Department of Physiology and Pharmacology, Alberta Children's Hospital Research Institute, Hotchkiss Brain Institute, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
Pain. 2022 Dec 1;163(12):2315-2325. doi: 10.1097/j.pain.0000000000002651. Epub 2022 Apr 20.
Trigeminal neuralgia (TN) is a rare but debilitating disorder characterized by excruciating facial pain, with a higher incidence in women. Recent studies demonstrated that TN patients present mutations in the gene encoding the Ca V 3.2 T-type calcium channel, an important player in peripheral pain pathways. We characterize the role of Ca V 3.2 channels in TN at 2 levels. First, we examined the biophysical properties of CACNA1H variants found in TN patients. Second, we investigated the role of Ca V 3.2 in an animal model of trigeminal neuropathic pain. Whole-cell patch-clamp recordings from 4 different mutants expressed in tsA-201 cells (E286K in the pore loop of domain I, H526Y, G563R, and P566T in the domain I-II linker) identified a loss of function in activation in the E286K mutation and gain of function in the G563R and P566T mutations. Moreover, a loss of function in inactivation was observed with the E286K and H526Y mutations. Cell surface biotinylation revealed no difference in channel trafficking among the variants. The G563R mutant also caused a gain of function in the firing properties of transfected trigeminal ganglion neurons. In female and male mice, constriction of the infraorbital nerve induced facial thermal heat hyperalgesia. Block of T-type channels with Z944 resulted in antihyperalgesia. The effect of Z944 was absent in Ca V 3.2 -/- mice, indicating that Ca V 3.2 is the molecular target of the antihyperalgesic Z944 effect. Finally, enzyme-linked immunosorbent assay analysis revealed increased Ca V 3.2 channel expression in the spinal trigeminal subnucleus caudalis. Altogether, the present study demonstrates an important role of Ca V 3.2 channels in trigeminal pain.
三叉神经痛（TN）是一种罕见但使人衰弱的疾病，其特征是极度面部疼痛，女性发病率较高。最近的研究表明，TN 患者的基因编码钙通道 Ca V 3.2 T 型钙通道存在突变，该通道是外周疼痛途径中的重要参与者。我们从 2 个水平研究了 Ca V 3.2 通道在 TN 中的作用。首先，我们检查了在 TN 患者中发现的 CACNA1H 变体的生物物理特性。其次，我们研究了 Ca V 3.2 在三叉神经病理性疼痛动物模型中的作用。在 tsA-201 细胞中表达的 4 种不同突变体（I 域孔环中的 E286K、H526Y、G563R 和 I-II 连接子中的 P566T）的全细胞膜片钳记录鉴定出 E286K 突变导致激活功能丧失，而 G563R 和 P566T 突变导致功能获得。此外，E286K 和 H526Y 突变观察到失活功能丧失。细胞表面生物素化显示变体之间通道转运没有差异。G563R 突变还导致转染的三叉神经节神经元放电特性的功能获得。在雌性和雄性小鼠中，眶下神经缩窄诱导面部热觉热痛觉过敏。用 Z944 阻断 T 型通道导致抗痛觉过敏。在 Ca V 3.2 -/- 小鼠中，Z944 的作用不存在，表明 Ca V 3.2 是 Z944 抗痛觉过敏作用的分子靶标。最后，酶联免疫吸附分析显示脊髓三叉神经尾核 Ca V 3.2 通道表达增加。总之，本研究表明 Ca V 3.2 通道在三叉神经痛中起重要作用。
