期刊
CELL CALCIUM
卷 54, 期 3, 页码 186-192出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.ceca.2013.06.002
关键词
Bax Inhibitor-1; Ca2+ signaling; Endoplasmic reticulum; Acidification
类别
资金
- Deutsche Forschungsgemeinschaft [ME1922/9-1]
- Forschungskommission of the Heinrich Heine University Dusseldorf
- Research Foundation-Flanders (F.W.O.) [G.0604.07N, G.0788.11N, G.0724.09]
- Research Council of the KU Leuven via the Concerted Actions program [GOA/09/012]
- OT START1 grant [STRT1/10/044]
- FONDECYT [1100176, 3130365]
- Millennium Institute [P09-015-F]
- Ring Initiative [ACT1109]
- [BIL/LA/10/09]
Bax Inhibitor-1 (BI-1) is an evolutionarily conserved six-transmembrane domain endoplasmic reticulum (ER)-localized protein that protects against ER stress-induced apoptotic cell death. This function is closely connected to its ability to lower steady-state ER Ca2+ levels. Recently, we elucidated BI-1's Ca2+-channel pore in the C-terminal part of the protein and identified the critical amino acids of its pore. Based on these insights, a Ca2+-channel pore-dead mutant BI-1 (BI-1(D213R)) was developed. We determined whether BI-1 behaves as a bona fide H+/Ca2+ antiporter or as an ER Ca2+-leak channel by investigating the effect of pH on unidirectional Ca2+-efflux rates. At pH 6.8, wild-type BI-1 expression in BI-1(-/-) cells increased the ER Ca2+-leak rate, correlating with its localization in the ER compartment. In contrast, BI-1(D213R) expression in BI-1(-/-), despite its ER localization, did not increase the ER Ca2+-leak rate. However, at pH <6.8, the BI-1-mediated ER Ca2+ leak was blocked. Finally, a peptide representing the Ca2+-channel pore of BI-1 promoting Ca2+ flux from the ER was used. Lowering the pH from 6.8 to 6.0 completely abolished the ability of the BI-1 peptide to mediate Ca2+ flux from the ER. We propose that this pH dependence is due to two aspartic acid residues critical for the function of the Ca2+-channel pore and located in the ER membrane-dipping domain, which facilitates the protonation of these residues. (C) 2013 Elsevier Ltd. All rights reserved.
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