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Cell spread area and traction forces determine myosin-II-based cortex thickness regulation. [Central Imaging and Flow Cytometry Facility]

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TitleCell spread area and traction forces determine myosin-II-based cortex thickness regulation. [Central Imaging and Flow Cytometry Facility]
Publication TypeJournal Article
Year of Publication2019
AuthorsKumar R, Saha S, Sinha B
JournalBiochim Biophys Acta Mol Cell Res
Date Published2019 Jul 23
ISSN1879-2596
Abstract

Actomyosin network under the plasma membrane of cells forms a cortical layer that regulates cellular deformations during different processes. What regulates the cortex? Characterized by its thickness, it is believed to be regulated by actin dynamics, filament-length regulators and myosin motor proteins. However, its regulation by cellular morphology (e.g. cell spread area) or mechanical microenvironment (e.g. substrate stiffness) has remained largely unexplored. In this study, super- and high-resolution imaging of actin in CHO cells demonstrates that at high spread areas (>450 μm), the cortex is thinner, better separated as layers, and sensitive to deactivation of myosin II motors or reduction of substrate stiffness (and traction forces). In less spread cells (<400 μm) such perturbations do not elicit a response. Myosin IIA's mechanosensing is limited here due to its lowered actin-bound fraction and higher turnover rate. Cofilin, in line with its competitive inhibitory role, is found to be overexpressed in these cells. To establish the causal relation, we initiate a spread area drop by de-adhesion and find enhanced actin dynamics and fragmentation along with oscillations and increase in thickness. This is more correlated to the reduction of traction forces than the endocytosis-based reduction in cell volume. Cortex thickness control by spread area is also found be true during differentiation of THP-1 monocytes to macrophages. Thus, we propose that spread area regulates cortex and its thickness by traction-based mechanosensing of myosin II.

DOI10.1016/j.bbamcr.2019.07.011
Alternate JournalBiochim Biophys Acta Mol Cell Res
PubMed ID31348954