Biomedical Research Foundation, Academy of Athens, Division of Genetics, Soranou Efessiou 4, 11527 Athens, Greece.
J Cell Sci. 2011 Apr 15;124(Pt 8):1316-27. doi: 10.1242/jcs.081422.
Integrin-linked kinase (ILK) is an essential component of a multiprotein complex that links actin to the plasma membrane. Here, we have used a genetic approach to examine the molecular interactions that are essential for the assembly of this ILK-containing complex at Drosophila muscle attachment sites (MASs). We show that, downstream of integrins, talin plays a decisive role in the recruitment of three proteins: ILK, PINCH and paxillin. The accumulation of ILK at MASs appears to follow an amplification mechanism, suggesting that numerous binding sites are generated by minimal levels of the upstream integrin and talin effectors. This property suggests that ILK functions as an essential hub in the assembly of its partner proteins at sites of integrin adhesion. We found that PINCH stability, and its subcellular localization at MASs, depends upon ILK function, but that ILK stability and localization is not dependent upon PINCH. An in vivo structure-function analysis of ILK demonstrated that each ILK domain has sufficient information for its independent recruitment at embryonic MASs, whereas at later developmental stages only the kinase domain was effectively recruited. Our data strengthen the view that the ILK complex is assembled sequentially at sites of integrin adhesion by employing multiple molecular interactions, which collectively stabilize the integrin-actin link.
整合素连接激酶（ILK）是一种将肌动蛋白与质膜连接的多蛋白复合物的重要组成部分。在这里，我们使用遗传方法研究了对于在果蝇肌球蛋白附着点（MASs）组装这种包含 ILK 的复合物至关重要的分子相互作用。我们表明，在整合素的下游，talin 在招募三种蛋白质：ILK、PINCH 和桩蛋白方面起着决定性的作用。ILK 在 MASs 的积累似乎遵循一种放大机制，表明通过最小水平的上游整合素和 talin 效应物产生了许多结合位点。这一特性表明，ILK 作为整合素黏附部位其伴侣蛋白组装的重要枢纽发挥作用。我们发现，PINCH 的稳定性及其在 MASs 的亚细胞定位依赖于 ILK 的功能，但 ILK 的稳定性和定位不依赖于 PINCH。对 ILK 的体内结构-功能分析表明，每个 ILK 结构域都具有足够的信息使其能够独立地在胚胎 MASs 上被招募，而在稍后的发育阶段，只有激酶结构域能有效地被招募。我们的数据强化了这样的观点，即通过采用多种分子相互作用，ILK 复合物在整合素黏附部位按顺序组装，从而共同稳定整合素-肌动蛋白连接。
