The Journal of Neuroscience, September 2, 2009, 29(35):11038-11042; doi:10.1523/JNEUROSCI.2367-09.2009
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Brief Communications
Rapid Endocytosis Does Not Recycle Vesicles within the Readily Releasable Pool
Xin-Sheng Wu and
Ling-Gang Wu
Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland 20892
Correspondence should be addressed to Ling-Gang Wu, Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, MD 20892. Email: wul{at}ninds.nih.gov
Endocytosis is essential in maintaining exocytosis at secretory cells. Rapid endocytosis with a time course less than a few seconds is widely observed at nerve terminals and non-neuronal secretory cells. It is generally assumed that rapid endocytosis recycles vesicles within the readily releasable pool (RRP) via a kiss-and-run mechanism that involves rapid opening and closure of a fusion pore at the release site. The present work suggests that both rapid (
less than
2 s) and slow (
=
10–20 s) endocytosis do not recycle vesicles to the RRP but to a recycling pool at least a few times larger than the RRP at a nerve terminal, the calyx of Held in rat brainstem. Challenging the long-held view that rapid endocytosis offers a rapid, local vesicle recycling within the RRP, our finding calls for reconsideration of the function and the underlying mechanism of rapid endocytosis. We suggest that rapid endocytosis provides the nerve terminal the ability to recycle vesicles rapidly via the recycling pool and to maintain the normal morphology of the nerve terminal, including the release site, by rapidly clearing the fused vesicle membrane from the release site during intense firing.
Received May 19, 2009;
revised July 9, 2009;
accepted July 24, 2009.
Correspondence should be addressed to Ling-Gang Wu, Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, 35 Convent Drive, Building 35, Room 2B-1012, Bethesda, MD 20892. Email: wul{at}ninds.nih.gov