Michikawa T, Hirota J, Kawano S, Hiraoka M, Yamada M, Furuichi T, Mikoshiba K
Department of Molecular Neurobiology, Institute of Medical Science, University of Tokyo, Japan.
Neuron. 1999 Aug;23(4):799-808. doi: 10.1016/s0896-6273(01)80037-4.
The dependency of purified mouse cerebellar type 1 inositol 1,4,5-trisphosphate receptor (IP3R1)/Ca2+ channel function on cytoplasmic Ca2+ was examined. In contrast to the channels in crude systems, the purified IP3R1 reconstituted into planar lipid bilayers did not show the bell-shaped dependence on Ca2+. It was activated with increasing Ca2+ sublinearly without inhibition even up to 200 microM. The addition of calmodulin to the cytoplasmic side inhibited the channel at high Ca2+ concentrations. Calmodulin antagonists reversed the Ca2+-dependent inactivation of the native channels in cerebellar microsomes. These results indicate that the bell-shaped dependence on cytoplasmic Ca2+ is not an intrinsic property of the IP3R1, and the Ca2+-dependent inactivation is directly mediated by calmodulin.
研究了纯化的小鼠小脑1型肌醇1,4,5-三磷酸受体（IP3R1）/Ca2+通道功能对细胞质Ca2+的依赖性。与粗制系统中的通道不同，重构到平面脂质双分子层中的纯化IP3R1对Ca2+没有呈现钟形依赖性。随着Ca2+浓度增加，它以亚线性方式被激活，甚至在高达200微摩尔时也没有受到抑制。在细胞质一侧添加钙调蛋白会在高Ca2+浓度下抑制该通道。钙调蛋白拮抗剂可逆转小脑微粒体中天然通道的Ca2+依赖性失活。这些结果表明，对细胞质Ca2+的钟形依赖性不是IP3R1固有的特性，并且Ca2+依赖性失活是由钙调蛋白直接介导的。
