Term Examples of assay principles
Accumulation Ca2+ or cAMP accumulation
Binding/coupling Proximity
Activation Receptor conformation and G protein activation e.g., GTPase activity, GTPγS binding, or recruitment of downstream effectors.
Dissociation G protein dissociation/rearrangement
Phosphorylation Incorporation of 32P in a specific protein. Two-dimensional phosphopeptide mapping after orthophosphate labelling, MS-based identification of phosphorylation sites, Phosphosite-specific antibody assays or arrays
Recruitment Subcellular redistribution
Signaling Downstream cellular second messenger levels
Internalization ELISA, Flow cytometry, diffusion-enhanced resonance energy transfer (DERET), enhanced bystander BRET (ebBRET), (confocal) microscopy, antibody-feeding experiments, real-time internalization by SNAP-tagged receptors
Tissue phenotype Blood vessel contraction, cell migration, hormone secretion, heart rate, force of contraction, glandular secretion etc.
Transcription Differential gene arrays after agonism, qPCR, and gene reporter assay.