Regulation of Rac and Cdc42 pathways by G(i) during lysophosphatidic acid-induced cell spreading.
The pertussis toxin-sensitive G protein, G(i), has been implicated in lysophosphatidic acid-induced cell mitogenesis and migration, but the mechanisms remain to be detailed. In the present study, we found that pertussis toxin blocks lysophosphatidic acid-induced cell spreading of NIH 3T3 fibroblasts on fibronectin. This prevention of cell spreading was eliminated by the expression of constitutively active mutants of Rho family small GTP-binding proteins, Rac and Cdc42, but not by Rho. In addition, activation of the endogenous forms was suppressed by pertussis toxin, indicating that G(i)-induced cell spreading is mediated through the Rac and Cdc42 pathway. Transfection of constitutively active mutants of G alpha(i) and G alpha(11) and G beta gamma subunits enhanced spreading of pertussis toxin-treated cells. G beta(1) with G gamma(12), a major G gamma form in fibroblasts, was more effective for increasing cell spreading than G beta(1)gamma(2) or G beta(1) plus G gamma(12)S2A, a mutant in which Ser-2, a phosphorylation site for protein kinase C, is replaced with alanine. In addition, a protein kinase C inhibitor diminished G beta(1)gamma(12)-induced cell spreading, suggesting a role for phosphorylation of the protein. These findings indicate that both G alpha(i) and G beta gamma stimulate Rac and Cdc42 pathways with lysophosphatidic acid-induced cell spreading on fibronectin.
Ueda
H
H
Department of Biochemistry, Institute for Developmental Research, Aichi Human Service Center, Kasugai, Aichi 480-0392, Japan.
Morishita
R
R
Yamauchi
J
J
Itoh
H
H
Kato
K
K
Asano
T
T
D016475:3T3 Cells; D000818:Animals; D005347:Fibroblasts / Q000187:drug effects / Q000502:physiology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000502:physiology*; D006160:Guanosine Triphosphate / Q000378:metabolism; D008246:Lysophospholipids / Q000494:pharmacology*; D051379:Mice; D037342:Pertussis Toxin; D010766:Phosphorylation; D021122:Protein Subunits; D010566:Virulence Factors, Bordetella / Q000494:pharmacology; D020764:cdc42 GTP-Binding Protein / Q000502:physiology*; D020744:rac GTP-Binding Proteins / Q000502:physiology*
D008246:Lysophospholipids; D021122:Protein Subunits; D010566:Virulence Factors, Bordetella; D006160:Guanosine Triphosphate; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins