substrate specificity in descending order: 1-phosphatidyl-1D-myo-inositol 3-phosphate, 1-phosphatidyl-1D-myo-inositol 4-phosphate, and 1-phosphatidyl-1D-myo-inositol, the enzyme also shows lipid kinase activity
the vacuolation phenotype in cultured Vps34 (EC 2.7.1.137)-deficient podocytes is caused by the absence of a substrate for the Vps34 downstream effector PtdIns 3-phosphate 5-kinase, which phosphorylates Vps34-generated 1-phosphatidyl-1D-myo-inositol 3-phosphate to produce + 1-phosphatidyl-1D-myo-inositol 3,5-bisphosphate. PtdIns 3-phosphate 5-kinase perturbation and 1-phosphatidyl-1D-myo-inositol 3,5-bisphosphate reduction result in massive membrane vacuolation along the endosomal system. Genetic deletion of the enzyme in endocytically active proximal tubular cells results in the development of large cytoplasmic vacuoles caused by arrested endocytic traffic progression at a late-endosome stage, while deletion of the enzyme in glomerular podocytes does not significantly alter the endosomal morphology, even in age 18-month-old mice
in Xenopus oocytes expressing mammalian excitatory amino acid transporter EAAT4, glutamate induces a current which is significantly enhanced by coexpression of isoform PIKfyve and glucocorticoid inducible kinase SGK1. This glutamate-induced current is significantly larger than the current in Xenopus oocytes expressing EAAT4 together with either kinase alone. Coexpression of the inactive SGK1 mutant K127N does not significantly alter glutamate-induced current in EAAT4-expressing Xenopus oocytes and abolishes the stimulation of glutamate-induced current by coexpression of isoform PIKfyve. The stimulating effect of PIKfyve is abrogated by mutation S318A in the SGK consensus sequence of PIKfyve. Coexpression of PIKfyve S318A mutant significantly blunts the stimulating effect of SGK1 on EAAT4 activity
PIKFYVE knockdown produces a 36% reduction in phosphatidylinositol 3,5-bisphosphate and a 13% increase in phosphatidylinositol 3-phosphate. PIKFYVE and class II phosphatidylinositol 3-kinase PI3K-C2alpha are necessary for activation of the kinase complex mechanistic target of rapamycin mTORC1 and its translocation to the plasma membrane in 3T3-L1 adipocytes. The mTORC1 component Raptor directly interacts with phosphatidylinositol 3,5-bisphosphate
the PIPkin type III family enzyme consists of 4 typical domains: the FYVE RING Zn-finger domain, the TCP-I/chaperone-like domain, the PIPkin domain, and the cysteine-rich domain, the mouse enzyme contains additionally a DEP domain
in Xenopus oocytes expressing mammalian excitatory amino acid transporter EAAT4, glutamate induces a current which is significantly enhanced by coexpression of isoform PIKfyve and glucocorticoid inducible kinase SGK1. The stimulating effect of PIKfyve is abrogated by mutation S318A in the SGK consensus sequence of PIKfyve. Coexpression of PIKfyve S318A mutant significantly blunts the stimulating effect of SGK1 on EAAT4 activity
Venkatareddy, M.; Verma, R.; Kalinowski, A.; Patel, S.R.; Shisheva, A.; Garg, P.
Distinct requirements for vacuolar protein sorting 34 downstream effector phosphatidylinositol 3-phosphate 5-kinase in podocytes versus proximal tubular cells