Coordinating Adhesion Receptors in Axon Growth

描述(申请人提供)：视网膜神经节细胞轴突在发育过程中被许多不同的黏附、吸引和排斥系统引导沿着它们的轨迹。正确的轴突生长和引导需要整合来自许多不同感受器系统的生长锥体信息。我们的长期目标是确定在神经视网膜轴突发育过程中整合黏附受体功能的环境线索和信号通路。N-钙粘附素和β1-整合素是两个在视网膜轴突延长和引导中起决定性作用的黏附系统。我们发现了一条在轴突生长过程中协同调节N-钙粘蛋白和β-1-整合素功能的途径。当细胞或生长锥接触到硫酸软骨素蛋白多糖神经胶时，N-钙粘附素和β1-整合素的功能都会丧失。这种协调功能的丧失与非受体酪氨酸激酶Fer从其通常在蛋白质钙粘素复合体中的结合转移到与β1整合素的细胞质结构域相关的蛋白质复合体中有关。我们的假设是，钙粘附素和整合素的协同调节在防止神经节细胞轴突偏离其适当的路径方面发挥了重要作用。本应用的目的是确定Fer在钙粘附素和整合素功能中的作用，并研究这一途径在视网膜神经节细胞轴突发育中的作用。目标1和目标2分别定义Fer在钙粘附素和整合素功能中的作用。我们将确定在Fer存在和不存在的情况下其存在或磷酸化改变的效应器，以及这些改变的成分如何调节功能。目的3定义钙粘蛋白胞质结构域中的调控位点，负责转导启动Fer穿梭的信号。这将通过N-钙粘蛋白的缺失和突变，以及神经视网膜中存在的其他I型和II型钙粘蛋白参与钙粘素和整合素之间交叉调节的能力的功能比较来实现。在目标4中，我们将通过抑制细胞外信号Neurcan的结合，以及通过使用细胞通透性多肽干扰钙粘素和/或整合素的功能，来确定这种交叉调节电路在视网膜神经节细胞轴突投射发育中的作用。

DESCRIPTION (provided by applicant): Retinal ganglion cell axons are guided along their trajectories during development by many different systems of adhesion, attraction and repulsion. Proper axon growth and guidance requires integration in the growth cone of information from many distinct receptor systems. Our long term goals are to identify the environmental cues and signaling paths that integrate adhesion receptor function during development of axons in the neural retina. N-cadherin and beta1-integrins are two of the adhesion systems that play decisive roles in retinal axon elongation and guidance. We have discovered a pathway which coordinately regulates N-cadherin and beta1-integrin function during axon outgrowth. When cells or growth cones contact the chondroitin sulfate proteoglycan neurocan, both N-cadherin and beta1-integrin function is lost. This coordinate loss of function correlates with translocation of the non-receptor tyrosine kinase Fer from its usual association in the cadherin complex of proteins to the complex of proteins associated with the cytoplasmic domain of beta1-integrin. Our hypothesis is that coordinate regulation of cadherin and integrin plays an important role in preventing ganglion cell axons from straying from their appropriate path. The goal of this application is to define the role of Fer in cadherin and integrin function and to examine the role of this pathway in the development of retina ganglion cell axons. Aims 1 and 2 define the role of Fer in the function of cadherin and integrin respectively. We will identify effectors whose presence or phosphorylation is altered in the presence and absence of Fer and how these altered components regulate function. Aim 3 defines the regulatory site in the cadherin cytoplasmic domain responsible for transducing the signal initiating the shuttling of Fer. This will be accomplished by deletion and mutagenesis of N-cadherin, as well as functional comparison of other Type I and II cadherins present in the neural retina for the ability to participate in cross-regulation between cadherin and integrin. In Aim 4 we will determine the role of this cross regulatory circuit in development of retinal ganglion cell axon projections through inhibition of the binding of neurocan, the extracellular signal that initiates coordinate regulation, and through the use of cell permeable peptides to perturb cadherin and/or integrin function.