Members of the Gq alpha subunit gene family activate phospholipase C beta isozymes.

C.H Lee,D Park,D Wu,S.G Rhee,M.I Simon

doi:10.1016/s0021-9258(18)41962-x

Abstract

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.

Highlights

Chang Ho Lee$, Dongeun Park§, Dianqing Wu$, Sue Goo Rheeg, and Melvin I
The preparations phospholipase C (PI-PLC) enzymes are subdivided on the basis of cDNA cloning and deduced amino acid sequence similarity into at least threewell defined groups: PI-PLC 0,y, and 6 [10]
The relative specificities omf embersof the Ga, family of GTP-binding proteins were tested for their ability taoctivatdeifferent phosphoinositide-specific proteins has led to reconstitution experiments which show that they activate PI-PLC p [11, 12] and not the PI-PLC y or 6 enzymes

Summary

Introduction

Chang Ho Lee$, Dongeun Park§, Dianqing Wu$, Sue Goo Rheeg, and Melvin I. In order to test the relative specificity of interaction between Ga, and PI-PLC isoforms we used a system in which members of the G, sub-family can be overproduced after transient transfection.

Results

Conclusion