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Biochim Biophys Acta. 2015 Sep;1853(9):2104-14. doi: 10.1016/j.bbamcr.2015.03.002. Epub 2015 Mar 9.

The transmembrane Bax inhibitor motif (TMBIM) containing protein family: Tissue expression, intracellular localization and effects on the ER CA²⁺-filling state.

Author information

1
Focus Program Translational Neuroscience (FTN), Rhine Main Neuroscience Network (rmn(2)), Department of Neurology, Johannes Gutenberg University Medical Center Mainz, Langenbeckstr. 1, Mainz D-55131, Germany.
2
Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine, KU Leuven, Campus Gasthuisberg O/N-I bus 802, Herestraat 49, Leuven BE-3000, Belgium.
3
Focus Program Translational Neuroscience (FTN), Rhine Main Neuroscience Network (rmn(2)), Department of Neurology, Johannes Gutenberg University Medical Center Mainz, Langenbeckstr. 1, Mainz D-55131, Germany. Electronic address: axel.methner@gmail.com.

Abstract

Bax inhibitor-1 (BI-1) is an evolutionarily conserved pH-dependent Ca²⁺ leak channel in the endoplasmic reticulum and the founding member of a family of six highly hydrophobic mammalian proteins named transmembrane BAX inhibitor motif containing (TMBIM) 1-6 with BI-1 being TMBIM6. Here we compared the structure, subcellular localization, tissue expression and the effect on the cellular Ca²⁺ homeostasis of all family members side by side. We found that all TMBIM proteins possess the di-aspartyl pH sensor responsible for pH sensing identified in TMBIM6 and its bacterial homologue BsYetJ. TMBIM1-3 and TMBIM4-6 represent two phylogenetically distinct groups that are localized in the Golgi apparatus (TMBIM1-3), endoplasmic reticulum (TMBIM4-6) or mitochondria (TMBIM5) but share a common structure of at least seven transmembrane domains with the last domain being semi-hydrophobic. TMBIM1 is mainly expressed in muscle, TMBIM2 and 3 in the nervous system, TMBIM4 and 5 are ubiquitously expressed and TMBIM6 in skeletal muscle, kidney, liver and spleen. All TMBIM proteins reduce the Ca²⁺ content of the endoplasmic reticulum, and all but TMBIM5 also reduce the cytosolic resting Ca²⁺ concentration. These results suggest that the TMBIM family has comparable functions in the maintenance of intracellular Ca²⁺ homeostasis in a wide variety of tissues. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

KEYWORDS:

FAIM2; GAAP; GHITM; GRINA; MICS1; RECS1

PMID:
25764978
DOI:
10.1016/j.bbamcr.2015.03.002
[Indexed for MEDLINE]
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