Distinct Human Macrophage Receptor for Abnormal VLDL

描述（由申请人提供）：血浆甘油三酯（TG）和富TG脂蛋白（TGRLP）升高，特别是餐后（pp） TGRLP，是动脉粥样硬化性血栓形成疾病的新危险因素。然而，关于它们与动脉壁细胞或周围细胞相互作用的分子基础知之甚少。我们鉴定并克隆了一种完全独特的膳食ppTGRLP受体——载脂蛋白48受体（apoB48R），该受体存在于人类单核巨噬细胞和动脉病变的泡沫细胞中。现在，一个缺乏这种受体的小鼠模型已经建立，证据表明，在动脉粥样硬化背景下，apoB48R的缺失显著减少动脉粥样硬化，进一步暗示它在巨噬细胞泡沫细胞形成中，减少正常表达受体的组织的外周摄取，并提高血浆胆固醇和甘油三酯（TG）。因此，利用这种新的小鼠模型，我们计划确定其在膳食脂蛋白代谢和ppTGRLP受体高表达的外周细胞（骨髓、脾脏、骨骼肌和脂肪）摄取ppTGRLP中的作用。此外，我们将确定分子机制和ppTGRLP在动脉粥样硬化小鼠模型中的致动脉粥样硬化程度，包括apoE-和LDL - r缺陷小鼠。在巨噬细胞和肝脏（正常情况下不存在）组织特异性载脂蛋白48r表达增强的载脂蛋白48r转基因小鼠中，我们将评估载脂蛋白48r对动脉粥样硬化的影响，当动物遭受致动脉粥样硬化和tg升高饮食，从而改变餐后环境时。我们进一步计划在体外确定apoB48 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率。受体的配体结合结构域将被寻找作为干预的最终靶向位点。最后，我们将确定巨噬细胞病理生物学的潜在其他修饰因子，这些修饰因子可能通过apoB48R途径通过干扰正常胆固醇稳态，包括产生（HMGCoA还原酶）和排出（通过ABC A1），而被ppTGRLP的摄取所加剧。该建议使用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apoB48 R在健康和疾病中的作用及其与ppTGRLP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.