Identification of an epidermal growth factor receptor homologue in trypanosomes

Considerable advances have been made in our understanding of cell growth regulation in mammalian cells. In particular, studies on transformed and normal cells have highlighted the contribution of growth factor-related control mechanisms in cell growth regulation. We set out to investigate whether host growth factors are involved in the growth regulation of the parasitic protozoan Trypanosoma brucei. We demonstrate that antibodies to the mammalian epidermal growth factor (EGF) receptor bind to the trypanosome T. brucei and, that these antibodies recognise a surface polypeptide of 135 kDa. This polypeptide is one of only two polypeptides in parasite extracts that bind EGF. Furthermore, EGF modifies protein kinase activity and growth rate of trypanosomes in vitro. These results lead to the conclusion that T. brucei has a surface growth factor receptor with considerable homology to the EGF receptor, and raise the possibility that growth factor interactions similar to those found in mammalian cells are involved in cell growth regulation in trypanosomes.