Targeting By mLin-7 Binding Partners In Renal Epithelia

描述（改编自申请人的摘要）：细胞靶向 上皮细胞的顶膜或基底膜的表面蛋白是 对肾功能至关重要最近的研究表明， 蛋白质-蛋白质相互作用结构域在这种极化靶向中的作用 proteins.这项工作主要集中在PSD-95 IDlg/ZO-1（PDZ）的作用上。 结构域蛋白在大脑中，PDZ结构域蛋白结合到羧基末端， 并将这些蛋白质聚集在突触中。PDZ 结构域蛋白可能在靶向细胞中发挥类似的作用， 上皮细胞表面蛋白。在秀丽隐杆线虫中，三个基因lin-2， lin-7和lin-10对于蠕虫的基底外侧靶向很重要 EGF-受体。我们的小组已经确定了这些PDZ结构域的哺乳动物同源物 蛋白质，并在基底外侧检测到mLin-2和mLin-7的稳定复合物 肾上皮细胞表面。哺乳动物Lin-7的PDZ结构域可以结合到 甜菜碱γ-氨基丁酸转运蛋白-i的羧基末端尾 （BGT-1），并且可能在BGT-1在细胞中的保留中具有重要作用。 肾上皮细胞的基底外侧表面。然而， 将mLin-7靶向至基底外侧表面尚不清楚。最近的研究表明 与mLin-2的结合可能在这一过程中发挥重要作用， 结合mLin-7的氨基末端的其它蛋白质也可以 重要.在本提案中，我们将重点关注其中两个新确定的 我们称之为帕尔斯1和Pals 2的mLin-7结合蛋白。像mLin-2这些 蛋白质几乎完全由蛋白质-蛋白质相互作用结构域组成 包括PDZ、Src同源物3和鸟苷酸激酶结构域，其具有可变的 氨基末端区域。我们还发现了一个名为L27的新结构域 在这些蛋白质中重复并介导与 mLin-7。我们已经证明了帕尔斯1和帕尔斯2的差异靶向， 肾上皮细胞，并已开始表征其与 不同的绑定伙伴。我们假设这些不同的结合伴侣 控制帕尔斯蛋白的差异靶向并影响其功能 靶向蛋白质如BGT-1。为了验证这些假设，我们将研究 细胞表面不同蛋白质-蛋白质相互作用域的作用 靶向这些蛋白质并鉴定与麻痹相关的新蛋白质 Pals 2的。我们还将研究mLin-7的重要性及其结合 BGT- 1转运蛋白的靶向和活性。这项工作 将允许对mLin-7系统在肾脏疾病中的功能有新的认识。 上皮细胞，并增加我们对基本机制的理解， 极化细胞中的蛋白质靶向。

DESCRIPTION (Adapted from the Applicant's Abstract): The targeting of cell surface proteins to apical or basolateral membranes of epithelial cells is crucial for proper renal function. Recent studies have suggested an important role for protein-protein interaction domains in this polarized targeting of proteins. Much of this work has focused on the role of PSD-95IDlg/ZO-1 (PDZ) domain proteins. In the brain, PDZ domain proteins bind to the carboxy-terminus of channels as well as receptors and cluster these proteins in synapses. PDZ domain proteins are likely to play a similar role in the targeting of cell surface proteins in epithelia. In Caenorhabditis elegans, three genes lin-2, lin-7 and lin-10, are important for the basolateral targeting of the worm EGF-Receptor. Our group has identified mammalian homologues of these PDZ domain proteins and detected a stable complex of mLin-2 and mLin-7 at the basolateral surface of renal epithelia. The PDZ domain of mammalian Lin-7 can bind to the carboxy-terminal tail of the betaine gamma amino butyric acid transporter-i (BGT-l) and may have an important role in the retention of BGT-1 at the basolateral surface of renal epithelia. However the exact mechanism that targets mLin-7 to the basolateral surface is unclear. Recent studies indicate that binding to mLin-2 may have an important role in this process but additional proteins that bind to the amino-terminus of mLin-7 may also be important. In this proposal we will focus on two of these newly identified mLin-7 binding proteins that we call Pals 1 and Pals2. Like mLin-2 these proteins are composed almost exclusively of protein-protein interaction domains including PDZ, Src Homology 3 and Guanylate Kinase domains with variable amino-terminal regions. We have also identified a new domain called the L27 domain that is repeated in these proteins and mediates the interaction with mLin-7. We have demonstrated differential targeting of Pals 1 and Pals2 in kidney epithelial cells and have begun to characterize their association with distinct binding partners. We hypothesize that these distinct binding partners control the differential targeting of the Pals proteins and affect the function of targeted proteins such as BGT-l. To test these hypotheses we will examine the role of the different protein-protein interaction domains on cell surface targeting of these proteins and identify new proteins that associate with Palsi and Pals2. We will also examine the importance of mLin-7 and its binding partners on the targeting and activity of the BGT- 1 transporter. This work will allow new insights into the function of the mLin-7 system in renal epithelia and increase our understanding of the basic mechanisms underlying protein targeting in polarized cells.