Mutant alpha subunit of Gz transforms Swiss 3T3 cells.
Many hormones and neurotransmitters induce cell proliferation by regulating signaling pathways controlled by heterotrimeric G proteins. Mutations that activate the alpha subunits of Gs and Gi2 produce the gsp and gip2 oncogenes that are found in certain human endocrine tumors. Similar mutations have conferred on other G alpha subunits the ability to promote neoplastic transformation in cultured mammalian cells. Gz, a G protein whose normal signaling function is poorly understood, shares with Gi2 the ability to inhibit adenylyl cyclase. We asked whether mutationally activated alpha z can stimulate cell proliferation in a cell line in which stimulation adenylyl cyclase is mitogenic, Swiss 3T3 cells. Stable expression of alpha z-Q205L in Swiss 3T3 cells induced focus formation, a faster growth rate with a higher saturation density, anchorage-independent growth in soft agar, and increased [3H]thymidine incorporation in the absence of growth factors. alpha z-Q205L produced a similar but less extensively transformed phenotype in NIH3T3 cells--increased saturation density in culture, a smaller number of foci and few colonies in soft agar. Stimulation of thymidine incorporation by alpha z-Q205L in Swiss 3T3 cells was increased by co-treatment with cholera toxin, a stimulator of adenylyl cyclase. Taken together, our results indicate that alpha z stimulates one or more mitogenic pathways in Swiss 3T3 cells, and that effectiveness of these mitogenic pathways does not require reducing the concentration of cellular cAMP.
Wong
Y H
YH
Department of Biology, Hong Kong University of Science and Technology, Kowloon.
Chan
J S
JS
Yung
L Y
LY
Bourne
H R
HR
D016475:3T3 Cells / Q000378:metabolism / Q000473:pathology*; D000818:Animals; D002448:Cell Adhesion; D002455:Cell Division; D002471:Cell Transformation, Neoplastic / Q000473:pathology*; D000242:Cyclic AMP / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis; D019204:GTP-Binding Proteins / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D009154:Mutation; D014410:Tumor Stem Cell Assay
D004247:DNA; D000242:Cyclic AMP; D019204:GTP-Binding Proteins