METABOLISM OF THE VLDL RECEPTOR AND APOE RECEPTOR 2

本应用的目的是研究低密度脂蛋白(LDL)受体基因家族的新功能，这些功能超出了其在配体内吞和控制甘油三酯和胆固醇稳态中的已知作用。我们将主要讨论这个进化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LR8B，也称为载脂蛋白受体-2。最近发现，细胞外配体与这些受体的相互作用可能会向某些类型的细胞传递信号，并诱导它们在周围组织中迁移，这一过程对这些基因在动脉粥样硬化和阿尔茨海默病中新出现的作用特别重要。利用基因打靶技术研究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了这样的假设，即由VLDL受体和LR8B传递的细胞外信号为大脑形成过程中的神经元提供迁移信号。这一信号可能涉及胞质适配蛋白和非受体酪氨酸激酶。为了剖析和充分描述潜在的途径，突变将被引入到两个受体的细胞质尾部，以阻止它们与接头蛋白相互作用，但不会影响它们经历内吞的能力。这将使我们能够确定，信号通路的阻断或特定配体的内吞作用的阻断是否导致VLDL受体和LR8B缺陷细胞的神经元迁移缺陷。我们将扩大这些研究，以寻找与其他组织，特别是肝脏和血管壁中的低密度脂蛋白受体基因家族成员的细胞质尾巴相互作用的新的接头蛋白。在那里，这些相互作用可能调节受体从循环中移除脂蛋白的能力，或者影响这一提议的重点机制，可能具有重要的临床意义，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.