Nonmuscle myosin II (NMII) generates cytoskeletal forces that drive cell division, embryogenesis, muscle contraction and many other cellular functions. However, at present there is no method that can directly measure the forces generated by myosins in living cells. Here, we describe a Förster resonance energy transfer (FRET)-based tension sensor that can detect myosin-associated force along the filamentous actin network. Fluorescence lifetime imaging microscopy (FLIM)-FRET measurements indicate that the forces generated by NMII isoform B (NMIIB) exhibit significant spatial and temporal heterogeneity as a function of donor lifetime and fluorophore energy exchange. These measurements provide a proxy for inferred forces that vary widely along the actin cytoskeleton. This initial report highlights the potential utility of myosin-based tension sensors in elucidating the roles of cytoskeletal contractility in a wide variety of contexts.

Author contributions

Conceptualization: A.R.D., J.L., I.C.; Methodology: R.G.H., D.K., F.L., M.Z., D.R., A.J.P., K.L.O., A.R.D., J.L., I.C.; Software: D.K., F.L., M.Z., A.R.D., J.L., I.C.; Validation: R.G.H., D.K., M.Z., D.R., A.J.P., K.L.O., J.L., I.C.; Formal analysis: R.G.H., D.K., F.L., M.Z., K.L.O., J.L., I.C.; Investigation: R.G.H., D.K., M.Z., D.R., A.J.P., K.L.O., A.R.D., J.L., I.C.; Resources: S.J.S., J.L., I.C.; Data curation: D.K., J.L., I.C.; Writing - original draft: J.L., I.C.; Writing - review & editing: R.G.H., D.K., S.J.S., A.R.D., J.L., I.C.; Visualization: R.G.H., D.K., F.L., J.L., I.C.; Supervision: S.J.S., M.O.H., J.L., I.C.; Project administration: J.L., I.C.; Funding acquisition: J.L., I.C.

Funding

Authors would like to acknowledge the funding support from the National Science Foundation EPSCoR program (grant number IIA - 1355423) and by the state of South Dakota to I.C., J.L. and S.J.S., National Institutes of Health (NIH) 1R35GM147412 (J.L.), National Science Foundation (NSF) 2347957 and NSF 2431792 (J.L.), and National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) R01 DK131020 (I.C.). R.G.H. is supported by NIDDK F31DK132954 and M.O.H. is supported by NIDDK R01 DK110276. Deposited in PMC for release after 12 months.

Data availability

All relevant data can be found within the article and its supplementary information.

Special Issue

This article is part of the Special Issue ‘Imaging Cell Architecture and Dynamics’, guest edited by Lucy Collinson and Guillaume Jacquemet. See related articles at https://journals.biologists.com/jcs/issue/137/20.

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