Figure 2.
Steps in the division of POs and mitochondria. (i) Growth of the organelle and signaling of division. Growth of POs and mitochondria occurs by the import of membrane and matrix proteins, as well as lipids, to the organelles. Signals that activate division can be cell intrinsic or extrinsic (see “Signals that determine when POs and mitochondria will divide” section). (ii) Membrane reorganization, tubulation, and elongation. Membrane reorganization involves lipid rearrangements. Membrane elongation and tubulation require lipid delivery from other organelles to the site of membrane synthesis and curvature by local lipid synthesis and/or transfer using vesicular and non-vesicular processes. (iii) Marking sites on organelles by membrane constriction. This involves organelle-specific proteins (see text) and contact with the ER. There is evidence for both POs (Koch et al., 2004) and mitochondria (Kraus and Ryan, 2017) that membrane tubulation, elongation, and constriction occur prior to Dnm1/DRP1 assembly and action. (iv) Relocalization and activation of organelle-specific components, typically involving PTMs. (v) Recruitment and activation of Dnm1/DRP1 and formation of a double-ring contractile structure. Dynamin-like proteins involved in peroxisomal and mitochondrial division are cytosolic. (vi) Membrane scission. See text for details. (vii) Disassembly of the fission machinery (see text). (A) Division of POs. In yeast, the phosphorylation of Pex11 is necessary for its movement from the ER to POs (Fig. 3; Knoblach and Rachubinski, 2010), although in P. pastoris Pex11 is phosphorylated at the POs (Joshi et al., 2012). Pex11 phosphorylation is also necessary for its interaction with Fis1 (Joshi et al., 2012), which recruits Dnm1 to the PO membrane for division. Since Pex11 can serve as a GAP for Dnm1, the activation of Pex11 by phosphorylation (Joshi et al., 2012; Knoblach and Rachubinski, 2010), its movement in the PO membranes to the membrane constriction sites (Nagotu et al., 2008), and its interaction with Dnm1 are necessary steps in triggering peroxisomal division (Williams et al., 2015). Vps1, which is involved only in peroxisomal division in glucose-grown yeast, interacts with Pex19, Vps27, and Inp1, as well as with actin-cytoskeleton proteins like Rvs161 and Mvp1 (see text), but its role is not shown here. (B) Division of mitochondria. Not much is known regarding how exactly mitochondria-specific proteins, such as ABHD16A, are activated, except that calcium signaling, reorganization of the membrane lipids by ABHD16A (Fig. 3), as well as contact with the ER membrane and actin precede the membrane constriction necessary for DRP1 recruitment (Lewis et al., 2016; Nguyen and Voeltz, 2022). The role of a second dynamin (Dyn2, DNM2) in membrane scission is not shown.

Steps in the division of POs and mitochondria. (i) Growth of the organelle and signaling of division. Growth of POs and mitochondria occurs by the import of membrane and matrix proteins, as well as lipids, to the organelles. Signals that activate division can be cell intrinsic or extrinsic (see “Signals that determine when POs and mitochondria will divide” section). (ii) Membrane reorganization, tubulation, and elongation. Membrane reorganization involves lipid rearrangements. Membrane elongation and tubulation require lipid delivery from other organelles to the site of membrane synthesis and curvature by local lipid synthesis and/or transfer using vesicular and non-vesicular processes. (iii) Marking sites on organelles by membrane constriction. This involves organelle-specific proteins (see text) and contact with the ER. There is evidence for both POs (Koch et al., 2004) and mitochondria (Kraus and Ryan, 2017) that membrane tubulation, elongation, and constriction occur prior to Dnm1/DRP1 assembly and action. (iv) Relocalization and activation of organelle-specific components, typically involving PTMs. (v) Recruitment and activation of Dnm1/DRP1 and formation of a double-ring contractile structure. Dynamin-like proteins involved in peroxisomal and mitochondrial division are cytosolic. (vi) Membrane scission. See text for details. (vii) Disassembly of the fission machinery (see text). (A) Division of POs. In yeast, the phosphorylation of Pex11 is necessary for its movement from the ER to POs (Fig. 3; Knoblach and Rachubinski, 2010), although in P. pastoris Pex11 is phosphorylated at the POs (Joshi et al., 2012). Pex11 phosphorylation is also necessary for its interaction with Fis1 (Joshi et al., 2012), which recruits Dnm1 to the PO membrane for division. Since Pex11 can serve as a GAP for Dnm1, the activation of Pex11 by phosphorylation (Joshi et al., 2012; Knoblach and Rachubinski, 2010), its movement in the PO membranes to the membrane constriction sites (Nagotu et al., 2008), and its interaction with Dnm1 are necessary steps in triggering peroxisomal division (Williams et al., 2015). Vps1, which is involved only in peroxisomal division in glucose-grown yeast, interacts with Pex19, Vps27, and Inp1, as well as with actin-cytoskeleton proteins like Rvs161 and Mvp1 (see text), but its role is not shown here. (B) Division of mitochondria. Not much is known regarding how exactly mitochondria-specific proteins, such as ABHD16A, are activated, except that calcium signaling, reorganization of the membrane lipids by ABHD16A (Fig. 3), as well as contact with the ER membrane and actin precede the membrane constriction necessary for DRP1 recruitment (Lewis et al., 2016; Nguyen and Voeltz, 2022). The role of a second dynamin (Dyn2, DNM2) in membrane scission is not shown.

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