MiD49 and MiD51: New mediators of mitochondrial fission and novel targets for cardioprotection.

Acute myocardial infarction (AMI) and the heart failure (HF) that often follows are among the leading causes of death and disability worldwide. As such novel therapies are needed to reduce myocardial infarct (MI) size, and preserve left ventricular (LV) systolic function in order to reduce the propensity for HF following AMI. Mitochondria are dynamic organelles that can undergo morphological changes by two opposing processes, mitochondrial fusion and fission. Changes in mitochondrial morphology and turnover are a vital part of maintaining mitochondrial health, DNA stability, energy production, calcium homeostasis, cellular division, and differentiation, and disturbances in the balance of fusion and fission can predispose to mitochondrial dysfunction and cell death. Changes in mitochondrial morphology are governed by mitochondrial fusion proteins (Mfn1, Mfn2 and OPA1) and mitochondrial fission proteins (Drp1, hFis1, and Mff). Recent experimental data suggest that mitochondria undergo fission during acute ischemia/reperfusion injury (IRI), generating fragmented dysfunctional mitochondrial and predisposing to cell death. We and others have shown that genetic and pharmacological inhibition of the mitochondrial fission protein Drp1 can protect cardiomyocytes from acute IRI and reduce MI size. Novel components of the mitochondrial fission machinery, mitochondrial dynamics proteins of 49 kDa (MiD49) and mitochondrial dynamics proteins of 51 kDa (MiD51), have been recently described, which have been shown to mediating mitochondrial fission by targeting Drp1 to the mitochondrial surface. In this review article, we provide an overview of MiD49 and MiD51, and highlight their potential as novel therapeutic targets for treating cardiovascular diseases such as AMI, anthracycline cardiomyopathy, and pulmonary arterial hypertension.