Mechanisms of AMPA receptor-mediated activity-dependent development

描述（由申请人提供）：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特性。这种情况发生在包括脊髓在内的整个神经轴上，其中含有AMPA受体（AMPA- r）的GluA-1的活性在出生后早期被翻译成前树突生长信号41,43。发生这种情况的精确分子机制尚不完全清楚。这个过程很重要，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各不相同。在这篇论文中，我着重于AMPA-R的GluA1亚基将突触活动转化为脊髓树突生长和分支的机制。先前的研究表明，GluA1亚基以独立于NMDA受体（NMDA- r）的方式在脊髓的活动依赖性发育中起关键作用41。在脊髓中，生命早期内源性GluA1的高表达对于运动神经元树突的适当发育、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的这种特性依赖于它与SAP97 （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，GluA1/SAP97的前枝晶生长活性依赖于SAP97的PDZ3结构域；没有PDZ3结合域，GluA1和SAP97的这些枝晶生长特性完全丧失。我进一步确定了CRIPT （pdz - 3的富含半胱氨酸的相互作用因子）是SAP97的PDZ3结构域的内源性特异性结合伙伴，并观察到过表达CRIPT会增加体外树突长度和分支。因此，我假设GluA1和SAP97在细胞表面的突触上或突触附近与CRIPT形成多蛋白复合物，从而GluA1含有AMPA-R利用SAP97/CRIPT将AMPA-R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 Recent unpublished work indicates that the pro-dendrite growth activity of the GluA1/SAP97 is dependent on the PDZ3 domain of SAP97; without a functional PDZ3 binding domain,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. )