Myosin II Tension Sensors Visualize Force Generation within the Actin Cytoskeleton in Living Cells

Abstract

Type II myosin motors generate cytoskeletal forces that are central to 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 measure forces generated by Nonmuscle Myosin IIB (NMIIB) in living cells with piconewton (pN) sensitivity. Fluorescence lifetime imaging microscopy (FLIM)-FRET measurements indicate that the forces generated by NMIIB exhibit significant spatial and temporal heterogeneity, with inferred tensions that vary widely in different regions of the cell. 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.

Insight into Mechanobiology: How Stem Cells Feel Mechanical Forces and Orchestrate Biological Functions

“…Noteworthy, the cytoskeleton contractility is mainly guaranteed by a network of actomyosin fibers that originates from the interaction of F-actin and non-muscle myosin-II [119,120]. F-actin and myosin II form stress fibers of 10–30 nm, together with other actin-linking proteins (e.g., α-actinin, fascin, filamin, spectrin, dystrophin, Arp2/3, profilin, ADF/cofilin, fimbrin, profilin, villin, formin family, and tropomyosins) [119,120]. These stress fibers may associate the cell–ECM interface directly through FAs complex or indirectly through a network between stress fibers [119,120].…”

“…F-actin and myosin II form stress fibers of 10–30 nm, together with other actin-linking proteins (e.g., α-actinin, fascin, filamin, spectrin, dystrophin, Arp2/3, profilin, ADF/cofilin, fimbrin, profilin, villin, formin family, and tropomyosins) [119,120]. These stress fibers may associate the cell–ECM interface directly through FAs complex or indirectly through a network between stress fibers [119,120]. Tension and mechanical forces transmission to the nucleus is typically due to actomyosin fibers and it is regulated by the levels of phosphorylation of the myosin light chain [120,121].…”

“…These stress fibers may associate the cell–ECM interface directly through FAs complex or indirectly through a network between stress fibers [119,120]. Tension and mechanical forces transmission to the nucleus is typically due to actomyosin fibers and it is regulated by the levels of phosphorylation of the myosin light chain [120,121].…”

Molecular Tension Microscopy of E-Cadherin During Epithelial-Mesenchymal Transition

“…Molecular tension sensors have been in use for nearly 10 years [3]. A variety of sensors with specific operating ranges have been designed [4,5], and have been used to measure tension in matrix, cytoskeleton, adhesion, glycocalyx, kinetochore, membranecytoskeleton linker or motor proteins [2,3,[6][7][8][9] in cultured cells, C. elegans, Xenopus, Zebrafish, or Drosophila [3,[10][11][12].…”

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