The tension mounts: Stress fibers as force-generating mechanotransducers

Abstract

Stress fibers (SFs) are often the most prominent cytoskeletal structures in cells growing in tissue culture. Composed of actin filaments, myosin II, and many other proteins, SFs are force-generating and tension-bearing structures that respond to the surrounding physical environment. New work is shedding light on the mechanosensitive properties of SFs, including that these structures can respond to mechanical tension by rapid reinforcement and that there are mechanisms to repair strain-induced damage. Although SFs are superficially similar in organization to the sarcomeres of striated muscle, there are intriguing differences in their organization and behavior, indicating that much still needs to be learned about these structures.

Endothelium-targeted overexpression of heat shock protein 27 ameliorates blood–brain barrier disruption after ischemic brain injury

“…Soon after cerebral I/R, endothelial ADF/cofilin is phosphorylated at serine 3, becoming disabled (9). Meanwhile, the RhoA/ROCK signaling pathway is activated, which may further promote the aggregation and cross-linking of F-actin into force-generating linear stress fibers through the phosphorylation/ activation of MLC (9,11,36,39). Our data presented here show that HSP27 attenuates I/R-induced actin polymerization and stress fiber formation, but without influencing the phosphorylation of either ADF/cofilin or MLC (Fig.…”

“…A cortical actin rim is formed in ECs under physiological conditions, serving as an important anchor for cell-cell and cell-matrix adhesions (36). Fluid shear stress experienced by quiescent ECs provides chronic mild stimulation toward the formation of stress fibers, which may interrupt the cortical actin network and break intercellular junctions through centripetal tension when homeostasis is disrupted (11,37). It is well established that HSP27 directly inhibits actin polymerization by capping the barbed end of actin (20), where rapid addition of actin monomers occurs.…”

“…Contractile stress fibers transmit tension to cell junctions that are anchored to the actin cytoskeleton and disassemble the junctional complexes (9,11). At 1 h after OGD, the distribution of TJ proteins occludin and zona occludens (ZO)-1, as well as the AJ protein vascular endothelial (VE)-cadherin partially shifted from the membrane fraction to the actin cytoskeleton fraction (ACF), whereas total protein levels in whole-cell lysates remained unchanged (Fig.…”

“…light chain (MLC) signal transduction cascade, resulting in the formation of force-generating, contractile stress fibers consisting of F-actin, myosin, and other proteins (9,11). Possibly as a consequence of tension transmission, at least in part, TJ and AJ proteins that are normally anchored to the actin cytoskeleton are disassembled at cell-cell contacts and internalized (12,13), thereby widening the paracellular space between ECs.…”

Talin determines the nanoscale architecture of focal adhesions

“…Actin stress fibers terminate at FAs where actomyosin contractility is transmitted to the ECM, generating traction (2)(3)(4)(5). Mechanical tension impinging on each FA is implicated in key steps including the elongation, reinforcement, and maintenance of the FA structures (6).…”