Gαi/o GPCR assays

Gi/o-coupled G protein-coupled receptors (GPCRs) are a subset of GPCRs that couple with the Gαi/o protein subunit.

Image of a cell membrane displaying a GIRK channel, or inward rectifying potassium channel
Image of a cell membrane displaying a Gi GPCR and GIRK channel, coupled through the alpha subunit
Image of a thallos being loaded into a cell expressing a Gi GPCR and GIRK channel for thallium flux assay
Gi GPCR GIRK Thallium flux assay principle, showing GPCR ligand binding activated GIRK channels, which enables thallium to go into the cell and increases fluorescence of Thallos

Gαi/o GPCRs are involved in physiological processes ranging from pain sensing, to neurotransmission, to autoimmune responses. Gi/o-coupled receptors include many neurotransmitter receptors such as serotonin, GABA, and dopamine receptors, some opioid receptors, and many more pharmacologically relevant targets for treating an array of medical conditions.

A key signaling pathway for Gi/o-coupled GPCRs, is through activation of G protein-gated Inward Rectifying Potassium (K⁺) channels, better known as GIRK channels. Not only is the GPCR-mediated modulation of GIRK channels of great physiological importance, it also provides a convenient means of measuring Gαi/o GPCR activity using fluorescence-based thallium flux assays.

A GIRK-based thallium flux assay approach offers some key advantages compared to other approaches that are used to measure the activity of Gαi/o GPCRs. Unlike the most common approach which utilizes fixed-endpoint measures of cAMP, the GIRK assay is a real-time measure of GPCR activation and does not require non-physiological elevations of intracellular cAMP. Another popular approach is the expression of chimeric Gα subunits (e.g. Gα16) to induce Gi/o GPCRs to promote intracellular calcium release through non-native coupling. However, GIRK-based thallium flux enables the measurement of Gαi/o GPCR activity through their native Gβ/γ coupling mechanism.

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Thallium flux assays for GPCRs

Examples of Gi/o GPCR assays using our kit
Gi GPCR assay data for Dopamine D2 receptor, including a kinetic trace and dose response curve
Gi GPCR high throughput screening data for Dopamine D2 receptor, including a kinetic trace and Z’ analysis for hit discovery.
Gi GPCR 96-well dose response curves for Dopamine D2 receptor, Serotonin receptor (5HT1A), muscarinic receptor (M2), and delta opioid receptor.
Gi GPCR 384-well dose response curves for Serotonin receptor (5HT1A), muscarinic receptor (M2), and delta opioid receptor.
Searching for thallium indicators instead?

Is your GPCR already GFP-tagged? Talk to us about using our red-shifted thallium indicator, Thallos Gold, for your assay.

Cell lines for Gi/o GPCR assays

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Gi GPCR GIRK Assay Packaging
Gi/o GPCR-GIRK Thallium Flux Assay
A complete Gi/o GPCR assay for discovering modulators through direct coupling to GIRK channels. Cell lines and thallium flux reagents are included.
$695.00 – $11,690.00
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