title: Phosphatidylinositol 4-phosphate 5-kinase type I is regulated through phosphorylation response by extracellular stimuli.
abstract: Phosphatidylinositol 4-phosphate 5-kinase (PIPK) catalyzes a final step in the synthesis of phosphatidylinositol 4,5-bisphosphate (PIP(2)), a lipid signaling molecule. Strict regulation of PIPK activity is thought to be essential in intact cells. Here we show that type I enzymes of PIPK (PIPKI) are phosphorylated by cyclic AMP-dependent protein kinase (PKA), and phosphorylation of PIPKI suppresses its activity. Serine 214 was found to be a major phosphorylation site of PIPK type Ialpha (PIPKIalpha) that is catalyzed by PKA. In contrast, lysophosphatidic acid-induced protein kinase C activation increased PIPKIalpha activity. Activation of PIPKIalpha was induced by dephosphorylation, which was catalyzed by an okadaic acid-sensitive phosphatase, protein phosphatase 1 (PP1). In vitro dephosphorylation of PIPKIalpha with PP1 increased PIPK activity, indicating that PP1 plays a role in lysophosphatidic acid-induced dephosphorylation of PIPKIalpha. These results strongly suggest that activity of PIPKIalpha in NIH 3T3 cells is regulated by the reversible balance between PKA-dependent phosphorylation and PP1-dependent dephosphorylation.
authors.affiliation: Department of Biochemistry, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo 108, Japan.
authors.forename: S J
authors.initials: SJ
authors.lastname: Park
authors.forename: T
authors.initials: T
authors.lastname: Itoh
authors.forename: T
authors.initials: T
authors.lastname: Takenawa
mesh_terms: D000818:Animals; D002460:Cell Line; D017868:Cyclic AMP-Dependent Protein Kinases / Q000502:physiology; D004789:Enzyme Activation; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D008954:Models, Biological; D010749:Phosphoprotein Phosphatases / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D010768:Phosphoserine / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D054645:Protein Phosphatase 1
chemical_list: D008246:Lysophospholipids; D010750:Phosphoproteins; D010768:Phosphoserine; D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D010749:Phosphoprotein Phosphatases; D054645:Protein Phosphatase 1