Inositol Polyphosphate-5-Phosphatase K (INPP5K)

INPP5K encodes a protein with 5-phosphatase activity toward polyphosphate inositol. The protein localizes to the cytosol in regions lacking actin stress fibers. It is thought that this protein may negatively regulate the actin cytoskeleton. Alternatively spliced transcript variants encoding different isoforms have been identified.recombinant SKIP expressed in insect cells showed 5-phosphatase activity toward inositol 1,4,5-trisphosphate (Ins(1,4,5)P3), Ins(1,3,4,5)P4, phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5,)P2), and PtdIns(3,4,5)P3. SKIP had 6-fold higher substrate specificity for PtdIns(4,5)P2 than for Ins(1,4,5)P3. Immunolocalization of endogenous Skip in rat neuroblastoma cells showed expression in the cytosol and loss of actin stress fibers where Skip was concentrated.