CaMKII autophosphorylation in opposing directions of synaptic plasticity

Ca 2 +/钙调素（CaM）依赖性蛋白激酶II（CaMKII）是细胞内Ca 2 +-ATP酶的主要介导剂。 信号. CaMKII是一种多功能蛋白激酶，参与多种不同的信号传导事件， 有趣的是，它们可以产生相反的信号结果（如细胞死亡与存活，增殖 相对于细胞周期停滞，以及增强相对于突触强度的抑制）。然而，机制 目前尚不清楚CaMKII介导的这种相反信号传导结果之间的区别。一 长期提出的有吸引力的机制是T286处的差异CaMKII自磷酸化， 激酶部分“自主”（即不依赖于Ca 2+）。然而，缺乏实验证据， 对这一建议的初步研究导致了另一种假设，即分化是由 在T305/306处的自磷酸化，其阻止Ca 2 +/CaM与激酶结合。具体 这里研究的信号传导结果是突触强度的长时程增强（LTP）和抑制（LTD）， 两种相反形式的钙依赖性突触可塑性，由高或低频率诱导 刺激，并被认为是学习和记忆的基础。经过22年的研究 将CaMKII与LTP监管紧密联系在一起，而LTD中的CaMKII要求才刚刚出现（包括 这一提案的初步结果）。与传统模型相反，T286自身磷酸化是有效的。 由LTP和LTD刺激诱导。初步结果表明，T305/306自动 磷酸化仅由LTD刺激而不是LTP刺激诱导。理论上可以论证 可能是这种刺激依赖性差异T305/306的生化机制 自磷酸化然而，与充分研究的T286自身磷酸化相反，目前很少有 关于T305/306磷酸化的实际全酶机制已知。另一个重要 问题是T305/306自身磷酸化如何导致相反的下游后果。 初步结果表明，它可以导致差异的CaMKII底物选择，这确实应该 促进LTD和抑制LTP。因此，本建议将：（1）确定全酶的机制， T305/306磷酸化的LTP特异性诱导（和LTP特异性抑制），（2）确定 LTD中T305/306磷酸化的特异性发生和需要;（3）确定LTD中T305/306磷酸化的需要 T305/306（和T286）磷酸化在将兴奋性LTP-或LTD-刺激与抑制性LTP-或LTD-刺激进行通信中的作用 突触，这些刺激在相反的方向诱导可塑性。 结果将提供一个新的概念和机制框架，如何一个单一的调解人可以 信号转导事件所需的相反结果。更好地了解具体的 这里的机制研究也将对Angelman综合征的新治疗策略产生影响， CaMKII T305/306过度磷酸化参与突触和学习功能障碍。

The Ca2+/calmodulin (CaM)-dependent protein kinase II (CaMKII) is a major mediator of cellular Ca2+- signals. CaMKII is a multifunctional protein kinase that participates in a variety of different signaling events, which intriguingly can have opposing signaling outcomes (such as cell death versus survival, proliferation versus cell cycle arrest, and potentiation versus depression of synaptic strength). However, the mechanisms that differentiate between such opposing signaling outcomes mediated by CaMKII are currently unclear. A long-proposed attractive mechanism is differential CaMKII auto-phosphorylation at T286, which renders the kinase partially “autonomous” (i.e. Ca2+-independent). However, experimental evidence is lacking, and preliminary studies of this proposal led to the alternative hypothesis that differentiation is instead mediated by auto-phosphorylation at T305/306, which prevents Ca2+/CaM binding to the kinase. The specific signaling outcomes studied here are long-term potentiation (LTP) and depression (LTD) of synaptic strength, two opposing forms of Ca2+-dependent synaptic plasticity that are induced by high or low frequency stimulation, respectively, and are thought to underlie learning and memory. Over 22 years of research has firmly linked CaMKII to LTP regulation, while CaMKII requirement in LTD is just emerging (including by the preliminary results of this proposal). Contrary to traditional models, T286 auto-phosphorylation is efficiently induced by both LTP- and LTD-stimuli. By contrast, preliminary results indicate that T305/306 auto- phosphorylation is induced exclusively by LTD- but not LTP-stimuli. Theoretical arguments can be made for the biochemical mechanisms that may underlie such stimulus-dependent differential T305/306 autophosphorylation. However, in contrast to the well-studied T286 auto-phosphorylation, little is currently known about the actual holoenzyme mechanisms governing T305/306 phosphorylation. Another important question is how T305/306 auto-phosphorylation may then lead to the opposing down-stream consequences. Preliminary results indicate that it can cause differential CaMKII substrate selection that should indeed promote LTD and suppress LTP. Thus, this proposal will: (1) determine the holoenzyme mechanism underlying the LTD-specific induction (and LTP-specific suppression) of T305/306 phosphorylation, (2) determine the specific occurance and requirement of T305/306 phosphorylation in LTD, (3) determine the requirement for T305/306 (and T286) phosphorylation in communicating excitatory LTP- or LTD-stimuli to inhibitory synapses, where these stimuli induce plasticity in the opposite direction. The results will provide a new conceptual and mechanistic framework of how a single mediator can be required in signal transduction events with opposing outcomes. A better understanding of the specific mechanism studies here will also have impact on new therapeutic strategies for Angelman Syndrome, where a CaMKII T305/306 hyper-phosphorylation is involved in synaptic and learning dysfunctions.