FIGURE 6.

Investigating biased agonism at the level of the LRT ternary complex. A, bias factors (log(α_Gq/α_βarr2)) calculated from molecular efficacies at AT₁R-G_q (α_Gq) and AT₁R-βarr2 (α_βarr2) fusion proteins. Positive bias values (blue) denote G_q-biased molecular efficacies, whereas negative values (red) denote βarr2-biased molecular efficacies. B, correlation analysis of molecular bias values calculated in vitro (Log(α_Gq/α_βarr2) relative to AngII) and bias values calculated in cells (β) according to the operational approach of Rajagopal et al. (17). Bias at the level of transducer-specific molecular efficacies was significantly correlated with cellular indices of bias (r² = 0.8605, p = 0.003 by two-tailed Pearson correlation), suggesting that biased molecular efficacies generate signaling bias in cells. Data represent the mean ± S.E. of at least three independent experiments. C, plotting molecular efficacy at each transducer (log α_Gq and log α_βarr2) versus the molecular bias between transducers (log α_Gq/α_βarr2)) uncovers a potential mechanism for generating bias at the AT₁R. βarr2-biased ligands (lower left) and G_q-biased ligands (upper right) clustered according to their transducer preferences. Trends in the vertical distances between log α_Gq (blue) and log α_βarr2 (red) suggest that βarr2 bias arises from a reciprocal loss in G_q molecular efficacy and gain in βarr2 efficacy, whereas G_q bias results from an increase in G_q molecular efficacy with no concomitant loss in βarr2 efficacy.