CELL SURFACE ACTIVITIES IN LIPOPROTEIN CATABOLISM

描述(改编自申请人的摘要)：本申请书中的研究 建议研究HSPG和HSPG之间的这种明显的协同关系 LRP或megalin，这是细胞清除脂蛋白/脂肪酶所必需的。 使用定量生化程序，我们将确定配体是否为1) 转移到内胞受体进行内化 最初与HSPG结合，或2)如果HSPG和内吞受体 与结合的配体共内化。这些研究将有助于确定LRP是否 而巨蛋白可以通过以下方式调节配体隔离或脂解酶的活性 通过控制细胞表面存在的HSPG的量 内吞作用。我们还计划鉴定类似蛋白多糖的分子， 与巨蛋白和LRP共沉淀，并确定是否破坏其 与LRP和megalin的相互作用阻止细胞摄取脂蛋白。 作为第二个目标，提出了定量评估这些变化的研究 在脂肪细胞分化过程中LRP和megalin的表达，并评估 这些受体在细胞内脂质堆积中的功能作用。 支持数据发现LRP和megalin在脑内的表达。 脂肪细胞分化对糖皮质激素和cAMP依赖的反应 信号通路。根据这一观察结果，申请人计划确定 并表征了LRP启动子中的顺式和反式激活元件 和巨蛋白，负责调节它们的表达水平 脂肪细胞发育。总之，这些研究将帮助1)更好地定义 LRP和megalin在脂蛋白清除中的功能作用，2)开始 了解其组织特异性表达的分子基础，以及3) 增进我们对心血管健康和疾病的知识，例如 动脉粥样硬化和肥胖。

DESCRIPTION(adapted from applicant's abstract): Studies in this application propose to investigate this apparent synergistic relationship between HSPG and LRP or megalin, that is necessary for lipoprotein/lipase clearance by cells. Using quantitative biochemical procedures we will determine if ligands are 1) transferred to the endocytic receptors for internalization following their initial binding to HSPG, or 2) if the HSPG and endocytic receptors are cointernalized with bound ligand. These studies will aid in determining if LRP and megalin can regulate ligand sequestration or lipolytic enzyme activities by controlling the amount of HSPG that is present on the cell surface through endocytosis. We also plan to identify the proteoglycan-like molecule that coprecipitates with megalin and LRP, and determine if disrupting its interactions with LRP and megalin prevents the uptake of lipoproteins by cells. As a second goal, studies are proposed to quantitatively evaluate the changes in LRP and megalin expression during adipocyte differentiation, and assess the functional role of these receptors in intracellular lipid accumulation. Supporting data have found that expression of LRP and megalin in differentiating adipocytes is responsive to glucocorticoid- and cAMP-dependent signaling pathways. Based on this observation the applicant plans to identify and characterize the cis- and trans-activating elements in the promoters of LRP and megalin that are responsible for regulating their expression levels during adipocyte development. Together, these studies will help 1) better define the functional roles of LRP and megalin in lipoprotein clearance, 2) begin to understand the molecular basis of their tissue-specific expression, and 3) advance our knowledge of cardiovascular health and disease such as atherosclerosis and obesity.