The mitotic kinesin-14 KlpA contains a context-dependent directionality switch

Abstract

Kinesins are microtubule-based motor proteins that convert chemical energy from ATP hydrolysis into mechanical work for a variety of essential intracellular processes. Kinesin-14s (i.e. kinesins with a C-terminal motor domain) are commonly considered to be nonprocessive minus end-directed motors that mainly function for mitotic spindle assembly and maintenance. Here, we show that KlpA – a mitotic kinesin-14 motor from the filamentous fungus Aspergillus nidulans – contains a context-dependent directionality switch. KlpA exhibits canonical minus end-directed motility inside microtubule bundles, but on individual microtubules it unexpectedly moves processively toward the plus ends. Removal of the N-terminal nonmotor microtubule-binding domain renders KlpA diffusive on individual microtubules but does not abolish its minus end-directed motility to collectively glide microtubules, suggesting that the nonmotor microtubule-binding domain likely acts as a switch for controlling the direction of KlpA motility. Collectively, these findings provide important insights into the mechanism and regulation of KlpA functions inside the mitotic spindle.

Drag-induced directionality switching of kinesin-5 Cin8 revealed by cluster-motility analysis

“…Our analysis suggests that such interactions lead to directionality switching, in agreement with recent findings indicating that crowding on MTs with nonmotor proteins switches the directionality of the bidirectional S. pombe kinesin-5 Cut7 (12). Last, directionality switching has also been observed for mitotic kinesin-14 motors (13,14), and an asymmetric response to force has been directly demonstrated for the S. cerevisiae kinesin-14 Kar3 (14). Thus, the suggested mechanism of an asymmetric response of motor motion to drag may also explain directionality switching of other kinesins, therefore providing a unified view of directionality switching of kinesin motors.…”

“…Cut7 is minus-end directed in single-molecule experiments and multimotor MT gliding assays (4,11) but switches directionality as a function of crowding of either motor or nonmotor proteins on MTs (12). Notably, two kinesin-14 motors were recently demonstrated to be bidirectional (13,14), indicating that switchable directionality is more common in the kinesin superfamily than was previously appreciated. The plethora of observations related to directionality switching may indicate that bidirectionality is of physiological importance, a notion that is also supported by a recent theoretical study (15).…”

Intrinsically Disordered Domain of Kinesin-3 Kif14 Enables Unique Functional Diversity

“…Similarly to crosslinkers of the kinesin-5 and -14 family members [6][7][8][9][33][34][35][36][37], kinesin-3, Kif14, can slide antiparallel microtubules relative to each other, while statically crosslinking parallel ones, consistent with the tug-of-war mechanism proposed earlier [5,7]. Intriguingly, unlike kinesin-14, crosslinking by Kif14 does not require the motor domain, showing that the Kif14 disordered anchoring domain can interact with two adjacent microtubules simultaneously and thereby establish diffusible crosslinks.…”

Control mechanisms of microtubule overlap regions

“…If this domain binds to the same microtubule as the heads, this results in minus end-directed movement. On the other hand, if this domain detaches it leads to plus end-directed motion (Popchock et al, 2016). In practice, this results in minus-end directed motion on single microtubules and in plus end-directed motion when sliding a pair of microtubules.…”

“…Note that although directional switching of yeast kinesin-5 proteins has been observed before, the cellular function of switching was not understood. So far only yeast kinesin-5 and yeast and Aspergillus kinesin-14 were observed to switch directionality (Roostalu et al, 2011;Thiede et al, 2012;Fridman et al, 2013;Edamatsu, 2014;Molodtsov et al, 2016;Popchock et al, 2016). Furthermore, Xenopus kinesin-5, Eg5, is known to switch between diffusive and directional modes (Kwok et al, 2006).…”