Mechanisms of AMPA receptor-mediated activity-dependent development

描述（由申请人提供）：突触活动塑造神经元的结构及其在发育过程中回路内的连接，以建立成熟中枢神经系统的最终结构和电特性。这发生在整个神经轴，包括脊髓，其中含有GluA-1的AMPA受体（AMPA-R）的活性在出生后早期转化为前树突生长信号41，43。发生这种情况的精确分子机制尚未完全了解。这个过程很重要，因为具有不同树枝树的神经元在接收、计算和传输信息的方式上是不同的5。在这个提议中，我专注于AMPA-R的GluA 1亚基将突触活动转化为脊髓中树突生长和分支的机制。先前的工作表明，GluA 1亚基在脊髓的活动依赖性发育中至关重要，其方式独立于NMDA受体（NMDA-R）41。在脊髓中，生命早期GluA 1的内源性高表达对于运动神经元树突的适当加工、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是必不可少的41。GluA 1的这种特性取决于其与SAP 97（97 kDa分子量的突触相关蛋白）的内源性物理相互作用43。最近未发表的研究表明，GluA 1/SAP 97的前树突生长活性依赖于SAP 97的PDZ 3结构域;如果没有功能性PDZ 3结合结构域，GluA 1和SAP 97的这些前树突生长特性完全丧失。我还鉴定了CRIPT（PDZ-3的富含半胱氨酸的相互作用物）作为SAP 97的PDZ 3结构域的内源性和特异性结合伴侣，并观察到CRIPT的过表达增加了体外树突长度和分支。因此，我假设GluA 1和SAP 97在突触处或附近的细胞表面与CRIPT形成多蛋白复合物，从而含有GluA 1的AMPA-R使用SAP 97/CRIPT将AMPA-R活性翻译成脊髓中的树突状生长和分支。)

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 Recent unpublished work indicates that the pro-dendrite growth activity of the GluA1/SAP97 is dependent on the PDZ3 domain of SAP97; without a functional PDZ3 binding domain,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. )