GTP-dependent hydrolysis of phosphatidylinositol-4,5-bisphosphate by soluble phospholipase C from adult human epidermis.
The regulation of soluble phosphoinositide-specific phospholipase C from adult human epidermis by guanine nucleotide was investigated. In the presence of physiologic concentrations of Ca++ (1 microM) and Mg++ (1.5 mM), neither phosphatidylinositol (PI) nor phosphatidylinositol-4,5-bisphosphate (PIP2) were appreciably hydrolyzed. Addition of guanosine-5'-triphosphate (GTP) or guanosine-5'-O-(3-thiotriphosphate) (GTP-gamma-S) significantly stimulated hydrolysis of PIP2, but not PI. Stimulation of PIP2 hydrolysis by GTP was dose-dependent between 1-100 microM GTP. Other nucleoside triphosphates and nucleotide analogues were unable to substitute for GTP or GTP-gamma-S. A GTP-gamma-S-stimulated PIP2 hydrolysis was inhibited by guanosine-5'-O-(2-thiodiphosphate (GDP-beta-S). The phospholipase C preparation specifically bound [35S]GTP-gamma-S and this binding was also inhibited by GDP-beta-S. In addition to a 41,000-dalton pertussis toxin substrate, the phospholipase C preparation contained 3-4 GTP binding proteins with molecular weights between 20,000-30,000. These data demonstrate that human epidermis contains a soluble GTP-dependent phospholipase C activity that specifically hydrolyzes PIP2 and suggest that this reaction is regulated by a GTP-binding protein(s).
Fisher
G J
GJ
Department of Dermatology, University of Michigan Medical School, Ann Arbor 48109.
Baldassare
J J
JJ
Voorhees
J J
JJ
D000328:Adult; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004817:Epidermis / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000032:analysis; D006160:Guanosine Triphosphate / Q000378:metabolism / Q000494:pharmacology*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism*; D010738:Type C Phospholipases / Q000378:metabolism*
D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D006160:Guanosine Triphosphate; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium