FUNCTIONAL STUDIES OF DAP3 IN MEDIATING MITOCHONDRIAL DYNAMICS AND CELL DEATH

Abstract

Mitochondrial morphology changes during time, which are tightly regulated by dynamics machinery proteins like Drp1, Mfn1/2 and OPA1. Evidence has been accumulated to indicate these molecules are essential in the fission and fusion processes, but the detailed mechanisms of how these molecules are regulated and cooperate to mediate fission and fusion are largely unknown. DAP3 is a mitochondrial protein that has been reported to involved in apoptosis. Here, we report that in addition to apoptosis, DAP3 also affects mitochondrial morphology and autophagic flux in a Drp1 dependent manner. Knock down of DAP3 induces mitochondrial fragmentation, which could be rescued by depletion of either Drp1 or Mff (a receptor critical in recruiting Drp1 onto mitochondria). Upon induction of fission, knock down of DAP3 decreases the phosphorylated Drp1 (Ser637) but not total Drp1 on mitochondria portion dramatically, which leads to Drp1 staying on mitochondria during fission process. Not only morphology, DAP3 depletion also affects cellular ATP production and mitochondrial membrane potential. Autophagic but not mitophagy is inhibited upon loss of DAP3 function, which might sensitize cell to death in response to the different kinds of stress. Taken together, our results demonstrate that DAP3 is important in maintaining mitochondrial structure and function through regulating Drp1 Ser637 phosphorylation status. These results also provide new insights into the mechanism of Drp1 function in mediating mitochondrial fission.