Phosphorylated derivatives of phosphatidylinositol (PtdIns) regulate cytoskeletal functions, membrane trafficking, and receptor signaling by recruiting protein complexes to cell- and endosomal-membranes. Humans have multiple PtdIns proteins that differ by the degree and position of phosphorylation of the inositol ring. This gene encodes an enzyme (PIKfyve; also known as phosphatidylinositol-3-phosphate 5-kinase type III or PIPKIII) that phosphorylates the D-5 position in PtdIns and phosphatidylinositol-3-phosphate (PtdIns3P) to make PtdIns5P and PtdIns(3,5)biphosphate. The D-5 position also can be phosphorylated by type I PtdIns4P-5-kinases (PIP5Ks) that are encoded by distinct genes and preferentially phosphorylate D-4 phosphorylated PtdIns. In contrast, PIKfyve preferentially phosphorylates D-3 phosphorylated PtdIns. In addition to being a lipid kinase, PIKfyve also has protein kinase activity. PIKfyve regulates endomembrane homeostasis and plays a role in the biogenesis of endosome carrier vesicles from early endosomes. Mutations in this gene cause corneal fleck dystrophy (CFD); an autosomal dominant disorder characterized by numerous small white flecks present in all layers of the corneal stroma. Histologically, these flecks appear to be keratocytes distended with lipid and mucopolysaccharide filled intracytoplasmic vacuoles. Alternative splicing results in multiple transcript variants encoding distinct isoforms.[provided by RefSeq, May 2010]
Function:
The PI(3,5)P2 regulatory complex regulates both the synthesis and turnover of phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2). Catalyzes the phosphorylation of phosphatidylinositol 3-phosphate on the fifth hydroxyl of the myo-inositol ring, to form phosphatidylinositol 3,5-bisphosphate. Required for endocytic-vacuolar pathway and nuclear migration. Plays a role in the biogenesis of endosome carrier vesicles (ECV)/ multivesicular bodies (MVB) transport intermediates from early endosomes.
Subcellular Location:
Endosome membrane
Post-translational modifications:
Phosphorylated in response to insulin at Ser-318 in a protein kinase B (PKB)-dependent manner.
DISEASE:
Corneal dystrophy, fleck (CFD) [MIM:121850]: A form of stromal corneal dystrophy characterized by numerous small white flecks scattered in all levels of the stroma, with configurations varying from semicircular to wreath-like, curvilinear, or punctate. Although CFD may occasionally cause mild photophobia, patients are typically asymptomatic and have normal vision.
Similarity:
Contains 1 DEP domain.
Contains 1 FYVE-type zinc finger.
Contains 1 PIPK domain.
SWISS:
Q9Y2I7
Gene ID:
200576
Database links:
Entrez Gene: 200576 Human
Omim: 609414 Human
SwissProt: Q9Y2I7 Human
Unigene: 173939 Human
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