Functions in mitochondrial and peroxisomal division. Mediates membrane fission through oligomerization into membrane-associated tubular structures that wrap around the scission site to constrict and sever the mitochondrial membrane through a GTP hydrolysis-dependent mechanism. The specific recruitment at scission sites is mediated by membrane receptors like MFF, MIEF1 and MIEF2 for mitochondrial membranes. While the recruitment by the membrane receptors is GTP-dependent, the following hydrolysis of GTP induces the dissociation from the receptors and allows DNM1L filaments to curl into closed rings that are probably sufficient to sever a double membrane. Acts downstream of PINK1 to promote mitochondrial fission in a PRKN-dependent manner. Plays an important role in mitochondrial fission during mitosis (By similarity). Through its function in mitochondrial division, ensures the survival of at least some types of postmitotic neurons, including Purkinje cells, by suppressing oxidative damage (By similarity). Required for normal brain development, including that of cerebellum (By similarity). Facilitates developmentally regulated apoptosis during neural tube formation. Required for a normal rate of cytochrome c release and caspase activation during apoptosis; this requirement may depend upon the cell type and the physiological apoptotic cues (By similarity). Required for formation of endocytic vesicles. Proposed to regulate synaptic vesicle membrane dynamics through association with BCL2L1 isoform Bcl-X(L) which stimulates its GTPase activity in synaptic vesicles; the function may require its recruitment by MFF to clathrin-containing vesicles. Required for programmed necrosis execution. Rhythmic control of its activity following phosphorylation at Ser-650 is essential for the circadian control of mitochondrial ATP production (By similarity). GTP + H2O = GDP + H(+) + phosphate Homotetramer; dimerizes through the N-terminal GTP-middle region of one molecule binding to the GED domain of another DNM1L molecule. Oligomerizes in a GTP-dependent manner to form membrane-associated tubules with a spiral pattern. Interacts with GSK3B and MARCHF5. Interacts (via the GTPase and B domains) with UBE2I; the interaction promotes sumoylation of DNM1L, mainly in its B domain. Interacts with PPP3CA; the interaction dephosphorylates DNM1L and regulates its transition to mitochondria. Interacts with BCL2L1 isoform BCL-X(L) and CLTA; DNM1L and BCL2L1 isoform BCL-X(L) may form a complex in synaptic vesicles that also contains clathrin and MFF. Interacts with MFF; the interaction is inhinited by C11orf65/MFI. Interacts with FIS1. Interacts with MIEF2 and MIEF1; GTP-dependent, regulates GTP hydrolysis and DNM1L oligomerization. Interacts with PGAM5; this interaction leads to dephosphorylation at Ser-656 and activation of GTPase activity and eventually to mitochondria fragmentation. Interacts with RALBP1; during mitosis, recruits DNM1L to the mitochondrion and mediates its activation by the mitotic kinase cyclin B-CDK1 (By similarity). Mainly cytosolic. Recruited by RALA and RALBP1 to mitochondrion during mitosis (By similarity). Translocated to the mitochondrial membrane through O-GlcNAcylation and interaction with FIS1. Colocalized with MARCHF5 at mitochondrial membrane. Localizes to mitochondria at sites of division. Localizes to mitochondria following necrosis induction. Recruited to the mitochondrial outer membrane by interaction with MIEF1. Mitochondrial recruitment is inhibited by C11orf65/MFI (By similarity). Associated with peroxisomal membranes, partly recruited there by PEX11B. May also be associated with endoplasmic reticulum tubules and cytoplasmic vesicles and found to be perinuclear. In some cell types, localizes to the Golgi complex (By similarity). Binds to phospholipid membranes (By similarity). The GED domain folds back to interact, in cis, with the GTP-binding domain and middle domain, and interacts, in trans, with the GED domains of other DNM1L molecules, and is thus critical for activating GTPase activity and for DNM1L dimerization. Phosphorylation/dephosphorylation events on two sites near the GED domain regulate mitochondrial fission. Phosphorylation on Ser-650 by CAMK1 and PKA inhibits the GTPase activity, leading to a defect in mitochondrial fission promoting mitochondrial elongation. Dephosphorylated on this site by PPP3CA which promotes mitochondrial fission. Phosphorylation on Ser-629 by CDK1 and PINK1 activates the GTPase activity and promotes mitochondrial fission. Phosphorylated in a circadian manner at Ser-650. Sumoylated on various lysine residues within the B domain, probably by MUL1. Sumoylation positively regulates mitochondrial fission. Desumoylated by SENP5 during G2/M transition of mitosis. Appears to be linked to its catalytic activity (By similarity). S-nitrosylation increases DNM1L dimerization, mitochondrial fission and causes neuronal damage. O-GlcNAcylation augments the level of the GTP-bound active form of DNM1L and induces translocation from the cytoplasm to mitochondria in cardiomyocytes. It also decreases phosphorylation at Ser-650 (By similarity). Ubiquitination by MARCHF5 affects mitochondrial morphology. Belongs to the TRAFAC class dynamin-like GTPase superfamily. Dynamin/Fzo/YdjA family.