Members of the Gq alpha subunit gene family activate phospholipase C beta isozymes.
The relative specificities of members of the G alpha q family of GTP-binding proteins were tested for their ability to activate different phosphoinositide-specific phospholipase C (PI-PLC) beta isozymes. Cos-7 cells were transfected with cDNA corresponding to G alpha q, G alpha 11, G alpha 14, and G alpha 16. Most of the recombinant protein was bound to the cell membrane and these membranes were washed to elute endogenous PI-PLC activity. The membrane preparation was reconstituted with purified preparations of the PI-PLC beta isozymes and guanosine 5'-O-thiotriphosphate (GTP gamma S)-stimulated enzyme activity was measured. All four proteins of the G alpha q family were found to stimulate PI-PLC beta 1, with G alpha q and G alpha 11 being most efficient. On the other hand, G alpha 16 was found to most effectively activate PI-PLC beta 2, while G alpha q, G alpha 11, and G alpha 14 showed less stimulation. Specific anti- G alpha 16 antibody blocked the stimulation of both PI-PLC beta 1 and PI-PLC beta 2 in the enriched membrane fraction. We conclude that there is specificity in the interaction of different members of the Gq family with different PI-PLC beta effectors. This specificity may be important in generating tissue- or receptor-specific responses in vivo.
Lee
C H
CH
Division of Biology, California Institute of Technology, Pasadena 91125.
Park
D
D
Wu
D
D
Rhee
S G
SG
Simon
M I
MI
D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D004789:Enzyme Activation; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D016244:Guanosine 5'-O-(3-Thiotriphosphate) / Q000494:pharmacology; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D046911:Macromolecular Substances; D008969:Molecular Sequence Data; D005810:Multigene Family; D010455:Peptides / Q000276:immunology; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism*; D014162:Transfection
D000906:Antibodies; D007527:Isoenzymes; D046911:Macromolecular Substances; D010455:Peptides; D016244:Guanosine 5'-O-(3-Thiotriphosphate); D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D019204:GTP-Binding Proteins; D043265:Phosphatidylinositol Diacylglycerol-Lyase