Proteolysis of Myelin as a Source of Neuropathic Pain

描述（由申请人提供）：神经性疼痛（NP）是“由影响体感觉神经系统的病变或疾病直接引起的疼痛”，具有神经免疫疾病的某些特征。在周围神经损伤的情况下，受损神经和节段性脊髓中的T辅助（Th）淋巴细胞运输和主要组织相容性复合体（MHC） II（对Th细胞识别的捕获和抗原递呈至关重要）的诱导对于NP的发展是“必要和充分的”。MHCII与NP的差异诱导有关，但与炎症性疼痛无关，但抗原及其形成过程仍然难以捉摸。我们开创性的项目集中在组织论点上，即在受损的髓鞘神经中形成的免疫优势抗原是低阈值机械性超感的来源。触摸是由非伤害性大髓鞘（Ab）传入的信号，在受伤后，它开始将轻微的触摸解释为毁灭性的疼痛（机械异常性痛）。我们的前沿初步数据已经确定了一个基本的新机制来解释这一现象：基质金属蛋白酶（MMPs）对髓鞘碱性蛋白（MBP）的选择性蛋白水解释放出隐性免疫显性表位MBP84-104和MBP69-86，这些表位通常不受免疫监视。我们清楚地证明，免疫优势的MBP肽在注射到完整的神经中时产生强大的异常性疼痛。一个有趣的发现是，内源性免疫显性MBP69-86表位与MHCII共定位在受损神经的抗原呈递的薛旺细胞中，靠近Ranvier的动作电位产生节点。使用最先进的生化和分子工具（例如Illumina BeadChip基因阵列，MALDI-TOF质谱，Ingenuity, NextBio， GeneGo和专有的MMP底物数据库）和基本（神经病理学，行为，系统）方法，我们将表征MBP残基在伤害感受中的T细胞依赖性和非依赖性作用（Aim 1）。髓鞘纤维在T细胞归巢和运动中负责MBP作用的分子结构域，以及神经中MBP残基的受体将被确定（Aim 2）。重要的是，我们确定电压门控钠通道表达和谷氨酸受体亚基的脊髓释放依赖于MMP活性。该提案的最后重点是调节T细胞运输和整合到脊髓神经胶质信号网络中的新型催化和非催化MMP靶点，促进中枢可塑性不良和异常的神经免疫突触发生（Aim 3）。这个多学科项目将金属蛋白水解生物化学的领先专业知识和最大资源（Alex Strongin博士，Sanford-Burnham医学研究所），外周髓鞘形成和神经炎症的MMPs神经生物学（Veronica Shubayev，医学博士，UCSD）和疼痛通路（Tony Yaksh博士，UCSD）与创新的研究设计相结合。我们相信这必然会改变我们的机制理解、诊断和治疗实践，预测和防止向NP状态的过渡。

DESCRIPTION (provided by applicant): Neuropathic pain (NP) is 'pain arising as a direct consequence of a lesion or disease affecting the somatosensory nervous system' that has certain features of a neuroimmune disorder. In response to peripheral nerve damage, T helper (Th) lymphocyte trafficking and induction of major histocompatibility complex (MHC) II (essential to the capture and antigen presentation for Th cell recognition) in the injured nerve and the segmental spinal cord are 'necessary and sufficient' for the development of NP. MHCII has been implicated in differential induction of NP but not inflammatory pain, but the antigens and the processes of their formation remain elusive. Our groundbreaking program centers on the organizing thesis that immunodominant antigens, formed in damaged myelinated nerves, are at the source of low-threshold mechanical hyperpathia. Touch is signaled by non-nociceptive large myelinated (Ab) afferents, which after injury begin interpreting light touch as devastating pain (mechanical allodynia). Our cutting-edge preliminary data have determined a fundamentally novel mechanism explaining this phenomenon: selective proteolysis of myelin basic protein (MBP) by matrix metalloproteinases (MMPs) releases the cryptic immunodominant epitopes, MBP84-104 and MBP69-86, normally sheltered from immunosurveillance. We clearly demonstrate that immunodominant MBP peptides produce robust allodynia upon injection into intact nerve. An intriguing finding is that endogenous immunodominant MBP69-86 epitope co-localizes with MHCII in antigen-presenting Schwann cells of the injured nerve, in close proximity to the action potential-generating nodes of Ranvier. Using state-of-the-art biochemical and molecular tools (e.g. Illumina BeadChip gene arrays, MALDI-TOF mass spectrometry, Ingenuity, NextBio, GeneGo and proprietary MMP substrate database) and fundamental (neuropathological, behavioral, systems) approaches, we will characterize the T cell-dependent and -independent actions of MBP residues in nociception (Aim 1). The molecular domains of myelinated fibers responsible for MBP action in T cell homing and locomotion, and also, the receptors for MBP residues in nerve will be determined (Aim 2). Importantly, we determined that voltage gated sodium channel expression and the spinal release of a glutamate receptor subunit depend on MMP activity. The concluding focus of the proposal are the novel catalytic and non- catalytic MMP targets in regulating T cell trafficking and integration into the spinal neuro-glial signaling network, facilitating maladaptive central plasticity and aberrant neuroimmune synaptogenesis (Aim 3). This multi- disciplinary program merges the leading expertise and utmost resources in biochemistry of metalloproteolysis (Alex Strongin, Ph.D., Sanford-Burnham Medical Research Inst.), neurobiology of MMPs in peripheral myelination and neuroinflammation (Veronica Shubayev, M.D., UCSD), and pain pathways (Tony Yaksh, Ph.D., UCSD) with innovative study designs, which we believe are bound to transform our mechanistic understanding diagnostic and therapeutic practices predicting and preventing the transition to the NP state.