Regulation of Drosophila Epithelial Polarity

描述（由申请人提供）：上皮细胞具有独特的结构，包括顶基极化质膜，这对其在胚胎发育和成人生理中的正常功能至关重要。上皮极性缺陷导致许多人类疾病，包括充血性心力衰竭和囊性纤维化，并与良性和恶性癌之间的转变有关。该项目的长期目标是了解产生上皮极性的细胞和分子机制。虽然细胞培养研究已经确定了负责启动上皮极化的表面线索，但调节细胞内部机制（如细胞骨架和蛋白质运输途径）执行极性的蛋白质的身份和机制尚不清楚。为了确定这些调节因子，我们在果蝇中使用遗传筛选来寻找胚胎、幼虫或成虫阶段上皮结构所需的蛋白质。我们的筛选已经确定了一种称为Scribble （Scrib）的细胞连接定位蛋白，它对上皮的极性在发育的所有三个阶段都是必不可少的。Scrib还作为肿瘤抑制因子，揭示了Scrib在果蝇中与极性和增殖控制有关。Scrib编码一种具有4个PDZ蛋白相互作用域的蛋白质，这表明它起着支架蛋白的作用。PDZ结构域存在于许多与细胞极性有关的蛋白质中，但PDZ介导的极化机制尚不清楚。本实验旨在通过分离Scrib与之相互作用介导极性的蛋白质来揭示Scrib极化活性的机制。

DESCRIPTION (provided by applicant): Epithelial cells have a distinct architecture, including an apico-basally polarized plasma membrane that is critical for their proper function in embryonic development and adult physiology. Defects in epithelial polarity contribute to many human diseases, including congestive heart failure and cystic fibrosis, and have been implicated in the transition between benign and malignant carcinomas. The long-term goal of this project is to understand the cellular and molecular mechanisms that generate epithelial polarity. While studies in cell culture have identified surface cues responsible for initiating epithelial polarization, the identity and mechanism of proteins that regulate the internal cellular machinery, such as the cytoskeleton and protein trafficking pathways, to execute polarity are not known. To identify such regulators we have used genetic screens in Drosophila to search for proteins required for epithelial architecture of the embryonic, larval, or adult stages. Our screens have identified a cell junction-localized protein called Scribble (Scrib) that is essential for the polarity of epithelia at all three stages of development. Scrib also acts as a tumor suppressor, revealing that Scrib links polarity and proliferation control in Drosophila. Scrib encodes a protein with four PDZ protein-protein interaction domains, suggesting that it acts as a scaffolding protein. PDZ domains are found in many proteins implicated in cell polarity, but the mechanism of PDZ-mediated polarization is not known. The experiments in this proposal are designed to uncover the mechanism of Scrib polarizing activity by isolating the proteins with which Scrib interacts to mediate polarity. The aims are: 1) Determine the Scrib interaction domains required for polarity regulation; 2) Biochemically isolate new members of the Scrib complex, and characterize their functions in epithelia; and 3) Genetically identify additional genes in the Scrib pathway as modifiers of Scrib activity. Given the strong conservation of Scrib structure, function, and localization across phylogeny, it is likely that our results will provide new insight into the mechanisms of epithelial polarity in all animals, and inform our understanding of how loss of epithelial cytoarchitecture may contribute to human tumor progression.