Partridge Michael A, David Frank S, Marcantonio Eugene E
Department of Pathology and Cell Biology, College of Physicians and Surgeons, Columbia University, New York, NY 10032, USA.
J Cell Sci. 2006 Mar 15;119(Pt 6):1175-83. doi: 10.1242/jcs.02827. Epub 2006 Feb 28.
Integrin-mediated ;outside-in' signaling requires the transmission of a conformational change from the extracellular domains to the cytoplasmic domains. Although one component of this conformational change is the separation of the alpha and beta cytoplasmic domains, it is not clear how this separation could result in the initiation of downstream signals necessary for focal adhesion (FA) formation. To address this question, we used a swapped integrin heterodimer, in which the extracellular domains of the alpha and beta chains were attached to their opposing transmembrane and cytoplasmic domains. This receptor was able to bind ligand normally, but could not promote FA formation. We then displaced the beta cytoplasmic domain with either a duplication of its membrane-proximal region or an unrelated alpha-helical spacer. This displacement partially restored FA formation in these swapped receptors and rescued other aspects of integrin-mediated signaling, including cytoskeletal organization, motility and several tyrosine-phosphorylation-dependent signals. We suggest that separation of the cytoplasmic domains leads to alteration of the secondary structure of the distal beta tail, which initiates downstream signals leading to cytoskeletal reorganization.
整合素介导的“由外向内”信号传导需要将构象变化从细胞外结构域传递到细胞质结构域。虽然这种构象变化的一个组成部分是α和β细胞质结构域的分离，但尚不清楚这种分离如何导致粘着斑（FA）形成所需的下游信号的启动。为了解决这个问题，我们使用了一种交换的整合素异二聚体，其中α和β链的细胞外结构域连接到它们相对的跨膜和细胞质结构域。这种受体能够正常结合配体，但不能促进FA形成。然后，我们用其膜近端区域的重复序列或不相关的α螺旋间隔物取代β细胞质结构域。这种取代部分恢复了这些交换受体中的FA形成，并挽救了整合素介导的信号传导的其他方面，包括细胞骨架组织、运动性和几种酪氨酸磷酸化依赖性信号。我们认为，细胞质结构域的分离导致远端β尾巴二级结构的改变，从而启动导致细胞骨架重组的下游信号。
