Background: Import of proteins into the mitochondria is regulated by the translocase of the outer mitochondrial membrane (TOM) complex, which facilitates transport through the outer mitochondrial membrane, and a complementary translocase of the inner membrane (TIM) complex, responsible for protein transport to the mitochondrial matrix. The TOM complex consists of the receptors Tom20, Tom22, and Tom70, and the channel-forming protein Tom40 (1). Tom20 is localized in the outer mitochondrial membrane and initially recognizes precursors with a presequence to facilitate protein import across the outer mitochondrial membrane (2).Changes in mitochondrial dynamics regulated by environmental cues affect mitochondrial size and shape and have been shown to dramatically impact mitochondrial metabolism, apoptosis, and autophagy (3). These processes are largely controlled by mitochondrial dynamin-related GTPases, including mitofusin-1, mitofusin-2, OPA1, and DRP1. DRP1 regulates mitochondrial fission, while the mitofusins and OPA1 control fusion at the outer and inner mitochondrial membrane, respectively. These proteins are tightly regulated. OPA1 activity is regulated through alternative splicing and post-translational modifications, including complex proteolytic processing by multiple proteases (4-9). In addition, OPA1 expression can be induced under conditions of metabolic demand through a pathway involving Parkin induced NF-κB activation (10). DRP1 is regulated in part through multiple phosphorylation sites (11). Phosphorylation of DRP1 at Ser616 by MAPK or during mitosis by CDKs stimulates mitochondrial fission (12-14). Mitochondrial fission factor (MFF) is a tail-anchored protein that resides within the outer mitochondrial membrane and is part of the mitochondrial fission complex. MFF participates in mitochondrial fission by serving as one of multiple receptors for the GTPase dynamin-related protein 1 (Drp1) (15-18). AMPK directly phosphorylates MFF at two sites to allow for enhanced recruitment of Drp1 to the mitochondria (19).