Neuronal Plasticity and Signaling in Neuropathic Pain

描述(由申请人提供)：神经病理性疼痛中的神经元可塑性和信号概述脊髓水平上依赖活动的突触可塑性对创伤性神经损伤和手术引起的神经病理性疼痛的发展至关重要。脊髓背角的N-甲基-D-天冬氨酸(NMDA)受体在神经病理性疼痛的中枢敏化和维持中起重要作用。然而，神经损伤后脊髓NMDA受体活性增强的机制仍不清楚。虽然神经损伤后NMDA受体的磷酸化增加是已知的，但在神经病理性疼痛中NMDA受体活性增加的上游机制仍有待确定。在我们的初步研究中，我们发现抑制脊髓中的蛋白激酶CK2完全逆转了NMDA受体活性的增加，并对神经损伤引起的痛觉过敏产生了长期的缓解作用。在这一应用中，我们将使用神经病理性疼痛的动物模型来检验这一中心假设，即神经损伤增加了脊髓中CK2的活性，从而促进了NMDA受体的NR1亚单位的磷酸化，并增强了NMDA介导的突触传递。本应用的具体目的是：(1)确定CK2(磷酸化)和钙调神经磷酸酶(去磷酸化)活性之间的失衡在脊髓水平NMDA介导的突触传递增强和神经病理性疼痛中的作用；(2)确定CK2活性水平及其在神经损伤后脊髓NMDA受体NR1亚单位磷酸化增强中的作用；以及(3)确定NR1和CK2亚单位之间的蛋白质相互作用，NMDA受体上的CK2磷酸化位点，及其在调节神经病理性疼痛中NMDA受体活性增加中的作用。CK2在神经损伤诱导的脊髓突触可塑性发展中的作用尚未被认识。我们预计，这一建议的新发现不仅对于显著提高我们对神经病理性疼痛的分子机制的理解至关重要，而且对于开发治疗神经病理性疼痛的新策略也至关重要。由于直接阻断NMDA受体会产生不可耐受的副作用，靶向CK2及其特异性NMDA受体磷酸化位点可能是降低NMDA受体活性和神经病理性疼痛的新策略。

DESCRIPTION (provided by applicant): Neuronal Plasticity and Signaling in Neuropathic Pain Project Summary Activity-dependent synaptic plasticity at the spinal cord level is fundamentally important to the development of neuropathic pain caused by traumatic nerve injury and surgery. N-methyl-D-aspartate (NMDA) receptors in the spinal dorsal horn are critically involved in central sensitization and maintenance of neuropathic pain. However, the mechanisms of potentiated NMDA receptor activity in the spinal cord after nerve injury remain poorly understood. Although increased phosphorylation of NMDA receptors after nerve injury is known, the upstream mechanisms of increased NMDA receptor activity in neuropathic pain remain to be determined. In our preliminary studies, we found that inhibition of the protein kinase CK2 in the spinal cord completely reversed increased NMDA receptor activity and produced long-lasting attenuation of allodynia caused by nerve injury. In this application, we will use an animal model of neuropathic pain to test the central hypothesis that nerve injury increases CK2 activity in the spinal cord, which facilitates phosphorylation of the NR1 subunit of NMDA receptors and potentiates NMDA-mediated synaptic transmission in neuropathic pain. The specific aims of this application are to (1) define the role of imbalance between the CK2(phosphorylation) and calcineurin(de-phosphorylation) activities in augmented NMDA-mediated synaptic transmission at the spinal cord level and neuropathic pain; (2) determine the level of CK2 activity and its role in increased phosphorylation of the NR1 subunit of NMDA receptors in the spinal cord after nerve injury; and (3) identify the protein interaction between NR1 and CK2 subunits, the CK2 phosphorylation sites on the NMDA receptor, and their roles in regulation of increased NMDA receptor activity in neuropathic pain. The role of CK2 in the development of synaptic plasticity in the spinal cord induced by nerve injury has not been recognized previously. We expect that new findings from this proposal will be critical not only to the significant improvement of our understanding of the molecular mechanisms of neuropathic pain but also to the development of new strategies to treat neuropathic pain. Because directly blocking NMDA receptors produces intolerable side effects, targeting CK2 and its specific NMDA receptor phosphorylation sites could represent novel strategies for reducing the NMDA receptor activity and neuropathic pain.