Structural and functional insight into regulation of kinesin-1 by microtubule-associated protein MAP7

Abstract

Microtubule (MT)–associated protein 7 (MAP7) is a required cofactor for kinesin-1–driven transport of intracellular cargoes. Using cryo–electron microscopy and single–molecule imaging, we investigated how MAP7 binds MTs and facilitates kinesin-1 motility. The MT-binding domain (MTBD) of MAP7 bound MTs as an extended α helix between the protofilament ridge and the site of lateral contact. Unexpectedly, the MTBD partially overlapped with the binding site of kinesin-1 and inhibited its motility. However, by tethering kinesin-1 to the MT, the projection domain of MAP7 prevented dissociation of the motor and facilitated its binding to available neighboring sites. The inhibitory effect of the MTBD dominated as MTs became saturated with MAP7. Our results reveal biphasic regulation of kinesin-1 by MAP7 in the context of their competitive binding to MTs.

Importin α/β Promote Kif18B Microtubule Association to Spatially Control Microtubule Destabilization

“…We postulate that importin binding to the tail relieves this autoinhibition, allowing Kif18B to bind to MTs. Alternatively, the importins could act as a co-factor for MT association, which would be consistent with MAP7 acting to help load Kinesin-1 to MTs to modulate its activity (Ferro et al ., 2022). These results suggest that the importins stimulate Kif18B MT destabilization activity by increasing binding to MTs, which results in increased plus-end localization.…”

Cholesterol in the cargo membrane reduces kinesin-1 binding to microtubules in the presence of tau

“…We next developed a model describing how membrane cholesterol reduces kinesin binding in the presence of tau. Cholesterol reduces the diffusion of kinesin in the cargo membrane (24,27) whereas tau occludes kinesin's binding sites on the microtubule (10)(11)(12). We therefore considered a simple 1-dimensional model in which a motor diffusively searches for open binding sites on the microtubule (Fig.…”

“…Kinesin transports cargos by processively stepping along microtubules (6,7); this processive motion is initiated when the motor binds the microtubule and is terminated when it unbinds from the microtubule. Tuning of the binding and unbinding rates of kinesin, for example via the presence of microtubule-associated proteins (MAPs) (8)(9)(10), has emerged as a key mechanism of kinesin regulation. In particular, the MAP tau occludes kinesin binding sites on the microtubule (10)(11)(12), inhibiting binding and promoting unbinding of kinesin in vitro (13)(14)(15).…”

“…Tuning of the binding and unbinding rates of kinesin, for example via the presence of microtubule-associated proteins (MAPs) (8)(9)(10), has emerged as a key mechanism of kinesin regulation. In particular, the MAP tau occludes kinesin binding sites on the microtubule (10)(11)(12), inhibiting binding and promoting unbinding of kinesin in vitro (13)(14)(15). However, in vivo, tau is essential for microtubule assembly and stabilization (16).…”

Molecular architecture of the autoinhibited kinesin-1 lambda particle

“…As it carries out its diverse functions in the transport of vesicles, organelles, mRNAs, and multi-protein complexes, kinesin-1 transitions from a compact autoinhibited state to an extended active state. This is controlled by the binding of both cargo adaptors and microtubule associated proteins (8,(11)(12)(13)(14)(15)(16)(17)(18)(19)(20). The compact state suppresses microtubule-dependent kinesin-1 ATPase activity because it allows a regulatory short-linear-motif (SLiM) residing near the C-terminus of the KHCs (known as the isoleucine-alanine-lysine (IAK) motif) (7,(21)(22)(23)(24)(25)(26)(27) to bind the N-terminal motor domains (Fig.…”