title: Dynamics of mitochondrial Ca2+ uptake in MICU1-knockdown cells.
abstract: MICU1 (Ca2+ uptake protein 1, mitochondrial) is an important regulator of the MCU (Ca2+ uniporter protein, mitochondrial) that has been shown recently to act as a gatekeeper of the MCU at low [Ca2+]c (cytosolic [Ca2+]). In the present study we have investigated in detail the dynamics of MCU activity after shRNA-knockdown of MICU1 and we have found several new interesting properties. In MICU1-knockdown cells, the rate of mitochondrial Ca2+ uptake was largely increased at a low [Ca2+]c (<2 μM), but it was decreased at a high [Ca2+]c (>4 μM). In the 2-4 μM range a mixed behaviour was observed, where mitochondrial Ca2+ uptake started earlier in the MICU1-silenced cells, but at a lower rate than in the controls. The sensitivity of Ca2+ uptake to Ruthenium Red and Ru360 was similar at both high and low [Ca2+]c, indicating that the same Ca2+ pathway was operating in both cases. The increased Ca2+-uptake rate observed at a [Ca2+]c below 2 μM was transient and became inhibited during Ca2+ entry. Development of this inhibition was slow, requiring 5 min for completion, and was hardly reversible. Therefore MICU1 acts both as a MCU gatekeeper at low [Ca2+]c and as a cofactor necessary to reach the maximum Ca2+-uptake rate at high [Ca2+]c. Moreover, in the absence of MICU1, the MCU becomes sensitive to a slow-developing inhibition that requires prolonged increases in [Ca2+]c in the low micromolar range.
authors: *Instituto de Biología y Genética Molecular (IBGM), Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Ramón y Cajal, 7, E-47005 Valladolid, Spain.
authors: Sergio
authors: S
authors: de la Fuente
authors: *Instituto de Biología y Genética Molecular (IBGM), Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Ramón y Cajal, 7, E-47005 Valladolid, Spain.
authors: Jessica
authors: J
authors: Matesanz-Isabel
authors: *Instituto de Biología y Genética Molecular (IBGM), Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Ramón y Cajal, 7, E-47005 Valladolid, Spain.
authors: Rosalba I
authors: RI
authors: Fonteriz
authors: *Instituto de Biología y Genética Molecular (IBGM), Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Ramón y Cajal, 7, E-47005 Valladolid, Spain.
authors: Mayte
authors: M
authors: Montero
authors: *Instituto de Biología y Genética Molecular (IBGM), Departamento de Bioquímica y Biología Molecular y Fisiología, Facultad de Medicina, Universidad de Valladolid and Consejo Superior de Investigaciones Científicas (CSIC), Ramón y Cajal, 7, E-47005 Valladolid, Spain.
authors: Javier
authors: J
authors: Alvarez
mesh_terms: D002118:Calcium / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D033681:Mitochondrial Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; C116241:MICU1 protein, human; D033681:Mitochondrial Membrane Transport Proteins; D002118:Calcium