Authors

M Carrington¹; P MacGregor¹; H Lane-Serff²; O J Macleod¹; M Higgins²;  ¹ University of Cambridge, Department of Biochemistry, UK;  ² University of Oxford, Department of Biochemistry, UK

Discussion

African trypanosomes are always extracellular and have evolved intricate surface coats that allow them to obtain nutrients while also protecting them from the immune defenses of either insects or mammals. The acquisition of macromolecular nutrients requires receptors that function within the context of these surface coats. The best understood of these is the haptoglobin-haemoglobin receptor (HpHbR) of Trypanosoma brucei, which is used by the mammalian bloodstream form of the parasite, allowing haem acquisition. However, in some primates it also provides an uptake route for trypanolytic factor-1, a mediator of innate immunity against trypanosome infection. Recent studies have shown that during the evolution of African trypanosome species the receptor has diversified in function from a haemoglobin receptor predominantly expressed in the tsetse fly to a haptoglobin-haemoglobin receptor predominantly expressed in the mammalian bloodstream. Structural and functional studies of homologous receptors from different trypanosome species have allowed us to propose an evolutionary history for how one receptor has adapted to different roles in different trypanosome species.