title: A three-pool model dissecting readily releasable pool replenishment at the calyx of held.
abstract: Although vesicle replenishment is critical in maintaining exo-endocytosis recycling, the underlying mechanisms are not well understood. Previous studies have shown that both rapid and slow endocytosis recycle into a very large recycling pool instead of within the readily releasable pool (RRP), and the time course of RRP replenishment is slowed down by more intense stimulation. This finding contradicts the calcium/calmodulin-dependence of RRP replenishment. Here we address this issue and report a three-pool model for RRP replenishment at a central synapse. Both rapid and slow endocytosis provide vesicles to a large reserve pool (RP) ~42.3 times the RRP size. When moving from the RP to the RRP, vesicles entered an intermediate pool (IP) ~2.7 times the RRP size with slow RP-IP kinetics and fast IP-RRP kinetics, which was responsible for the well-established slow and rapid components of RRP replenishment. Depletion of the IP caused the slower RRP replenishment observed after intense stimulation. These results establish, for the first time, a realistic cycling model with all parameters measured, revealing the contribution of each cycling step in synaptic transmission. The results call for modification of the current view of the vesicle recycling steps and their roles.
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Jun
authors.initials: J
authors.lastname: Guo
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Jian-long
authors.initials: JL
authors.lastname: Ge
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Mei
authors.initials: M
authors.lastname: Hao
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Zhi-cheng
authors.initials: ZC
authors.lastname: Sun
authors.affiliation: Synaptic Transmission Section, National Institute of Neurological Disorders and Stroke, Bethesda, Maryland, 20892.
authors.forename: Xin-sheng
authors.initials: XS
authors.lastname: Wu
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Jian-bing
authors.initials: JB
authors.lastname: Zhu
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Wei
authors.initials: W
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Pan-tong
authors.initials: PT
authors.lastname: Yao
authors.affiliation: School of Mathematical Sciences, Centre for Computational Systems Biology and Shanghai Centre for Mathematical Sciences, Fudan University, P.R.China, 200433.
authors.forename: Wei
authors.initials: W
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Genetic Engineering, Collaborative Innovation Center of Genetics and Development, Department of Physiology and Biophysics, School of Life Sciences, Fudan University, Shanghai, P.R. China, 200433.
authors.forename: Lei
authors.initials: L
authors.lastname: Xue
mesh_terms: D000465:Algorithms; D000818:Animals; D004705:Endocytosis / Q000502:physiology*; D005089:Exocytosis / Q000502:physiology*; D005260:Female; D008297:Male; D008954:Models, Biological; D051381:Rats; D009435:Synaptic Transmission; D013572:Synaptic Vesicles
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