Alternate pleckstrin homology domain orientations regulate dynamin-catalyzed membrane fission

Abstract

The isolated dynamin PH domain is an assembly-independent sensor of membrane curvature but not a curvature generator. In full-length dynamin, the PH alternates between two different orientations on the membrane surface during the GTP hydrolysis cycle, causing dramatic fluctuations in the diameter of dynamin polymers.

A Dynamin Mutant Defines a Superconstricted Prefission State

“…The PH domain can also actively destabilize the lipid bilayer, possibly promoting the fission reaction (Bethoney et al, 2009; Ramachandran and Schmid, 2008; Shnyrova et al, 2013). We suggest that the PH domain rearrangement we observe in the super-constricted state represents either the initiation of the PH domain ‘tilting’ proposed to evoke fission (Shnyrova et al, 2013) or the observed ‘retracted’ state of the PH domain proposed to keep dynamin on the membrane surface during the GTP hydrolysis cycle (Mehrotra et al, 2014). …”

Geometry of membrane fission

“…In the case of PHD, strong electrostatic adhesion between PHD and lipids drives small hydrophobic parts of the domain to wedge into the membrane (Lenoir et al, 2010). The PHD of FAPP has been shown to both discriminate and generate membrane curvature (Cao et al, 2009;Lenoir et al, 2010), while the PHD of dynamin was only a sensor of membrane curvature (Mehrotra et al, 2014).…”

“…Similarly, multiple PHDs have to be coordinated by a larger protein structure, e.g. dynamin polymer, to produce fission (Mehrotra et al, 2014). We are just starting to understand how the interplay between membrane wedging and the shape of the proteins and protein oligomers affects fission reaction (Boucrot et al, 2012;Shnyrova et al, 2013).…”

“…Dynamin-1 is a large GTPase forming dense collars on the necks of endocytic vesicles (Schmid and Frolov, 2011). Dynamin interacts with lipids via its atypical PHD that discriminate membrane curvature by the variable loop 1 (VL1) (Mehrotra et al, 2014). Cryo-electron micrographs of dynamin collars assembled in vitro revealed helical structures with a pitch of approximately 10 nm encaging the lipid bilayer cylinder (Zhang and Hinshaw, 2001).…”

“…The model described the stochastic coupling of constriction with fission, seen in the periodic disassembly of the dynamin scaffold upon GTP hydrolysis (Shnyrova et al, 2013). It also accounted for the critical dependence of fission on membrane wedging, evident in the inhibition of fission by mutations in VL1 interfering with the membrane insertion of PHD (Mehrotra et al, 2014;Ramachandran et al, 2009). The model proposed that fission is achieved by actively limiting the length of dynamin helix to just two rungs, the configuration maximizing the cumulative effect of PHDs situated on the helix.…”