Koch Leonie, Feicht Sabine, Sun Rui, Sen Arnab, Krahn Michael P
Molecular and Cellular Anatomy , University of Regensburg , Universitätsstr. 31, 93053 Regensburg , Germany.
R Soc Open Sci. 2016 Nov 16;3(11):160776. doi: 10.1098/rsos.160776. eCollection 2016 Nov.
In , the adaptor protein Stardust is essential for the stabilization of the polarity determinant Crumbs in various epithelial tissues, including the embryonic epidermis, the follicular epithelium and photoreceptor cells of the compound eye. In turn, Stardust recruits another adaptor protein, PATJ, to the subapical region to support adherens junction formation and morphogenetic events. Moreover, Stardust binds to Lin-7, which is dispensable in epithelial cells but functions in postsynaptic vesicle fusion. Finally, Stardust has been reported to bind directly to PAR-6, thereby linking the Crumbs-Stardust-PATJ complex to the PAR-6/aPKC complex. PAR-6 and aPKC are also capable of directly binding Bazooka (the homologue of PAR-3) to form the PAR/aPKC complex, which is essential for apical-basal polarity and cell-cell contact formation in most epithelia. However, little is known about the physiological relevance of these interactions in the embryonic epidermis of . Thus, we performed a structure-function analysis of the annotated domains with GFP-tagged Stardust and evaluated the localization and function of the mutant proteins in epithelial cells of the embryonic epidermis. The data presented here confirm a crucial role of the PDZ domain in binding Crumbs and recruiting the protein to the subapical region. However, the isolated PDZ domain is not capable of being recruited to the cortex, and the SH3 domain is essential to support the binding to Crumbs. Notably, the conserved N-terminal regions (ECR1 and ECR2) are not crucial for epithelial polarity. Finally, the GUK domain plays an important role for the protein's function, which is not directly linked to Crumbs stabilization, and the L27N domain is essential for epithelial polarization independently of recruiting PATJ.
在[具体生物或组织名称未提及]中，衔接蛋白星尘对于多种上皮组织中极性决定因子面包屑的稳定至关重要，这些上皮组织包括胚胎表皮、滤泡上皮和复眼中的感光细胞。反过来，星尘会将另一种衔接蛋白PATJ招募到顶下区域，以支持黏附连接的形成和形态发生事件。此外，星尘与Lin-7结合，Lin-7在上皮细胞中并非必需，但在突触后囊泡融合中发挥作用。最后，据报道星尘可直接与PAR-6结合，从而将面包屑-星尘-PATJ复合物与PAR-6/aPKC复合物连接起来。PAR-6和aPKC也能够直接结合巴祖卡（PAR-3的同源物）形成PAR/aPKC复合物，这对于大多数上皮细胞的顶-基极性和细胞-细胞接触形成至关重要。然而，对于这些相互作用在[具体生物或组织名称未提及]胚胎表皮中的生理相关性知之甚少。因此，我们用绿色荧光蛋白标记的星尘对注释结构域进行了结构-功能分析，并评估了突变蛋白在胚胎表皮上皮细胞中的定位和功能。此处呈现的数据证实了PDZ结构域在结合面包屑并将该蛋白招募到顶下区域中起着关键作用。然而，分离的PDZ结构域无法被招募到皮质，而SH3结构域对于支持与面包屑的结合至关重要。值得注意的是，保守的N端区域（ECR1和ECR2）对于上皮极性并非至关重要。最后，GUK结构域对该蛋白的功能起着重要作用，这与面包屑的稳定并无直接关联，而L27N结构域对于上皮极化至关重要，且与招募PATJ无关。
