Galler Annette B, García Arguinzonis Maísa I, Baumgartner Werner, Kuhn Monika, Smolenski Albert, Simm Andreas, Reinhard Matthias
Institute for Clinical Biochemistry and Pathobiochemistry, University of Würzburg, Josef-Schneider-Str. 2, 97080, Würzburg, Germany.
Histochem Cell Biol. 2006 May;125(5):457-74. doi: 10.1007/s00418-005-0091-z. Epub 2005 Nov 3.
Enabled/vasodilator-stimulated phosphoprotein (Ena/VASP) proteins are established regulators of actin-based motility, platelet aggregation, and growth cone guidance. However, the molecular mechanisms involved essentially remain elusive. Here we report on a novel mechanism of VASP action, namely the regulation of tensile strength, contractility, and rigidity of the actin cytoskeleton. Compared to wild-type cells fibroblasts derived from VASP-deficient mice have thicker and more stable actin stress fibres. Furthermore focal adhesions are enlarged, myosin light chain phosphorylation is increased, and the rigidity of the filament-supported plasma membrane is elevated about three- to fourfold, as is evident from atomic force microscopy. Moreover, fibronectin-coated beads adhere stronger to the surface of VASP-deficient cells. The resistance of these beads to mechanical displacement by laser tweezers is dramatically increased in an F-actin-dependent mode. Cytoskeletal stabilization coincides with slower cell adhesion and detachment, while overall adhesion is increased. Interestingly, many of these effects observed in VASP (-/-) cells are recapitulated in VASP-overexpressing cells, hinting towards a balanced stoichiometry necessary for appropriate VASP function. Taken together, our results suggest that VASP regulates surface protrusion formation and cell adhesion through modulation of the mechanical properties of the actin cytoskeleton.
Enabled/血管舒张刺激磷蛋白（Ena/VASP）家族蛋白是肌动蛋白运动、血小板聚集和生长锥导向过程中公认的调节因子。然而，其中涉及的分子机制仍基本不清楚。在此，我们报告了一种VASP作用的新机制，即对肌动蛋白细胞骨架的抗张强度、收缩性和刚性的调节。与野生型细胞相比，源自VASP基因敲除小鼠的成纤维细胞具有更粗且更稳定的肌动蛋白应力纤维。此外，粘着斑增大，肌球蛋白轻链磷酸化增加，并且从原子力显微镜观察可知，丝状支撑的质膜刚性提高了约三到四倍。而且，纤连蛋白包被的珠子与VASP基因敲除细胞表面的粘附更强。这些珠子在激光镊子作用下抵抗机械位移的能力以F-肌动蛋白依赖的方式显著增加。细胞骨架的稳定与细胞粘附和脱离变慢同时出现，而总体粘附增加。有趣的是，在VASP基因敲除细胞中观察到的许多这些效应在VASP过表达细胞中也会重现，这表明适当的VASP功能需要平衡的化学计量。综上所述，我们的结果表明VASP通过调节肌动蛋白细胞骨架的机械特性来调控表面突起形成和细胞粘附。
