| 1. |
- Farsi, Zohreh, et al.
(författare)
-
Clathrin coat controls synaptic vesicle acidification by blocking vacuolar ATPase activity
- 2018
-
Ingår i: eLIFE. - : ELIFE SCIENCES PUBLICATIONS LTD. - 2050-084X. ; 7
-
Tidskriftsartikel (refereegranskat)abstract
- Newly-formed synaptic vesicles (SVs) are rapidly acidified by vacuolar adenosine triphosphatases (vATPases), generating a proton electrochemical gradient that drives neurotransmitter loading. Clathrin-mediated endocytosis is needed for the formation of new SVs, yet it is unclear when endocytosed vesicles acidify and refill at the synapse. Here, we isolated clathrin-coated vesicles (CCVs) from mouse brain to measure their acidification directly at the single vesicle level. We observed that the ATP-induced acidification of CCVs was strikingly reduced in comparison to SVs. Remarkably, when the coat was removed from CCVs, uncoated vesicles regained ATP-dependent acidification, demonstrating that CCVs contain the functional vATPase, yet its function is inhibited by the clathrin coat. Considering the known structures of the vATPase and clathrin coat, we propose a model in which the formation of the coat surrounds the vATPase and blocks its activity. Such inhibition is likely fundamental for the proper timing of SV refilling.
|
|
| 2. |
- Gowrisankaran, Sindhuja, et al.
(författare)
-
Cells Control BIN1-Mediated Membrane Tubulation by Altering the Membrane Charge
- 2020
-
Ingår i: Journal of Molecular Biology. - : ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD. - 0022-2836 .- 1089-8638. ; 432:4, s. 1235-1250
-
Tidskriftsartikel (refereegranskat)abstract
- The Bridging integrator 1 (BIN1)/Amphiphysin/Rvs (BAR) protein family is an essential part of the cell's machinery to bend membranes. BIN1 is a muscle-enriched BAR protein with an established role in muscle development and skeletal myopathies. Here, we demonstrate that BIN1, on its own, is able to form complex interconnected tubular systems in vitro, reminiscent of t-tubule system in muscle cells. We further describe how BIN1's electrostatic interactions regulate membrane bending: the ratio of negatively charged lipids in the bilayer altered membrane bending and binding properties of BIN1 and so did the manipulation of BIN1's surface charge. We show that the electrostatically mediated BIN1 membrane binding depended on the membrane curvature-it was less affected in liposomes with high curvature. Curiously, BIN1 membrane binding and bending was diminished in cells where the membrane's charge was experimentally reduced. Membrane bending was also reduced in BIN1 mutants where negative or positive charges in the BAR domain have been eliminated. This phenotype, characteristic of BIN1 mutants linked to myopathies, was rescued when the membrane charge was made more negative. The latter findings also show that cells can control tubulation at their membranes by simply altering the membrane charge and through it, the recruitment of BAR proteins and their interaction partners (e.g. dynamin).
|
|
