Distinct Human Macrophage Receptor for Abnormal VLDL

描述（由申请方提供）：血浆甘油三酯（TG）和富TG脂蛋白（TGRLP）升高，尤其是餐后（pp）TGRLP，是动脉粥样硬化血栓形成疾病的新风险因素。然而，人们对它们与动脉壁或外周细胞相互作用的分子基础知之甚少。我们确定并克隆了一个完全独特的受体饮食ppTGRLP，apoB 48受体（apoB 48 R），发现在人类单核细胞-巨噬细胞和动脉病变的泡沫细胞。现在，已经建立了这种受体缺陷的小鼠模型，并且有证据表明，在致动脉粥样硬化背景下，apoB 48 R的缺失显著降低了动脉粥样硬化，进一步暗示其参与巨噬细胞泡沫细胞形成，并降低了正常表达受体的组织中的外周摄取，并升高了血浆胆固醇和甘油三酯（TG）。因此，使用这种新的小鼠模型，我们计划确定其在饮食脂蛋白代谢和ppTGRLP摄取的外周细胞中的作用，其中受体高度表达（骨髓，脾脏，骨骼肌和脂肪）。此外，我们将确定分子机制和程度，ppTGRLP是致动脉粥样硬化的小鼠模型，包括载脂蛋白E和低密度脂蛋白R缺陷的小鼠，与apoB 48 R缺陷小鼠和我们新开发的apoB 48 R转基因小鼠杂交，在巨噬细胞和肝脏中增强了组织特异性apoB 48 R表达（通常不存在），我们将评估当动物接受致动脉粥样硬化和TG升高饮食，从而改变餐后里程时apoB 48 R对动脉粥样硬化形成的影响。我们进一步计划在体外确定apoB 48 R运作的分子和细胞机制，即细胞内脂质的快速有效积累。体外研究将确定受体再循环速率、内体/溶酶体运输、微管和/或微丝的可能参与以及合成和降解速率。受体的配体结合结构域将被视为最终的干预靶向位点。最后，我们将确定潜在的额外的巨噬细胞病理生物学的修饰剂，可能会加剧通过apoB 48 R途径的ppTGRLP的摄取，通过干扰正常的胆固醇稳态，生产（HMGCoA还原酶）和流出（通过ABC A1）。该提案使用了强大的小鼠遗传学技术，结合体内饮食操作，以及体外细胞和分子生物学方法，旨在回答有关apoB 48 R及其与ppTGRLP在健康和疾病中的相互作用的关键问题。

DESCRIPTION (provided by applicant): Elevated plasma triglycerides (TG) and TG-rich lipoproteins (TGRLP), especially postprandial (pp) TGRLP, are emerging risk factors for atherothrombotic disease. However, little is known about the molecular basis for their interaction with cells of the artery wall or in the periphery. We identified and cloned a wholly unique receptor for dietary ppTGRLP, the apoB48 receptor (apoB48R), found in human monocyte-macrophages and in foam cells in arterial lesions. Now a mouse model, deficient in this receptor, has been created, and evidence demonstrates that in an atherogenic background the loss of the apoB48R reduces atherosclerosis significantly, further implicating it in macrophage foam cell formation and reduces peripheral uptake in tissues that normally express the receptor and elevates plasma cholesterol and triglycerides (TG). Therefore, using this new mouse model, we plan to determine its role in dietary lipoprotein metabolism and ppTGRLP uptake by cells in the periphery where the receptor is highly expressed (bone marrow, spleen, skeletal muscle and adipose). Furthermore, we will identify the molecular mechanisms and the extent to which ppTGRLP are atherogenic in mouse models of atherogenesis, including the apoE- and LDL R-deficient mice, crossed into the apoB48R-deficient mouse and in our newly developed apoB48R transgenic mice with enhanced tissue specific apoB48R expression in macrophages and liver (where it is not normally found) and we will evaluate the impact of the apoB48R on atherogenesis when animals are subjected to atherogenic and TG-elevating diets, thereby altering the postprandial mileau. We further plan to determine in vitro the molecular and cellular mechanisms by which the apoB48 R operates, that is, rapid, efficient accumulation of intracellular lipid. In vitro studies will identify the receptor recycling rates, endosomal/lysosomal trafficking, possible involvement of microtubules and/or microfilaments and rates of synthesis and degradation. The ligand-binding domain of the receptor will be sought as an eventual targeting site for intervention. Finally we will identify potential additional modifiers of macrophage pathobiology that may be exacerbated by the uptake of ppTGRLP via the apoB48R pathway by interfering in the normal cholesterol homeostasis, both production (HMGCoA reductase) and efflux (via ABC A1). The proposal uses the powerful techniques of mouse genetics coupled with dietary manipulations in vivo coupled with cell and molecular biology approaches in vitro aimed to answer key questions about the role of the apoB48 R and its interaction with ppTGRLP in health and disease.