Lysosomal and endocytic protein trafficking routes and machinery in Trypanosoma brucei.

摘要

Trypanosoma brucei ssp. are the causative agents of African sleeping sickness. Currently available drug treatments for this lethal disease are highly unsatisfactory due to expense and side effects. Although the number of cases is currently low, sub-Saharan Africa is still in grave threat of future sleeping sickness epidemics and therefore novel drug development is urgently needed. A good area to target for drug development is the post-Golgi secretory pathway because of the crucial role it plays in host-parasite interaction. For example, host serum proteins are taken up by the parasite for nutrition and endocytosis may be critical for protection against host immune complexes bound to the cell surface. Although much is known about T. brucei post-Golgi protein trafficking, much is also unknown. The routes proteins take to reach the cell surface and the degradative lysosome are only partially defined. There are many homologues of mammalian trafficking machinery present with unclear or unstudied function. Therefore, a major goal of this dissertation was to further define the biosynthetic, endocytic, and default post-Golgi protein trafficking pathways in T. brucei..;Here, the functions of the adapter protein complex-1 (AP-1), late endosomal small GTPase TbRab7, and endosomal sorting complexes required for transport (ESCRT) machinery in T. brucei were investigated. The effect on biosynthetic, endocytic, and default protein trafficking after silencing the above machinery was analyzed mostly in the mammalian bloodstream form. Similarities but also significant differences in function between the T. brucei machinery and homologues in other eukaryotes were revealed. In addition, biosynthetic and endocytic trafficking routes were further defined, particularly the role of the late endosome in these routes. Also elucidated was an ESCRT-driven trafficking pathway containing machinery that is closely associated with the late endosome. Finally, a default trafficking pathway was further validated and defined.