In Drosophila, both Bcl-2 family proteins Buffy and Death executioner Bcl-2 homologue (Debcl) bind to mitochondria with, in most cases, anti- and pro-apoptotic functions, respectively. In mammals, Bcl-2 proteins play a role in mitochondrial dynamics during apoptosis, but the molecular details of how these processes are linked remain unknown. Now (p. ), Isabelle Guénal and colleagues provide novel insights into the interplay between the major mitochondrial fission regulator dynamin-related protein 1 (Drp1), mitochondrial fragmentation and Bcl-2 proteins during Rbf1-induced cell death. They observed that overexpression of Rbf1 in wing imaginal discs induced mitochondrial fragmentation, which increased ROS production, leading to the activation of c-Jun N-terminal kinase (JNK) and apoptosis. Interestingly, these phenotypes were attenuated in a Debcl loss-of-function mutant and reproduced upon Debcl overexpression, indicating that Debcl was sufficient to induce the mitochondrial effects of Rbf1 overexpression. The authors also observed that mitochondrial fragmentation and apoptosis were decreased when either Rbf1 or Debcl was expressed in a Drp1 mutant background. Importantly, they showed a direct interaction between Debcl and Drp1, which was disrupted by overexpressing Buffy. Finally, the authors found that Debcl was necessary for mitochondrial enrichment of Drp1 upon Rbf1 overexpression, consistent with a model in which Rbf1 repression of Buffy allows Debcl to interact with Drp1, which increases mitochondrial fission and triggers downstream effects that eventually lead to apoptosis.
