MAP7 family proteins regulate kinesin-1 recruitment and activation

Abstract

Kinesin-1 is responsible for microtubule-based transport of numerous cellular cargoes. Here, we explored the regulation of kinesin-1 by MAP7/ensconsin family proteins. We found that all four mammalian MAP7 family members bound to kinesin-1, and MAP7, MAP7D1 and MAP7D3 acted redundantly to enable kinesin-1-dependent transport in HeLa cells. Microtubule recruitment of the truncated kinesin-1 KIF5B-560, which contains the stalk but not the cargo-binding and autoregulatory regions, was inhibited in cells co-depleted of these three MAP7 proteins. In vitro, purified MAP7 and MAP7D3 increased microtubule landing rate and processivity of KIF5B-560.The same was true for MAP7D3 C-terminus, which weakly bound to microtubules and exchanged rapidly on motile KIF5B-560 motors. A C-terminal MAP7 fragment lacking microtubule affinity increased KIF5B-560 recruitment to microtubules in vitro and in cells, and partially rescued kinesin-1-dependent transport in the absence of full-length MAP7 proteins. We propose that MAP7 proteins are microtubule-tethered kinesin-1 activators, with which the motor transiently interacts as it moves along microtubules. SummaryA combination of experiments in cells and in vitro reconstitution assays demonstrated that mammalian MAP7 family proteins act redundantly to activate kinesin-1 and promote its microtubule binding and processivity by transiently associating with the stalk region of the motor.All rights reserved. No reuse allowed without permission.was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.

Microtubule-Associated Proteins: Structuring the Cytoskeleton

“…In a similar manner, other MAPs such as MAP1B [109], MAP2, MAP4 [110,111], MAP6 [112] and MAP7 [113][114][115][116] were shown to influence intracellular transport but perhaps not with the same selectivity (Fig. 3F).…”

MAP7 Prevents Axonal Branch Retraction by Creating a Stable Microtubule Boundary to Rescue Polymerization

“…Thus, this unique microtubule binding property of MAP7, likely mediated by peptides outside the N domain, provides a novel mechanism to regulate microtubule stability in neurons. As recent work (Hooikaas et al, 2019;Pan et al, 2019) reported diverse functions of mammalian MAP7 homologs, it would thus be interesting to determine whether these homologs have similar microtubule binding properties as MAP7.…”

Roles of motor on-rate and cargo mobility in intracellular transport

“…The binding rate of the motor is k on = π 0 microtubule within reach 0 microtubule not within reach (5) The microtubule is within reach of the motor if the distance between the location of the anchor and any point on the surface of the microtubule is less than the motor length away and the motor would not have to go through the bead to reach it. Motors are allowed to bind if the motor could reach around the surface of the bead to the surface of the microtubule.…”

“…At a single-molecule level, motor behavior involves attachment to the microtubule, stepping, and detachment from the microtubule. While the stepping and detachment processes have been extensively studied -including under load in backward, forward [1], left, right [2], and upward [3] directions, and as modified by MAPs [4,5] and tubulin state [6] -the attachment rate is less well-understood.…”