Recombinant Gq alpha. Mutational activation and coupling to receptors and phospholipase C

J Biol Chem. 1992 Jan 5;267(1):31-4.


Gq mediates hormonal stimulation of phosphoinositide-specific phospholipase C (PI-PLC). We mutated the alpha subunit of Gq (alpha q) to replace arginine 183 with cysteine. Mutations that substitute cysteine for the corresponding arginine residues of alpha s and alpha i2 constitutively activate their respective effector pathways, creating the gsp and gip2 oncogenes. Transient expression of alpha q-R183C in COS-7 and HEK-293 cells constitutively activates PI-PLC, but wild type (WT) alpha q does not. This suggests that the mutated arginines in alpha s, alpha i2, and alpha q share a common function in regulating the active state of these proteins and that the alpha q gene may serve as a target for oncogenic mutations in human tumors. In an attempt to develop an assay for receptor stimulation of recombinant alpha q, we co-expressed receptors with alpha q-WT. We found that the alpha 2-adrenoceptor stimulates PI-PLC activation in HEK-293 cells in a fashion that depends completely on co-expression of alpha q-WT. These findings create an experimental model, similar to that provided for alpha s by S49 cyc- cells, that should make it possible to analyze receptor and effector coupling by mutant alpha q against a null background.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Adenylyl Cyclase Inhibitors
  • Amino Acid Sequence
  • Base Sequence
  • Cell Line
  • Cyclic AMP / metabolism
  • DNA / genetics
  • Enzyme Activation
  • GTP-Binding Proteins / genetics
  • GTP-Binding Proteins / metabolism*
  • Gene Expression
  • Humans
  • Inositol Phosphates / biosynthesis
  • Molecular Sequence Data
  • Mutation*
  • Oncogenes
  • Phosphatidylinositol Diacylglycerol-Lyase
  • Phosphoinositide Phospholipase C
  • Phosphoric Diester Hydrolases / metabolism*
  • Plasmids
  • Receptors, Adrenergic, alpha / genetics
  • Receptors, Adrenergic, alpha / metabolism*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Transfection


  • Adenylyl Cyclase Inhibitors
  • Inositol Phosphates
  • Receptors, Adrenergic, alpha
  • Recombinant Proteins
  • DNA
  • Cyclic AMP
  • Phosphoric Diester Hydrolases
  • Phosphoinositide Phospholipase C
  • GTP-Binding Proteins
  • Phosphatidylinositol Diacylglycerol-Lyase