Mammalian epidermal growth factor stimulates G-protein activity in Trypanosoma brucei

The life cycle of Trypanosoma brucei is tightly controlled within its mammalian and insect hosts. The involvement of host signals in this process is becoming more apparent, but little is yet known of the mechanisms of transduction of these signals in the trypanosome. The present study shows that three previously described trypanosome growth promoters, foetal calf serum, bombesin and epidermal growth factor (EGF), elicit high-affinity guanosine triphosphate (GTP) hydrolysis activity in trypanosome membranes, indicating that G-proteins are involved in the transduction of these signals. In particular, GTP hydrolysis was found to increase significantly with increasing concentrations of EGF over the range 0-20 nM, the normal physiological range of EGF concentration in mammalian tissues, further supporting the view that trypanosomes may be specifically using EGF as a signal.