G alpha 12 and G alpha 13 stimulate Rho-dependent stress fiber formation and focal adhesion assembly.
Rho, a member of the Ras superfamily of GTP-binding proteins, regulates actin polymerization resulting in the formation of stress fibers and the assembly of focal adhesions. In Swiss 3T3 cells, heterotrimeric G protein-coupled receptors for lysophosphatidic acid and gastrin releasing peptide stimulate Rho-dependent stress fiber and focal adhesion formation. The specific heterotrimeric G protein subunits mediating Rho-dependent stress fiber and focal adhesion formation have not been defined previously. We have expressed GTPase-deficient, constitutively activated G protein alpha subunits and mixtures of beta and gamma subunits in Swiss 3T3 cells. Measurement of actin polymerization and focal adhesion formation indicated that GTPase-deficient alpha 12 and alpha 13, but not the activated forms of alpha 12 or alpha q stimulated stress fiber and focal adhesion assembly. Combinations of beta and gamma subunits were unable to stimulate stress fiber or focal adhesion formation. G alpha 12- and alpha 13-mediated stress fiber and focal adhesion assembly was inhibited by botulinum C3 exoenzyme, which ADP-ribosylates and inactivates Rho, indicating that alpha 12 and alpha 13, but not other G protein alpha subunits or beta gamma complexes, regulate Rho-dependent responses. The results define the integration of G12 and G13 with the regulation of the actin cytoskeleton.
Buhl
A M
AM
Department of Chemistry, Aarhus University, Denmark.
Johnson
N L
NL
Dhanasekaran
N
N
Johnson
G L
GL
D016475:3T3 Cells; D036002:ADP Ribose Transferases / Q000494:pharmacology; D000199:Actins / Q000378:metabolism*; D000818:Animals; D001905:Botulinum Toxins; D002448:Cell Adhesion; D003599:Cytoskeleton / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000502:physiology*; D051379:Mice; D020742:rhoA GTP-Binding Protein
D000199:Actins; D036002:ADP Ribose Transferases; C063007:exoenzyme C3, Clostridium botulinum; D001905:Botulinum Toxins; D019204:GTP-Binding Proteins; D020742:rhoA GTP-Binding Protein