Molecular diversity and double regulatory mechanism of activation of phospholipase C in rat brain.
Whereas evidence for a G protein-dependent stimulation of phospholipase C (PLC) is abundant, reports on the inhibition of PLC through a G protein-mediated pathway have only recently begun to appear. In the present study, cerebral cortex membranes were chosen since they have a readily measurable Gpp[NH]p and Ca2+-stimulated PLC activity. Nanomolar concentrations of Gpp[NH]p, a hydrolysis-resistant GTP analogue, inhibited basal inositol 1,4,5-trisphosphate (IP3) production, with a maximum inhibition of 25% at 10 nM. Increasing the concentrations of Gpp[NH]p to over 10 nM resulted in a reversal of the inhibitory effect and onset of stimulation of IP3 production. GDPbetaS as a G protein inhibitor and U-73122 as a putative PLC-beta inhibitor had little effect on basal IP3 production at 100 microM and 1 microM, respectively. However, GDPbetaS and U-73122 completely antagonized both the inhibition and the stimulation of IP3 production produced by lower and higher concentrations, respectively, of Gpp[NH]p. Rat cortical membranes expressed a greater amount of PLC-beta1. These data suggest that PLC-beta1 isozymes may be regulated by both inhibitory and stimulatory G protein-mediated mechanisms.
Miyamoto
A
A
Department of Pharmacology, Sapporo Medical University School of Medicine, Japan.
Ohshika
H
H
D000818:Animals; D002540:Cerebral Cortex / Q000201:enzymology*; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000096:biosynthesis; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism*; D008297:Male; D010716:Phosphatidylinositols / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013379:Substrate Specificity; D014316:Tritium; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors / Q000378:metabolism*
D007527:Isoenzymes; D010716:Phosphatidylinositols; D014316:Tritium; D006165:Guanylyl Imidodiphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D015544:Inositol 1,4,5-Trisphosphate; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins