TABLE 2

Receptor signaling in second messenger assays conducted with either chimeric GαΔ6qi4myr protein or native Gi

Mutation of W6.48 mainly altered potency but not efficacy (Emax). Curves were analyzed with the classic logistic function (columns 1 and 2) and the operational model of agonism (columns 3–5). The efficacy term τ was corrected to the surface expression of each construct to retrieve τc. The Hill slope was set to unity for both analyses. All values are given as the mean (95% CI) corrected for multiple comparisons. Significance levels of log (τc/KA) relative to WT Y2R were evaluated by one-way analysis of variance followed by Dunnett’s post-test.

3H-IP (via GαΔ6qi4myr)cAMP (via Gαi)
logEC50Emax/%log τclogKAlog (τc/KA)logEC50Emax/%log τclogKAlog (τc/KA)
WT Y2R−9.48 (9.22–9.74)1001.466 (0.927–2.005)−8.02 (9.07–6.96)9.48 (9.32–9.65)−10.67 (11.25–10.09)1001.63 (−0.83–4.08)−9.04 (11.66–6.41)10.66 (10.22–11.10)
W6.48Y−8.70 (8.39–9.01)91 (80–102)1.153 (0.895–1.411)−7.87 (8.40–7.33)9.02 (8.75–9.28)*−10.06 (10.60–9.52)90 (65–114)1.26 (0.60–1.91)−9.08 (9.93–8.24)10.34 (9.85–10.83)ns
W6.48H−7.94 (7.94–8.83)89 (72–106)0.758 (0.344–1.172)−7.59 (8.35–6.83)8.35 (7.85–8.85)***−9.46 (10.26–8.67)79 (50–108)0.52 (−0.16–1.20)−8.80 (9.76–7.84)9.32 (8.51–10.12)***
W6.48T−8.43 (8.01–8.85)85 (70–100)0.822 (0.444–0.998)−7.80 (8.39–7.22)8.52 (8.11–9.93)***−9.53 (10.24–8.83)89 (60–117)1.13 (−0.05–2.32)−8.50 (9.89–7.10)9.63 (8.98–10.29)**
  • * P < 0.05;

  • ** P < 0.01;

  • *** P < 0.001; ns, not significant.