Pertussis toxin alters the growth characteristics of Swiss 3T3 cells

Pertussis toxin (islet-activating protein) treatment of intact Swiss 3T3 cells causes a time- and dose-dependent loss of availability of a 40 kDa membrane protein for toxin-catalyzed ADP-ribosylation in subsequent incubations with [32P]NAD. In parallel, [3H]thymidine uptake by quiescent cells stimulated with fresh serum, cell doubling time and cell saturation density are all decreased 30-50%. These results cannot be accounted for by the potential effect of the toxin on cell cAMP levels. They suggest that a pertussis toxin substrate, probably Gi, modulates some component of growth regulation in Swiss 3T3 cells.