Effect of growth factor on GTPase-activating protein (Ras GAP) in Chinese hamster ovary cells.

GTPase-activating proteins (GAPs) stimulate the hydrolysis of GTP bound to small G-proteins and regulate the signal transduction pathway. Changes in the expression of p21-Ras pl20-GAP induced by growth factor treatment were examined in cultured Chinese hamster ovary (CHO) and human choriocarcinoma (BeWo) cells. Expression of pl20-GAP and GAP activity were measured. Fetal bovine serum induced a significant increased level of GAP in CHO cells, but did not increase GAP in BeWo cells. The results suggest that growth factors affect Ras GAP expression in CHO cells, while they do not in other cells such as BeWo cells.