ABSTRACT
Selective bradykinin (BK) B 1 receptor antagonists could be novel therapeutic agents for the treatment of pain and inflammation. Elucidation of the structure activity relationships of the structurally novel HTS lead compound 1 provided potent hBK B 1 receptor antagonists with excellent receptor occupancy in the CNS of hBK B 1 transgenic rats.
Subject(s)
Amines/chemistry , Benzophenones/chemistry , Benzophenones/pharmacology , Bradykinin B1 Receptor Antagonists , Animals , Benzophenones/chemical synthesis , Cell Line , Dogs , Humans , Molecular Structure , Rats , Receptor, Bradykinin B1/metabolism , Structure-Activity RelationshipABSTRACT
Selective bradykinin (BK) B(1) receptor antagonists have been shown to be antinociceptive in animal models and could be novel therapeutic agents for the treatment of pain and inflammation. Elucidation of the structure-activity relationships of the biphenyl moiety of the lead compound 1 provided a potent new structural class of BK B(1) receptor antagonists.
Subject(s)
Analgesics/chemistry , Anti-Inflammatory Agents, Non-Steroidal/chemistry , Bradykinin B1 Receptor Antagonists , Cyclohexanes/chemistry , Hydrocarbons, Fluorinated/chemistry , Pyridines/chemistry , Analgesics/chemical synthesis , Analgesics/pharmacology , Animals , Animals, Genetically Modified , Anti-Inflammatory Agents, Non-Steroidal/chemical synthesis , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Cyclohexanes/chemical synthesis , Cyclohexanes/pharmacology , Humans , Hydrocarbons, Fluorinated/chemical synthesis , Hydrocarbons, Fluorinated/pharmacology , Pyridines/chemical synthesis , Pyridines/pharmacology , Rats , Receptor, Bradykinin B1/genetics , Structure-Activity RelationshipABSTRACT
We report the critical residues for the interaction of the kinins with human bradykinin receptor 1 (B1) using site-directed mutagenesis in conjunction with molecular modeling of the binding modes of the kinins in the homology model of the B1 receptor. Mutation of Lys118 in transmembrane (TM) helix 3, Ala270 in TM6, and Leu294 in TM7 causes a significant decrease in the affinity for the peptide agonists des-Arg10kallidin (KD) and des-Arg9BK but not the peptide antagonist des-Arg10Leu9KD. In contrast, mutations in TM2, TM3, TM6, and TM7 cause a significant decrease in the affinity for both the peptide agonists and the antagonist. These data indicate that the B1 bradykinin binding pocket for agonists and antagonists is similar, but the manners in which they interact with the receptor do not completely overlap. Therefore, there is a potential to influence the receptor's ligand selectivity.
Subject(s)
Kinins/chemistry , Kinins/metabolism , Models, Molecular , Receptor, Bradykinin B1/chemistry , Receptor, Bradykinin B1/metabolism , Amino Acid Sequence , Animals , Binding Sites , Cell Membrane/chemistry , Cell Membrane/metabolism , Conserved Sequence , Humans , Molecular Sequence Data , Mutagenesis, Site-Directed , Mutation/genetics , Protein Binding , Protein Structure, Quaternary , Protein Structure, Secondary , Receptor, Bradykinin B1/genetics , Sequence AlignmentABSTRACT
We report the first homology model of human bradykinin receptor B1 generated from the crystal structure of bovine rhodopsin as a template. Using an automated docking procedure, two B1 receptor antagonists of the dihydroquinoxalinone structural class were docked into the receptor model. Site-directed mutagenesis data of the amino acid residues in TM1, TM3, TM6, and TM7 were incorporated to place the compounds in the binding site of the homology model of the human B1 bradykinin receptor. The best pose in agreement with the mutation data was selected for detailed study of the receptor-antagonist interaction. To test the model, the calculated antagonist-receptor binding energy was correlated with the experimentally measured binding affinity (K(i)) for nine dihydroquinoxalinone analogs. The model was used to gain insight into the molecular mechanism for receptor function and to optimize the dihydroquinoxalinone analogs.
Subject(s)
Models, Molecular , Quinoxalines/chemistry , Receptor, Bradykinin B1/chemistry , Amino Acid Sequence , Binding Sites , Humans , Molecular Sequence Data , Mutagenesis, Site-Directed , Protein Binding , Protein Structure, Secondary , Receptor, Bradykinin B1/genetics , Receptor, Bradykinin B1/metabolism , Rhodopsin/chemistry , Sequence Alignment , Structural Homology, ProteinABSTRACT
We have developed an efficient and selective radioligand, the [35S]-radiolabeled dihydroquinoxalinone derivative, 4, for an ex vivo receptor occupancy assay in transgenic rats over-expressing the human bradykinin B1 receptor.
