Mechanosensing through direct binding of tensed F-actin by LIM domains

Sun, X.; Phua, D. Y. Z.; Axiotakis, L.; Smith, M. A.; Blankman, E.; Gong, R.; Cail, R. C.; Espinosa de los Reyes, S.; Beckerle, M. C.; Waterman, C. M.; Alushin, G. M.

doi:10.1101/2020.03.06.979245

bioRxiv · 10.1101/2020.03.06.979245

Mechanosensing through direct binding of tensed F-actin by LIM domains

Sun, X.·Phua, D. Y. Z.·Axiotakis, L.·Smith, M. A.·Blankman, E.·Gong, R.·Cail, R. C.·Espinosa de los Reyes, S.·Beckerle, M. C.·Waterman, C. M.·Alushin, G. M.

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Abstract

Mechanical signals transmitted through the cytoplasmic actin cytoskeleton must be relayed to the nucleus to control gene expression. LIM domains are protein-protein interaction modules found in cytoskeletal proteins and transcriptional regulators; however, it is unclear if there is a direct link between these two functions. Here we identify three LIM protein families (zyxin, paxillin, and FHL) whose members preferentially localize to the actin cytoskeleton in mechanically-stimulated cells through their tandem LIM domains. A minimal actin-myosin reconstitution system reveals that representatives of all three families directly bind F-actin only in the presence of mechanical force. Point mutations at a site conserved in each LIM domain of these proteins selectively disrupt tensed F-actin binding in vitro and cytoskeletal localization in cells, demonstrating a common, avidity-based mechanism. Finally, we find that binding to tensed F-actin in the cytoplasm excludes the cancer-associated transcriptional co-activator FHL2 from the nucleus in stiff microenvironments. This establishes direct force-activated F-actin binding by FHL2 as a mechanosensing mechanism. Our studies suggest that force-dependent sequestration of LIM proteins on the actin cytoskeleton could be a general mechanism for controlling nuclear localization to effect mechanical signaling.

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Sun, X., Phua, D. Y. Z., Axiotakis, L., Smith, M. A., Blankman, E., Gong, R., Cail, R. C., Espinosa de los Reyes, S., Beckerle, M. C., Waterman, C. M., Alushin, G. M.. 2020-03-07. Mechanosensing through direct binding of tensed F-actin by LIM domains. https://doi.org/10.1101/2020.03.06.979245

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