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

描述（由申请人提供）：小电导 Ca2 激活的 K 通道（SK 通道）通过组成型相关的钙调蛋白（CaM）直接由 Ca2 离子门控。在许多中枢神经元中，例如 CA1 海马神经元，SK 通道活性是动作电位后超极化 (mAHP) 的中间成分的基础，影响动作电位的数量和动作电位爆发期间的峰间间隔，从而调节神经元的兴奋性。此外，CA1 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 通道可降低在 Schaffer 侧支突触处诱导 NMDA 受体依赖性长期增强所需的刺激强度，并减少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综合功能产生深远的影响。我们发现第三种蛋白质，丝氨酸/苏氨酸蛋白激酶 CK2，形成 SK2 通道复合物的稳定且不可或缺的成分。 SK2 相关的 CK2 磷酸化 CaM 的 T80，并诱导 SK2 通道门控的 Ca2 敏感性发生变化。其他数据表明 SK2 通道的 N 端和 C 端结构域在空间上接近 CaM 结合结构域，并且所有三个结构域都与 CK2 相互作用。此外，N 端结构域是 CK2 的强激活剂，而 C 端结构域包含许多磷酸化位点。该应用的驱动假设是 SK2 通道的 N 端和 C 端结构域响应动态代谢信号调节相关的 CK2 活性，并且 SK2 相关的 CK2 活性影响神经元兴奋性和突触可塑性的诱导。为了检验这一假设，我们将确定 SK2 和 CK2 之间相互作用的精确位点，并确定 N 端和 C 端结构域对 CK2 活性的贡献。我们将确定 SK2-CaM-CK2 复合物的高分辨率结构。我们将把不依赖于 CK2 的 SK2 通道引入 SK2 缺失小鼠的 CA1 区域，并确定其对兴奋性和突触可塑性的影响。这些研究将采用一系列新颖的试剂和技术，以形成对多蛋白 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的综合理解。此外，降低 SK2 相关 CK2 活性并从而降低神经元兴奋性的药物可能是治疗精神分裂症和癫痫等过度兴奋性疾病的治疗途径。

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.