title: Activation of type I phosphatidylinositol 4-phosphate 5-kinase isoforms by the Rho GTPases, RhoA, Rac1, and Cdc42.
abstract: Type I phosphatidylinositol 4-phosphate 5-kinase (PIP5K) catalyzes the formation of the phospholipid, phosphatidylinositol 4,5-bisphosphate (PIP(2)), which is implicated in many cellular processes. The Rho GTPases, RhoA and Rac1, have been shown previously to activate PIP5K and to bind PIP5K. Three type I PIP5K isoforms (Ialpha,Ibeta, and Igamma) have been identified; however, it is unclear whether these isoforms are differentially or even sequentially regulated by Rho GTPases. Here we show that RhoA and Rac1, as well as Cdc42, but not the Ras-like GTPases, RalA and Rap1A, markedly stimulate PIP(2) synthesis by all three PIP5K isoforms expressed in human embryonic kidney 293 cells, both in vitro and in vivo. RhoA-stimulated PIP(2) synthesis by the PIP5K isoforms was mediated by the RhoA effector, Rho-kinase. Stimulation of PIP5K isoforms by Rac1 and Cdc42 was apparently independent of and additive with RhoA- and Rho-kinase, as shown by studies with C3 transferase and Rho-kinase mutants. RhoA, and to a lesser extent Rac1, but not Cdc42, interacted in a nucleotide-independent form with all three PIP5K isoforms. Binding of PIP5K isoforms to GTP-bound, but not GDP-bound, RhoA could be displaced by Rho-kinase, suggesting a direct and constitutive PIP5K-Rho GTPase binding, which, however, does not trigger PIP5K activation. In summary, our findings indicate that synthesis of PIP(2) by the three PIP5K isoforms is controlled by RhoA, acting via Rho-kinase, as well as Rac1 and Cdc42, implicating that regulation of PIP(2) synthesis has a central position in signaling by these three Rho GTPases.
authors.affiliation: Institut für Pharmakologie, Universitätsklinikum Essen, Essen 45122, Germany. paschal.oudeweernink@uni-essen.de
authors.forename: Paschal A Oude
authors.initials: PA
authors.lastname: Weernink
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Meletiadis
authors.forename: Silvia
authors.initials: S
authors.lastname: Hommeltenberg
authors.forename: Matthias
authors.initials: M
authors.lastname: Hinz
authors.forename: Hisamitsu
authors.initials: H
authors.lastname: Ishihara
authors.forename: Martina
authors.initials: M
authors.lastname: Schmidt
authors.forename: Karl H
authors.initials: KH
authors.lastname: Jakobs
mesh_terms: D000818:Animals; D002460:Cell Line; D004622:Embryo, Mammalian; D004789:Enzyme Activation / Q000187:drug effects; D015870:Gene Expression; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000378:metabolism; D006153:Guanosine Diphosphate / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes / Q000378:metabolism*; D007668:Kidney; D051379:Mice; D016296:Mutagenesis; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000096:biosynthesis; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D020830:rac1 GTP-Binding Protein / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D007527:Isoenzymes; D019269:Phosphatidylinositol 4,5-Diphosphate; D011993:Recombinant Fusion Proteins; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D017853:Phosphotransferases (Alcohol Group Acceptor); C020077:1-phosphatidylinositol-4-phosphate 5-kinase; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein