Nicholas E. Hoffman a , b , Harish C. Chandramoorthy a , b , Santhanam Shanmughapriya a , b , Xueqian Q. Zhang b , Sandhya Vallem b , Patrick J. Doonan a , b , * , Karthik Malliankaraman a , b , † , Shuchi Guo b , Sudarsan Rajan a , b , John W. Elrod b , Walter J. Koch b , Joseph Y. Cheung b , Muniswamy Madesh a , b , 1
15 March 2014
Knockdown of SLC25A23 decreases mitochondrial Ca 2+ uptake, and SLC25A23 interacts with MCU and MICU1, components of mitochondrial Ca 2+ uniporter. Expression of SLC25A23 EF-hand-domain mutants has a dominant-negative phenotype of reduced mitochondrial Ca 2+ uptake. It also attenuates basal ROS and oxidant-induced ATP decline and cell death.
Emerging findings suggest that two lineages of mitochondrial Ca 2+ uptake participate during active and resting states: 1) the major eukaryotic membrane potential–dependent mitochondrial Ca 2+ uniporter and 2) the evolutionarily conserved exchangers and solute carriers, which are also involved in ion transport. Although the influx of Ca 2+ across the inner mitochondrial membrane maintains metabolic functions and cell death signal transduction, the mechanisms that regulate mitochondrial Ca 2+ accumulation are unclear. Solute carriers—solute carrier 25A23 (SLC25A23), SLC25A24, and SLC25A25—represent a family of EF-hand–containing mitochondrial proteins that transport Mg-ATP/Pi across the inner membrane. RNA interference–mediated knockdown of SLC25A23 but not SLC25A24 and SLC25A25 decreases mitochondrial Ca 2+ uptake and reduces cytosolic Ca 2+ clearance after histamine stimulation. Ectopic expression of SLC25A23 EF-hand–domain mutants exhibits a dominant-negative phenotype of reduced mitochondrial Ca 2+ uptake. In addition, SLC25A23 interacts with mitochondrial Ca 2+ uniporter (MCU; CCDC109A) and MICU1 (CBARA1) while also increasing I MCU. In addition, SLC25A23 knockdown lowers basal mROS accumulation, attenuates oxidant-induced ATP decline, and reduces cell death. Further, reconstitution with short hairpin RNA–insensitive SLC25A23 cDNA restores mitochondrial Ca 2+ uptake and superoxide production. These findings indicate that SLC25A23 plays an important role in mitochondrial matrix Ca 2+ influx.