The Q205LGo-alpha subunit expressed in NIH-3T3 cells induces transformation.


Journal Article

The growth functions of the heterotrimeric G protein G(o) was studied by expression in heterologous systems. The alpha-subunit of G(o) was mutated to convert Gln-205 to Leu (Q205L). Mutation of this conserved glutamine residue in G protein alpha-subunits is thought to persistently activate G proteins by inhibiting their GTPase activity. The wild type and mutant G(o)-alpha subunits were expressed in NIH-3T3 fibroblasts. These cells do not contain any measurable amounts of G(o)-alpha mRNA or protein. Transfection of wild type or Q205LG(o)-alpha subunit cDNA under the control of a dexamethasone-inducible promoter results in dexamethasone-dependent transcription of the mRNA and expression of the protein. The Q205LG(o)-alpha, but not wild type G(o)-alpha, stimulates mitogenesis in NIH-3T3 fibroblasts without significantly stimulating phospholipase C activity. Continuous expression of mutant G(o)-alpha induces focus formation, whereas transfections with vector alone or vector containing the native G(o)-alpha cDNA were without significant transforming effect in NIH-3T3 cells. Q205L G(o)-alpha did not induce focus formation in RAT-1 fibroblasts. Q205LG(o)-alpha-transformed NIH-3T3 cells are capable of anchorage-independent growth, as assessed by colony formation in soft agar. Q205LG(o)-alpha transformed cells induced tumors when injected into Nu/Nu mice. These results indicate that mutant G(o)-alpha subunits whose GTPase activity is presumably inhibited can induce the neoplastic transformation of NIH-3T3 cells in a phospholipase C-independent manner.

Full Text

Cited Authors

  • Kroll, SD; Chen, J; De Vivo, M; Carty, DJ; Buku, A; Premont, RT; Iyengar, R

Published Date

  • November 1992

Published In

Volume / Issue

  • 267 / 32

Start / End Page

  • 23183 - 23188

PubMed ID

  • 1429665

Pubmed Central ID

  • 1429665

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

International Standard Serial Number (ISSN)

  • 0021-9258


  • eng