Abstract
SummaryCells recognize and respond to changes in intra- and extracellular mechanical conditions to maintain their mechanical homeostasis. Linear contractile bundles of actin filaments and myosin II known as stress fibres (SFs) mediate mechanical signals. Mechanical cues such as excessive stress driven by myosin II and/or external force may damage SFs and induce the local transient accumulation of SF-repair complexes (zyxin and VASP) at the damaged sites. Using an atomic force microscope mounted on a fluorescence microscope, we applied mechanical damage to cells expressing fluorescently tagged cytoskeletal proteins and recorded the subsequent mobilization of SF-repair complexes. We found that a LIM protein, paxillin, transiently accumulated at the damaged sites earlier than zyxin, while paxillin knockdown did not affect the kinetics of zyxin translocation. The C-terminal half of paxillin, comprising four-tandem LIM domains, can still translocate to damaged sites on SFs, suggesting that the LIM domain is essential for the mechanosensory function of paxillin. Our findings demonstrate a crucial role of the LIM domain in mechanosensing LIM proteins.
Highlights
The ability to sense and respond to intra- and extracellular mechanical load is vital for many types of living cells to maintain their normal physiology
Linear contractile bundles of actin filaments and myosin II known as stress fibres (SFs) mediate mechanical signals
Mechanical cues such as excessive stress driven by myosin II and/or external force may damage SFs and induce the local transient accumulation of SF-repair complexes at the damaged sites
Summary
The ability to sense and respond to intra- and extracellular mechanical load is vital for many types of living cells to maintain their normal physiology. SFs can be induced through the Rho signaling pathway and are often linked to the extracellular matrix (ECM) via focal adhesions (FAs), which include the integrin family of transmembrane ECM receptors (Tojkander et al, 2012). This transmembrane network comprising SFs, FAs and ECM enables bidirectional communication across the cell membrane. The inside-out signaling of changes in the actomyosin-dependent contractile force in SFs is transmitted to the ECM and plays critical roles in cell motility, ECM remodeling and tissue morphogenesis (Harris et al, 1980; Lauffenburger and Horwitz, 1996; Wang et al, 1993). The SF-FA system itself is a bidirectional mechanochemical transduction network
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