Kobayashi Takeshi, Yamada Yoichi, Fukao Mitsuhiro, Shiratori Kaori, Tsutsuura Masaaki, Tanimoto Katsumasa, Tohse Noritsugu
Department of Cellular Physiology and Signal Transduction, Sapporo Medical University School of Medicine, South 1 West 17, Chuo-ku, Sapporo 060-8556, Japan.
Biochem Biophys Res Commun. 2007 Aug 31;360(3):679-83. doi: 10.1016/j.bbrc.2007.06.112. Epub 2007 Jun 28.
The beta subunits of voltage-dependent calcium channels bind the pore-forming alpha(1) subunit and play an important role in the regulation of calcium channel function. Recently, we have identified a new splice variant of the beta(4) subunit, which we have termed the beta(4d) subunit. The beta(4d) subunit is a truncated splice variant of the beta(4b) subunit and lacks parts of the guanylate kinase (GK) domain and the C-terminus. The calcium current in BHK cells expressing alpha(1C) and alpha(2)delta with the beta(4d) subunit was as small as that without the beta(4d) subunit. Western blot analysis revealed that beta(4d) protein was expressed to a lesser extent that the beta(4b) protein. In addition, a GST pull down assay showed that the beta(4d) subunit could not interact with the alpha(1) subunit of the calcium channel. Collectively, our results suggest that the GK domain of the beta subunit is essential for the expression of the functional calcium channel.
电压依赖性钙通道的β亚基与形成孔道的α(1)亚基结合，并在钙通道功能调节中发挥重要作用。最近，我们鉴定出β(4)亚基的一种新的剪接变体，我们将其命名为β(4d)亚基。β(4d)亚基是β(4b)亚基的截短剪接变体，缺少部分鸟苷酸激酶（GK）结构域和C末端。在表达α(1C)和α(2)δ以及β(4d)亚基的BHK细胞中，钙电流与不表达β(4d)亚基时一样小。蛋白质免疫印迹分析显示，β(4d)蛋白的表达程度低于β(4b)蛋白。此外，谷胱甘肽S-转移酶（GST）下拉试验表明，β(4d)亚基不能与钙通道的α(1)亚基相互作用。总体而言，我们的结果表明，β亚基的GK结构域对于功能性钙通道的表达至关重要。
