FAZ27 cooperates with FLAM3 and ClpGM6 to maintain cell morphology in Trypanosoma brucei

Abstract

The human parasite Trypanosoma brucei transitions from the trypomastigote form to the epimastigote form in the insect vector by re-positioning its mitochondrial genome and flagellum-associated cytoskeleton. The molecular mechanisms underlying such morphology changes remain elusive, but recent works demonstrated the involvement of three flagellar proteins, FLAM3, ClpGM6, and KIN-E, in this process by controlling the elongation of the flagellum attachment zone (FAZ). In this report, we identified a FAZ flagellum domain-localizing protein named FAZ27 and characterized its role in cell morphogenesis. Depletion of FAZ27 in the trypomastigote form caused major morphology changes and re-positioning of the mitochondrial genome and flagellum-associated cytoskeleton, generating epimastigote-like cells. Further, proximity biotinylation and co-immunoprecipitation identified FLAM3 and ClpGM6 as FAZ27-interacting proteins, and analyses of the functional interplay revealed their interdependency for assembly. Finally, we showed that assembly of FAZ27 occurred proximally, identical to the assembly pattern of other FAZ sub-domain proteins. Together, these results demonstrate a crucial role of the FAZ flagellum domain in controlling cell morphogenesis and suggest a coordinated assembly of all the FAZ sub-domains at the proximal end of the FAZ.