Mechanics of cell spreading: role of myosin II

Wakatsuki, Toshiyuki; Wysolmerski, Robert B.; Elson, Elliot L.

doi:10.1242/jcs.00340

Cited by 144 publications

(125 citation statements)

References 38 publications

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“…However, in late P2, the unfragmented cells spread significantly to a larger area than control cells (P<0.05, n≥27 cells; Fig. 2B,C), consistent with previous studies (Cramer and Mitchison, 1995;Sandquist et al, 2006;Senju and Miyata, 2009;Wakatsuki et al, 2003). In contrast to the unfragmented cells, the fragmented cells spread to a similar area as control cells during the entire spreading period (P<0.08, n≥27 cells, Fig.…”

Section: Loss Of Cytoplasmic Coherence Is Accompanied By Disruption Osupporting

confidence: 91%

Cytoskeletal coherence requires myosin-IIA contractility

Cai

Rossier

Gauthier

et al. 2010

Journal of Cell Science

187

166

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SummaryMaintaining a physical connection across cytoplasm is crucial for many biological processes such as matrix force generation, cell motility, cell shape and tissue development. However, in the absence of stress fibers, the coherent structure that transmits force across the cytoplasm is not understood. We find that nonmuscle myosin-II (NMII) contraction of cytoplasmic actin filaments establishes a coherent cytoskeletal network irrespective of the nature of adhesive contacts. When NMII activity is inhibited during cell spreading by Rho kinase inhibition, blebbistatin, caldesmon overexpression or NMIIA RNAi, the symmetric traction forces are lost and cell spreading persists, causing cytoplasm fragmentation by membrane tension that results in 'C' or dendritic shapes. Moreover, local inactivation of NMII by chromophore-assisted laser inactivation causes local loss of coherence. Actin filament polymerization is also required for cytoplasmic coherence, but microtubules and intermediate filaments are dispensable. Loss of cytoplasmic coherence is accompanied by loss of circumferential actin bundles. We suggest that NMIIA creates a coherent actin network through the formation of circumferential actin bundles that mechanically link elements of the peripheral actin cytoskeleton where much of the force is generated during spreading. Adelstein, 2008;Vicente-Manzanares et al., 2009;Wylie and Chantler, 2008). NMIIA and NMIIB are the primary force generators in fibroblasts (Cai et al., 2006;Lo et al., 2004). Phosphorylation of myosin light chains (MLC), primarily by Rho kinases (ROCK) and MLC kinase (Totsukawa et al., 2004), regulates the NMII activity. ROCK has multiple protein targets including MLC, MLC phosphatase, adducin and moesin (Totsukawa et al., 2004). ROCK activates NMII by phosphorylating MLC and also by inactivating MLC phosphatase to inhibit MLC dephosphorylation (Totsukawa et al., 2004). Specific inhibitors have been developed for studying the functions of NMII, i.e. Y27632 inhibits ROCK and blebbistatin inhibits the ATPase activity of myosin-II. In addition to MLC phosphatase, some other proteins also negatively regulate NMII activity. For example, caldesmon interacts with actin, myosin-II and tropomyosin, and inhibits the ATPase activity of myosin-II (Marston et al., 1998). Caldesmon overexpression causes suppression of traction forces and focal adhesions (Helfman et al., 1999). Thus, there are a variety of ways to inhibit force generation on substrates.The plasma membrane limits the spreading of cells on substrates, and tension in the plasma membrane inhibits the ability of actin to polymerize at the periphery (Raucher and Sheetz, 2000). Although the tension in the membrane is typically very low (Sheetz, 2001), it can influence the behavior of cells (Keren et al., 2008) and the final shape of cells is heavily influenced by the final membrane area.We here demonstrate that NMIIA is crucial for the mechanical coherence of cytoplasm. Inhibition of NMII contractility or depletion of NMIIA causes cytoplasm to ...

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Section: Loss Of Cytoplasmic Coherence Is Accompanied By Disruption Osupporting

confidence: 91%

Cytoskeletal coherence requires myosin-IIA contractility

Cai

Rossier

Gauthier

et al. 2010

Journal of Cell Science

187

166

View full text Add to dashboard Cite

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“…In both cases, substantial reduction of GTP-loading on RhoA was observed, leading Burridge and colleagues to propose that it may be necessary to keep cellular contractility low to avoid tension being applied to the newly formed cell-cell junctions (Noren et al, 2001(Noren et al, , 2003. Indeed, during the process of chicken embryo fibroblast spreading, the rate of spreading is inversely related to myosin activity (Wakatsuki et al, 2003). It therefore appears that relaxation of contractile forces may be a common feature of the early stages of actin remodeling events that accompany formation of a number of adhesion types.…”

Section: Discussionmentioning

confidence: 99%

Src SH3/2 Domain-mediated Peripheral Accumulation of Src and Phospho-myosin Is Linked to Deregulation of E-cadherin and the Epithelial-Mesenchymal Transition

Avizienyte

Fincham

Brunton

et al. 2004

MBoC

110

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“…8). MLC phosphorylation, in turn, would be expected to promote actomyosin assembly, which is likely to exert contractile effects, such as those involving stress fibers or that limit spreading of the leading edge of cells (Wakatsuki et al, 2003), thereby limiting inappropriate branch formation. Data presented here (Fig.…”

Section: Role Of Rock In Myelin Sheath Formationmentioning

confidence: 99%

Rho Kinase Regulates Schwann Cell Myelination and Formation of Associated Axonal Domains

Melendez‐Vasquez

Einheber²,

Salzer³

2004

J. Neurosci.

105

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The myelin sheath forms by the spiral wrapping of a glial membrane around an axon. The mechanisms involved are poorly understood but are likely to involve coordinated changes in the glial cell cytoskeleton. Because of its key role as a regulator of the cytoskeleton, we investigated the role of Rho kinase (ROCK), a major downstream effector of Rho, in Schwann cell morphology, differentiation, and myelination. Pharmacologic inhibition of ROCK activity results in loss of microvilli and stress fibers in Schwann cell cultures and strikingly aberrant myelination in Schwann cell-neuron cocultures; there was no effect on Schwann cell proliferation or differentiation. Treated Schwann cells branch aberrantly and form multiple, small, independent myelin segments along the length of axons, each with associated nodes and paranodes. This organization partially resembles myelin formed by oligodendrocytes rather than the single long myelin sheath characteristic of Schwann cells. ROCK regulates myosin light chain phosphorylation, which is robustly, but transiently, activated at the onset of myelination. These results support a key role of Rho through its effector ROCK in coordinating the movement of the glial membrane around the axon at the onset of myelination via regulation of myosin phosphorylation and actomyosin assembly. They also indicate that the molecular machinery that promotes the wrapping of the glial membrane sheath around the axon is distributed along the entire length of the internode.

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Mechanics of cell spreading: role of myosin II

Cited by 144 publications

References 38 publications

Cytoskeletal coherence requires myosin-IIA contractility

Cytoskeletal coherence requires myosin-IIA contractility

Src SH3/2 Domain-mediated Peripheral Accumulation of Src and Phospho-myosin Is Linked to Deregulation of E-cadherin and the Epithelial-Mesenchymal Transition

Rho Kinase Regulates Schwann Cell Myelination and Formation of Associated Axonal Domains

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