MCL-1Matrix maintains neuronal survival by enhancing mitochondrial integrity and bioenergetic capacity under stress conditions

Mitochondria play a crucial role in neuronal survival through efficient energy metabolism. In pathological conditions, mitochondrial stress leads to neuronal death, which is regulated by the anti-apoptotic BCL-2 family of proteins. MCL-1 is an anti-apoptotic BCL-2 protein localized to mitochondria either in the outer membrane (OM) or inner membrane (Matrix), which have distinct roles in inhibiting apoptosis and promoting bioenergetics, respectively. While the anti-apoptotic role for Mcl1 is well characterized, the protective function of MCL-1 (Matrix) remains poorly understood. Here, we show MCL-1(OM) and MCL-1(Matrix) prevent neuronal death through distinct mechanisms. We report that MCL-1(Matrix) functions to preserve mitochondrial energy transduction and improves respiratory chain capacity by modulating mitochondrial oxygen consumption in response to mitochondrial stress. We show that MCL-1(Matrix) protects neurons from stress by enhancing respiratory function, and by inhibiting mitochondrial permeability transition pore opening. Taken together, our results provide novel insight into how MCL-1(Matrix) may confer neuroprotection under stress conditions involving loss of mitochondrial function.