Abstract
The evolutionarily early divergent human parasite Trypanosoma brucei proliferates through binary cell fission in both its tsetse fly vector and mammalian host. The parasite divides unidirectionally along the longitudinal cell axis from the anterior cell tip toward the posterior cell tip through a mechanism distinct from that in the cells of its human host. Initiation of cytokinesis in T. brucei is regulated by two evolutionarily conserved protein kinases, the Polo-like kinase TbPLK and the Aurora B kinase TbAUK1, and a cohort of trypanosome-specific proteins, including the three cytokinesis initiation factors CIF1, CIF2, and CIF3. Here, using RNAi, in situ epitope tagging of proteins, GST pulldown, and coimmunoprecipitation assays, and immunofluorescence and scanning electron microscopy analyses, we report the identification and functional characterization of two trypanosome-specific proteins, flagellum attachment zone tip-localizing protein required for cytokinesis (FPRC) and CIF4. We found that the two proteins colocalize to the distal tips of the new and the old flagellum attachment zones and are required for cytokinesis initiation. Knockdown of FPRC or CIF4 disrupted the localization of CIF1, suggesting that they function upstream of CIF1. Moreover, depletion of CIF4 abolished FPRC localization, indicating that CIF4 acts upstream of FPRC. Together, these results identify two new cytokinesis regulators in T. brucei and integrate them into the CIF1-mediated cytokinesis regulatory pathway. These findings highlight the existence of a cytokinesis pathway in T. brucei that is different from that of its mammalian host and therefore suggest that cytokinesis in T. brucei could potentially be exploited as a new drug target.
Highlights
The evolutionarily early divergent human parasite Trypanosoma brucei proliferates through binary cell fission in both its tsetse fly vector and mammalian host
2 The abbreviations used are: FAZ, flagellum attachment zone; CIF, cytokinesis initiation factor; BioID, biotin identification; FPRZ, FAZ tip–localizing protein required for cytokinesis; KLIF, kinesin localized in ingressing furrow; CC, coiled coil; ZnF, zinc finger; NTD, N-terminal domain; IDR, intrinsically disordered region; CTD, C-terminal domain; N, nucleus; K, kinetoplast; aa, amino acids; DIC, differential interference contrast; DAPI, 4Ј,6-diamidino-2-phenylindole; PTP, protein A-tobacco etch virus-protein C
Among these trypanosome-specific proteins is a CIF1interacting protein called FAZ tip–localizing protein required for cytokinesis (FPRC) [18] whose subcellular localization and physiological function have not been characterized in the previous work
Summary
The evolutionarily early divergent human parasite Trypanosoma brucei proliferates through binary cell fission in both its tsetse fly vector and mammalian host. The order of action of these cytokinesis regulators has been determined, with BOH1 functioning at the most upstream of the cytokinesis pathway, followed by TbPLK, the three CIF proteins, TbAUK1, and FRW1 and KLIF, acting sequentially at the new FAZ tip and the cleavage furrow (14 –16, 18, 21). Despite these advance, much remains to be learned about the functional interplay among these cytokinesis regulators and their mechanistic roles in controlling cytokinesis initiation and/or completion
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
