Department of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
J Cell Biol. 2010 Jan 11;188(1):157-73. doi: 10.1083/jcb.200908045. Epub 2010 Jan 4.
Increased affinity of integrins for the extracellular matrix (activation) regulates cell adhesion and migration, extracellular matrix assembly, and mechanotransduction. Major uncertainties concern the sufficiency of talin for activation, whether conformational change without clustering leads to activation, and whether mechanical force is required for molecular extension. Here, we reconstructed physiological integrin activation in vitro and used cellular, biochemical, biophysical, and ultrastructural analyses to show that talin binding is sufficient to activate integrin alphaIIbbeta3. Furthermore, we synthesized nanodiscs, each bearing a single lipid-embedded integrin, and used them to show that talin activates unclustered integrins leading to molecular extension in the absence of force or other membrane proteins. Thus, we provide the first proof that talin binding is sufficient to activate and extend membrane-embedded integrin alphaIIbbeta3, thereby resolving numerous controversies and enabling molecular analysis of reconstructed integrin signaling.
整合素与细胞外基质（激活）的亲和力增加调节细胞黏附和迁移、细胞外基质组装和机械转导。主要的不确定性涉及到桩蛋白是否足以激活整合素，没有聚类的构象变化是否会导致激活，以及机械力是否是分子延伸所必需的。在这里，我们在体外重建了生理状态下的整合素激活，并利用细胞、生化、生物物理和超微结构分析表明，桩蛋白结合足以激活整合素αIIbbeta3。此外，我们合成了纳米盘，每个纳米盘都含有一个单一的脂嵌入整合素，并利用它们表明，桩蛋白可以激活未聚类的整合素，导致分子延伸，而不需要力或其他膜蛋白。因此，我们首次证明了桩蛋白结合足以激活和延伸膜嵌入的整合素αIIbbeta3，从而解决了许多争议，并使重建的整合素信号的分子分析成为可能。
