SCAVENGER RECEPTOR AND G PROTEIN FUNCTION IN MACROPHAGES

描述：(改编自《调查者摘要》)：A类食腐动物 受体(SR-A)的特征是其结合乙酰化低密度脂蛋白的能力 (AcLDL)，并介导细胞内大量的胆固醇酯蓄积。它 通常认为SR-A是通过内吞作用被结构性内化的 在笼罩着笼罩的坑里。然而，细胞质部分的重要性 SR-A一直被相对忽视，以至于一个内化基序 受体尚未确定，关于细胞质的了解也很少 调节SR-A介导的内吞作用的信号。此外，越来越多的证据表明 提示AcLDL激活百日咳毒素敏感的细胞内 信号级联表明SR-A介导的摄取偶联到 Gi/o蛋白的激活。私家侦探和他的团队积累了 数据显示，在巨噬细胞中，AcLDL的摄取被减弱 百日咳毒素治疗提示抑制Gi/o可减弱SR-A 功能。SR-A与GI/O相互作用的机制细节 蛋白质和这些PTX敏感G对脂蛋白摄取的调节 巨噬细胞中的蛋白质缺乏。这一提议是为了考验中央银行 AcLDL促进特定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蛋白激活和 增加脂蛋白摄取。PI将首先通过以下方式确定机制 抑制Gi/o可减少SR-A依赖的脂蛋白摄取。他会的 定义三种可能的机制对减少的 PTX处理的巨噬细胞摄取修饰的脂蛋白包括：a) 细胞表面受体数量减少，b)能力降低 SR-A结合脂蛋白，以及c)SR-A介导的比率降低 内部化。贡献机制对GI/O的依赖程度 -介导的蛋白激酶的激活也将被确定。第二个目标 是用突变分析来确定SR-A的细胞质序列 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.