Journal Article

FZJ-2025-03030

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Allosteric modulation of proton binding confers Cl- activation and glutamate selectivity to vesicular glutamate transporters

Borghans, B.FZJ* ; Kortzak, D.FZJ* ; Longo, P.FZJ* ; Kolen, B.FZJ* ; Machtens, J.-P.FZJ* ; Fahlke, C. (Corresponding author)FZJ*

2025
Public Library of Science San Francisco, Calif.

This record in other databases:  

Please use a persistent id in citations: doi:10.1371/journal.pcbi.1013214  doi:10.34734/FZJ-2025-03030

Abstract: Vesicular glutamate transporters (VGLUTs) fill synaptic vesicles with glutamate andremove luminal Cl- via an additional anion channel mode. Both of these transportfunctions are stimulated by luminal acidification, luminal-positive membrane potential,and luminal Cl-. We studied VGLUT1 transporter/channel activation using acombination of heterologous expression, cellular electrophysiology, fast solutionexchange, and mathematical modeling. Cl- channel gating can be described with akinetic scheme that includes two protonation sites and distinct opening, closing, andCl--binding rates for each protonation state. Cl- binding promotes channel openingby modifying the pKa values of the protonation sites and rates of pore opening andclosure. VGLUT1 transports glutamate and aspartate at distinct stoichiometries:H+-glutamate exchange at 1:1 stoichiometry and aspartate uniport. Neurotransmittertransport with variable stoichiometry can be described with an alternating accessmodel that assumes that transporters without substrate translocate in the doubly protonatedstate to the inward-facing conformation and return with the bound amino acidsubstrate as either singly or doubly protonated. Glutamate, but not aspartate, promotesthe release of one proton from inward-facing VGLUT1, resulting in preferentialH+-coupled glutamate exchange. Cl- stimulates glutamate transport by making theglutamate-binding site accessible to cytoplasmic glutamate and by facilitating transitionsto the inward-facing conformation after outward substrate release. We concludethat allosteric modification of transporter protonation by Cl- is crucial for both VGLUT1transport functions.

---

Contributing Institute(s):

1. Molekular- und Zellphysiologie (IBI-1)

Research Program(s):

1. 5241 - Molecular Information Processing in Cellular Systems (POF4-524) (POF4-524)
2. 5244 - Information Processing in Neuronal Networks (POF4-524) (POF4-524)
3. DFG project G:(GEPRIS)291198853 - FOR 2518: Funktionale Dynamik von Ionenkanälen und Transportern - DynIon - (291198853) (291198853)
4. DFG project G:(GEPRIS)394431587 - FOR 2795: Synapsen unter Stress: akute Veränderungen durch mangelnde Energiezufuhr an glutamatergen Synapsen (394431587) (394431587)

---

Database coverage:
; ; ; ; Article Processing Charges ; BIOSIS Previews ; Biological Abstracts ; Clarivate Analytics Master Journal List ; DOAJ Seal ; Ebsco Academic Search ; Essential Science Indicators ; Fees ; IF < 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

---