Functional analyses of an axonemal inner‐arm dynein complex in the bloodstream form of Trypanosoma brucei uncover its essential role in cytokinesis initiation

Abstract

Summary The flagellated eukaryote Trypanosoma brucei alternates between the insect vector and the mammalian host and proliferates through an unusual mode of cell division. Cell division requires flagellum motility‐generated forces, but flagellum motility exerts distinct effects between different life cycle forms. Motility is required for the final cell abscission of the procyclic form in the insect vector, but is necessary for the initiation of cell division of the bloodstream form in the mammalian host. The underlying mechanisms remain elusive. Here we carried out functional analyses of a flagellar axonemal inner‐arm dynein complex in the bloodstream form and investigated its mechanistic role in cytokinesis initiation. We showed that the axonemal inner‐arm dynein heavy chain TbIAD5‐1 and TbCentrin3 form a complex, localize to the flagellum, and are required for viability in the bloodstream form. We further demonstrated the interdependence between TbIAD5‐1 and TbCentrin3 for maintenance of protein stability. Finally, we showed that depletion of TbIAD5‐1 and TbCentrin3 arrested cytokinesis initiation and disrupted the localization of multiple cytokinesis initiation regulators. These findings identified the essential role of an axonemal inner‐arm dynein complex in cell division, and provided molecular insights into the flagellum motility‐mediated cytokinesis initiation in the bloodstream form of T. brucei.

Control of Variant Surface Glycoprotein Expression by CFB2 in Trypanosoma brucei and Quantitative Proteomic Connections to Translation and Cytokinesis

“…6B ), potentially explaining the continued endoreduplication and mitosis. In T. brucei , centrin3 forms a complex with the inner-arm dynein heavy chain IAD5-1, and disruption of this complex yields endoreduplicated and multinucleated cells and also reduced CIF3 expression ( 25 , 26 ), which is similar to what we observe here following CFB2 knockdown ( Fig. 1C and D ).…”

Genome-scale RNA interference profiling of Trypanosoma brucei cell cycle progression defects

“…3e shows examples of RIT-seq read-mapping profiles for twenty-six individual genes that register >4 C enrichment following knockdown. In addition to the categories above, these include the inner arm dynein 5-1 38 , FAZ proteins which mediate attachment of the flagellum to the cell body 39 ; all four cytokinesis initiation factors CIF1-4 40 , and chromosomal passenger complex components, including CPC1 and the aurora B kinase, AUK1. AUK1 and CPC1 are spindle-associated and regulate mitosis and cytokinesis 26 , 41 .…”

Who Needs a Contractile Actomyosin Ring? The Plethora of Alternative Ways to Divide a Protozoan Parasite

“…do not possess any functional myosins, relying on cytoskeletal elements/proteins and flagellar motility to bring about cytokinesis (Ribeiro et al, 2000; Benchimol, 2004b; Hardin et al, 2017). Flagellar/ciliary motility is also important for cytokinesis in T. brucei (Branche et al, 2006; Ralston et al, 2006; Zhang et al, 2019b) and Tetrahymena (Brown et al, 1999a), and during exflagellation in Plasmodium spp. (Billker et al, 1998).…”

“…An alternative explanation is that the “posterior-anterior furrowing” instead reflects continued normal nascent daughter cell posterior end remodeling (Wheeler et al, 2013) in the absence of furrow ingression, as previously observed following FAZ10 or katanin depletion (Benz et al, 2012; Moreira et al, 2017), with continued flagellar motility acting to pull apart the nascent posterior ends (Sinclair-Davis et al, 2017). Intriguingly, one further difference between bloodstream and procyclic trypanosomes, is that a flagellar axonemal inner-arm dynein complex, comprising dynein heavy chain ortholog TbIAD5-1 and TbCentrin3,is essential for CIF1-3 localization, and therefore, for cytokinesis in the bloodstream form, but not in the procyclic form (Zhang et al, 2019b). However, how an axonemal complex is able to modulate the localization of cytokinesis proteins at the new FAZ tip, and why this only occurs in one life cycle stage, is currently unclear.…”