Identification of synaptic alpha2delta binding partners

描述（由申请人提供）：突触代表关键的转导机器，将基于动作电位的信号转换为分泌的化学信息，这些信息反过来又转换回突触后电反应。这些过程的调节被认为是学习和记忆的关键机制的基础，突触通信功能障碍被怀疑是许多脑功能病变状态的核心。人们早就知道，神经递质释放的关键触发因素是突触前末端电压门控钙通道的打开，这反过来导致钙的流入。钙进入和胞吐效率之间的高度非线性关系使钙通道功能和丰度的控制成为塑造突触强度的潜在杠杆点。我们最近证明，钙通道亚基alpha2delta的表达在决定海马神经元神经末梢存在多少钙通道方面是限速的。我们的工作表明，它在两个不同的分子步骤中起作用：它在向前运输步骤中起作用，允许钙通道运输到突触，它在神经末梢局部起作用，允许通道在突触前膜上起作用。第二步需要alpha2delta中预测区域的完整性，该区域编码金属离子依赖性粘附位点。在许多其他蛋白质中，该结构域与细胞外伴侣结合。我们预测，适当的alpha2delta功能需要与突触表面上尚未发现的结合伙伴相互作用。本提案的目标是使用生化方法来识别这种（ese）结合伙伴。

DESCRIPTION (provided by applicant): Synapses represent key transduction machines that convert action potential-based signals into secreted chemical messages which in turn are converted back into postsynaptic electrical responses. Modulation of these processes is thought to underlie critical mechanisms of learning and memory, and dysfunction of synaptic communication is suspected to be central in a number of diseased states of brain function. It has long been known that the critical trigger for neurotransmitter release is the opening of voltage-gated calcium channels within the presynaptic terminal which in turn leads to the influx of calcium. The highly-non-linear relationship between calcium entry and exocytosis efficiency places the control of calcium channel function and abundance as a potent potential leverage point in sculpting synaptic strength. We recently demonstrated that expression of a calcium channel subunit, alpha2delta, is rate-limiting in determining how many calcium channels are present at nerve terminals in hippocampal neurons. Our work showed that it acts at 2 distinct molecular steps: it acts in a forward trafficking step to allow calcium channels to traffic to synapses and it acts locally at nerve terminals to allow channels to function at the presynaptic membrane. This second step requires the integrity of a predicted domain within alpha2delta that encodes a metal-ion-dependent adhesion site. In many other proteins this domain confers binding to an extracellular partner. We predict that proper alpha2delta function requires interaction with an as-yet-discovered binding partner on the synaptic surface. The goal of this proposal is to use biochemical approaches to identify this(ese) binding partner(s).