title: Regulation of synaptic vesicle recycling by calcineurin in different vesicle pools.
abstract: The synaptic vesicles keep recycling by the processes of endocytosis and exocytosis to maintain the normal synaptic transmission. The synaptic vesicles are classified as the readily releasable pool (RRP) and the reserve pool (RP). In the endocytosis process, calcineurin (CaN), a Ca2+/calmodulin-dependent protein phosphatase, has been shown to play important roles. However, it is unclear about its roles in different vesicle pools. Here, we investigated the role of CaN in the regulation of vesicle recycling in the RRP and RP. Vesicle recycling was monitored by using fluorescent dyes FM1-43 and FM4-64 in the primary cultures of hippocampal neurons. Inhibition of CaN by FK506 and cyclosporin A suppressed the endocytosis in the RP, but not in the RRP. Inhibition of CaN also restrained the exocytic process triggered by 10 Hz stimulation, but had no effect on 3-5 Hz stimulation-induced exocytosis. FK506 also reduced the total vesicle pool size in the synaptic terminals. A synthesized CaN inhibitory peptide showed the similar effects as FK506 and cyclosporin A. These results revealed a novel mechanism that CaN plays critical roles in the distinct vesicle recycling processes.
authors.affiliation: Department of Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kumashiro
authors.forename: Yun-Fei
authors.initials: YF
authors.lastname: Lu
authors.forename: Kazuhito
authors.initials: K
authors.lastname: Tomizawa
authors.forename: Masayuki
authors.initials: M
authors.lastname: Matsushita
authors.forename: Fan-Yan
authors.initials: FY
authors.lastname: Wei
authors.forename: Hideki
authors.initials: H
authors.lastname: Matsui
mesh_terms: D000818:Animals; D019703:Calcineurin / Q000187:drug effects / Q000378:metabolism*; D002478:Cells, Cultured; D016572:Cyclosporine / Q000494:pharmacology; D004705:Endocytosis / Q000187:drug effects / Q000502:physiology*; D005089:Exocytosis / Q000187:drug effects / Q000502:physiology*; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism; D007166:Immunosuppressive Agents / Q000494:pharmacology; D008856:Microscopy, Fluorescence; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D009435:Synaptic Transmission / Q000502:physiology; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D016559:Tacrolimus / Q000494:pharmacology
chemical_list: D007166:Immunosuppressive Agents; D016572:Cyclosporine; D019703:Calcineurin; D016559:Tacrolimus