Building a fission machine – structural insights into dynamin assembly and activation

Abstract

SummaryDynamin is a large multidomain GTPase that assembles into helical arrays around the necks of deeply invaginated clathrin-coated pits and catalyzes membrane fission during the final stages of endocytosis. Although it is well established that the function of dynamin in vivo depends on its oligomerization and its capacity for efficient GTP hydrolysis, the molecular mechanisms governing these activities have remained poorly defined. In recent years, there has been an explosion of structural data that has provided new insights into the architecture, organization and nucleotide-dependent conformational changes of the dynamin fission machine. Here, we review the key findings of these efforts and discuss the implications of each with regard to GTP hydrolysis, dynamin assembly and membrane fission.

Toxicity of an α-Pore-forming Toxin Depends on the Assembly Mechanism on the Target Membrane as Revealed by Single Molecule Imaging

“…Interestingly, in the case of the less active EqtII form, the single molecule approach allowed the detection of a small population of EqtII particles that diffuse freely, which interestingly corresponds to monomeric and dimeric forms of the toxin. This suggests that the confined diffusion observed for EqtII particles is due to the formation of larger oligomers, which would increase the likelihood of particle diffusion being affected by membrane crowding, interactions with the cytoskeleton and/or presence of raft-like domains (37,38).…”

Molecular Structure, Function, and Dynamics of Clathrin-Mediated Membrane Traffic

“…alytic domain (Chappie et al 2009;Faelber et al 2011;Ford et al 2011;Chappie and Dyda 2013). In human cells, three isoforms-dynamins 1, 2, and 3-drive the pinching off of endocytic-coated vesicles at the plasma membrane, through a cycle of oligomerization and GTP hydrolysis.…”

“…Release of a coated vesicle thus requires that dynamin enable the neck of a coated pit to reorganize into a transition state that leads to pinching, although the mechanism remains unknown (for recent reviews, see Schmid and Frolov 2011;Chappie and Dyda 2013;Morlot and Roux 2013;Johannes et al 2014). Acute inhibition of the dynamin GTPase activity with the compound dynasore causes accumulation of coated pits at two stages-pits with a fully constricted neck ("omega"-shaped cross sections) (Heuser 1980;Macia et al 2006) as might be expected from the properties of dynamin collars and helices on lipid tubes in vitro, and pits just at the point at which a constriction is beginning to form ("U"-shaped cross sections).…”

Cargo adaptors: structures illuminate mechanisms regulating vesicle biogenesis

“…A number of proteins and lipid components are known to be important for vesicle fission, including proteins that physically insert into the membrane such as the Sar1 GTPase [93] and epsin [94, 92] , proteins that constrict the diameter of the budding vesicle neck such as dynamin [4, 91, 95] or otherwise generate membrane curvature such as the banana-shaped BAR-domain proteins [96, 92, 97] , structural protein scaffolds such as the Sec13/31 COPII subcomplex [98] , and specific lipids encouraging membrane deformation by altering the biophysical properties of the bilayer [99, 100] . In fact, multiple factors are important for driving and regulating fission of a nascent vesicle or membrane tubule [101–104] .…”