Regulation of synaptic vesicle recycling by calcineurin in different vesicle pools.
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.
Kumashiro
Susumu
S
Department of Physiology, Okayama University Graduate School of Medicine and Dentistry, Okayama 700-8558, Japan.
Lu
Yun-Fei
YF
Tomizawa
Kazuhito
K
Matsushita
Masayuki
M
Wei
Fan-Yan
FY
Matsui
Hideki
H
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
D007166:Immunosuppressive Agents; D016572:Cyclosporine; D019703:Calcineurin; D016559:Tacrolimus