Mitochondrial binding of α-enolase stabilizes mitochondrial membrane: its role in doxorubicin-induced cardiomyocyte apoptosis.

α-Enolase is a metabolic enzyme in the catabolic glycolytic pathway. In eukaryotic cells, the subcellular compartmentalization of α-enolase as well as its multifaceted functions has been identified. Here, we report that α-enolase is a regulator of cardiac mitochondria; it partially located in the mitochondria of rat cardiomyocytes. Doxorubicin treatment displaced α-enolase from mitochondria, accompanied by activation of mitochondrial cell death pathway. Furthermore, in isolated mitochondria, recombinant α-enolase significantly alleviated Ca(2+)-induced loss of membrane potential, swelling of matrix and permeabilization of membrane. In contrast, mitochondria from α-enolase knockdown H9c2 myoblasts underwent more severe membrane depolarization and swelling after Ca(2+) stimulation. In addition, α-enolase was further identified to interact with voltage dependent anion channel 1 in the outer membrane of mitochondria, which was weakened by doxorubicin. Collectively, the present study indicates that mitochondria-located α-enolase has a beneficial role in stabilizing mitochondrial membrane. In cardiomyocytes, the displacement of α-enolase from mitochondria by doxorubicin may involve in activation of the intrinsic cell death pathway.