Biology subjects

Cleetus, A.

Publications and source records attributed to Cleetus, A..

3 recordsLinked to original sources

bioRxiv2026

Life without heterotrimeric kinesins: trypanosomatids use a combination of homodimeric kinesin-2 motors to drive intraflagellar transport

Heterotrimeric kinesin 2 is the canonical motor protein for anterograde intraflagellar transport (IFT), driving movement of protein complexes towards the tip of cilia and flagella. Here, we show that all members of the Euglenozoa group lack genes for heterotrimeric kinesins and instead possess a variable number of genes for two homodimeric kinesins termed KIN2A and KIN2B. When expressed in vitro, both Trypanosoma brucei kinesins form homodimers and move processively along brain microtubules, KIN2A being faster than KIN2B. Studies in T. brucei and Leishmania mexicana show anterograde and retrograde IFT of both kinesins, with KIN2A travelling throughout the whole length of the flagellum, while KIN2B is concentrated at its base. In the proximal portion of the flagellum, most KIN2B molecules travel without IFT proteins, except for a few particles that are associated with IFT proteins and reach the tip. Surprisingly, the absence of KIN2A has mild effects on IFT and flagellum assembly, whereas KIN2B is essential for both. Investigation of trypanosome flagella deprived of KIN2B revealed that IFT proteins do not access these flagella but that KIN2A can still circulate. We propose a division-of-labour model where KIN2B would be responsible for the import of IFT proteins while KIN2A would ensure most of the anterograde transport.

cell biology↗

bioRxiv2020

Retracing the evolution of kinesin-2 deployment from mouse to worm

During the course of evolution, cells have repurposed homologous motor proteins for the transport of an astonishingly diverse set of intracellular cargo. One prominent example of such diversification is the deployment of the respective kinesin-2 homologs in C. elegans (CeOSM-3) and mouse (MmKIF-17). While CeOSM-3 is deployed exclusively inside the cilium as a transport motor, its mouse counterpart behaves as a ciliary cargo. Instead, MmKIF-17 powers many different transport processes in the cytoplasm. Here we turned to functional reconstitution assays to uncover the molecular underpinnings of kinesin-2 deployment. Based on our findings, we propose that cells specified adaptor proteins as strictly conserved on- and off-switches, and tailored the motors to fit the respective switches. This is exemplified by the surprising ability of the mouse adaptor to function as a ciliary on-switch for the distantly related CeOSM-3, but not for its own MmKIF-17 motor. Worms, in contrast, retained ciliary on- and off-switches, and can thus deploy CeOSM-3 as a regulatable transport motor inside the cilium. MmKIF-17 escaped this regulatory control by losing its interaction with the ciliary on-switch and has evidently been tailored to fit many different cytoplasmic adaptors over the course of evolution. We could further trace the robustness of an adaptor to serve as a conserved on-switch back to a few strictly conserved residues, which are also present in unicellular organisms. It is therefore conceivable that eukaryotes started to engineer dedicated on- and off-switches early in the evolution and kept their function conserved up to mammals.

molecular biology↗

bioRxiv2019

Kinesin-2 from C. reinhardtii is an atypically fast and auto-inhibited motor that is activated by heterotrimerization for intraflagellar transport

The construction and function of virtually all cilia require the universally conserved process of Intraflagellar Transport (IFT) [1, 2]. During the atypically fast IFT in the green alga C. reinhardtii, up to ten kinesin-2 motors line up in a tight assembly on the trains [3], provoking the question of how these motors coordinate their action to ensure smooth and fast transport along the flagellum without standing in each others way. Here, we show that the heterodimeric FLA8/10 kinesin-2 alone is responsible for the atypically fast IFT in C. reinhardtii. Notably, in single-molecule studies, FLA8/10 moved at speeds matching those of in vivo IFT [4], but additionally displayed a slow velocity distribution, indicative of auto-inhibition. Addition of the KAP subunit to generate the heterotrimeric FLA8/10/KAP relieved this inhibition, thus providing a mechanistic rationale for heterotrimerization with the KAP subunit in fully activating FLA8/10 for IFT in vivo. Finally, we link fast FLA8/10 and slow KLP11/20 kinesin-2 from C. reinhardtii and C. elegans through a DNA tether to understand the molecular underpinnings of motor coordination during IFT in vivo. For motor pairs from both species, the co-transport velocities very nearly matched the single-molecule velocities, and the complexes both spent roughly 80% of the time with only one of the two motors attached to the microtubule. Thus, irrespective of phylogeny and kinetic properties, kinesin-2 motors prefer to work alone without sacrificing efficiency. Our findings thus offer a simple mechanism for how efficient IFT is achieved across diverse organisms despite being carried out by motors with different properties.

biophysics↗