Biophysical Society Thematic Meeting | Bucharest 2026

Biophysics of Membrane Reactions in Brian

Tuesday Speaker Abstracts

MOLECULAR PHYSIOLOGY OF VESICULAR GLUTAMATE TRANSPORTERS Christoph Fahlke ; Victor Lugo Forschungszentrum Juelich, Molecular and Cell Physiology, Juelich, Germany Vesicular glutamate transporters accumulate glutamate in synaptic vesicles, where they also function as Cl- efflux pathway to permit osmotically neutral neurotransmitter accumulation. We combined cellular electrophysiology with mathematical modeling to describe this dual function in rat as well as in Drosophila melanogaster VGLUT. Rat VGLUT1 functions as stoichiometrically coupled H+-glutamate exchanger, with a transport rate of around 600 s-1 at - 160 mV. Transport of other large anions, including aspartate, is not stoichiometrically coupled to H+ transport, and Cl- permeates VGLUT1 through an aqueous anion channel with unitary transport rates of 1.5 × 105 s-1 at -160 mV. DVGLUT and rVGLUT1 closely resemble in glutamate transport. In both, luminal Cl- is necessary as allosteric activator, however, the allosteric affinity is higher in fly than in rat transporters. DVGLUT anion channels exhibit lower unitary currents, but higher anion channel open probabilities, resulting in larger Cl- currents for the fly transporter in the presence of cytoplasmic glutamate. The higher allosteric affinity together with the enhanced anion channel activity may serve as evolutionary adaptation of VGLUTs to lower ion concentrations in Drosophila, illustrating the impact of these particular features for synaptic vesicle filling.

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