STRUCTURE/FUNCTION OF TRK RECEPTORS FOR NEUROTROPHINS

多肽激素、生长因子或 细胞因子及其质膜受体释放特异性分子 识别和信号转导。 本提案涉及 神经营养因子家族，特别是神经生长因子 (NGF)，与Trk受体家族，特别是TrkA，和 胞外结构域的所有亚结构域对配体的影响 约束力 本提案的总体目标是界定 决定Trk受体的能力的基本相互作用， 结合神经营养因子并启动信号传导。 被测试的假设 TrkA胞外结构域多个亚结构域 受体同时与NGF的许多不同区域相互作用。 具体目标是：确定 TrkA的每个细胞外亚结构域对 NGF结合;确定相互作用的焓和熵 在NGF和关键结合子域之间;以推断 从微量热分析中得到配体结合后的构象变化 数据;以确定TrkA胞外结构域的亚结构域是否 能够二聚化;并确定该安排的作用， 以及亚结构域的间隔对细胞内结合和信号传导的影响。 这些研究将用纯化的细胞外受体进行 TrkA的结构域（RED）及其各种突变体，并利用 包括表面等离子体共振的生物物理仪器 生物传感器和微量热计来测定动力学的改变 以及神经营养因子与突变的 Trk-RED的变体，以及细胞信号转导测定。的 结果将为配体-受体 相互作用，受体特异性的基础，和启动 酪氨酸激酶受体中的信号传导。了解分子 神经营养因子-Trk受体相互作用的机制将提供 允许设计治疗试剂的基础， 最终导致了阿尔茨海默氏症，帕金森氏症， 疾病、相关神经系统疾病与儿童神经母细胞瘤。 描述了特异性，分子基础和动力学， 神经营养因子与Trk受体细胞外结构域的结合将有助于 利用可溶性受体的有意义和合理的使用， 神经营养素或其类似物在这些疾病状态中的作用。

The initial interaction of a polypeptide hormone, growth factor, or cytokine with its plasma membrane receptor elicits specific molecular recognition and signal transduction. This proposal deals with the interaction of the neurotrophin family, particularly nerve growth factor (NGF), with the Trk receptor family, particularly TrkA, and the influence of all subdomains of the extracellular domain on ligand binding. The overall objective of this proposal is to define the elementary interactions that determine the ability of a Trk receptor to bind a neurotrophin and initiate signaling. The hypothesis being tested is that multiple subdomains of the extracellular domain of the TrkA receptor simultaneously interact with numerous distinct regions of NGF. The specific aims are: to determine the quantitative contribution of each extracellular subdomain of TrkA to the kinetics and equilibrium of NGF binding; to determine the enthalpy and entropy of interaction between NGF and the critical binding subdomain(s); to deduce the extent of the conformational change upon ligand binding from microcalorimetric data; to determine if subdomains of the TrkA extracellular domain are capable of dimerization; and to determine the role of the arrangement and spacing of the subdomains on binding and signaling within cells. These studies will be done with the purified receptor extracellular domain (RED) of TrkA, and various mutants thereof, and utilize biophysical instrumentation including a surface plasmon resonance biosensor and a microcalorimeter to assay alterations in the kinetics and thermodynamics of binding of the neurotrophins to mutational variants of Trk-REDs, as well as cell signal transduction assays. The results should provide new general insights into ligand-receptor interactions, the basis for receptor specificity, and the initiation of signaling in tyrosine kinase receptors. Understanding the molecular mechanism of neurotrophin-Trk receptor interactions will provide the basis with which allow the design of therapeutic reagents that could eventually lead to novel treatments of Alzheimer's Disease, Parkinson's Disease, related neurological disorders, and childhood neuroblastomas. Delineating the specificity, molecular basis, and dynamics of neurotrophin binding to the Trk receptor extracellular domain will help exploit the meaningful and rational use of soluble receptors, neurotrophins, or their analogs in these disease states.