Mitochondrial morphology regulates organellar Ca uptake and changes cellular Ca homeostasis.

Changes in mitochondrial size and shape have been implicated in several physiologic processes, but their role in mitochondrial Ca uptake regulation and overall cellular Ca homeostasis is largely unknown. Here we show that modulating mitochondrial dynamics toward increased fusion through expression of a dominant negative (DN) form of the fission protein [dynamin-related protein 1 (DRP1)] markedly increased both mitochondrial Ca retention capacity and Ca uptake rates in permeabilized C2C12 cells. Similar results were seen using the pharmacological fusion-promoting M1 molecule.