title: Control of neurotransmitter release by an internal gel matrix in synaptic vesicles.
abstract: Neurotransmitters are stored in synaptic vesicles, where they have been assumed to be in free solution. Here we report that in Torpedo synaptic vesicles, only 5% of the total acetylcholine (ACh) or ATP content is free, and that the rest is adsorbed to an intravesicular proteoglycan matrix. This matrix, which controls ACh and ATP release by an ion-exchange mechanism, behaves like a smart gel. That is, it releases neurotransmitter and changes its volume when challenged with small ionic concentration change. Immunodetection analysis revealed that the synaptic vesicle proteoglycan SV2 is the core of the intravesicular matrix and is responsible for immobilization and release of ACh and ATP. We suggest that in the early steps of vesicle fusion, this internal matrix regulates the availability of free diffusible ACh and ATP, and thus serves to modulate the quantity of transmitter released.
authors.affiliation: Laboratory of Cellular and Molecular Neurobiology, Department of Cell Biology and Pathology, Medical School, Bellvitge Hospital, University of Barcelona-Campus of Bellvitge, Hospitalet de Llobregat, E-08907 Barcelona, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Reigada
authors.forename: Ismael
authors.initials: I
authors.lastname: Díez-Pérez
authors.forename: Pau
authors.initials: P
authors.lastname: Gorostiza
authors.forename: Albert
authors.initials: A
authors.lastname: Verdaguer
authors.forename: Inmaculada
authors.initials: I
authors.lastname: Gómez de Aranda
authors.forename: Oriol
authors.initials: O
authors.lastname: Pineda
authors.forename: Jaume
authors.initials: J
authors.lastname: Vilarrasa
authors.forename: Jordi
authors.initials: J
authors.lastname: Marsal
authors.forename: Joan
authors.initials: J
authors.lastname: Blasi
authors.forename: Jordi
authors.initials: J
authors.lastname: Aleu
authors.forename: Carles
authors.initials: C
authors.lastname: Solsona
mesh_terms: D000109:Acetylcholine / Q000737:chemistry / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D004557:Electric Organ / Q000378:metabolism; D005782:Gels; D066298:In Vitro Techniques; D018625:Microscopy, Atomic Force; D008958:Models, Molecular; D018377:Neurotransmitter Agents / Q000378:metabolism*; D010539:Permeability; D013572:Synaptic Vesicles / Q000378:metabolism*; D014101:Torpedo / Q000502:physiology
chemical_list: D005782:Gels; D018377:Neurotransmitter Agents; D000255:Adenosine Triphosphate; D000109:Acetylcholine