TY - JOUR T1 - The Effect of Mutations in the DRY Motif on the Constitutive Activity and Structural Instability of the Histamine H<sub>2</sub>Receptor JF - Molecular Pharmacology JO - Mol Pharmacol SP - 890 LP - 898 VL - 57 IS - 5 AU - Astrid E. Alewijnse AU - Henk Timmerman AU - Edwin H. Jacobs AU - Martine J. Smit AU - Edwin Roovers AU - Susanna Cotecchia AU - Rob Leurs Y1 - 2000/05/01 UR - http://molpharm.aspetjournals.org/content/57/5/890.abstract N2 - In previous studies we showed that the wild-type histamine H2 receptor stably expressed in Chinese hamster ovary cells is constitutively active. Because constitutive activity of the H2 receptor is already found at low expression levels (300 fmol/mg protein) this receptor is a relatively unique member of the G-protein-coupled receptor (GPCR) family and a useful tool for studying GPCR activation. In this study the role of the highly conserved DRY motif in activation of the H2 receptor was investigated. Mutation of the aspartate 115 residue in this motif resulted in H2 receptors with high constitutive activity, increased agonist affinity, and increased signaling properties. In addition, the mutant receptors were shown to be highly structurally instable. Mutation of the arginine 116 residue in the DRY motif resulted also in a highly structurally instable receptor; expression of the receptor could only be detected after stabilization with either an agonist or inverse agonist. Moreover, the agonist affinity at the Arg-116 mutant receptors was increased, whereas the signal transduction properties of these receptors were decreased. We conclude that the Arg-116 mutant receptors can adopt an active conformation but have a decreased ability to couple to or activate the Gs-protein. This study examines the pivotal role of the aspartate and arginine residues of the DRY motif in GPCR function. Disruption of receptor stabilizing constraints by mutation in the DRY motif leads to the formation of active GPCR conformations, but concomitantly to GPCR instability. The American Society for Pharmacology and Experimental Therapeutics ER -