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Store-operated Ca2+ channels in the plasma membrane (PM) are activated by the depletion of Ca2+ from the endoplasmic reticulum (ER) and constitute a widespread and highly conserved Ca2+ influx pathway. After store emptying, the ER Ca2+ sensor STIM1 forms multimers, which then migrate to ER-PM junctions where they activate the Ca2+ release-activated Ca2+ channel Orai1. Movement of an intracellular protein to such specialized sites where it gates an ion channel is without precedence, but the fundamental question of how STIM1 migrates remains unresolved. Here, we show that trafficking of STIM1 to ER-PM junctions and subsequent Ca2+ release-activated Ca2+ channel activity is impaired following mitochondrial depolarization. We identify the dynamin-related mitochondrial protein mitofusin 2, mutations of which causes the inherited neurodegenerative disease Charcot-Marie-Tooth IIa in humans, as an important component of this mechanism. Our results reveal a molecular mechanism whereby a mitochondrial fusion protein regulates protein trafficking across the endoplasmic reticulum and reveals a homeostatic mechanism whereby mitochondrial depolarization can inhibit store-operated Ca2+ entry, thereby reducing cellular Ca2+ overload.

Original publication

DOI

10.1074/jbc.M110.174029

Type

Journal article

Journal

J Biol Chem

Publication Date

08/04/2011

Volume

286

Pages

12189 - 12201

Keywords

Animals, Biological Transport, Calcium, Cell Line, Cell Line, Tumor, Cell Membrane, Endoplasmic Reticulum, GTP Phosphohydrolases, Humans, Membrane Glycoproteins, Membrane Proteins, Microscopy, Confocal, Microscopy, Electron, Mitochondria, Mitochondrial Proteins, Neoplasm Proteins, Patch-Clamp Techniques, Rats