Distinct interaction of human and guinea pig histamine H2-receptor with guanidine-type agonists.

Publisher: American Society for Pharmacology and Experimental Therapeutics Country of Publication: United States NLM ID: 0035623 Publication Model: Print Cited Medium: Print ISSN: 0026-895X (Print) Linking ISSN: 0026895X NLM ISO Abbreviation: Mol Pharmacol Subsets: MEDLINE

Original Publication: Bethesda, MD : American Society for Pharmacology and Experimental Therapeutics

Cimetidine/*analogs & derivatives ; Guanidine/*pharmacology ; Histamine Agonists/*pharmacology ; Receptors, Histamine H2/*metabolism; Alternative Splicing ; Amino Acid Sequence ; Animals ; Binding Sites ; Cell Membrane/metabolism ; Cells, Cultured ; Cimetidine/metabolism ; GTP-Binding Protein alpha Subunits, Gs/genetics ; GTP-Binding Protein alpha Subunits, Gs/metabolism ; Guanidine/analogs & derivatives ; Guanidine/chemistry ; Guanidines/pharmacology ; Guanosine 5'-O-(3-Thiotriphosphate)/metabolism ; Guinea Pigs ; Humans ; Insecta ; Models, Molecular ; Molecular Sequence Data ; Piperidines/pharmacology ; Protein Conformation/drug effects ; Protein Isoforms ; Ranitidine/pharmacology ; Receptors, Histamine H2/drug effects ; Receptors, Histamine H2/genetics ; Sequence Homology, Amino Acid ; Species Specificity ; Structure-Activity Relationship ; Sulfur Radioisotopes ; Tritium

It is unknown why the potencies and efficacies of long-chained guanidine-type histamine H2-receptor (H2R) agonists are lower at the H2R of human neutrophils than at the H2R of the guinea pig atrium. To elucidate these differences, we analyzed fusion proteins of the human H2R (hH2R) and guinea pig H2R (gpH2R), respectively, and the short splice variant of Gsalpha (GsalphaS) expressed in Sf9 cells. The potencies and efficacies of small H2R agonists in the GTPase assay and the potencies of antagonists at inhibiting histamine-stimulated GTP hydrolysis by hH2R-GsalphaS and gpH2R-GsalphaS were similar. In contrast, the potencies and efficacies of guanidines were lower at hH2R-GsalphaS than at gpH2R-G(salphaS). Guanidines bound to hH2R-GsalphaS with lower affinity than to gpH2R-GsalphaS, and high-affinity binding of guanidines at gpH2R-GsalphaS was more resistant to disruption by GTPgammaS than binding at hH2R-GsalphaS. Molecular modeling suggested that the nonconserved Asp-271 in transmembrane domain 7 of gpH2R (Ala-271 in hH2R) confers high potency to guanidines. This hypothesis was confirmed by Ala-271-->Asp-271 mutation in hH2R-GsalphaS. Intriguingly, the efficacies of guanidines at the Ala-271-->Asp-271 mutant and at hH2R/gpH2R chimeras were lower than at gpH2R. Our model suggests that a Tyr-17/Asp-271 H-bond, present only in gpH2R-GsalphaS but not the other constructs studied, stabilizes the active guanidine-H2R state. Collectively, our data show 1) distinct interaction of H2R species isoforms with guanidines, 2) that a single amino acid in transmembrane domain 7 critically determines guanidine potency, and 3) that an interaction between transmembrane domains 1 and 7 is important for guanidine efficacy.

1-P20-RR15563 United States RR NCRR NIH HHS

0 (Guanidines)
0 (Histamine Agonists)
0 (Piperidines)
0 (Protein Isoforms)
0 (Receptors, Histamine H2)
0 (Sulfur Radioisotopes)
10028-17-8 (Tritium)
140873-27-4 (aminopotentidine)
37589-80-3 (Guanosine 5'-O-(3-Thiotriphosphate))
80061L1WGD (Cimetidine)
884KT10YB7 (Ranitidine)
EC 3.6.5.1 (GTP-Binding Protein alpha Subunits, Gs)
EZU9AIZ69M (tiotidine)
JU58VJ6Y3B (Guanidine)

Date Created: 20011128 Date Completed: 20011221 Latest Revision: 20190607

20231215

10.1124/mol.60.6.1210

11723228