ORGANIZATION OF APICAL CELL JUNCTIONS IN EYE

描述(申请人提供)：顶基细胞的极性对上皮形态发生是必不可少的。视网膜分化涉及细胞间相互作用和连接组织的动态过程。果蝇的复眼为研究这种细胞过程提供了一个极好的生殖模型。感光细胞分化的一个标志是顶端细胞膜中感光器官或横纹肌层的爆炸性生长。果蝇Crumbs(CRB)蛋白在组织光感受器的横纹节和粘着连接(AJ)中起着关键作用。我们的目标是剖析CRB在光感受器形态发生中作用的分子基础。 CRB是一种跨膜蛋白，具有较短的细胞质尾巴。这个胞内区(CRB Intra)可以招募一个Maguk家族蛋白Stardust(SDT)和一个PDZ结构域蛋白Discs-Lost(DLT)形成蛋白质复合体。CRB复合体的一个重要功能是招募AJ，诱导和/或维持横纹肌的生长。由Bazooka、Par6和非典型PKC(APKC)组成的另一个保守的蛋白质复合体对上皮的极性至关重要。有趣的是，Par6在顶膜上与DLT共定位并直接相互作用。一种新的DLT同系物DLT-like(DLK)也直接与Par6结合。因此，DLT和DLK可能调节CRB和PAR复合体之间的串扰。 为了验证这一假说，我们将用遗传学、分子和细胞化学的方法分析CRB和PAR复合体在光感受器形态发生中的作用。将讨论CRB和PAR功能是否需要DLT和DLK。将研究DLT和DLK的特定相互作用结构域及其在PAR复合体中的功能。此外，还将确定参与细胞骨架向CRB和PAR复合体运输的特定蛋白质，以了解AJ的形成机制。 果蝇和人类CRB蛋白在结构和功能上都是保守的。人类CRB1与视网膜疾病有关，包括视网膜色素变性12和Leber先天性黑便。因此，研究CRB和PAR复合体之间的新的相互作用将为人类CRB1在正常视网膜发育和与CRB1突变相关的疾病中的作用机制提供重要的见解。

DESCRIPTION (provided by applicant): Apico-basal cell polarity is essential for epithelial morphogenesis. Retinal differentiation involves dynamic process of cell-cell interactions and junctional organizations. The Drosophila compound eye provides an excellent gentic model for studying such cellular processes. A hallmark of photoreceptor differentiation is an explosive growth of the photosensitive organ, or rhabdomere, in the apical cell membrane. Drosophila Crumbs (Crb) protein plays a key role in organizing the rhabdomere and adherens junction (AJ) of photoreceptors. Our goal is to dissect the molecular basis of Crb function in the photoreceptor morphogenesis. Crb is a transmembrane protein with a short cytoplasmic tail. This intracellular domain (Crb intra) can recruit a MAGUK family protein Stardust (Sdt) and a PDZ domain protein Discs-lost (Dlt) to form a protein complex. An important function of Crb complex is to recruit AJs and to induce and/or maintain growth of rhabdomeres. Another conserved protein complex composed of Bazooka, Par6 and atypical PKC (aPKC) is critical for epithelial polarity. Interestingly, Par6 colocalizes and directly interacts with Dlt at the apical membrane. A novel Dlt homolog, Dlt-like (Dlk), also directly binds Par6. Therefore, it is proposed that Dlt and Dlk may regulate the cross-talk between the Crb and Par complexes. To test this hypothesis, the function of Crb and Par complexes in photoreceptor morphogenesis will be analyzed by genetic, molecular and cytochemical methods. Whether Dlt and Dlk are required for Crb and Par functions will be addressed. Specific interaction domains of Dlt and Dlk and their functions in the Par complex will be examined. In addition, specific proteins involved in trafficking of cytoskeletons to the Crb and Par complexes will be identified to understand the mechanism of AJ formation. Drosophila and human Crb proteins are conserved in structure and function. Human CRB1 is associated with retinal diseases including retinitis pigmentosa 12 and Leber Congenital Amaurosis. Therefore, studies on novel interaction of Crb and Par complexes will provide important insights into the mechanism of human CRB 1 in normal retinal development and diseases associated with CRB1 mutations.