Rearrangement of MICU1 multimers for activation of MCU is solely controlled by cytosolic Ca(2.).
Mitochondrial Ca(2+) uptake is a vital process that controls distinct cell and organelle functions. Mitochondrial calcium uptake 1 (MICU1) was identified as key regulator of the mitochondrial Ca(2+) uniporter (MCU) that together with the essential MCU regulator (EMRE) forms the mitochondrial Ca(2+) channel. However, mechanisms by which MICU1 controls MCU/EMRE activity to tune mitochondrial Ca(2+) signals remain ambiguous. Here we established a live-cell FRET approach and demonstrate that elevations of cytosolic Ca(2+) rearranges MICU1 multimers with an EC50 of 4.4 μM, resulting in activation of mitochondrial Ca(2+) uptake. MICU1 rearrangement essentially requires the EF-hand motifs and strictly correlates with the shape of cytosolic Ca(2+) rises. We further show that rearrangements of MICU1 multimers were independent of matrix Ca(2+) concentration, mitochondrial membrane potential, and expression levels of MCU and EMRE. Our experiments provide novel details about how MCU/EMRE is regulated by MICU1 and an original approach to investigate MCU/EMRE activation in intact cells.
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Markus
M
Waldeck-Weiermair
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Roland
R
Malli
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Warisara
W
Parichatikanond
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Benjamin
B
Gottschalk
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Corina T
CT
Madreiter-Sokolowski
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Christiane
C
Klec
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Rene
R
Rost
Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria.
Wolfgang F
WF
Graier
D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000096:biosynthesis* / Q000235:genetics; D002135:Calcium-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D027682:Cation Transport Proteins / Q000235:genetics* / Q000378:metabolism; D003600:Cytosol / Q000378:metabolism; D057809:HEK293 Cells; D006367:HeLa Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial / Q000235:genetics; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics* / Q000378:metabolism; D055503:Protein Multimerization / Q000235:genetics
D015220:Calcium Channels; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; C116241:MICU1 protein, human; D033681:Mitochondrial Membrane Transport Proteins; C585180:SMDT1 protein, human; C034703:mitochondrial calcium uniporter; D002118:Calcium