Clathrin coat controls synaptic vesicle acidification by blocking vacuolar ATPase activity

• Main Authors: Zohreh Farsi, Sindhuja Gowrisankaran, Matija Krunic, Burkhard Rammner, Andrew Woehler, Eileen M Lafer, Carsten Mim, Reinhard Jahn, Ira Milosevic
• Format: Article
• Language: English
• Published: eLife Sciences Publications Ltd 2018-04-01
• Series: eLife
• Subjects: synaptic vesicle; proton pump; clathrin coat; endocytosis; vATPase; acidification
• Online Access: https://elifesciences.org/articles/32569

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.