The fusion and fission of mitochondria is part of their dynamic behaviour, which is required for mitochondrial homeostasis. Disruptions of mitochondrial dynamics have been observed in disorders such as Alzheimer's or Parkinson's disease. The mitochondrial fission regulator dynamin-related GTPase Drp1 is linked to the control of mitochondrial homeostasis. Recently, endocytic regulators, such as the retromer complex member VPS35, have also been proposed to control this process. Still, the mechanisms underlying mitochondrial dynamics are poorly understood. Now (p. 2359), Steve Caplan, Naava Naslavsky and co-workers identify a role for the ATPase and endocytic fission protein EHD1 in mitochondrial dynamics as loss of EHD1 leads to a static, elongated mitochondrial network. When the authors induce mitochondrial fragmentation through addition of staurosporine, they find that the depletion of EHD1 does not prevent fragmentation, unlike the loss of Drp1 and dynamin-2, which likely act downstream of EHD1. Interestingly, depletion of EHD1 induces reduced VPS35 expression, and depletion of its binding partner rabankyrin-5 sequesters VPS35 in the Golgi; this may prevent retromer-mediated removal of inactive Drp1 from the mitochondrial membrane, which is required for proper mitochondrial fission and dynamics. Therefore, this study describes a new role for the endocytic protein EHD1 through its effect on the retromer in the regulation of mitochondrial dynamics, the loss of which has been linked to neurodegenerative diseases.
