G protein-mediated inhibition of phospholipase C activity in a solubilized membrane preparation.
In solubilized bovine brain membrane preparations AlF4- (20 microM AlCl3 plus 10 mM NaF) and 50 nM guanosine 5-O-(2-thiotriphosphate) (GTP gamma S) promoted a rapid but transient inhibition of phospholipase C (PLC) activity. Maximal inhibition was evident within 7 min of incubation, followed by reversal of inhibition. In contrast, 10 microM GTP gamma S did not induce inhibition of PLC activity but rather produced a time-dependent stimulation of PLC activity. GTP gamma S-dependent inhibition of PLC activity was concentration-dependent with half-maximal inhibition at 1 nM. Inhibition was antagonized by guanosine 5-O-(2-thiodiphosphate (GDP beta S). Pertussis toxin delayed the onset of inhibition by GTP gamma S but did not prevent the inhibitory effect. alpha o-GTP gamma S or alpha o-GDP had little effect on PLC activity. alpha i-GTP gamma S and alpha i-GDP produced a 15% inhibition of PLC activity. Beta gamma subunits did not inhibit basal PLC activity but did attenuate the net degree of inhibition due to GTP gamma S. Inhibition was associated with a decrease in the Ca2+ sensitivity of PLC. Preincubation of membranes with anti-PLC-beta 1 antibody, but not anti-PLC-gamma 1 or anti-PLC-delta 1, prevented the GTP gamma S-mediated inhibition of PLC. These studies implicate PLC-beta 1 as an effector system that is under negative modulation by a G protein-dependent mechanism.
Litosch
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I
Department of Molecular and Cellular Pharmacology, University of Miami School of Medicine, Florida 33101.
Sulkholutskaya
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I
Weng
C
C
D000818:Animals; D001921:Brain / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D002417:Cattle; D002462:Cell Membrane / Q000201:enzymology*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D006153:Guanosine Diphosphate / Q000378:metabolism; D007700:Kinetics; D037342:Pertussis Toxin; D012996:Solutions; D010738:Type C Phospholipases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D012996:Solutions; D010566:Virulence Factors, Bordetella; D006153:Guanosine Diphosphate; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D037342:Pertussis Toxin; D010738:Type C Phospholipases; D019204:GTP-Binding Proteins; D002118:Calcium