Long-chain fatty acyl-coenzyme A activates the mitochondrial fission factors MiD49 and MiD51 by inducing their oligomerization

Mitochondrial fission occurs in many cellular processes, but the regulation of fission is poorly understood. We show that long-chain acyl coenzyme A (LCACA) activates two related mitochondrial fission proteins, MiD49 and MiD51, by inducing their oligomerization, activating their ability to stimulate DRP1 GTPase activity. The 1:1 stoichiometry of LCACA:MiD in the oligomer suggests interaction in the previously identified nucleotide-binding pocket, and a point mutation in this pocket reduces LCACA binding and LCACA-induced oligomerization for MiD51. In cells, this LCACA binding mutant does not assemble into puncta on mitochondria or rescue MiD49/51 knock-down effects on mitochondrial length and DRP1 recruitment. Furthermore, cellular treatment with the fatty acid analogue 2-bromopalmitate, which causes increased acyl-CoA, promotes mitochondrial fission in an MiD49/51-dependent manner. These results suggest that LCACA is an endogenous ligand for MiDs, inducing mitochondrial fission and providing a potential mechanism for fatty acid-induced mitochondrial fragmentation. Finally, MiD49 or MiD51 oligomers synergize with MFF, but not with actin filaments, in DRP1 activation, suggesting distinct pathways for DRP1 activation.