GABAA Receptor Alpha 1 Beta 3 Gamma 2
Family:
GABA Receptors (Cys-loop ligand-gated ion channels)
Subgroups:
The GABA receptor family has further been divided into GABAA, GABAB and GABAA-ρ (also called GABAC) receptors.
Topology:
As typical for Cys-loop receptors, generally four transmembrane spanning domains TM1-TM4 form one receptor subunit, five or four subunits form a pore, several heteromeric combinations are known.
GABAA: Oligomerization of typically five subunits, heteromeric combinations are known of α subunits (GABRA1 - GABRA6), β subunits (GABRB1 - GABRB3) and γ subunits (GABRG1 - GABRG3), as well as δ (GABRD), an ε (GABRE), a π (GABRP), and a θ (GABRQ). The most common type is (α1)2(β2)2(γ2), minimal requirement is the inclusion of α and β subunits.
GABAB: Heterodimer (GABBR1, GABBR2)
GABAA-ρ: Oligomerization of five subunits, heteromeric combinations of three GABAA-ρ subunits are known (GABRR1, GABRR2, GABRR3)
Regulation and Function:
GABAA and GABAA-ρ receptors are ligand-gated ion channels (ionotropic receptors); whereas GABAB receptors are G protein-coupled receptors (metabotropic receptors). All respond to the neurotransmitter gamma-aminobutyric acid (GABA), the main inhibitory transmitter in the mammalian CNS.
Data and Applications
GABAA Receptor (a1b3g2) - Success Rates
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by Millipore.
Statistic of hGABAA a1b3g2 cells recorded on one NPC-96 1-hole (1x) patch clamp chip. Cslow = 18.8 ±1.6 (n=32), Rs = 8.6 ± 1.5 (n=32). 41.66 % of the cells on one NPC-96 chip (total n=96) had seal resistance > 1 GOhm at the beginning and at the end of experiment. 63.4 % of the cells had a seal resistance above 500 MOhm, which remained stable throughout the experiment.
GABAA Receptor (a1b3g2) - Screening & User Interface
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by Millipore.
Graphical user interface of the screening software used on the SyncroPatch96. Screenshot of depiction of raw data traces of hGABAA a1b3g2 expressing cells as recorded on one NPC-96 multihole (4x) patch clamp chip. 96 small color-coded pictures as seen in the upper left part display the individual recording wells. One highlighted experiment is displayed below, 16 other selected experiments are displayed on the right. Highlighted graphs show raw data current traces of the sum of 4 cells which were exposed to 3 μM GABA consecutively 7 times, including intermittent wash steps.
GABAA Receptor (a1b3g2) - Bicuculline Dose Response
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by Millipore.
Pharmacology on GABAA α1β3γ2 as recorded on a multihole (4x) plate. Raw data traces of one exemplary recording using control solution (A) and increasing Bicuculline concentrations and a subsequent washout (B). Cells were held at a constant holding potential of -70 mV and GABA was applied for approximately 2 s. After 3 control applications of 3 μM GABA, increasing concentrations of inhibitors were applied. Cells were preincubated with antagonists before co-applicaiton with GABA.
GABAA Receptor (a1b3g2) - Antagonists
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Cells were kindly provided by Millipore.
Pharmacology on GABAA α1β3γ2 as recorded on a multihole (4x) plate. Mean concentration response curves for Bicuculline, IC50 = 470 nM (n = 14); for a5IA IC50 = 461.19 pM (n = 9), maximum block was 29% at 100 nM; for FG7142 IC50= 54.52 nM (n = 15), maximum block was 58% at 10 μM; for MRK016 maximum current inhibition was 44.8% at 1 uM, IC50= 5.98 nM (n = 11).
Application Notes
GABAA a1b3g2 - "Characterization of hGABAA α1β3γ2 on Nanion's SyncroPatch 96"
SyncroPatch 96 application note, (a predecessor model of the SyncroPatch 384PE) 
(0.5 MB)
Cells were kibndly provided by Millipore.
GABAA: Further Readings
GABAA receptors - Investigation of Modulators
Patchliner data and applications:
Cells were kindly provided by AstraZeneca.
The top images show dose dependent block of GABAA currents by bicuculline. The IC50 was determined as 1.2 ± 0.2 μM (n=11). The lower graph shows the positive modulation of glycine activation of hGlyRα1. Here, six co-applications of 20 μM glycine and increasing concentrations of a positive modulator are shown.
GABAA Receptor - Stacked Application Technology
Patchliner data and applications:
Ligand gated ion channels often display receptor desensitization. A method was developed to minimize ligand exposure times and intervals between ligand exposures. The pipette first aspirates buffer, then compound. When expelling this stack, the cell is first exposed to ligand and then buffer. Exposure times as low as 400 ms are possible with this method. A GABA dose response curve, aquired in this manner, is shown on the left.
GABAA Receptor - Modulator Diazepam
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Shown is a raw current response of a HEK293 cell expressing GABAA receptors to initial exposure to GABA, followed by joint exposure to GABA and diazepam (as indicated). Solutions were stacked (layered) in the pipette to achieve brief exposure times.
GABAA Receptor - Dose Response Curves
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Increasing concentrations of GABA were applied to each cell. Cells were from frozen stocks and were prepared for a FliPR experiment running alongside.
The corresponding online analysis of this experiment is shown in the data set "GABAA - CRC Analysis".
GABAA Receptor - Currents in iCell Neurons
Patchliner data and applications:
Cells were kindly provided by Cellular Dynamics.
Activation of GABAA receptor currents by 30 μM GABA and partial block of the current response by 1 μM bicuculline. Bicuculline was pre-applied for at least 30 s before co-application with GABA (30 μM). Approximately 50% of the current was blocked by 1 μM bicuculline.
GABAA Receptor - CRC Analysis
SyncroPatch 96 (a predecessor model of SyncroPatch 384PE) data and applications:
Online analysis results of the dose response curves were obtained with a few mouse clicks. The color code of the online analysis helps to visualize different concentrations applied.
The corresponding data traces is shown in the data set "GABAA - Dose Response Curves".
2016 - Automated Patch Clamp Meets High-Throughput Screening: 384 Cells Recorded in Parallel on a Planar Patch Clamp Module
SyncroPatch 384PE (a predecessor model of SyncroPatch 384i) publication in Journal of Lab Automation (2016)
Authors:
Obergrussberger A., Brüggemann A., Goetze T.A., Rapedius M., Haarmann C., Rinke I., Becker N., Oka T., Ohtsuki A., Stengel T., Vogel M., Steindl J., Mueller M., Stiehler J., George M., Fertig N.
2015 - Novel screening techniques for ion channel targeting drugs
Patchliner, SyncroPatch 384PE (a predecessor model of SyncroPatch 384i) and 
CardioExcyte 96 publication in Channels (2015)
Authors:
Obergrussberger A., Stölzle-Feix S., Becker N., Brüggemann A., Fertig N., Möller C.
2014 - Crystal structure of a human GABAA receptor
Port-a-Patch publication in Nature (2014)
Authors:
Miller P.S., Aricescu A.R.
2012 - Characterizing Human Ion Channels in Induced Pluripotent Stem Cell-Derived Neurons
Patchliner publication in Journal of Biomolecular Screening (2012)
Authors:
Haythornthwaite A, Stoelzle S, Hasler A, Kiss A, Mosbacher J, George M, Brüggemann A, Fertig N.
2009 - Port-a-Patch and Patchliner: High fidelity electrophysiology for secondary screening and safety pharmacology
Port-a-Patch and Patchliner publication in Combinatorial Chemistry & High Throughput Screening (2009)
Authors:
Farre C., Haythornthwaite A., Haarmann C., Stoelzle S., Kreir M., George M., Brüggemann A., Fertig N.
2007 - Automated ion channel screening: patch clamping made easy
Port-a-Patch and Patchliner publication in Expert Opinion Therapeutic Targets (2007)
Authors:
Farre C., Stoelzle S., Haarman C., George M., Brueggemann A., Fertig N.
2006 - Microchip technology for automated and parallel patch clamp recording
Port-a-Patch and Patchliner publication in Small Journal (2006)
Authors:
Brüggemann A., Stoelzle S., George M., Behrends J.C., Fertig N.