Presynaptic regulation of quantal size: K+/H+ exchange stimulates vesicular glutamate transport

Department of Physiology, Graduate Program in Neuroscience, University of California, San Francisco, San Francisco, California, USA.
Nature Neuroscience (Impact Factor: 16.1). 08/2011; 14(10):1285-92. DOI: 10.1038/nn.2898
Source: PubMed


The amount of neurotransmitter stored in a single synaptic vesicle can determine the size of the postsynaptic response, but the factors that regulate vesicle filling are poorly understood. A proton electrochemical gradient (Δμ(H+)) generated by the vacuolar H(+)-ATPase drives the accumulation of classical transmitters into synaptic vesicles. The chemical component of Δμ(H+) (ΔpH) has received particular attention for its role in the vesicular transport of cationic transmitters as well as in protein sorting and degradation. Thus, considerable work has addressed the factors that promote ΔpH. However, synaptic vesicle uptake of the principal excitatory transmitter glutamate depends on the electrical component of Δμ(H+) (Δψ). We found that rat brain synaptic vesicles express monovalent cation/H(+) exchange activity that converts ΔpH into Δψ, and that this promotes synaptic vesicle filling with glutamate. Manipulating presynaptic K(+) at a glutamatergic synapse influenced quantal size, indicating that synaptic vesicle K(+)/H(+) exchange regulates glutamate release and synaptic transmission.

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    • "ΔpH was determined by measuring the fluorescence quench - ing of acridine orange ( 1 . 5 μM ) in a Spectra Max M5 microplate reader spectrophotometer as previously described using an exci - tation wavelength of 492 nm and an emission wavelength of 537 nm ( Goh et al . , 2011 ) . The reaction was initiated by the addition of 1 mM MgCl2 in the presence of 1 mM ATP to a reaction medium contain - ing 30 μg of synaptic vesicle protein , 140 mM KCl , and 10 mM Mops – Tris ( pH 7 . 4 ) . The reaction was terminated by the addition of Triton X - 100 to a final concentration of 10 μM . JM - 20 effects were evalu - a"
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