Bousquet, H. | Search bioRxiv

bioRxiv2018

A new actin depolymerase: a catch bond Myosin 1 motor

The 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 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 myosin II, although 5 times faster, has no effect. This work reveals a non-conventional myosin motor as a new type of depolymerase and points to its singular interactions with the actin barbed end.

biophysics↗

bioRxiv2018

Ezrin enrichment on curved membranes requires a specific conformation or interaction with a curvature-sensitive partner

One challenge in current cell biology is to decipher the biophysical mechanisms governing protein enrichment on curved membranes and the resulting membrane deformation. The ERM protein ezrin is abundant and associated with cellular membranes that are flat or with positive or negative curvatures. Using in vitro and cell biology approaches, we assess mechanisms of ezrins enrichment on curved membranes. We evidence that ezrin (ezrinWT) and its phosphomimetic mutant T567D (ezrinTD) do not deform membranes but self-assemble anti-parallelly, zipping adjacent membranes. EzrinTDs specific conformation reduces intermolecular ezrin interactions, allows binding to actin filaments, and promotes ezrin binding to positively curved membranes. While neither ezrinTD nor ezrinWT senses negative membrane curvature alone, we demonstrate that interacting with curvature sensors I-BAR-domain proteins facilitates ezrin enrichment in negatively curved membrane protrusions. Overall, our work reveals new mechanisms, specific conformation or binding to a curvature sensor partner, for targeting curvature insensitive proteins to curved membranes.

biophysics↗