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. 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

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The Transmembrane Bax Inhibitor Motif (TMBIM) Containing Protein Family: Tissue Expression, Intracellular Localization and Effects on the ER CA²⁺-filling State

Dmitrij A Lisak et al. Biochim Biophys Acta. .
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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.

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