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G-protein coupled receptors (GPCRs) are a large family of receptors 520-620 nm which have a broad involvement in cellular responses affecting many important body functions both in health and disease. On activation GPCRs signal through different G-proteins (e.g. Gs, Gi or Gq) to elicit a cellular response which can be mediated through the activation of a number of different signaling cascades which include intracellular Ca2+ mobilization and the formation or inhibition of adenylate cyclase. Although these technologies have been successful in many cases they have had their limitation. Responses for many GPCRs such as Gi coupled GPCRs are not easily measured in current assay formats and other methods have been investigated as alternative readout. One such pathway is the ERK phosphorylation cascade, which results in the phosphorylation of both cytoplasmic and nuclear proteins regulating gene transcription. Hence this type of assay has the ability to measure cellular changes activated by Gs, Gi anf Gq coupled receptors giving potential to use a single assay format for screening.

Here the POLARstar Omega is used to detect ERK phosphorylation using a AlphaScreen® SureFire® proximity-based assay. ERK phosphorylation is demonstrated at receptors which signal via Gi and Gq G-proteins.

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