METABOLISM OF THE VLDL RECEPTOR AND APOE RECEPTOR 2

本申请的目的是研究低密度脂蛋白（LDL）受体基因家族的新功能，该功能超出了其在配体的内吞作用和甘油三酯和胆固醇稳态控制中的公认作用。我们将主要解决这个进化上高度保守的基因家族的两个成员的细胞代谢，极低密度脂蛋白（VLDL）受体和LR 8B，也被称为载脂蛋白受体-2。最近的研究发现，细胞外配体与这些受体的相互作用可能会将信号传递给某些细胞类型，并诱导它们通过周围组织迁移，这一过程对这些基因在动脉粥样硬化和阿尔茨海默病中的新兴作用特别重要。利用基因打靶技术研究了这些基因在小鼠体内的生理功能。这些初步实验的结果支持这样的假设，即由VLDL受体和LR 8B传递的细胞外信号在大脑形成期间向神经元提供迁移线索。这种信号传导可能涉及胞质衔接蛋白和非受体酪氨酸激酶。为了剖析和充分表征潜在的途径，将突变引入到两种受体的细胞质尾中，以防止它们与接头蛋白相互作用，但不会影响它们进行内吞作用的能力。这将使我们能够确定，是否阻断信号传导途径或阻断特定配体的内吞作用是导致VLDL受体和LR 8B缺陷细胞中神经元迁移缺陷的原因。我们将扩展这些研究，以寻找新的衔接蛋白，与其他组织，特别是肝脏和血管壁中的LDL受体基因家族成员的细胞质尾相互作用。在那里，这些相互作用可能调节受体从循环中去除脂蛋白的能力或影响作为该提议的焦点的机制，可能具有显著的临床意义，并可能为治疗脑和血管壁退行性疾病的药物设计提供新的靶点。

The purpose of this application is to investigate novel functions of the low density lipoprotein (LDL) receptor gene family that go beyond its recognized role in the endocytosis of ligands and the control of triglyceride and cholesterol homeostasis. We will primarily address the cellular metabolism of two members of this evolutionarily highly conserved gene family, the very low density lipoprotein (VLDL) receptor and the LR8B, also known as apolipoprotein receptor-2. Recent findings that extracellular ligand interactions with these receptors may transmit signals to certain cell types and induce them to migrate through the surrounding tissue, a process of particular importance to the emerging roles of these genes in atherosclerosis and Alzheimer disease. Gene targeting was used to investigate the physiological functions of these genes in the mouse. The results of these preliminary experiments support the hypothesis that extracellular signals, transmitted by the VLDL receptor and LR8B, provide migratory cues to neurons during the formation of the brain. This signaling likely involves cytosolic adaptor proteins and non-receptor tyrosine kinases. To dissect and fully characterize the underlying pathway, mutations will be introduced into the cytoplasmic tails of both receptors that prevent them from interacting with the adaptor proteins, but will not affect their ability to undergo endocytosis. This will allow us to determine, whether a block of a signaling pathway or block of endocytosis of a specific ligand are responsible for the neuronal migration defect in VLDL receptor and LR8B deficient cells. We will extend these studies to search for novel adaptor proteins that interact with the cytoplasmic tails of LDL receptor gene family members in other tissues, in particular the liver and the vascular wall. There these interactions might modulate the ability of the receptors to remove lipoproteins from the circulation or affect the mechanisms that are the focus of this proposal are likely to have significant clinical implications and may provide new targets for drug design in the treatment of degenerative diseases of the brain and vascular wall.