SK2-associated protein kinase CK2: molecular basis and physiological roles

描述（由申请人提供）：小电导Ca 2+激活的K+通道（SK通道）通过组成型相关钙调蛋白（CaM）直接由Ca 2+离子门控。在许多中枢神经元如CA 1海马神经元中，SK通道活动是动作电位后超极化（mAHP）的中间成分的基础，影响动作电位爆发期间的动作电位数量和峰间间期，从而调节神经元的兴奋性。此外，CA 1神经元中的SK通道调节突触可塑性并改变记忆编码。阻断SK通道降低了在Schaffer侧支突触诱导NMDA受体依赖性长时程增强所需的刺激强度，并减少了海马依赖性学习所需的训练试验次数。因此，SK通道的调节剂将对神经元的整合功能产生深远的影响。我们已经发现，第三种蛋白质，丝氨酸/苏氨酸蛋白激酶CK 2，形成一个稳定的和完整的组成部分的SK2通道复合物。SK2相关的CK 2磷酸化CaM的T80，并诱导SK2通道门控的Ca 2+敏感性的转变。额外的数据表明，N-和C-末端域的SK2通道是在空间上接近钙调素结合域，和所有三个域与CK 2相互作用。此外，N-末端结构域是CK 2的强激活剂，而C-末端结构域含有许多磷酸化位点。该应用的驱动假设是SK 2通道的N-和C-末端结构域响应于动态代谢信号调节相关的CK 2活性，并且SK 2相关的CK 2活性影响神经元兴奋性和突触可塑性的诱导。为了验证这一假设，我们将确定SK2和CK 2之间相互作用的精确位点，并确定N-和C-末端结构域对CK 2活性的贡献。我们将确定SK 2-CaM-CK 2复合物的高分辨率结构。我们将引入CK 2非依赖性SK2通道到SK2基因敲除小鼠的CA 1区，并确定其对兴奋性和突触可塑性的影响。这些研究将采用一种新的试剂和技术，以综合了解多蛋白SK2通道复合物及其在神经元兴奋性和突触可塑性基本方面的作用。此外，降低SK2相关CK 2活性从而降低神经元兴奋性的药物可能是治疗过度兴奋性疾病（如精神分裂症和癫痫）的治疗途径。

DESCRIPTION (provided by applicant): Small conductance Ca2+-activated K+ channels (SK channels) are gated directly by Ca2+ ions, via constitutively associated calmodulin (CaM). In many central neurons such as CA1 hippocampal neurons, SK channel activity underlies a medium component of the after hyperpolarization (mAHP) that follows an action potential, influencing the number of action potentials and the interspike interval during a burst of action potentials, thereby regulating neuronal excitability. In addition, SK channels in CA1 neurons modulate synaptic plasticity and alter memory encoding. Blocking SK channels reduces the stimulus intensity that is required to induce NMDA receptor-dependent long-term potentiation at Schaffer collateral synapses, and reduces the number of training trials required for hippocampal dependent learning. Therefore, modulators of SK channels will exert profound effects on integrated neuronal functions. We have found that a third protein, the serine/threonine protein kinase CK2, forms a stable and integral component of the SK2 channel complex. SK2-associated CK2 phosphorylates T80 of CaM and induces a shift in the Ca2+ sensitivity of SK2 channel gating. Additional data suggest that the N- and C-terminal domains of SK2 channels are in spatial proximity to the CaM binding domain, and all three domains interact with CK2. Further, the N-terminal domain is a strong activator of CK2, while the C-terminal domain contains numerous phosphorylation sites. The driving hypothesis for this application is that the N- and C-terminal domains of the SK2 channel regulate associated CK2 activity in response to dynamic metabolic signals and that SK2-associated CK2 activity influences neuronal excitability and the induction of synaptic plasticity. To test this hypothesis, we will identify the precise sites of interaction between SK2 and CK2 and determine the contributions of the N- and C-terminal domains to CK2 activity. We will determine high resolution structures of SK2-CaM-CK2 complexes. We will introduce CK2-independent SK2 channels into the CA1 area of SK2-null mice and determine the consequences for excitability and synaptic plasticity. These studies will employ a novel repertoire of reagents and techniques to engender an integrated understanding of multi-protein SK2 channel complexes, and their roles in fundamental aspects of neuronal excitability as well as synaptic plasticity. In addition, drugs that decrease SK2-associated CK2 activity and thereby decrease neuronal excitability may be therapeutic avenues for treatments of hyperexcitability disorders such as schizophrenia and epilepsy.