PI4K2A

PI4K2A is a type II phosphatidylinositol 4-kinase whose central function is to deposit PtdIns4P on a defined set of intracellular membranes, thereby controlling membrane identity, vesicle sorting, and organelle homeostasis (PMID:32418222). Its catalytic output depends on direct electrostatic engagement of the membrane through residue R275, and a natural R275W loss-of-function mutation reduces kinase activity and depletes specific PI4P and PI(4,5)P2 acyl-chain pools in patient fibroblasts (PMID:32418222). In the endo-lysosomal and autophagic system, PI4K2A-generated PtdIns4P regulates R-SNARE sorting and transferrin receptor recycling via direct, kinase-independent binding to VAMP3 (PMID:25002402), drives autophagosome-lysosome fusion through isoform-specific recruitment to autophagosomes by GABARAP via a 7-residue GABARAP interaction motif (GIM) in an exposed catalytic-domain loop absent from PI4K2B (PMID:26391226, PMID:39344512), and tunes autophagic lysosome reformation by setting autolysosomal PtdIns4P that recruits clathrin and DNM2 (PMID:33618608). PI4K2A also supports lysosomal membrane repair: it is delivered to damaged lysosomes on ATG9A vesicles and, through interaction with the ER lipid-transfer protein OSBPL6/ORP6, channels phosphatidylserine to damaged membranes to promote repair and limit lipid droplet accumulation (PMID:41556583). In cancer, PI4K2A forms a lysosomal complex with PKR that sustains cell survival (PMID:31554935) and, in EMT-activated lung cancer, becomes the dominant PI4P source downstream of ZEB1, assembling a MYOIIA-containing Golgi complex to drive secretory vesicle biogenesis and stabilizing AXL via HSP90 (PMID:36757799).

1. 2014 High

   Established that PI4K2A regulates R-SNARE sorting both as a PtdIns4P source and as a direct binding partner, distinguishing kinase-dependent from kinase-independent roles in membrane recycling.

   Evidence Co-IP/binding assays, siRNA knockdown, transferrin receptor recycling and endosomal PtdIns4P depletion in cells

   PMID:25002402

   Open questions at the time

   • Structural basis of the VAMP3-PI4K2A interaction not defined
   • How PtdIns4P specifically promotes VAMP3-Vti1a pairing remains unresolved
2. 2015 Medium

   Showed PI4K2A is recruited to autophagosomes by the ATG8 adaptor GABARAP, where its PtdIns4P facilitates autophagosome-lysosome fusion in an isoform-specific manner.

   Evidence Co-IP, localization imaging, and autophagosome-lysosome fusion assays with PI4K2A and GABARAP depletion

   PMID:26391226

   Open questions at the time

   • Molecular determinant of GABARAP specificity not yet mapped at this stage
   • Downstream fusion machinery linking PtdIns4P to fusion not identified
3. 2019 Medium

   Identified a lysosomal PI4K2A-PKR complex as a survival factor in cancer cells and a druggable node, linking PI4K2A to lysosomal stability.

   Evidence Co-IP of PKR/PI4K2A, small-molecule (Pac 1) disruption, viability assays, and xenograft tumor models

   PMID:31554935

   Open questions at the time

   • Mechanism by which the complex stabilizes lysosomes is inferred
   • Whether kinase activity is required for the PKR complex function is unclear
4. 2020 High

   Linked PI4K2A enzymatic activity to human disease and defined the membrane-binding R275 residue as essential for catalysis through a natural loss-of-function mutation.

   Evidence Exome sequencing, kinase activity assay in patient fibroblasts, lipidomics, and structural modeling

   PMID:32418222

   Open questions at the time

   • Tissue-specific consequences of the lipid pool changes not fully resolved
   • Genotype-phenotype relationship across the patient population not established
5. 2021 Medium

   Demonstrated PI4K2A bidirectionally modulates autophagic lysosome reformation by controlling autolysosomal PtdIns4P and recruitment of clathrin/DNM2.

   Evidence spg11/zfyve26 mouse KO models, MEF starvation assays, PI4K2A OE/KD, and tubulation quantification

   PMID:33618608

   Open questions at the time

   • Precise PtdIns4P threshold governing tubulation versus inhibition not defined
   • How clathrin/DNM2 read out PtdIns4P at autolysosomes unclear
6. 2023 Medium

   Revealed a ZEB1-driven PI4P kinase dependency switch in which PI4K2A drives hypersecretion and receptor stability in EMT-activated cancer.

   Evidence Co-IP of PI4K2A-MYOIIA, knockdown, vesicle biogenesis and receptor recycling assays, HSP90 interaction, and PI4K2A antagonists

   PMID:36757799

   Open questions at the time

   • Composition and assembly order of the MYOIIA Golgi complex not fully resolved
   • Direct versus indirect role in AXL/HSP90 stabilization not separated
7. 2024 High

   Mapped the isoform-specific GABARAP interaction motif to a 7-residue exposed loop in the PI4K2A catalytic domain, explaining selective recruitment over PI4K2B.

   Evidence GIM mutagenesis, co-IP, localization imaging, and PI4K2A/PI4K2B sequence alignment

   PMID:39344512

   Open questions at the time

   • Whether GIM-mediated recruitment is regulated dynamically is unknown
   • Co-structure of the GIM-GABARAP complex not determined
8. 2026 Medium

   Defined PI4K2A as a driver of lysosomal membrane repair by recruiting OSBPL6/ORP6 to deliver phosphatidylserine to damaged lysosomes, with in vivo neuroprotective consequences.

   Evidence Co-IP-MS, in vivo PI4K2A overexpression, lysosomal integrity and lipid droplet assays, and SCI functional recovery

   PMID:41556583

   Open questions at the time

   • Order of PtdIns4P deposition and PS counter-transport not kinetically resolved
   • Generality beyond the neuronal SCI context not established

• Whether reported nuclear (Star-PAP) and lipid-droplet (CIDE) roles of PI4K2A represent bona fide functions and how membrane-targeting selects among its many organellar destinations remain open.
• Direct PI4K2A-lipid droplet engagement not validated
• Nuclear catalytic contribution to Star-PAP not mechanistically dissected
• Determinants routing PI4K2A to specific organelles unknown