Graduate Program in Genetics, University of Wisconsin-Madison, 1117 W. Johnson Street, Madison, WI 53706, USA.
Curr Biol. 2012 Oct 23;22(20):1891-9. doi: 10.1016/j.cub.2012.08.024. Epub 2012 Sep 13.
In multicellular organisms, cell-cell junctions are involved in many aspects of tissue morphogenesis. α-catenin links the cadherin-catenin complex (CCC) to the actin cytoskeleton, stabilizing cadherin-dependent adhesions.
To identify modulators of cadherin-based cell adhesion, we conducted a genome-wide RNAi screen in C. elegans and uncovered MAGI-1, a highly conserved protein scaffold. Loss of magi-1 function in wild-type embryos results in disorganized epithelial migration and occasional morphogenetic failure. MAGI-1 physically interacts with the putative actin regulator AFD-1/afadin; knocking down magi-1 or afd-1 function in a hypomorphic α-catenin background leads to complete morphogenetic failure and actin disorganization in the embryonic epidermis. MAGI-1 and AFD-1 localize to a unique domain in the apical junction and normal accumulation of MAGI-1 at junctions requires SAX-7/L1CAM, which can bind MAGI-1 via its C terminus. Depletion of MAGI-1 leads to loss of spatial segregation and expansion of apical junctional domains and greater mobility of junctional proteins.
Our screen is the first genome-wide approach to identify proteins that function synergistically with the CCC during epidermal morphogenesis in a living embryo. We demonstrate novel physical interactions between MAGI-1, AFD-1/afadin, and SAX-7/L1CAM, which are part of a functional interactome that includes components of the core CCC. Our results further suggest that MAGI-1 helps to partition and maintain a stable, spatially ordered apical junction during morphogenesis.
在多细胞生物中，细胞-细胞连接参与组织形态发生的许多方面。α-连环蛋白将钙粘蛋白-连环蛋白复合物（CCC）与肌动蛋白细胞骨架连接起来，稳定钙粘蛋白依赖性附着。
为了鉴定基于钙粘蛋白的细胞黏附的调节剂，我们在秀丽隐杆线虫中进行了全基因组 RNAi 筛选，发现了高度保守的蛋白支架 MAGI-1。野生型胚胎中 magi-1 功能的丧失导致上皮细胞迁移紊乱和偶尔的形态发生失败。MAGI-1 与假定的肌动蛋白调节因子 AFD-1/afadin 物理相互作用；在弱α-连环蛋白背景下敲低 magi-1 或 afd-1 功能会导致胚胎表皮中的完全形态发生失败和肌动蛋白紊乱。MAGI-1 和 AFD-1 定位于顶端连接的独特域，并且 MAGI-1 在连接中的正常积累需要 SAX-7/L1CAM，它可以通过其 C 末端结合 MAGI-1。MAGI-1 的耗竭导致顶端连接域的空间分离和扩展的丧失以及连接蛋白的更大流动性。
我们的筛选是首次在活体胚胎中鉴定在表皮形态发生过程中与 CCC 协同作用的蛋白质的全基因组方法。我们证明了 MAGI-1、AFD-1/afadin 和 SAX-7/L1CAM 之间存在新的物理相互作用，它们是包括核心 CCC 组件的功能相互作用组的一部分。我们的结果进一步表明，MAGI-1 有助于在形态发生过程中划分和维持稳定的、空间有序的顶端连接。
