CELL SURFACE ACTIVITIES IN LIPOPROTEIN CATABOLISM

描述（改编自申请人摘要）：本申请中的研究 建议研究HSPG与 LRP或巨蛋白，其是细胞清除脂蛋白/脂肪酶所必需的。 使用定量生物化学程序，我们将确定配体是否是1） 转移到内吞受体进行内化后， 初始结合HSPG，或2）如果HSPG和内吞受体是 与结合的配体共内化。这些研究将有助于确定LRP是否 并且巨蛋白可以通过以下方式调节配体螯合或脂解酶活性： 控制存在于细胞表面上的HSPG的量， 内吞作用我们还计划鉴定蛋白聚糖样分子， 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，建议进行研究，以定量评估变化 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积累中的功能作用。 支持性数据已经发现，LRP和巨蛋白的表达在 分化的脂肪细胞对糖皮质激素和cAMP依赖性 信号通路根据这一观察，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，负责调节其表达水平， 脂肪细胞发育总之，这些研究将有助于1）更好地定义 LRP和巨蛋白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） 提高我们对心血管健康和疾病的认识， 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.