Molecular computation by the CaMKII holoenzyme

项目摘要 学习、认知和记忆需要海马突触的动态重塑，这反过来又需要 Ca 2 +/钙调蛋白依赖性激酶II（CaMKII）。CaMKII介导突触可塑性的两种相反模式，长 长时程增强（LTP）和抑郁（LTD），这是由不同的Ca 2+刺激诱导的。低钙和高钙 在T286处诱导CaMKII自磷酸化（p），这是LTP和LT所需的。此外，LTP需要 在高[Ca 2 +]期间，CaMK II与NMDA受体亚基GluN 2B结合，而LTD需要CaMK II 低[Ca 2 +]时T305/306的自磷酸化。此外，这三种机制可以经历复杂的 交叉调节需要CaMKII 12梅里克全酶。有趣的是，pT 286正向调节这两种基因， GluN 2B结合和pT 305/306，而GluN 2B结合和pT 305/306是互斥的。不知道是怎么回事 这些反应和相互作用在全酶中被时空编码，因此LTP与 LTD信号的计算由CaMKII完成。例如，已经表明，pT 286必须发生 在全酶中两个相邻的激酶结构域之间。目前还不清楚是什么决定了函数 激酶结构域邻居。此外，体外结合研究表明，需要CaMK II全酶 结合GluN 2B，这表明这种相互作用可能需要多个亚基。不过，目前还不清楚 CaMKII-GluN 2B结合所需的化学计量和亚基几何结构。初步结果表明， pT 286和GluN 2B结合的全酶规则根本不同。因此，这项建议将 研究我的假设，LTP与LTD机制是由结构上不同的特点， CaMKII全酶。该方法将利用几种CaMKII“结构突变体”， 全酶结构（六聚体、二聚体和单体）。这些突变体将用作定义 全酶内自磷酸化的时空动力学和亚基化学计量学， GluN 2B结合所需的几何结构。这项提案的结果将提供深入了解分子信号如何 作为LTP与LTD决定的基础的计算在CaMKII全酶内编码。

PROJECT SUMMARY Learning, cognition, and memory require dynamic remodeling of hippocampal synapses, which in turn requires Ca2+/calmodulin-dependent kinase II (CaMKII). CaMKII mediates two opposing modes of synaptic plasticity, long term potentiation (LTP) and depression (LTD), that are induced by distinct Ca2+ stimuli. Both low and high Ca2+ induce CaMKII autophosphorylation (p) at T286, that is required for both LTP and LTD. Additionally, LTP requires CaMKII binding to the NMDA receptor subunit, GluN2B, during high [Ca2+] while LTD requires CaMKII autophosphorylation at T305/306 during low [Ca2+]. Further, these three mechanisms can undergo complex cross-regulation which requires the CaMKII 12-meric holoenzyme. Interestingly, pT286 positively regulates both GluN2B binding and pT305/306 while GluN2B binding and pT305/306 are mutually exclusive. It is unknown how these reactions and interactions are spatiotemporally encoded within holoenzymes and thus how LTP versus LTD signal computation is accomplished by CaMKII. For example, it has been shown that pT286 must occur between two neighboring kinase domains in the holoenzyme. It is still unclear what determines a functional kinase domain neighbor. Moreover, in vitro binding studies have shown that CaMKII holoenzymes are required for binding to GluN2B, suggesting that this interaction may require multiple subunits. Still, it is unknown what is the required stoichiometry and subunit geometry required for CaMKII-GluN2B binding. Initial results suggest that the holoenzyme rules for pT286 and GluN2B binding are fundamentally different. Therefore, this proposal will investigate my hypothesis that LTP versus LTD mechanisms are regulated by structurally distinct features within CaMKII holoenzymes. The approach will utilize several CaMKII “structural mutants” that have disrupted holoenzyme structure (hexamers, dimers, and monomers). These mutants will be used as tools to define the spatiotemporal dynamics of autophosphorylation within holoenzymes and the subunit stoichiometry and geometry required for GluN2B binding. The results of this proposal will provide insight into how molecular signal computation underlying the LTP versus LTD decision is encoded within CaMKII holoenzymes.