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. Author manuscript; available in PMC: 2023 Dec 1.
Published in final edited form as: Nat Chem Biol. 2023 Jan 16;19(6):687–694. doi: 10.1038/s41589-022-01231-z

Figure 6.

Figure 6.

Many orphan GPCRs may not activate G proteins. a, Heat maps showing basal BRET between 32 well-studied GPCRs and four different G protein 4A mutants. Only three of these receptors (GLP1R, ADCYAP1R1 and TBXA2, shown in red bold italic font) show basal BRET that fails to exceed 0.1 with their cognate 4A mutant. b, Three bona fide chemokine GPCRs show high basal BRET with Gi1 4A, whereas three known decoy receptors do not. c, Most orphan receptors that show constitutive coupling to wt G proteins (top) also interact spontaneously with at least one G protein 4A mutant, whereas a substantial fraction of orphan receptors that lack spontaneous coupling to wt G proteins also do not interact spontaneously with 4A mutants, suggesting that many of these receptors may not activate G proteins. Exceptions were GPR150, GPR151, GPR157 and GPR31, all of which showed basal BRET that exceeded 0.1 with Gi1 4A, although this was sensitive to pertussis toxin (PTX) only for the latter two receptors. Most adhesion receptors (expressed as C terminal fragments) also interact spontaneously with 4A mutants. Each cell represents the mean of at least 3 independent experiments.