Removal of the extreme C-terminus of the P2Y₁₂ receptor does not affect surface expression or G protein coupling. (A) Sequence comparison of the COOH terminus domains of the human P2Y₁₂ receptor constructs. Potential phosphorylation sites are in bold and the PDZ ligand found at the extreme C-terminus of the receptor is underlined. (B) Receptor levels were measured in CHO cells stably expressing wild-type or mutant receptor with the use of [³H]2MeSADP (0.1-10μM) in the presence of the P2Y₁₂ receptor antagonist AR-C69931MX (1μM) to determine specific binding. Data are expressed as specific binding of [³H]2MeSADP (cpm) per milligram of protein and represent means ± SEMs of 5 independent experiments. (C) Agonist (ADP; 0.01pM to 10μM)–dependent inhibition of forskolin (1μM; 10 minutes)–stimulated adenylyl cyclase activity was assessed in CHO cells stably expressing wild-type and mutant receptor constructs. Data are expressed as percentage inhibition of forskolin-stimulated adenylyl cyclase and represent means ± SEMs of 5 independent experiments.