Dynamin-related protein 1 has membrane constricting and severing abilities sufficient for mitochondrial and peroxisomal fission

Abstract

Dynamin-related protein 1 (Drp1) is essential for mitochondrial and peroxisomal fission. Recent studies propose that Drp1 does not sever but rather constricts mitochondrial membranes allowing dynamin 2 (Dnm2) to execute final scission. Here, we report that unlike Drp1, Dnm2 is dispensable for peroxisomal and mitochondrial fission, as these events occurred in Dnm2 knockout cells. Fission events were also observed in mouse embryonic fibroblasts lacking Dnm1, 2 and 3. Using reconstitution experiments on preformed membrane tubes, we show that Drp1 alone both constricts and severs membrane tubes. Scission required the membrane binding, self-assembling and GTPase activities of Drp1 and occurred on tubes up to 250 nm in radius. In contrast, Dnm2 exhibited severely restricted fission capacity with occasional severing of tubes below 50 nm in radius. We conclude that Drp1 has both membrane constricting and severing abilities and is the dominant dynamin performing mitochondrial and peroxisomal fission.

Peroxisomal fission is modulated by the mitochondrial Rho‐GTPases, Miro1 and Miro2

“…Through overexpression, knockout and rescue studies, we find that Miro has a direct regulatory role in the control of peroxisomal size, number and morphology, supporting the idea that Miro has a shared morphological function at both mitochondria and peroxisomes [31,55]. Strikingly, in a subset of variant 4-expressing cells, the peroxisomes formed a long, reticulated network reminiscent of the phenotype observed upon the loss of the fission machinery [8,10,11]. Strikingly, in a subset of variant 4-expressing cells, the peroxisomes formed a long, reticulated network reminiscent of the phenotype observed upon the loss of the fission machinery [8,10,11].…”

“…Comparison of peroxisomal area between WT and DKO MEFs showed a significant decrease in peroxisomal size in the DKO MEFs (Fig 5A and B). Additionally, in variant 4-expressing DKO MEFs we observed an extensive, reticulated peroxisomal network (reminiscent of the peroxisomal phenotype upon the loss of the fission machinery [8,10,11]) in approximately 20% of cells (Fig EV5E). Exploring the role of either Miro1 or Miro2 in the single knockout MEFs showed that both Miro1 and Miro2 could compensate in their role in maintaining peroxisomal size, with no difference in peroxisomal area or number being observed in comparison with the WT MEFs (Fig 5A-C).…”

“…Importantly, mitochondria and peroxisomes have both been shown to use a Drp1-dependent mechanism for fission, utilising the receptors Fis1 and Mff to recruit Drp1 from the cytoplasm [8,9,11,58]. Importantly, mitochondria and peroxisomes have both been shown to use a Drp1-dependent mechanism for fission, utilising the receptors Fis1 and Mff to recruit Drp1 from the cytoplasm [8,9,11,58].…”

“…Mechanistically, we find that the ability of Miro to modulate peroxisomal and mitochondrial size and morphology is through negatively regulating the recruitment of Drp1 by Fis1. Indeed, Drp1 activity has been shown to be sufficient for the scission of both mitochondria and peroxisomes, making the recruitment of Drp1 to membranes an essential step in fission [11]. Indeed, Drp1 activity has been shown to be sufficient for the scission of both mitochondria and peroxisomes, making the recruitment of Drp1 to membranes an essential step in fission [11].…”

“…To initiate peroxisomal fission, the peroxisome must first elongate through the membrane curving properties of Pex11b [6,7]. Once recruited to the peroxisomal membrane, Drp1 is proposed to oligomerise, which leads to sufficient force to sever the peroxisomal membrane [11]. Strikingly, the latter steps of peroxisomal fission require overlapping machinery with mitochondrial fission, with Fis1 and Mff being localised to peroxisomes for the recruitment of the GTPase Drp1 from the cytoplasm [8][9][10].…”