Caveolae structure and function

描述（由申请人提供）：小窝是在大多数细胞表面上发现的众所周知的膜结构域，其部分由烧瓶状形态、细胞质表面上由小窝蛋白和相对于周围膜的高浓度胆固醇组成的丝状被膜限定。小窝参与一种独特的内吞活动，能够携带分子到细胞质，特殊的内体区室和ER。该结构域对于致病性病毒和细菌的感染也是至关重要的。现在，小窝途径是更好地定义，重要的问题出现了有关的机制，内陷，出芽和交通，小窝如何实现其独特的蛋白质和脂质组成，以及机制参与提供结构脂质，如胆固醇。本提案概述了解决这三个问题的项目。第一个项目的重点是小窝内化的机制。我们已经确定了一个新的家庭的居民小窝蛋白，似乎通过连接不同亚型的PKC小窝蛋白-1和内化机制，调节内化机制。实验计划确定这些小窝蛋白适配器如何调节内化，并确定参与的分子。小窝包含一组独特的蛋白质，包括酪氨酸激酶受体和GPI锚定蛋白。在目标2中，我们将研究控制蛋白质定位于小窝的三种潜在机制。我们将探讨的一种机制是基于最近的发现，即由胆固醇和鞘脂组成的脂质壳包围的蛋白质被小窝特异性保留。最近，我们发现PDGF刺激PDGFRB在小窝中的泛素化，因此实验计划确定泛素化在控制PDGFRB从小窝退出中的作用。此外，我们将确定是否保留的蛋白质在小窝控制膜外和膜内的蛋白水解。第三个目标将集中在确定机制，供应胆固醇小窝和机制细胞使用的感觉量的胆固醇小窝和调节交付。这些研究将集中在三种蛋白质，涉及维持小窝胆固醇：小窝蛋白，胆固醇传感分子SR-BI和胆固醇调节的支架蛋白OSBP。更好地了解基本的小窝生物学可能会导致治疗人类疾病的新策略。

DESCRIPTION (provided by applicant): Caveolae are well-known membrane domains found on the surface of most cells that are defined in part by a flask-shaped morphology, a filamentous coat on the cytoplasmic surface composed of caveolin and a high concentration of cholesterol relative to surrounding membrane. Caveolae engage in a distinctive endocytic activity capable of carrying molecules to the cytoplasm, to special endosomal compartments and to the ER. This domain is also critical for infection by pathogenic viruses and bacteria. Now that the caveolae pathway is better defined, important questions arise about the mechanism of invagination, budding and traffic, how caveolae achieve their unique protein and lipid composition, and the machinery involved in supplying structural lipids like cholesterol. This proposal outlines projects to address these three issues. The first project focuses on the mechanism of caveolae internalization. We have identified a new family of resident caveolae proteins that appear to regulate the internalization machinery by linking different isoforms of PKC to caveolin-1 and the internalization machinery. Experiments are planned to define how these caveolin adapters regulate internalization and identify the molecules involved. Caveolae contain a unique set of proteins that includes tyrosine kinase receptors and GPI anchored proteins. In aim 2, we will look at three potential mechanisms for controlling the localization of proteins to caveolae. One mechanism we will explore is based on recent findings that proteins surrounded by a lipid shell composed of cholesterol and sphingolipid are specifically retained by caveolae. Recently we found that PDGF stimulates the ubiquitination of PDGFRB in caveolae, so experiments are planned to determine the role of ubiquitination in controlling the exit of PDGFRB from caveolae. In addition, we will determine if retention of proteins in caveolae is controlled by extramembrane and intramembrane proteolysis. The third aim will focus on identifying the machinery that supplies cholesterol to caveolae and the mechanism cells use to sense the amount of cholesterol in caveolae and regulate delivery. These studies will focus on three proteins that have been implicated in maintaining caveolae cholesterol: caveolin, the cholesterol sensing molecule SR-BI and the cholesterol-regulated scaffolding protein OSBP. A better understanding of basic caveolae biology may lead to new strategies for treating human disease.