CaMKII autophosphorylation in opposing directions of synaptic plasticity

钙/钙调蛋白(CaM)依赖的蛋白激酶II(CaMKII)是细胞内钙离子的主要介体。 信号。CaMKII是一种多功能蛋白激酶，参与多种不同的信号事件， 耐人寻味的是，它可能产生相反的信号结果(例如细胞死亡与存活、增殖 对比细胞周期停滞，以及突触强度的增强和抑制)。然而，这些机制 CaMKII介导的这些相反的信号转导结果之间的区别目前尚不清楚。一个 长期以来提出的吸引人的机制是T286处不同的CaMKII自动磷酸化，这使得 该激酶部分“自主”(即不依赖于钙离子)。然而，缺乏实验证据，而且 对这一提议的初步研究导致了另一种假说，即分化是由 T305/306处的自动磷酸化，阻止了钙/钙调素与该激酶的结合。具体的 这里研究的信号结果是突触强度的长时程增强(LTP)和抑制(LTD)， 高频或低频诱导的两种相反形式的钙依赖性突触可塑性 刺激分别被认为是学习和记忆的基础。经过22年的研究， 将CaMKII与LTP法规紧密联系在一起，而LTD对CaMKII的要求才刚刚出现(包括 这项提案的初步结果)。与传统模型相反，T286自动磷酸化是有效的 LTP-和LTD-刺激均可诱导。相比之下，初步结果表明，T305/306自动- 磷酸化只由LTD-刺激诱导，而不是LTP-刺激。可以从理论上论证 这种刺激依赖差异T305/306的生化机制 自动磷酸化。然而，与研究得很好的T286自动磷酸化相比，目前几乎没有 了解控制T305/306磷酸化的实际全酶机制。另一项重要的 问题是T305/306的自动磷酸化是如何导致相反的下游后果的。 初步结果表明，它可以引起不同的CaMKII底物选择，这确实应该 提升LTD，抑制LTP。因此，这一提议将：(1)确定潜在的全酶机制 LTD特异性诱导(和LTP特异性抑制)T305/306磷酸化，(2)决定 T305/306磷酸化在LTD的具体发生和要求，(3)确定对 T305/306(和T286)磷酸化在兴奋性LTP-或LTD-刺激向抑制性传递中的作用 突触，在那里这些刺激以相反的方向诱导可塑性。 结果将提供一个新的概念性和机械性的框架，说明单一调解人是如何 在结果相反的信号转导事件中需要。更好地了解具体情况 这里的机制研究也将对Angelman综合征的新治疗策略产生影响，其中 CaMKII T305/306过度磷酸化与突触和学习功能障碍有关。

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.