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. 2020 Oct;98(4):462–474. doi: 10.1124/mol.120.119404

Fig. 4.

Fig. 4.

KOR full agonists signaling through the KOR and different Gα subunits. (A) Opioids were tested at a 10 µM final concentration with a 50-minute incubation in HEK 293T cells transiently expressing the KOR, Gα subunit of interest, Gβγ-Venus, and masGRK3ct-nLuc. No statistically significant (n.s.) differences were observed between the various Gα subunits for U50,488, enadoline, salvinorin A, or nalfurafine. Data are mean percentages of maximal stimulation ± S.D.; measurements were performed in duplicate in three independent experiments. (B) Concentration-response curves were generated for salvinorin A when the KOR was signaling through Gαi1 and Gαz. Salvinorin A was equally efficacious whether the KOR was signaling through Gαi1 (Emax values of 99% ± 13%) or Gαz (Emax value of 100% ± 11%) (P > 0.05). In contrast, salvinorin A was more potent when the KOR was signaling through Gαz with an EC50 value of 0.36 ± 0.048 nM vs. 3.2 ± 0.83 nM through Gαi1 (P < 0.01). (C) Nalfurafine had similar Emax values of 99% ± 1.1% and 110% ± 8.2% through Gαi1 and Gαz, respectively. Nalfurafine was more potent when the KOR was signaling through Gαz (EC50 value of 0.10 ± 0.050 nM) than through Gαi1 (EC50 value of 0.46 ± 0.0040 nM) (P < 0.01).