Departments of Physiological Science and Molecular Biology and Morphological Biology, Fukuoka Dental College, Sawara-ku, Fukuoka, 814-0193, Japan.
Division of Cell Signaling, National Institute for Physiological Sciences, Okazaki Institute for Integrative Bioscience, National Institutes of Natural Sciences, Higashiyama 5-1, Myodaiji, Okazaki, Aichi, 444-8787, Japan.
J Physiol Sci. 2019 Jul;69(4):623-634. doi: 10.1007/s12576-019-00677-6. Epub 2019 Apr 22.
TRPM3 is a non-selective cation channel that is activated by neural steroids such as pregnenolone sulfate, nifedipine, and clotrimazole. Despite the number of TRPM3 variants, few reports have described functional analyses of these different TRPM3 types. Here we identified a new TRPM variant from mouse dorsal root ganglion, termed TRPM3γ3. We classified TRPM3γ3 and another known variant (variant 6) into the γ subtype, and analyzed the TRPM3γ variants. mRNA expression of TRPM3γ was higher than that of TRPM3α variants in the mouse dorsal root ganglion. In Ca-imaging of HEK293 cells expressing either the TRPM3γ variants or TRPM3α2, increases in cytosolic Ca concentrations ([Ca]) induced by pregnenolone sulfate or nifedipine were smaller in cells expressing the TRPM3γ variants compared to those expressing TRPM3α2. On the other hand, co-expression of TRPM3γ variants had no effect on [Ca] increases induced by pregnenolone sulfate or nifedipine treatment of HEK293 cells expressing TRPM3α2. In Xenopus oocytes, small responses of TRPM3γ variants to chemical agonists compared to TRPM3α2 were also observed. Interestingly, Xenopus oocytes expressing TRPM3α2 displayed heat-evoked currents with clear thresholds of about 40 °C that were larger than those evoked in oocytes expressing TRPM3γ variants. Overall, these findings indicate that TRPM3γ variants have low channel activity compared to TRPM3α.
TRPM3 是一种非选择性阳离子通道，可被孕烯醇酮硫酸盐、硝苯地平和克霉唑等神经甾体激活。尽管存在多种 TRPM3 变体，但很少有报道描述这些不同类型的 TRPM3 的功能分析。在这里，我们从小鼠背根神经节中鉴定出一种新的 TRPM 变体，称为 TRPM3γ3。我们将 TRPM3γ3 和另一种已知变体（变体 6）归类为 γ 亚型，并分析了 TRPM3γ 变体。在表达 TRPM3γ 变体或已知变体（变体 6）的 HEK293 细胞中，用孕烯醇酮硫酸盐或硝苯地平诱导的细胞内 Ca2+浓度 ([Ca]) 的增加，在表达 TRPM3γ 变体的细胞中比在表达 TRPM3α2 的细胞中要小。另一方面，在表达 TRPM3α2 的 HEK293 细胞中，TRPM3γ 变体的共表达对孕烯醇酮硫酸盐或硝苯地平诱导的 [Ca] 增加没有影响。在非洲爪蟾卵母细胞中，与 TRPM3α2 相比，TRPM3γ 变体对化学激动剂的反应较小。有趣的是，表达 TRPM3α2 的非洲爪蟾卵母细胞显示出对热的电流反应，其阈值约为 40°C，大于表达 TRPM3γ 变体的卵母细胞。总的来说，这些发现表明 TRPM3γ 变体的通道活性低于 TRPM3α。
