High throughput platform to study cell membrane fission
29 Oct 2015
A high throughput platform to study cell membrane fission
By Dr Thomas Pucadyil, Intermediate Fellow, IISER Pune
Membrane fission requires the localized application of curvature stresses to the lipid bilayer in order for a membrane tube to go from a highly constricted to a cut state. Since these topological transformations require the bilayer to deviate from its preferred planar configuration, membrane fission is an energetically unfavorable process. The GTPase dynamin represent a group of specialized protein machines that catalyze membrane fission. Dynamin manages this process by self-assembling into a helical scaffold that hydrolyzes GTP to constrict and cut the underlying membrane tube. How it does it has been a subject of intense controversy.
Membrane fission reactions are carried out in a confined region of the membrane enclosed within a 10 nm wide, 2-rung scaffold comprised of ~26 molecules of dynamin. Thus, the changes in shape of the underlying membrane tube have been difficult to probe. The team led by Thomas Pucadyil at IISER Pune have now devised a novel model membrane system comprised of narrow membrane tubes laid on a non-reactive glass surface, which they call supported membrane tubes or SMrTs. Membrane tubes represent an ideal mimic of the necks of clathrin-coated pits, the physiological substrate upon which dynamin is thought to act in cells. Since the tubes are stably laid out on a glass surface, one can now use conventional wide field microscopic approaches to locally probe changes in membrane shape during a single dynamin-catalyzed fission event. Indeed, results from such experiments reveal the necessity for GTP hydrolysis during dynamin-caatlyzed membrane fission. Dynamin self-assembly into a helical scaffold constricts the underlying tube but does so to a moderate extent. GTP hydrolysis is required for further constricting the underlying tube for it to reach dimensions necessary for fission.
The paper titled “A high-throughput platform for real-time analysis of membrane fission reactions reveals dynamin function” and authored by Srishti Dar, Sukrut Kamerkar and Thomas Pucadyil has appeared as an advance online publication of Nature Cell Biology. The paper can be accessed here