Regulation of SMG Development by Adhesion Receptors

描述（由申请人提供）：本研究的长期目标是阐明细胞-细胞和细胞-基质粘附受体在调节唾液颌下腺（SMG）发育中的作用。SMG通过分支形态发生从上皮芽发育成树形结构，由一系列导管终止于分泌腺泡。SMG的形态发生涉及生长周期和新芽形成，与导管结构的扩张和分支紧密协调。引导腺泡和导管祖细胞形成有组织的三维结构的规范、扩张和分化的调控信号在很大程度上是未知的。由于细胞-细胞和细胞-基质相互作用已被证明可调节上皮组织发育过程中的形态发生变化，因此我们将重点放在了e -钙粘蛋白（一种主要的唾液细胞-细胞粘附受体）和1321整合素（层粘连蛋白的受体）上，层粘连蛋白是SMG基底膜的主要成分。我们的研究表明，腺泡细胞和导管细胞的命运模式是在萌芽阶段建立的，并在整个形态发生过程中维持。腺泡祖细胞局限于与基底膜接触的外周细胞层，而内部芽细胞包括增殖性导管祖细胞和非增殖性分化性导管细胞。在SMG形态发生过程中，这些细胞的多种功能都需要e -钙粘蛋白。在腺泡祖细胞中，E-cadherin通过与1321整合素的相互作用稳定连接，调节腺泡祖细胞增殖与新芽形成的协调。在肾细胞中也发现了e -钙粘蛋白连接稳定的类似机制，其中1321整合素组织了多蛋白支架。我们的研究还表明，大量增殖的导管祖细胞通过Src的活性维持未成熟的e -钙粘蛋白连接。在后来的形态发生中，Src似乎被磷酸酶、SHP2和/或PTP<的募集所抵消，以促进导管的形成。在导管发育过程中，稳定的E-cadherin连接可能通过激活PI3K/Akt通路来信号分化和保护细胞免于凋亡死亡。我们的假设是，e -钙粘蛋白介导的SMG形态发生和分化的不同方面的功能是通过与结构和信号分子的关联来调节的。我们建议通过研究SMG形态发生过程中不同细胞群中E-cadherin粘附活性变化的机制来验证这一假设，目的有三个：1)研究1321整合素是否通过支架蛋白的募集来稳定腺泡祖细胞中的E-cadherin连接；2)检查SMG生长与导管细胞分化的协调是否涉及Src对E-cadherin功能的调节以及随后从E-cadherin连接点到PI3激酶的信号传导；3)检验蛋白磷酸酶在发育中的SMG中唾液细胞成熟过程中调节e -钙粘蛋白细胞-细胞接触的假设。唾液腺疾病，包括癌症和干燥综合征，其特征是细胞-基质和细胞-细胞粘附的破坏。我们主要研究细胞-细胞和细胞-基质黏附受体的功能及其在唾液腺发育过程中的调控。了解这些粘附受体如何驱动形态发生事件，对于设计针对患病唾液组织的有效治疗方法，以及唾液腺和组织替代的生物工程至关重要。

DESCRIPTION (provided by applicant): The long term goal of this study is to elucidate the roles of cell-cell and cell-matrix adhesion receptors in the regulation of the salivary submandibular gland (SMG) development. SMG develops through branching morphogenesis from an epithelial bud into a tree-like structure consisting of an array of ducts terminating in secretory acini. SMG morphogenesis involves cycles of growth and new bud formation that are tightly coordinated with the expansion and branching of ductal structures. The regulatory signals that guide the specification, expansion and differentiation of acinar and ductal progenitors into an organized three dimensional structure are largely unknown. Because cell-cell and cell-matrix interactions have been shown to regulate morphogenetic changes during epithelial tissue development, we have focused on E-cadherin, a principal salivary cell-cell adhesion receptor, and 1321 integrin, the receptor for laminin, a major component of the basement membrane in the SMG. Our studies have shown that the patterns of acinar and ductal cell fate are established at the initial bud stage and maintained throughout morphogenesis. Acinar progenitors are restricted to the peripheral cell layer in contact with the basement membrane, while the interior bud cells comprise proliferating ductal progenitors and non-proliferating differentiating duct cells. E-cadherin is required for diverse functions of these cells during SMG morphogenesis. In the acinar progenitor cells, E-cadherin junctions are stabilized through the interaction with 1321 integrin to regulate the coordination of acinar progenitor cell proliferation with new bud formation. Similar mechanism for stabilization of E-cadherin junctions is found in renal cells, where 1321 integrin organizes multiprotein scaffolds. Our studies also show that the mass producing proliferating ductal progenitors maintain immature E-cadherin junctions by the activity of Src. Later in morphogenesis, Src appears to be counteracted by the recruitment of phosphatases, SHP2 and/or PTP< to promote duct formation. During duct development, stable E-cadherin junctions signal differentiation and protection from apoptotic death most likely through the activation of PI3K/Akt pathway. Our hypothesis is that E-cadherin-mediated functions in different aspects of SMG morphogenesis and differentiation are regulated by association with structural and signaling molecules. We propose to test this hypothesis by investigating the mechanisms underlying changes in E-cadherin adhesive activity in distinct cell populations during SMG morphogenesis in three aims: 1) examine whether 1321 integrin stabilizes E-cadherin junctions in the acinar progenitor cells through the recruitment of scaffold proteins; 2) examine if coordination of SMG growth with ductal cell differentiation involves regulation of E-cadherin function by Src and subsequent signaling from E-cadherin junctions to PI3 kinase; and 3) examine the hypothesis that protein phosphatases regulate E-cadherin cell-cell contacts during maturation of salivary cells in the developing SMG. Diseases of the salivary glands, including cancer and Sjogren's Syndrome, are characterized by the disruption of cell-matrix and cell-cell adhesion. Our studies focus on the functions of cell-cell and cell-matrix adhesion receptors and their regulation during salivary gland development. Understanding how these adhesion receptors drive morphogenetic events is essential for the design of effective therapeutics that will target diseased salivary tissues, as well as for the bioengineering of salivary glands and tissue replacement.