Kelley, Melissa T. and Bürckstümmer, Tilmann and Wenzel-Seifert, Katharina and Dove, Stefan and Buschauer, Armin and Seifert, Roland (2001) Distinct interaction of human and guinea pig histamine H_2-Receptor with guanidine-type agonists,. Molecular Pharmacology 60 (6), pp. 1210-1225.
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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 (Gsalpha S) 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-Gsalpha S and gpH2R-Gsalpha S were similar. In contrast, the potencies and efficacies of guanidines were lower at hH2R-Gsalpha S than at gpH2R-Gsalpha S. Guanidines bound to hH2R-Gsalpha S with lower affinity than to gpH2R-Gsalpha S, and high-affinity binding of guanidines at gpH2R-Gsalpha S was more resistant to disruption by GTPgamma S than binding at hH2R-Gsalpha S. 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-271right-arrowAsp-271 mutation in hH2R-Gsalpha S. Intriguingly, the efficacies of guanidines at the Ala-271right-arrowAsp-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-Gsalpha S 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.
|Institutions:|| Chemistry and Pharmacy > Institute of Pharmacy > Pharmaceutical/Medicinal Chemistry II (Prof. Buschauer) |
Chemistry and Pharmacy > Institute of Pharmacy > Pharmacology and Toxicology (Prof. Schlossmann formerly Prof. Seifert)
|Subjects:||500 Science > 570 Life sciences|
500 Science > 540 Chemistry & allied sciences
600 Technology > 610 Medical sciences Medicine
|Refereed:||Yes, this version has been refereed|
|Created at the University of Regensburg:||Partially|
|Owner:||Prof. Armin Buschauer|
|Deposited On:||22 Feb 2008 08:34|
|Last Modified:||05 Aug 2009 15:42|
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