title: A forty-kilodalton protein of the inner membrane is the mitochondrial calcium uniporter.
abstract: Mitochondrial Ca(2+) homeostasis has a key role in the regulation of aerobic metabolism and cell survival, but the molecular identity of the Ca(2+) channel, the mitochondrial calcium uniporter, is still unknown. Here we have identified in silico a protein (named MCU) that shares tissue distribution with MICU1 (also known as CBARA1), a recently characterized uniporter regulator, is present in organisms in which mitochondrial Ca(2+) uptake was demonstrated and whose sequence includes two transmembrane domains. Short interfering RNA (siRNA) silencing of MCU in HeLa cells markedly reduced mitochondrial Ca(2+) uptake. MCU overexpression doubled the matrix Ca(2+) concentration increase evoked by inositol 1,4,5-trisphosphate-generating agonists, thus significantly buffering the cytosolic elevation. The purified MCU protein showed channel activity in planar lipid bilayers, with electrophysiological properties and inhibitor sensitivity of the uniporter. A mutant MCU, in which two negatively charged residues of the putative pore-forming region were replaced, had no channel activity and reduced agonist-dependent matrix Ca(2+) concentration transients when overexpressed in HeLa cells. Overall, these data demonstrate that the 40-kDa protein identified is the channel responsible for ruthenium-red-sensitive mitochondrial Ca(2+) uptake, thus providing a molecular basis for this process of utmost physiological and pathological relevance.
authors.affiliation: Department of Biomedical Science, University of Padua, 35121 Padua, Italy.
authors.forename: Diego
authors.initials: D
authors.lastname: De Stefani
authors.forename: Anna
authors.initials: A
authors.lastname: Raffaello
authors.forename: Enrico
authors.initials: E
authors.lastname: Teardo
authors.forename: Ildikò
authors.initials: I
authors.lastname: Szabò
authors.forename: Rosario
authors.initials: R
authors.lastname: Rizzuto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000737:chemistry* / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D002463:Cell Membrane Permeability; D017124:Conserved Sequence; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D017136:Ion Transport; D008051:Lipid Bilayers / Q000378:metabolism; D053078:Membrane Potential, Mitochondrial / Q000502:physiology; D051379:Mice; D008928:Mitochondria / Q000378:metabolism*; D051336:Mitochondrial Membranes / Q000378:metabolism*; D008969:Molecular Sequence Data; D008970:Molecular Weight; D017434:Protein Structure, Tertiary; D021381:Protein Transport
chemical_list: D015220:Calcium Channels; D008051:Lipid Bilayers; C034703:mitochondrial calcium uniporter; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium