Sentrin proteases, CRMP2 deSUMOylation, and Chronic Pain

摘要 慢性疼痛是一种病理状态，感觉神经元变得过度兴奋，导致伤害性 在没有痛苦刺激的情况下进行神经传递。遗传和功能研究已经建立了 电压门控钠通道Nav1.7是人类疼痛信号的主要贡献者。更改 Nav1.7的转运似乎是神经病理性疼痛病因学的核心机制。尽管 对Nav1.7的调控失调知之甚少，它被认为涉及与地表贩运有关的机制 以及通过蛋白质-蛋白质相互作用进行调节。Nav1.7的膜转运和功能活性在 轴突塌陷反应介质蛋白2(CRMP2)的调控。而CRMP2可以调节多效性 在功能上，Nav1.7的调节是由小泛素样修饰物(SUMO)特异性地指导的。 苏莫化是靶蛋白中赖氨酸残基的动态和可逆的翻译后fi阳离子。 相扑。CRMP2的SUMO化依赖于其先前被CDK5磷酸化。磷酸化的CRMP2也可以 调节其他离子通道，如Cav2.2，但其SUMO化是Nav1.7独有的。在慢性神经病中 疼痛，CRMP2 SUMO化增加与Nav1.7功能增强相关。CRMP2基因的遗传干扰 在神经病理性疼痛的大鼠中，通过表达相扑缺失CRMP2突变体(K374A)来实现相扑甲基化是足够的 逆转机械性异位痛觉。同样，在CRMP2K374A/K374A小鼠中，CRMP2 SUMO化被取消， 背根神经节(DRG)的Nav1.7电流、转运和与CRMP2的相互作用减少。这些 小鼠在神经病理性疼痛损伤后表现出对机械性超敏的抵抗力。在……学习 更多关于CRMP2 SUMO化在慢性神经病理性疼痛中的作用，我对发送蛋白/相扑- 催化蛋白质去糖化的特异蛋白酶(SENPs)。有趣的是，增加脱硫基 过表达SENP1和/或SENP2 CRMP2的异源SENP1/SUMO专一性蛋白酶 细胞减少表面Nav1.7的表达和电流。虽然相扑-1和SENP1在 脊髓和背根节神经元中它们在Nav1.7功能和疼痛中的作用从未被研究过。大多数 过去的工作集中在研究CRMP2 SUMO化的影响；关于CRMP2 SUMO化的证据有限 对这一修饰的反向研究。因此，我们的总体假设是通过增强CRMP2 SENP1的去SUMO可以反过来控制依赖Nav1.7的DRG神经元的兴奋性，并有助于 慢性神经病理性疼痛的始发和维持。

ABSTRACT Chronic pain is a pathological state where sensory neurons become hyperexcitable leading to nociceptive neurotransmission in the absence of a painful stimulus. Genetic and functional studies have established the voltage-gated sodium channel Nav1.7 as a major contributor to human pain signaling. Alterations of the trafficking of Nav1.7 appears to be a central mechanism in the etiology of neuropathic pain. Although the dysregulation of Nav1.7 is poorly understood, it is thought to involve mechanisms related to surface trafficking and regulation via protein-protein interactions. Membrane trafficking and functional activity of Nav1.7 is under the control of the axonal collapsin response mediator protein 2 (CRMP2). While CRMP2 can regulate a pleiotropy of functions, regulation of Nav1.7 is specifically guided by small ubiquitin-like modifier (SUMO)ylation. SUMOylation is a dynamic and reversible posttranslational modification of lysine residues in target proteins by SUMOs. CRMP2 SUMOylation relies on its prior phosphorylation by Cdk5. Phosphorylated CRMP2 can also regulate other ion channels such as CaV2.2 but its SUMOylation is exclusive for Nav1.7. In chronic neuropathic pain, increased CRMP2 SUMOylation correlates with enhanced Nav1.7 function. Genetic interference of CRMP2 SUMOylation via expression of a SUMO-null CRMP2 mutant (K374A) in rats with neuropathic pain was sufficient to reverse mechanical allodynia. Similarly, in CRMP2K374A/K374A mice, where CRMP2 SUMOylation is abolished, Nav1.7 currents, trafficking and interaction with CRMP2 were reduced in the dorsal root ganglia (DRG). These mice showed resistance to the development of mechanical allodynia after a neuropathic pain injury. To study in more details the role of CRMP2 SUMOylation in chronic neuropathic pain, I got interested in the sentrin/SUMO- specific protease (SENPs) that catalyze the deSUMOylation of proteins. Interestingly, increasing deSUMOylation with overexpression of sentrin/SUMO-specific protease SENP1 and/or SENP2 CRMP2-expressing heterologous cells decreases surface Nav1.7 expression and currents. Although SUMO-1 and SENP1 are expressed in the spinal cord and in DRG neurons their roles in Nav1.7 function and pain as never been investigated. Most of the past work focused on studying the effects of CRMP2 SUMOylation; there is only limited evidence regarding the study of this modification in reverse. Therefore, our overall hypothesis is that by enhancing CRMP2 deSUMOylation by SENP1 can, in turn, control Nav1.7-dependent DRG neuron excitability and contribute to initiation and maintenance of chronic neuropathic pain.