and eukaryotic initiation factor 2 (eIF2α) to reduce the growth of intraerythrocytic development of the malaria parasite Plasmodium falciparum. Scientific reports 15 26915471
2023 A non-canonical sensing pathway mediates Plasmodium adaptation to amino acid deficiency. Communications biology 13 36810637
2019 The Adaptive Proline Response in P. falciparum Is Independent of PfeIK1 and eIF2α Signaling. ACS infectious diseases 12 30773881
2016 Cellular stress associated with the differentiation of Plasmodium berghei ookinetes. Biochemistry and cell biology = Biochimie et biologie cellulaire 8 28177775
2016 Translational Repression in Malaria Sporozoites. Microbial cell (Graz, Austria) 8 28357358
2023 Short tandem repeat polymorphism in the promoter region of cyclophilin 19B drives its transcriptional upregulation and contributes to drug resistance in the malaria parasite Plasmodium falciparum. PLoS pathogens 7 36696458
2023 Distinct evolution of type I glutamine synthetase in Plasmodium and its species-specific requirement. Nature communications 6 37452051
2025 PfPPM2 signalling regulates asexual division and sexual conversion of human malaria parasite Plasmodium falciparum. Nature communications 2 40410154
2022 Anti-malarial activity of HCl salt of SKM13 (SKM13-2HCl). International journal for parasitology. Drugs and drug resistance 2 36375338
2025 Mechanistic Insights into the Plasmodium Phosphatase UIS2 in eIF2α Dephosphorylation via Integrated Structure-Based Modeling. bioRxiv : the preprint server for biology 0 40463039
2025 PfPI3K inhibition reversed artemisinin resistance by increasing ROS and ubiquitinated protein levels in Plasmodium falciparum. Communications biology 0 41286015
2017 Plasmodium Peekaboo: PK4 Mediates Parasite Latency. Cell host & microbe 0 29241036