PIP4K2A

PIP4K2A is a phosphatidylinositol-5-phosphate 4-kinase that generates PI(4,5)P2 at multiple subcellular compartments, thereby regulating diverse membrane-associated and signaling processes including ion channel activation, receptor trafficking, organelle contact site formation, and PI3K pathway modulation. At peroxisomal membranes, PIP4K2A-generated PI(4,5)P2 is required for lysosome–peroxisome membrane contacts that mediate LDL-derived cholesterol transport (PMID:29353240), while at the plasma membrane its lipid kinase activity activates KCNQ2/3 and KCNQ3/5 neuronal M channels (PMID:18545987) and increases surface abundance of EAAT3 and GluA1 (PMID:19644675, PMID:24389605). Beyond canonical lipid kinase functions, PIP4K2A directly phosphorylates MIF at Ser91 to drive cilia biogenesis through MIF nuclear translocation and transcriptional regulation of ciliogenesis genes (PMID:38052787), negatively regulates PI3K signaling in PTEN-deficient glioblastoma by promoting proteasomal degradation of the p85 regulatory subunit (PMID:30898893), and is essential for AML cell survival through control of CDKN1A/CDKN1B levels and mTOR signaling (PMID:24681948).

1. 2008 High

   Establishing that PIP4K2A lipid kinase activity directly controls neuronal ion channel function resolved how PI(4,5)P2 synthesis couples to electrical excitability, and the schizophrenia-associated N251S mutation provided a loss-of-function tool linking kinase activity to channel activation.

   Evidence Xenopus oocyte electrophysiology with WT vs. N251S PIP4K2A, acute PI(4,5)P2 injection controls, and subunit requirement analysis for KCNQ2/3 and KCNQ3/5 channels

   PMID:18545987

   Open questions at the time

   • Whether PIP4K2A-dependent KCNQ activation occurs at endogenous expression levels in mammalian neurons
   • Structural basis for how N251S abolishes kinase activity
   • Whether other PIP4K family members compensate in vivo
2. 2009 Medium

   Demonstrating that PIP4K2A promotes EAAT3 membrane abundance and glutamate transport extended PI(4,5)P2-dependent membrane trafficking beyond ion channels to neurotransmitter transporters.

   Evidence Xenopus oocyte dual electrode voltage clamp and HEK293 membrane fractionation comparing WT and N251S PIP4K2A effects on EAAT3

   PMID:19644675

   Open questions at the time

   • Whether PI(4,5)P2 directly binds EAAT3 or acts through an intermediary
   • In vivo relevance in neuronal glutamate homeostasis
   • Single lab observation
3. 2014 High

   Identification of PIP4K2A as essential for AML cell proliferation, with its loss causing CDKN1A/CDKN1B accumulation and mTOR-dependent apoptosis, established the kinase as a cancer dependency factor and linked its activity to cell cycle control.

   Evidence RNAi knockdown screen in human and murine MLL-AF9 AML cells, clonogenic assays, and Western blotting for downstream mTOR and CDK inhibitor effectors

   PMID:24681948

   Open questions at the time

   • Whether the requirement is for lipid kinase activity specifically versus a scaffolding function
   • The direct mechanistic link between PI(4,5)P2 pools and CDKN1A/CDKN1B stabilization
   • Whether selective PIP4K2A inhibitors phenocopy knockdown in AML
4. 2014 Medium

   Mapping the PI(4,5)P2-binding site on GluA1 (K813–K823) and showing PIP4K2A-dependent membrane insertion of AMPA receptors broadened the kinase's role to excitatory synaptic receptor trafficking.

   Evidence Alanine scanning mutagenesis of GluA1 C-terminus, PIP strip lipid-binding assay, Xenopus oocyte electrophysiology, and HEK293 membrane fractionation

   PMID:24389605

   Open questions at the time

   • Endogenous validation in hippocampal or cortical neurons
   • Whether the effect involves direct PI(4,5)P2–GluA1 interaction in a bilayer context
   • Single lab
5. 2018 High

   Reconstitution of PIP4K2A-generated PI(4,5)P2 at peroxisomal membranes as the trigger for lysosome–peroxisome contact formation and cholesterol transport revealed a new organelle contact site regulated by this kinase.

   Evidence In vitro membrane contact reconstitution with recombinant PIP4K2A, rescue with peroxisome-targeted kinase-active vs. kinase-dead constructs, and cholesterol accumulation assays

   PMID:29353240

   Open questions at the time

   • Identity of the PI(4,5)P2 effector tethering the two organelle membranes beyond synaptotagmin VII
   • Physiological consequences in tissues with high cholesterol flux
   • Whether PIP4K2B or PIP4K2C contribute at peroxisomes
6. 2019 Medium

   Showing that PIP4K2A promotes proteasomal degradation of p85 to restrain PI3K signaling in PTEN-deficient GBM uncovered a tumor-suppressive mechanism operating through PI3K complex destabilization rather than through PI(4,5)P2 itself.

   Evidence In vivo RNAi screen in patient-derived xenograft GBM models, PIP4K2A overexpression with proteasome inhibitor experiments, and tumor growth assays

   PMID:30898893

   Open questions at the time

   • Whether PIP4K2A directly ubiquitinates or recruits an E3 ligase for p85
   • Whether this mechanism operates outside of PTEN-null contexts
   • Single lab
7. 2021 Low

   Discovery of conserved RNA-binding activity independent of kinase function suggested PIP4K2A has a moonlighting role beyond lipid phosphorylation, though the functional significance remains undefined.

   Evidence RNA binding assays with kinase-dead mutants, cross-species comparison in Drosophila, C. elegans, and human cells

   PMID:34124142

   Open questions at the time

   • Limited mechanistic follow-up on human PIP4K2A RNA targets
   • No defined biological function for the RNA-binding activity
   • Single lab with no independent replication
8. 2021 Medium

   Selective chemical inhibitors (BAY-091 and BAY-297) confirmed cellular target engagement but failed to reproduce the antiproliferative phenotype predicted from genetic loss in p53-deficient cells, dissociating kinase activity from at least some proposed tumor-suppressive functions.

   Evidence High-throughput screening, crystal structure-guided design, CETSA target engagement, and antiproliferative assays in p53-deficient cell lines

   PMID:34699202

   Open questions at the time

   • Whether kinase-independent scaffolding functions explain the discrepancy between genetic and pharmacological perturbation
   • Whether longer treatment durations or specific cancer genotypes would reveal sensitivity
   • Impact of inhibitors on PI5P pools not assessed
9. 2022 Medium

   Identification of lncSAMD11-1:1 as a PIP4K2A-binding partner that redirects the kinase to the cytoplasm to inhibit AKT and promote FoxO1 nuclear retention during decidualization revealed a physiological context where non-catalytic protein–RNA interactions control kinase signaling output.

   Evidence Co-immunoprecipitation of lncRNA with PIP4K2A, AKT phosphorylation assays, FoxO1 localization by confocal microscopy in primary human endometrial stromal cells

   PMID:35987479

   Open questions at the time

   • Whether the PIP4K2A–lncRNA interaction requires the RNA-binding activity described separately
   • Mechanism by which PIP4K2A binding to lncSAMD11-1:1 inhibits AKT
   • Single lab, no reciprocal validation of lncRNA specificity
10. 2023 Medium

    Discovery that PIP4K2A directly phosphorylates the non-lipid substrate MIF at Ser91 to promote its nuclear import and transcriptional activation of ciliogenesis genes fundamentally expanded the kinase's substrate repertoire from lipids to proteins.

    Evidence Co-immunoprecipitation, in vitro phosphorylation assays, S91A mutagenesis, confocal microscopy of cilia formation, and gene expression analysis

    PMID:38052787

    Open questions at the time

    • Whether PIP4K2A phosphorylates other protein substrates
    • In vivo validation of cilia defects upon PIP4K2A loss
    • Single lab, not independently replicated
11. 2023 Medium

    Identification of the gain-of-function S316R mutation causing enhanced kinase activity, upregulated β-globin expression, and impaired erythroid differentiation linked PIP4K2A to hemoglobin gene regulation and erythropoiesis.

    Evidence Family hematological analysis, kinase activity and protein stability assays, lentiviral S316R expression in HUDEP-2 erythroid cells

    PMID:37423903

    Open questions at the time

    • Mechanism connecting PI(4,5)P2 levels to β-globin transcriptional regulation
    • Whether loss-of-function PIP4K2A mutations produce reciprocal erythroid phenotypes
    • Single lab, single family

• The relative contributions of lipid kinase activity, protein kinase activity, RNA binding, and scaffolding functions to PIP4K2A's diverse cellular roles remain unresolved, as does the question of which functions are pharmacologically targetable.
• No unified model integrating lipid kinase, protein kinase, and RNA-binding functions
• Discrepancy between genetic and pharmacological perturbation in cancer models is unexplained
• Structural basis for protein substrate recognition (e.g., MIF Ser91) is unknown