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）由Ca2+离子直接门控，通过组成相关钙调蛋白（CaM）。在许多中枢神经元（如CA1海马神经元）中，SK通道的活性是动作电位后超极化（mAHP）的一个中等成分的基础，影响动作电位爆发时动作电位的数量和峰间间隔，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通道降低了诱导Schaffer侧突触NMDA受体依赖性长期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，形成了SK2通道复合物的稳定和完整的组成部分。SK2相关的CK2磷酸化CaM的T80，并诱导SK2通道门控Ca2+敏感性的改变。其他数据表明，SK2通道的N端和c端结构域与CaM结合结构域在空间上接近，并且这三个结构域都与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。这一应用的驱动假说是，SK2通道的N端和c端结构域根据动态代谢信号调节相关的CK2活性，SK2相关的CK2活性影响神经元兴奋性和突触可塑性的诱导。为了验证这一假设，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配合物的高分辨率结构。我们将把ck2独立的SK2通道引入SK2缺失小鼠的CA1区，并确定其对兴奋性和突触可塑性的影响。这些研究将采用一系列新的试剂和技术来全面了解多蛋白SK2通道复合物，以及它们在神经元兴奋性和突触可塑性的基本方面所起的作用。此外，降低sk2相关的CK2活性从而降低神经元兴奋性的药物可能是治疗高兴奋性疾病（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.