Myosin-18B Promotes Mechanosensitive CaMKK2-AMPK-VASP Regulation of Contractile Actin Stress Fibers.

Shuangshuang Zhao,Yue Zhang,Yanqin Cui,Kun Shi,Jiayi Xu,Baohua Ji,Yifei Zheng,Wei Gao,Zeyu Wen,Xuemeng Shi,Yaming Jiu,Yanjun Liu,Hui Li,Jinping Cai

doi:10.1016/j.isci.2020.100975

Abstract

SummaryActin stress fibers guide cell migration and morphogenesis. During centripetal flow, actin transverse arcs fuse accompanied by the formation of myosin II stacks to generate mechanosensitive actomyosin bundles. However, whether myosin II stack formation plays a role in cell mechano-sensing has remained elusive. Myosin-18B is a “glue” molecule for assembling myosin II stacks. By examining actin networks and traction forces, we find that cells abolishing myosin-18B resemble Ca2+∕calmodulin-dependent kinase kinase 2 (CaMKK2)-defective cells. Inhibition of CaMKK2 activity reverses the strong actin network to thin filaments in myosin-18B-overexpressing cells. Moreover, AMP-activated protein kinase (AMPK) activation is able to relieve the thin stress fibers by myosin-18B knockout. Importantly, lack of myosin-18B compromises AMPK-vasodilator-stimulated phosphoprotein and RhoA-myosin signaling, thereby leading to defective persistent migration, which can be rescued only by full-length and C-extension-less myosin-18B. Together, these results reveal a critical role of myosin-18B in the mechanosensitive regulation of migrating cells.

Highlights

The ability of cells to do persistent migration, to exert forces to the environment, and to conduct mechanotransduction depends on the actin cytoskeleton (Burridge and Wittchen, 2013; Kassianidou and Kumar, 2015; Tojkander et al, 2012)
Actin transverse arcs fuse accompanied by the formation of myosin II stacks to generate mechanosensitive actomyosin bundles
By examining actin networks and traction forces, we find that cells abolishing myosin-18B resemble Ca2+∕calmodulindependent kinase kinase 2 (CaMKK2)-defective cells

Summary

Introduction

The ability of cells to do persistent migration, to exert forces to the environment, and to conduct mechanotransduction depends on the actin cytoskeleton (Burridge and Wittchen, 2013; Kassianidou and Kumar, 2015; Tojkander et al, 2012). Based on protein compositions and associations with focal adhesions, stress fibers can be divided into three subcategories (Naumanen et al, 2008; Small et al, 1998). They are non-contractile ‘‘dorsal stress fibers,’’ thin ‘‘transverse arcs’’ that undergo retrograde flow toward the cell center, and ‘‘ventral stress fibers’’ that are thick actomyosin bundles generated through coalescence of multiple thin transverse arcs during the centripetal flow. The fusion of transverse arcs and consequent formation of ventral stress fibers are accompanied by an increased contractile force (Soine et al, 2015; Tojkander et al, 2015). Due to lack of specific methods to inhibit myosin II stack formation, the function of myosin II stacks has not been completely studied, such as whether integrated myosin II stack formation involves in the regulation of mechanosensitive assembly of contractile stress fibers

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