マツウラ トオル   MATSUURA TORU
  松浦 徹
   所属   関西医科大学  病理学講座
   職種   講師
論文種別 原著(症例報告除く)
言語種別 英語
査読の有無 査読あり
表題 Mechanistic basis of bell-shaped dependence of inositol 1,4,5-trisphosphate receptor gating on cytosolic calcium
掲載誌名 正式名:Proceedings of the National Academy of Sciences of the United States of America
略  称:Proc Natl Acad Sci U S A
ISSNコード:00278424
掲載区分国外
巻・号・頁 108(37),15486-15491頁
著者・共著者 Tadashi Shinohara, Takayuki Michikawa, Masahiro Enomoto, Jun-ichi Goto, Miwako Iwai, Toru Matsu-ura, Haruka Yamazaki, Akitoshi Miyamoto, Akio Suzuki, Katsuhiko Mikoshiba
発行年月 2011/09
概要 The inositol 1,4,5-trisphosphate (IP(3)) receptor (IP(3)R) is an intracellular Ca(2+) release channel, and its opening is controlled by IP(3) and Ca(2+). A single IP(3) binding site and multiple Ca(2+) binding sites exist on single subunits, but the precise nature of the interplay between these two ligands in regulating biphasic dependence of channel activity on cytosolic Ca(2+) is unknown. In this study, we visualized conformational changes in IP(3)R evoked by various concentrations of ligands by using the FRET between two fluorescent proteins fused to the N terminus of individual subunits. IP(3) and Ca(2+) have opposite effects on the FRET signal change, but the combined effect of these ligands is not a simple summative response. The bell-shaped Ca(2+) dependence of FRET efficiency was observed after the subtraction of the component corresponding to the FRET change evoked by Ca(2+) alone from the FRET changes evoked by both ligands together. A mutant IP(3)R containing a single amino acid substitution at K508, which is critical for IP(3) binding, did not exhibit this bell-shaped Ca(2+) dependence of the subtracted FRET efficiency. Mutation at E2100, which is known as a Ca(2+) sensor, resulted in ∼10-fold reduction in the Ca(2+) dependence of the subtracted signal. These results suggest that the subtracted FRET signal reflects IP(3)R activity. We propose a five-state model, which implements a dual-ligand competition response without complex allosteric regulation of Ca(2+) binding affinity, as the mechanism underlying the IP(3)-dependent regulation of the bell-shaped relationship between the IP(3)R activity and cytosolic Ca(2+).