title: Quisqualate-stimulated phosphatidylinositol breakdown in rat cerebellar membranes.
abstract: The effect of quisqualate, an excitatory amino acid agonist, on the breakdown of exogenously added phosphatidylinositol was investigated in a membrane preparation from the cerebellum of young rats. Quisqualate stimulated phospholipase C activity in a dose-dependent manner in the presence of guanosine 5'-O-(3-thiotriphosphate) (GTP gamma S). Half-maximal activation of the quisqualate response required 0.15 microM GTP gamma S and was optimal at a free Ca2+ concentration of 300 nM. Phosphoinositide breakdown was also stimulated by quisqualate using either exogenous phosphatidylinositides 4,5-bisphosphate or endogenous labeled phosphoinositides as the substrate for phospholipase C in cerebellar membranes. In the presence of guanine nucleotides, other excitatory amino acid agonists, such as L-glutamate, trans-D,L-1-aminocyclopentyl-1,3-dicarboxylic acid, and ibotenate, but not N-methyl-D-aspartate, stimulated phosphatidylinositol breakdown. However, quisqualate displayed the highest response among these excitatory amino acid agonists. These data indicate that there is a direct activation of phosphoinositide-specific phospholipase C by excitatory amino acids through a process dependent on the presence of guanine nucleotides.
authors.affiliation: Department of Biochemistry, University of Tennessee, Memphis 38163.
authors.forename: S
authors.initials: S
authors.lastname: Llahi
authors.forename: E
authors.initials: E
authors.lastname: Claro
authors.forename: J N
authors.initials: JN
authors.lastname: Fain
mesh_terms: D000596:Amino Acids / Q000502:physiology; D000818:Animals; D002531:Cerebellum / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006868:Hydrolysis; D008274:Magnesium / Q000494:pharmacology; D008566:Membranes / Q000378:metabolism; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism* / Q000494:pharmacology; D016318:Quisqualic Acid / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D010738:Type C Phospholipases / Q000378:metabolism
chemical_list: D000596:Amino Acids; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D016318:Quisqualic Acid; D010738:Type C Phospholipases; D008274:Magnesium