Finally, we identify two different mechanisms by which the specific mitochondrial lipid CL could regulate Drp1 function. First, Drp1 directly interacts with CL leading to assembly of the protein into higher order oligomers; and second, the interaction with CL stimulates Drp1 GTPase activity. During the revision of our manuscript, similar findings were reported by Mcdonald et al. . We speculate that stimulation of GTPase activity is dependent on generation of the higher molecular weight forms characteristic of the lipid bound form although this still needs to be shown directly. Interestingly, it is well established that dynamins have a relatively high basal GTPase activity that increases when the protein self-assembles in PIP2 containing membranes. Moreover, in contrast to previous results, it has been proposed that the GTPase activity may be altered by mutations in the PH domain. Similar molecular mechanisms have been described for proteins implicated in shaping mitochondria. The dynamin related GTPase Opa1 has a low basal rate of GTP hydrolysis that is enhanced by association with membranes containing anionic phospholipids. As described for dynamins, lipid association triggers protein oligomerization and enhancement of GTP hydrolysis rate. Also in this case, mutations that affects lipid-binding such as Dominant optic atrophy causing Q785R results in defective CLstimulated GTP hydrolysis. In the case of the yeast ortholog Mgm1, lipid binding through several conserved lysines is required for protein assembly and stimulated GTPase activity. Our data pinpoint the requirement for lipid association of Drp1 and suggest that its functional activation follows a similar molecular mechanism as that described for other members of the dynamin superfamily. To sum up, we have found that a module of four lysines located in the B insert is essential for Drp1 interaction with CL. Importantly, it has been previously found that these lysines can be SUMOylated, although the impact of SUMOylation on Drp1 function remains controversial. Drp1 SUMOylation has been shown to be promoted by Bax during apoptosis, Tofacitinib resulting in the stable association of the protein with mitochondria. On the other hand, the role of this post-translational modification has been proposed to be a way to induce Drp1 oligomers disassembly and probably to inactivate Drp1, in a manner similar to what has been proposed for septins in S. cerevisiae. Consistently, it has been found that SUMO-2/3-specific protease SENP3 mediates Drp1 deSUMOylation facilitating protein localization at mitochondria and promoting fragmentation. In line with the latter results, we propose that upon deSUMOylation by SENP3, Drp1 would be recruited at mitochondria by Mff, MiD49 or MiD51. Once in contact with the membrane, CL would stimulate its self-assembly and GTPase activity. As a working hypothesis, we propose that this mechanism may be important in physiological events linked to MOM externalization of CL accompanied with increased mitochondrial fission including apoptosis or mitophagy.