Distinct Human Macrophage Receptor for Abnormal VLDL

描述(申请人提供)：血浆甘油三酯(TG)和富含甘油三酯的脂蛋白(TGRLP)升高，特别是餐后(PP)TGRLP，是动脉粥样硬化血栓形成疾病的新的危险因素。然而，对于它们与动脉壁细胞或外周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唯一的膳食ppTGRLP受体，apoB48受体(ApoB48R)，发现于人单核巨噬细胞和动脉病变的泡沫细胞中。现在已经建立了一个缺乏这种受体的小鼠模型，有证据表明，在动脉粥样硬化的背景下，apoB48R的丢失显著减少了动脉粥样硬化，进一步表明它参与了巨噬细胞泡沫细胞的形成，并减少了正常表达该受体的组织的外周摄取，并提高了血浆胆固醇和甘油三酯(TG)。因此，利用这一新的小鼠模型，我们计划确定其在膳食脂蛋白代谢中的作用以及受体高表达的外周细胞(骨髓、脾、骨骼肌和脂肪)对ppTGRLP的摄取。此外，我们将确定在动脉粥样硬化的小鼠模型中，包括apoE和低密度脂蛋白R缺乏的小鼠，以及我们新开发的apoB48R转基因小鼠(在巨噬细胞和肝脏中组织特异性apoB48R表达增强(通常不存在))中，ppTGRLP导致动脉粥样硬化的分子机制和程度，我们还将评估当动物遭受致动脉粥样硬化和升高甘油三酯的饮食时，apoB48R对动脉粥样硬化的影响，从而改变餐后的时间。我们进一步计划在体外确定apoB48 R运作的分子和细胞机制，即快速、有效地积累细胞内脂肪。体外研究将确定受体循环率、内体/溶酶体运输、可能参与的微管和/或微丝以及合成和降解速率。受体的配体结合域将被寻找作为最终的干预靶点。最后，我们将确定潜在的额外的巨噬细胞病理生物学调节剂，这些调节剂可能会因通过apoB48R途径摄取ppTGRLP而干扰正常的胆固醇稳态，包括产生(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apoB48 R的作用及其与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.