The Trypanosoma Brucei KIFC1 Kinesin Ensures the Fast Antibody Clearance Required for Parasite Infectivity

Summary Human innate immunity to Trypanosoma brucei involves the trypanosome C-terminal kinesin TbKIFC1, which transports internalized trypanolytic factor apolipoprotein L1 (APOL1) within the parasite. We show that TbKIFC1 preferentially associates with cholesterol-containing membranes and is indispensable for mammalian infectivity. Knockdown of TbKIFC1 did not affect trypanosome growth in vitro but rendered the parasites unable to infect mice unless antibody synthesis was compromised. Surface clearance of Variant Surface Glycoprotein (VSG)-antibody complexes was far slower in these cells, which were more susceptible to capture by macrophages. This phenotype was not due to defects in VSG expression or trafficking but to decreased VSG mobility in a less fluid, stiffer surface membrane. This change can be attributed to increased cholesterol level in the surface membrane in TbKIFC1 knockdown cells. Clearance of surface-bound antibodies by T. brucei is therefore essential for infectivity and depends on high membrane fluidity maintained by the cholesterol-trafficking activity of TbKIFC1.
Graphical Abstract
Highlights • The TbKIFC1 kinesin preferentially transports cholesterol-containing membranes • TbKIFC1 is absolutely required for parasite growth in mice • Cholesterol trafficking by TbKIFC1 confers high fluidity to the plasma membrane • High membrane fluidity allows antibody clearance necessary for parasite infectivity
Immunology; Microbiology Parasite; Cell Biology