Defective isoforms of ApoE induce atherogenesis via unfolded protein responses

描述（由申请方提供）：本项目研究了载脂蛋白E受体2（apoER 2）和极低密度脂蛋白受体（VLDLR）的抗动脉粥样硬化作用，使用部分reelin肽（R5-6C）作为激活这些受体的工具。这些研究扩展了我们对动脉粥样硬化发病机制和治疗策略的研究。我们最近报道，在小鼠巨噬细胞中，apoER 2和VLDLR被它们的天然配体apoE和reelin激活，导致失能蛋白-1（Dab 1）激活，ATP结合盒转运蛋白A1（ABCA 1）表达上调，加速胆固醇流出和减少细胞胆固醇积累。然而，许多研究VLDLR和apoER 2对动脉粥样硬化发病机制影响的其他研究者指出，这些受体的激活能够诱导促动脉粥样硬化或抗动脉粥样硬化作用，可能取决于所涉及的特定配体和信号传导途径。具体而言，抗动脉粥样硬化配体，如reelin，apoE和活化蛋白C（APC），激活Dab 1依赖性信号传导途径，并抑制可能导致炎症和泡沫细胞形成的细胞事件。在 对比促动脉粥样硬化配体如脂蛋白、嗜中性粒细胞肽和凝血因子Xi，可能通过激活p38介导的途径，提高细胞内胆固醇积累并诱导细胞粘附。本项目旨在确定VLDLR/apoER 2在体外和体内的抗动脉粥样硬化作用，使用部分reelin肽（R5-6C）作为激动剂。我们选择reelin是因为它仅结合VLDLR和apoER 2。相反，apoE和APC能够与其他受体以及VLDLR和apoER 2相互作用。我们的中心假设是，通过R5-6C激活VLDLR/apoER 2-Dab 1通路将上调抗动脉粥样硬化分子，下调促动脉粥样硬化分子，从而抑制动脉粥样硬化的发展。SA 1将在小鼠模型中研究R5-6C基因转移对动脉粥样硬化的影响。虽然主要焦点是动脉粥样硬化病变，我们也将研究R5-6C基因转移对动脉粥样硬化区域中促动脉粥样硬化蛋白和抗动脉粥样硬化蛋白的表达以及对血浆脂质/葡萄糖水平的影响。SA 2将测试一个工作假设，即R5-6C通过激活apoER 2/VLDLR-Dab 1途径抑制oxLP诱导的单核细胞（MNC）与内皮细胞（EC）的粘附。重点将放在VLDLR/apoER 2-Dab 1通路的贡献，R5- 6C诱导的变化，单核细胞粘附到内皮细胞和内皮细胞的表达的抗粘附分子和促粘附分子。SA 3将检验R5-6C通过激活apoER 2/VLDLR-Dab 1通路抑制泡沫细胞形成的工作假设。实验旨在探索R5-6C是否阻断巨噬细胞结合和摄取脂蛋白，以及VLDLR/apoER 2-Dab 1通路的激活是否是R5-6C调节胆固醇代谢相关基因表达并抑制泡沫细胞形成的机制。如果成功，该项目将提供一个 为设计VLDLR/apoER 2激动剂，如reelin模拟物治疗动脉粥样硬化提供科学依据。

DESCRIPTION (provided by applicant): This project investigates the anti-atherogenic role of apolipoprotein E receptor 2 (apoER2) and very low- density lipoprotein receptor (VLDLR), using a partial reelin peptide (R5-6C) as a tool to activate these receptors. These studies extend our research on the pathogenesis of, and therapeutic strategies for atherosclerosis. We recently reported that activation of apoER2 and VLDLR by their natural ligands apoE and reelin in murine macrophages results in activation of disabled-1 (Dab1), upregulation of ATP-binding cassette transporter A1 (ABCA1) expression, accelerated cholesterol efflux and reduced cellular cholesterol accumulation. However a number of other investigators studying the impact of VLDLR and apoER2 on the pathogenesis of atherosclerosis noted that activation of these receptors is able to induce either pro- or anti- atherogenic effects, possibly dependent on the particular ligands and signaling pathways involved. Specifically, anti-atherogenic ligands, such as reelin, apoE and activated protein C (APC), activate a Dab1-dependent signaling pathway and inhibit cellular events that potentially contribute to inflammation and foam cell formation. In contrast pro-atherogenic ligands such as lipoproteins, neutrophil peptides and coagulation factor XI, elevate intracellular cholesterol accumulation and induce cell adhesion, possibly by activation of a p38-mediated pathway. This project is designed to define the anti-atherogenic role of VLDLR/apoER2 in vitro and in vivo, using a partial reelin peptide (R5-6C) as an agonist. We chose reelin because it exclusively binds VLDLR and apoER2. In contrast, apoE and APC are able to interact with other receptors as well as VLDLR and apoER2. Our central hypothesis is that activation of the VLDLR/apoER2-Dab1 pathway by R5-6C will upregulate anti- atherogenic molecules, down-regulate pro-atherogenic molecules, and therefore inhibit atherosclerosis development. SA1 will study the effect of R5-6C gene transfer on atherosclerosis in mouse models. Though the primary focus is atherosclerotic lesions, we will also study the effect of R5-6C gene transfer on the expression of pro- and anti-atherogenic proteins in the atherosclerotic area as well as on the level of plasma lipids/glucose. SA2 will tes a working hypothesis that R5-6C inhibits oxLP-induced adhesion of monocytes (MNCs) to endothelial cells (ECs) by activation of the apoER2/VLDLR-Dab1 pathway. An emphasis will be placed on the contribution of VLDLR/apoER2-Dab1 pathway to R5-6C-induced changes in adhesion of MNCs to ECs and the expression of endothelial anti- and pro-adhesion molecules. SA3 will test a working hypothesis that R5-6C inhibits foam cell formation by activation of the apoER2/VLDLR-Dab1 pathway. Experiments are designed to explore whether R5-6C blocks macrophage binding and uptake of lipoproteins, and whether activation of the VLDLR/apoER2- Dab1 pathway is a mechanism by which R5-6C regulates the expression of genes related to cholesterol metabolism and inhibits foam cell formation. If successful, this project will provide a scientific basis for designing VLDLR/apoER2 agonists, such as reelin mimetics, to treat atherosclerosis.