Mechanisms of AMPA receptor-mediated activity-dependent development

描述(申请人提供)：突触活动在发育过程中塑造神经元的结构及其在电路中的连接，以建立成熟中枢神经系统的最终结构和电学特性，5.这发生在整个神经轴，包括脊髓，在那里包含AMPA受体(AMPA-R)的GluA-1的活动在出生后早期41，43被转化为有利于树突的生长信号。这种现象发生的确切分子机制尚不完全清楚。这一过程很重要，因为具有不同树突树的神经元在接收、计算和传输信息的方式上是不同的。在这项提议中，我将重点放在AMPA-R的GluA1亚单位将突触活动转化为脊髓中树突的生长和分支的机制上。先前的工作表明，GluA1亚单位以一种独立于NMDA受体(NMDA-R)41的方式在脊髓的活动依赖性发育中起关键作用。在脊髓中，早期生命中内源性高表达的GluA1对于运动神经元树突的正确阐述、突触前输入到运动神经元的特定模式以及正常运动行为的出现至关重要。GluA1的这一特性依赖于它与SAP97(97 kDa分子量的突触相关蛋白)43的内源性物理相互作用。最近未发表的工作表明，GluA1/SAP97的亲枝晶生长活性依赖于SAP97的PDZ3结构域；如果没有功能性的PDZ3结合结构域，GluA1和SAP97的这些亲枝晶生长特性将完全丧失。我进一步确定CRIPT(PDZ-Three的富含半胱氨酸的相互作用蛋白)是SAP97的PDZ3结构域的内源性和特异性结合伙伴，并观察到CRIPT的过表达在体外增加了树突状细胞的长度和分支。因此，我假设GluA1和SAP97在突触或突触附近的细胞表面与CRIPT形成一个多蛋白复合体，从而含有GluA1的AMPA-R利用SAP97/CRIPT将AMPA-R的活性转化为脊髓中的树突生长和分支。)

DESCRIPTION (provided by applicant): Synaptic activity sculpts the architecture of neurons and their connections within circuits during development to establish the final structural and electrical properties of the mature central nervous system,5. This occurs throughout the neuraxis including the spinal cord where activity of GluA-1 containing AMPA receptors (AMPA-R) is translated into a pro-dendrite growth signal during early postnatal life41,43. The precise molecular mechanism by which this occurs is incompletely understood. This process is important because neurons with different dendritic trees are distinctive in the way they receive, compute, and transmit information5. In this proposal, I focus on the mechanism by which the GluA1 subunit of AMPA-R translates synaptic activity into dendrite growth and branching in the spinal cord. Prior work indicates that the GluA1 subunit is critical in activity-dependent development of the spinal cord in a manner that is independent of NMDA receptors (NMDA-R)41. In the spinal cord, endogenous high expression of GluA1 in early life is essential for the proper elaboration of motor neuron dendrites, the specific patterns of pre-synaptic input onto motor neurons, and the emergence of normal locomotor behavior41. This property of GluA1 is dependent on its endogenous, physical interaction with SAP97 (synapse-associated protein of 97 kDa molecular weight)43. Recent unpublished work indicates that the pro-dendrite growth activity of the GluA1/SAP97 is dependent on the PDZ3 domain of SAP97; without a functional PDZ3 binding domain, these pro-dendrite growth properties of GluA1 and SAP97 are completely lost. I have furthermore identified CRIPT (cysteine-rich interactor of PDZ-three) as an endogenous and specific binding partner of the PDZ3 domain of SAP97 and observed that overexpression of CRIPT increases dendritic length and branching in vitro. I thereby hypothesize that GluA1 and SAP97 form a multi-protein complex with CRIPT at the cell surface either at, or near, synapses whereby GluA1-containing AMPA-R use SAP97/CRIPT to translate AMPA-R activity into dendritic growth and branching in the spinal cord. )