Characterization of the role of ARH on LDLR function

描述（由申请人提供）：低密度脂蛋白受体（LDLR）是主要的内吞受体，可将低密度脂蛋白及其脂蛋白前体VLDL残体从循环中清除。LDLR功能缺陷可提高ldl -胆固醇水平（高胆固醇血症），促进动脉粥样硬化和冠状动脉疾病的早期发病。LDLR长期以来被认为是一种简单的内吞受体，当受体进行组成性内吞作用时携带结合脂蛋白。先前资助期支持的研究表明，LDLR更复杂，因为LDLR在脂蛋白摄取过程中区分LDL和VLDL残留物。本提案的初步数据表明LDL和VLDL通过内体的运输方式不同，这种运输差异使得LDL比VLDL残余物降解得更快。对每种脂蛋白使用不同的内吞机制提供了独立调节每个过程的机会。与这种可能性相一致的是，我们的初步数据表明，LDLR摄取LDL需要ARH接头蛋白的s -亚硝基化，而不是VLDL残体的摄取。本提案的两个目标是：(i)确定LDLR在脂蛋白摄取过程中如何区分LDL和VLDL残留物；（ii）确定ARH亚硝基化如何调节LDL的摄取。为了实现第一个目标，拟议的研究将验证这样一个假设，即多个LDLR结合单个VLDL残余物的能力决定了LDLR如何内化VLDL残余物。这些研究还将描述LDL和VLDL在核内体中的加工差异。为了实现第二个目标，提出的研究将验证ARH亚硝基化对于将LDLR-LDL复合物靶向涂覆凹坑是必要的假设。第二个目标下的研究也将验证一氧化氮调节ARH功能控制体内LDL摄取的假设。

DESCRIPTION (provided by applicant): The LDL receptor (LDLR) is the principal endocytic receptor that removes both LDL and its lipoprotein precursor, VLDL remnants, from the circulation. Defects in LDLR function elevate LDL-cholesterol levels (hypercholesterolemia), promoting atherosclerosis and early onset of coronary artery disease. The LDLR has long been viewed as a simple endocytic receptor, carrying in bound lipoprotein when the receptor undergoes constitutive endocytosis. Studies supported by the prior funded period show that the LDLR is more sophisticated in that the LDLR distinguishes between LDL and VLDL remnants during lipoprotein uptake. Preliminary data for this proposal shows that LDL and VLDL traffic differently through endosomes and that this trafficking difference allows LDL to be degraded faster than VLDL remnants. Use of different endocytic mechanisms for each lipoprotein provides the opportunity to regulate each process independently. Consistent with this possibility, our preliminary data show that S-nitrosylation of the ARH adaptor protein is required for LDL uptake, but not VLDL remnant uptake, by the LDLR. The two goals of this proposal are (i) to determine how the LDLR distinguishes between LDL and VLDL remnants during lipoprotein uptake and (ii) to determine how ARH nitrosolation regulates LDL uptake. To achieve the first goal, proposed studies will test the hypothesis that the ability of multiple LDLRs to bind individual VLDL remnants informs how the LDLR internalizes VLDL remnants. These studies will also characterize how LDL and VLDL are differentially processed in endosomes. To achieve the second goal, the proposed studies will test the hypothesis that ARH nitrosylation is necessary for targeting LDLR-LDL complexes to coated pits. Studies under the second goal will also test the hypothesis that nitric oxide regulation of ARH function controls LDL uptake in vivo.