Phosphoinositides, kinases and adaptors coordinating endocytosis in Trypanosoma brucei

In the kinetoplastid parasite Trypanosoma brucei clathrin-mediated endocytosis is essential for survival and aids immune evasion in the mammalian host. The formation of endocytic clathrin coated vesicles in T. brucei is via a unique mechanism owing to an evolutionarily recent loss of the adaptor protein (AP)2 complex, a central hub in endocytic vesicle assembly. Despite this loss, recent studies examining endocytic clathrin coat assembly have highlighted a high degree of conservation between trypanosomes and their mammalian hosts. In particular phosphatidylinositol 4,5-bisphosphate (PI(4,5)P(2)) and its putative effectors, TbCALM and TbEpsinR, are central to clathrin-mediated endocytosis in the trypanosome, just as they are in animal cells. In addition to providing insights into the cell biology of T. brucei, these studies also suggest an ancient, possibly pan-eukaryotic connection between PtdIns(4,5)P(2) and endocytosis.