Work

Calmodulin enhancement of mitochondrial calcium uniporter function in isolated mitochondria

Year: 2025

Type: article

Abstract: • Mitochondrial Ca 2+ uptake is enhanced in the presence of CaM. • Both CaM and MCU are required for enhancement of mitochondrial Ca 2+ uptake. • Small molecule CaM interactions impair enhancement of Ca 2+ uptake. • CaM enhanced mitochondrial Ca 2+ uptake persists in the presence of the PTP inhibitor CsA. • Subtle mutation highlights the importance of CaM C-domain for enhancement effect. Mitochondrial calcium (Ca 2+ ) uptake and factors that regulate this process have been an area of immense interest given the roles in cellular energetics. Here, we have investigated the ability of the Ca 2+ sensing protein Calmodulin (CaM) to modify the function of the Mitochondrial Ca 2+ Uniporter (MCU). Our data leveraged recombinantly produced CaM and mitochondria isolated from healthy and MCU impaired/diseased mice (Barth syndrome model). We found CaM enhanced Ca 2+ uptake in both the absence and presence of CaMKII inhibition (KN93 as well as AIP). Mitochondria lacking function MCU (Barth syndrome model) validated that MCU was responsible for Ca 2+ uptake in our experiments. Control experiments demonstrate that the observed CaM enhancement does not arise from CaM Ca 2+ buffering. Fitting the Ca 2+ fluorescence data supported a monophasic decay process where the presence of CaM yielded enhanced kinetic rates of Ca 2+ uptake. This CaM enhancement effect persisted in the presence of PTP impairment (cyclosporin), and subtle modification to the CaM protein sequence (D131E) revealed that an intact CaM-C domain Ca 2+ binding was required for enhancement of MCU function.

Source: Cell Calcium

DOI: 10.1016/j.ceca.2025.103056