A new actin depolymerase: a Myosin 1 motor

Abstract

Sentence summary Due to its catch bond, Myosin 1b depolymerizes sliding actin filaments at their barbed end by exerting a prolonged force.All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/375923 doi: bioRxiv preprint first posted online Jul. 24, 2018; 2 AbstractThe regulation of actin dynamics is essential for various cellular processes. Former evidence suggests a correlation between the function of non-conventional myosin motors and actin dynamics. We investigate the contribution of the catch-bond Myosin1b to actin dynamics using sliding motility assays. We observe that sliding on Myosin1b immobilized or bound to a fluid bilayer enhances actin depolymerization at the barbed end, while sliding on the weak catch-bond MyosinII has no effect. Our theoretical model supports that the catch-bond prolongs the attachment time of the motor at the barbed end due to the friction force exerted by the sliding filament; thereby this motor exerts a sufficient force on this end to promote depolymerization. This work reveals a non-conventional myosin motor as a new type of depolymerase.All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/375923 doi: bioRxiv preprint first posted online Jul. 24, 2018; 3 Actin filaments (F-actin) form a variety of dynamical architectures that govern cell morphology and cell movements. The dynamics of the actin networks are regulated in space and time by the assembly and disassembly of actin polymers under the control of regulatory proteins. Cortical actin organizes lateral movement of transmembrane proteins and participates in membrane signaling by interacting transiently with the plasma membrane (1). One class of actin-associated molecular motors, the single-headed myosin 1 proteins, bridges cortical actin to the plasma membrane. Polymerization of actin filaments at the plasma membrane generates forces on the membrane as well as on their membrane linkers. Inversely myosin 1 can exert and sustain pN forces on F-actin (2).This important class of myosins contains a motor domain at its N-terminus that binds Factin in response to ATP hydrolysis, a light chain binding domain (LCBD) that binds calmodulin (in most cases), and a Tail domain at the C-terminus (Fig. 1A) (3). The Tail domain encompasses a tail homology domain (TH1) with a pleckstrin homology motif (PH) that binds phosphoinositides (Fig. 1A). Beside the involvement of myosin 1 proteins in a large variety of cellular processes including cell migration and membrane trafficking (3), manipulation of myosin 1 expression has revealed a correlation between these myosins and actin network architecture (4-7). In particular, down-or overexpression of one of the...

Membrane-cytoskeleton mechanical feedback mediated by myosin-I controls phagocytic efficiency

“…Moreover, myo1e has been reported to bind actin regulatory proteins such as WASP or CARMIL 67,68 , and we have found no difference in the recruitment of these proteins to the phagocytic cup or in resting macrophages lacking myo1e/f (data not shown). Intriguingly, a recent paper has reported that F-actin depolymerization rates increase when actin filaments slide on myosin 1b (myo1b) 69 . However, since the kinetics of the myo1b motor domain are distinct from that of long-tailed class 1 myosins, this feature is unlikely to be generalizable to myo1e/f.…”