Fig. S2.

Receptor-specific effect of tethered Gα subunits on signaling via Gq-coupled receptors. (A) Schematics of GPCR G-protein sensors used here. The GPCR (β2-AR or α1-AR or V_1A-R), mCitrine, 10 nm ER/K linker, mCerulean and Gα subunit (Gαs or Gαq) are expressed as a single polypeptide, separated from each other by Gly–Ser–Gly (GSG) ′ 4 linkers. Sensors that terminated at a Gly–Ser–Gly ′ 4 peptide without Gα are indicated as (−) and were used as controls. (B) Gs-coupled β2 receptor sensors do not show an increase in IP₁ upon treatment with isoproterenol (10 μM) indicating cAMP increase from tethered Gαq occurs through Gαs pathway (A, Bottom). Gq-coupled α1 receptor sensors show increase in IP₁ levels upon treatment with phenylephrine (10 μM). Cognate Gαq-tethered sensor shows the greatest increase. Gαs-tethered sensor shows similar increase in IP₁ as the control sensor. (C) Gq-coupled V_1A-R receptor sensors show increase in IP₁ levels upon treatment with arginine vasopressin peptide (AVP, 100 nM). Gαs-tethered sensor exhibits the greatest increase in IP₁, consistent with priming. (B and C) Values are mean ± SEM from n ≥ 5 observations over at least three independent experiments. *P < 0.05, **P < 0.01, ***P < 0.005 by unpaired t test.