Pain is a major health problem, affecting over fifty million adults in the US alone, with significant economic cost in medical care and lost productivity. Despite evidence implicating nicotinic acetylcholine receptors (nAChRs) in pathological pain, their specific contribution to pain processing in the spinal cord remains unclear given their presence in both neuronal and non-neuronal cell types. Here we investigated if loss of neuronal-specific TMEM35a (NACHO), a novel chaperone for functional expression of the homomeric α7 and assembly of the heteromeric α3, α4, and α6-containing nAChRs, modulates pain in mice. Mice with tmem35a deletion exhibited thermal hyperalgesia and mechanical allodynia. Intrathecal administration of nicotine and the α7-specific agonist, PHA543613, produced analgesic responses to noxious heat and mechanical stimuli in tmem35a KO mice, respectively, suggesting residual expression of these receptors or off-target effects. Since NACHO is expressed only in neurons, these findings indicate that neuronal α7 nAChR in the spinal cord contributes to heat nociception. To further determine the molecular basis underlying the pain phenotype, we analyzed the spinal cord transcriptome. Compared to WT control, the spinal cord of tmem35a KO mice exhibited 72 differentially-expressed genes (DEGs). These DEGs were mapped onto functional gene networks using the knowledge-based database, Ingenuity Pathway Analysis, and suggests increased neuroinflammation as a potential contributing factor for the hyperalgesia in tmem35a KO mice. Collectively, these findings implicate a heightened inflammatory response in the absence of neuronal NACHO activity. Additional studies are needed to determine the precise mechanism by which NACHO in the spinal cord modulates pain.

疼痛是一个主要的健康问题，仅在美国就影响了超过 5000 万成年人，在医疗保健和生产力方面造成了巨大的经济成本。尽管有证据表明烟碱型乙酰胆碱受体 (nAChRs) 与病理性疼痛有关，但鉴于它们存在于神经元和非神经元细胞类型中，它们对脊髓疼痛处理的具体贡献仍不清楚。在这里，我们研究了神经元特异性 TMEM35a (NACHO) 的缺失是否调节小鼠的疼痛，这是一种用于同聚 α7 的功能表达和异聚 α3、α4 和 α6 的 nAChR 组装的新型伴侣。带有tmem35a的小鼠缺失表现出热痛觉过敏和机械异常性疼痛。尼古丁和 α7 特异性激动剂 PHA543613 的鞘内给药分别在tmem35a KO 小鼠中产生了对有害热和机械刺激的镇痛反应，表明这些受体的残留表达或脱靶效应。由于 NACHO 仅在神经元中表达，这些发现表明脊髓中的神经元 α7 nAChR 有助于热伤害感受。为了进一步确定疼痛表型的分子基础，我们分析了脊髓转录组。与 WT 对照相比， tmem35a的脊髓KO 小鼠表现出 72 个差异表达基因 (DEG)。使用基于知识的数据库 Ingenuity Pathway Analysis 将这些 DEG 映射到功能基因网络上，并表明增加的神经炎症是tmem35a KO小鼠痛觉过敏的潜在促成因素。总的来说，这些发现暗示在没有神经元 NACHO 活性的情况下炎症反应增强。需要更多的研究来确定 NACHO 在脊髓中调节疼痛的精确机制。