| Two Potential pathways for the entry of toxins into eukaryotic cells have been proposed by other investigators: namely receptor-mediated endocytosis (RME) or direct plasma membrane penetration. Very little is known about the mode of entry of pertussis toxin (PT), an A-B toxin produced by Bordetella pertussis, although it has been suggested that it may enter via direct membrane penetration (Burns et al. 1990; Hausman and Burns, 1992).;The purpose of the present study has been to investigate the surface binding and subsequent fate of pertussis toxin in Chinese hamster ovary (CHO) cells, using ultrastructural imnunocytochemical techniques.;Time course studies of the internalization of PT were conducted using (1) a complex of PT bound by colloidal gold labelled PT specific antibodies, (2) PT without antibody label, and (3) a genetically detoxified PT. Results obtained by these studies indicate that contrary to results obtained by others, internalization of PT by CHO cells occurs via receptor-mediated endocytosis. |
