Foetal-calf serum stimulates a pertussis-toxin-sensitive high-affinity GTPase activity in rat glioma C6 BU1 cells.
Cellular proliferation of rat glioma C6 BU1 cells in tissue culture is dependent on the presence of either calf or foetal-calf serum in the medium. Foetal-calf serum stimulated a high-affinity GTPase in membranes derived from C6 BU1 cells. Pretreatment of the cells with pertussis toxin decreased the high-affinity GTPase activity substantially, and attenuated the foetal-calf-serum-stimulated increase in this GTPase activity. Cholera toxin, in contrast, did not modulate the response to foetal-calf serum. Foetal-calf serum did not inhibit adenylate cyclase activity in membranes of these cells, indicating that the G-protein that was stimulated by foetal-calf serum was not Gi (the inhibitory one). Although the nature of the specific component of foetal-calf serum responsible for this pertussis-toxin-sensitive receptor-mediated stimulation of high-affinity GTPase activity has not been identified, it was mimicked neither by bombesin, which can stimulate inositol phospholipid turnover via a guanine nucleotide binding protein, nor by platelet-derived growth factor, which is present in substantial concentrations in foetal-calf serum. This report represents the first demonstration of a pertussis-toxin-substrate-mediated response in this cell line and provides further evidence that G-proteins other than Gi can be functionally inactivated by pertussis toxin.
Milligan
G
G
Department of Biochemistry, University of Glasgow, U.K.
D000244:Adenosine Diphosphate / Q000378:metabolism; D037361:Adenylate Cyclase Toxin; D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D002417:Cattle; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology; D002772:Cholera Toxin / Q000494:pharmacology; D004790:Enzyme Induction / Q000187:drug effects; D005312:Fetal Blood / Q000378:metabolism*; D020558:GTP Phosphohydrolases / Q000096:biosynthesis*; D006160:Guanosine Triphosphate / Q000378:metabolism; D037342:Pertussis Toxin; D010744:Phosphoric Monoester Hydrolases / Q000096:biosynthesis*; D010566:Virulence Factors, Bordetella / Q000494:pharmacology*
D037361:Adenylate Cyclase Toxin; D010566:Virulence Factors, Bordetella; D000244:Adenosine Diphosphate; D006160:Guanosine Triphosphate; D002772:Cholera Toxin; D037342:Pertussis Toxin; D010744:Phosphoric Monoester Hydrolases; D020558:GTP Phosphohydrolases; D000262:Adenylyl Cyclases