Acts as an inhibitor of mitochondrial fission. Interacts with MFF and prevents DNM1L recruitment to mitochondria, promoting a more fused mitochondrial network. Can homodimerize (PubMed:30059978). Interacts with MFF; the interaction inhibits MFF interaction with DNM1L (PubMed:30059978). Predominantly localizes to the cytosol, with a minor fraction at the outer mitochondrial membrane. Enriched in the pancreatic beta cell and the testis and is expressed at low levels in other tissues tested.