Control of neurotransmitter release by an internal gel matrix in synaptic vesicles.
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.
Reigada
David
D
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.
Díez-Pérez
Ismael
I
Gorostiza
Pau
P
Verdaguer
Albert
A
Gómez de Aranda
Inmaculada
I
Pineda
Oriol
O
Vilarrasa
Jaume
J
Marsal
Jordi
J
Blasi
Joan
J
Aleu
Jordi
J
Solsona
Carles
C
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
D005782:Gels; D018377:Neurotransmitter Agents; D000255:Adenosine Triphosphate; D000109:Acetylcholine