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Actomyosin Contractility (actomyosin + contractility)
Selected AbstractsPlectin deposition at podosome rings requires myosin contractilityCYTOSKELETON, Issue 8 2008Annica Gad Abstract Metalloproteinase-dependent tissue invasion requires the formation of podosomes and invadopodia for localized matrix degradation. Actin cytoskeleton remodeling via Arp2/3-mediated actin polymerization is essential for podosome formation, and dynamic microtubules have an important role in maintaining podosome turnover in macrophages and osteoclasts. Little is known, however, about the involvement of the intermediate filament cytoskeleton in formation, stabilization, and turnover of podosomes. Here we show that vimentin intermediate filaments colocalize with the early sites of podosome formation at the stress fiber - focal adhesion interface in cultured vascular smooth muscle cells, but do not directly contribute to podosome formation, or stabilization. In unstimulated A7r5 cells the cytolinker protein plectin poorly colocalized with vimentin and the microdomains, but following induction by phorbol ester accumulated in the rings that surround the podosomes. In plectin-deficient A7r5 cells actin stress fiber remodelling is reduced in response to PDBu, and small podosomes remain localized at stable actin stress fibres. Pharmacological inhibition of actomyosin contractility by blebbistatin leads to an aberrant localization of podosomes away from the cell periphery and induces failure of plectin to surround the outer perimeter of these invasive adhesions. Taken together, we conclude that plectin is involved in growth and maturation of podosomes by reducing focal adhesion and stress fiber turnover, and that actomyosin-dependent contractility is required for the peripheral localization and specific deposition of plectin at the podosome rings. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Regulation of actomyosin contractility by PI3K in sensory axonsDEVELOPMENTAL NEUROBIOLOGY, Issue 14 2007Irina Orlova Abstract Phosphatidylinositol 3-kinase (PI3K) activity is known to be required for the extension of embryonic sensory axons. Inhibition of PI3K has also been shown to mediate axon retraction and growth cone collapse in response to semaphorin 3A. However, the effects of inhibiting PI3K on the neuronal cytoskeleton are not well characterized. We have previously reported that semaphorin 3A-induced axon retraction involves activation of myosin II, the formation of an intra-axonal F-actin bundle cytoskeleton, and blocks the formation of F-actin patches that serve as precursors to filopodial formation in axons. We now report that inhibition of PI3K results in activation of myosin II in axons. Inhibition of myosin II activity, or its upstream regulatory kinase RhoA-kinase, blocked axon retraction induced by inhibition of PI3K. In addition, inhibition of PI3K also induced intra-axonal F-actin bundles, which likely serve as a substratum for myosin II-based force generation during axon retraction. In axons, filopodia are formed from axonal F-actin patch precursors. Analysis of axonal F-actin patch formation in eYFP-actin expressing neurons revealed that inhibition of PI3K blocked formation of axonal F-actin patches, and thus filopodial formation. These data provide insights into the regulation of the neuronal cytoskeleton by PI3K and are consistent with the notion that decreased levels of PI3K activity mediate axon retraction and growth cone collapse in response to semaphorin 3A. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007. [source] Non-muscle myosin IIB helps mediate TNF cell death signaling independent of actomyosin contractility (AMC)JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2010Patrick G. Flynn Abstract Non-muscle myosin II (NM II) helps mediate survival and apoptosis in response to TNF-alpha (TNF), however, NM II's mechanism of action in these processes is not fully understood. NM II isoforms are involved in a variety of cellular processes and differences in their enzyme kinetics, localization, and activation allow NM II isoforms to have distinct functions within the same cell. The present study focused on isoform specific functions of NM IIA and IIB in mediating TNF induced apoptosis. Results show that siRNA knockdown of NM IIB, but not NM IIA, impaired caspase cleavage and nuclear condensation in response to TNF. NM II's function in promoting cell death signaling appears to be independent of actomyosin contractility (AMC) since treatment of cells with blebbistatin or cytochalasin D failed to inhibit TNF induced caspase cleavage. Immunoprecipitation studies revealed associations of NM IIB with clathrin, FADD, and caspase 8 in response to TNF suggesting a role for NM IIB in TNFR1 endocytosis and the formation of the death inducing signaling complex (DISC). These findings suggest that NM IIB promotes TNF cell death signaling in a manner independent of its force generating property. J. Cell. Biochem. 9999: 1365,1375, 2010. © 2010 Wiley-Liss, Inc. [source] | ||||||||||