SCAVENGER RECEPTOR AND G PROTEIN FUNCTION IN MACROPHAGES

描述：（改编自研究者摘要）：A类清道夫 受体（SR-A）的特征在于其结合乙酰化LDL的能力 （AcLDL）和介导细胞中大量胆固醇酯积累。它 一般认为SR-A通过胞吞作用组成性内化 在网格蛋白覆盖的凹坑里然而，细胞质部分的重要性， SR-A相对被忽视，因此， 受体尚未确定，关于细胞质 调节SR-A介导的内吞作用的信号。越来越多的证据表明， 表明AcLDL激活百日咳毒素敏感的细胞内 信号级联表明SR-A介导的摄取与 激活Gi/o蛋白。私家侦探和他的团队已经积累了 数据表明，在巨噬细胞中，AcLDL的摄取被 百日咳毒素治疗表明抑制Gi/o减弱SR-A 功能关于SR-A与Gi/o相互作用的机制细节 这些PTX敏感的G蛋白对脂蛋白摄取的调节 巨噬细胞中缺乏蛋白质。这一提议是为了考验中央 AcLDL促进特定细胞质间相互作用的假说 SR-A的结构域与Gi/o蛋白结合，导致Gi/o蛋白活化， 增加脂蛋白摄取。PI将首先通过以下方式确定机制： 其抑制Gi/o降低SR-A依赖性脂蛋白摄取。他将 确定三种可能的机制对减少 PTX处理的巨噬细胞中修饰的脂蛋白的摄取，包括： 细胞表面上存在的受体数量减少，B）降低的能力 c）SR-A介导的结合脂蛋白的速率降低， 内化贡献机制对Gi/o的依赖程度 还将测定β-介导的蛋白激酶活化。第二个目标 是利用突变分析来确定SR-A的胞质序列 参与受体内化、Gi/o激活和Gi/o调节 信号通路

DESCRIPTION: (Adapted from the Investigator's Abstract): Class A scavenger receptors (SR-A) are characterized by their ability to bind acetylated LDL (AcLDL) and to mediate substantial cholesterol ester accumulation in cells. It is generally thought that SR-A is constitutively internalized via endocytosis in clathrin-coated pits. However, the importance of the cytoplasmic portion of SR-A has been relatively neglected such that an internalization motif for the receptor has not been identified and little is known regarding the cytoplasmic signals that regulate SR-A-mediated endocytosis. Moreover, increasing evidence indicates that AcLDL activates pertussis toxin-sensitive intracellular signaling cascades indicating that SR-A-mediated uptake is coupled to activation of a Gi/o protein. The PI and his team have accumulated substantial data demonstrating that in macrophages, uptake of AcLDL is attenuated by pertussis toxin treatment suggesting that inhibiting Gi/o attenuates SR-A function. Mechanistic details regarding the interaction of SR-A with Gi/o proteins and the regulation of lipoprotein uptake by these PTX-sensitive G proteins in macrophages are lacking. This proposal is to test the central hypothesis that AcLDL promotes an interaction between specific cytoplasmic domains of SR-A with Gi/o proteins resulting in Gi/o protein activation and increased lipoprotein uptake. The PI will first determine the mechanism by which inhibiting Gi/o decreases SR-A dependent lipoprotein uptake. He will define the relative contribution of three possible mechanisms for the reduced uptake of modified lipoprotein in PTX-treated macrophages including; a) decreased number of receptors present on the cell surface, b) a reduced ability of SR-A to bind lipoprotein, and c) a decreased rate of SR-A-mediated internalization. The extent to which a contributing mechanism depends on Gi/o -mediated activation of protein kinase will also be determined. The second goal is to use mutational analysis to define the cytoplasmic sequence of SR-A involved in receptor internalization, Gi/o activation, and regulation by Gi/o signaling pathways.