Inhibition of mink lung epithelial cell proliferation by transforming growth factor-beta is coupled through a pertussis-toxin-sensitive substrate.
Transforming growth factor beta 1 (TGF beta 1) inhibits the proliferative response of mink lung epithelial cells (CCL64) to serum and to epidermal growth factor (EGF). This response to TGF beta 1 can be inhibited by prior exposure of the cells to nanogram concentrations of pertussis toxin (PT), suggesting the involvement of a guanine-nucleotide-binding regulatory protein (G-protein) in mediating TGF beta 1-induced growth inhibition. To characterize further this G-protein dependence, we have isolated, by chemical mutagenesis, a CCL64 variant (CCL64-D1) that is resistant to TGF beta 1. Whereas in the parental CCL64 cells TGF beta 1 stimulates both GTP[35S] (guanosine 5'-[gamma-[35S]thio]triphosphate) binding and GTPase activity, in the CCL64-D1 variants TGF beta 1 is without effect. Quantitative immunoblotting with antisera for G-protein alpha- and beta-subunits, as well as PT-catalysed ADP-ribosylation analyses, revealed no appreciable changes in the level of G-protein expression in the CCL64-D1 variants compared with parental cells. In contrast with another TGF beta-resistant clone, MLE-M, which we show lacks detectable type I receptor protein, the CCL64-D1 cells retain all three TGF beta cell-surface binding proteins. On the basis of these studies, we propose that a necessary component of TGF beta 1-mediated growth inhibition in CCL64 epithelial cells is the coupling of TGF beta 1 receptor binding to G-protein activation.
Howe
P H
PH
Department of Cell Biology, School of Medicine, Vanderbilt University, Nashville, TN 37232.
Cunningham
M R
MR
Leof
E B
EB
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003432:Cross-Linking Reagents; D004847:Epithelial Cells; D019204:GTP-Binding Proteins / Q000502:physiology*; D006131:Growth Inhibitors; D066298:In Vitro Techniques; D008907:Mink; D037342:Pertussis Toxin; D011956:Receptors, Cell Surface / Q000502:physiology*; D018125:Receptors, Transforming Growth Factor beta; D015398:Signal Transduction; D015291:Transforming Growth Factors / Q000494:pharmacology*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D003432:Cross-Linking Reagents; D006131:Growth Inhibitors; D011956:Receptors, Cell Surface; D018125:Receptors, Transforming Growth Factor beta; D010566:Virulence Factors, Bordetella; D015291:Transforming Growth Factors; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins