Revised Ion/Substrate Coupling Stoichiometry of GABA Transporters
Sepehr Eskandari1, Samantha L Willford2, Cynthia M Anderson2
1Biological Sciences Department, California State Polytechnic University, Pomona, CA, 91768, USA. seskandari@cpp.edu.
Advances in Neurobiology
|August 23, 2017
Summary
This study confirms a 3 Na+:1 Cl-:1 GABA stoichiometry for plasma membrane GABA transporters. This finding refines our understanding of GABA homeostasis in the brain under various conditions.
Area of Science:
- Neuroscience
- Molecular Biology
- Biophysics
Background:
- Plasma membrane GABA transporters (e.g., SLC6A1) are crucial for regulating neurotransmitter levels in the brain.
- Understanding the precise stoichiometry of these transporters is essential for comprehending GABA homeostasis.
- Previous models of GABA transporter stoichiometry lacked definitive experimental validation.
Purpose of the Study:
- To present compelling evidence for a 3 Na+:1 Cl-:1 GABA coupling stoichiometry for plasma membrane GABA transporters.
- To elucidate how this revised stoichiometry impacts the understanding of GABA transporter function in synaptic and extrasynaptic brain regions.
- To analyze the contribution of GABA transporters to GABA homeostasis under physiological and pathophysiological conditions.
Main Methods:
- Analysis of six independent experimental measurements, including thermodynamic transporter reversal potential shifts.
- Investigating the impact of varying extracellular Na+, Cl-, and GABA concentrations.
- Utilizing voltage-clamp conditions to determine charge flux to substrate flux ratios for Na+, Cl-, and GABA.
Main Results:
- Experimental data strongly supported a 3 Na+:1 Cl-:1 GABA stoichiometry, accurately predicting all six measurements.
- Shifts in transporter reversal potential for tenfold concentration changes were 84 mV (Na+), 30 mV (Cl-), and 29 mV (GABA).
- Charge flux to substrate flux ratios were 0.7 charges/Na+, 2.0 charges/Cl-, and 2.1 charges/GABA.
Conclusions:
- The 3 Na+:1 Cl-:1 GABA stoichiometry is the most accurate model for plasma membrane GABA transporters.
- This revised stoichiometry suggests GABA transporters primarily mediate GABA uptake under physiological conditions.
- Transporter-mediated GABA release is likely restricted to pathophysiological or extreme physiological states.
Keywords:
Forward transportGABAReleaseReverse transportSLC6SLC6A1SLC6A11SLC6A12SLC6A13StoichiometryTransportTransporterUptakeMore Related Videos
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