title: Efficient synaptic vesicle recycling after intense exocytosis concomitant with the accumulation of non-releasable endosomes at early developmental stages.
abstract: Following the exocytosis of neurotransmitter-containing synaptic vesicles, endocytosis is fundamental to re-establishing conditions for synaptic transmission. As there are distinct endocytotic pathways that each differ in their efficiency to generate releasable synaptic vesicles, we used the dye FM1-43 to track vesicle recycling, and to determine whether nerve terminals use multiple pathways of endocytosis. We identified two types of synaptic boutons in cultured cerebellar granule cells that were characterized by weak or strong FM1-43-unloading profiles. Decreasing the extent of exocytosis dramatically increased the proportion of synaptic boutons that exhibited strong FM1-43-unloading and dramatically reduced the number of endosome-like structures. Hence, we concluded that efficient recycling of synaptic vesicles is concomitant with the formation of non-releasable endosomes in both types of synaptic boutons, although to different extents. Furthermore, cell maturation in culture increased the proportion of synaptic boutons that were capable of an intense release response, whereas the chronic blockage of synaptic activity diminished the capacity of boutons to release dye.
authors.affiliation: Departamento de Bioquímica, Facultad de Veterinaria, Universidad Complutense, Madrid 28040, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Bartolomé-Martín
authors.forename: Jorge
authors.initials: J
authors.lastname: Ramírez-Franco
authors.forename: Enrique
authors.initials: E
authors.lastname: Castro
authors.forename: José
authors.initials: J
authors.lastname: Sánchez-Prieto
authors.forename: Magdalena
authors.initials: M
authors.lastname: Torres
mesh_terms: D000818:Animals; D065095:Calcineurin Inhibitors; D002478:Cells, Cultured; D002531:Cerebellum / Q000166:cytology / Q000378:metabolism; D034281:Dynamins / Q000502:physiology; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism*; D005089:Exocytosis; D005260:Female; D005456:Fluorescent Dyes; D008297:Male; D017729:Presynaptic Terminals / Q000145:classification / Q000378:metabolism; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D051381:Rats; D017208:Rats, Wistar; D013572:Synaptic Vesicles / Q000187:drug effects / Q000378:metabolism*; D016559:Tacrolimus / Q000494:pharmacology
chemical_list: D065095:Calcineurin Inhibitors; C073804:FM1 43; D005456:Fluorescent Dyes; D011726:Pyridinium Compounds; D000644:Quaternary Ammonium Compounds; D034281:Dynamins; D016559:Tacrolimus