Brunskole, Irena and Strasser, Andrea and Seifert, Roland and Buschauer, Armin (2011) Role of the second and third extracellular loops of the histamine H-4 receptor in receptor activation. NAUNYN-SCHMIEDEBERGS ARCHIVES OF PHARMACOLOGY, 384 (3). pp. 301-317. ISSN 0028-1298,
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The histamine H-4 receptor subtype (H4R) belongs to the class 1 of G protein-coupled receptors and is involved in inflammatory and immunological processes. The aim of this study was to elucidate the importance of extracellular regions for the large species differences between human (h) and canine (c) H4R. Therefore, chimeric receptors were generated by replacing corresponding domains of the hH(4)R with canine N-terminus (h(cNT)H(4)R) and three canine extracellular loops, respectively (h(cE1)H(4)R, h(cE2)H(4)R and h(cE3)H(4)R). Wild type and chimeric H-4 receptors were expressed in Sf9 insect cells and subsequently characterized in [H-3]histamine-binding experiments and in steady-state GTPase activity assays, where standard H4R ligands histamine, 5-methylhistamine, thioperamide, 1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine (JNJ7777120) and clozapine were examined. The exchange of N-terminus or first extracellular loop did not influence hH(4)R pharmacology. The effect of altered second extracellular loop (E2-loop) and third extracellular loop (E3-loop) was rather ligand specific than agonist/inverse agonist specific. At h(cE3)H(4)R, the potency of histamine and 5-methylhistamine significantly decreased. The efficacy of the inverse agonist thioperamide was strongly reduced at h(cE2)H(4)R and h(cE3)H(4)R. Surprisingly, JNJ7777120 as weak inverse agonist at hH(4)R exhibited partial agonistic activity at h(cE2)H(4)R and h(cE3)H(4)R. Molecular dynamic simulations suggest that the E2- and E3-loops are independently of each other involved in the partial/inverse agonism of JNJ7777120 and that E2- as well as E3-loop do not directly interact with JNJ7777120 in the binding pocket. In conclusion, our study indicates an involvement of the E2- and E3-loops in H4R activation process after binding of some but not all examined ligands.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | PROTEIN-COUPLED RECEPTOR; SF9 INSECT CELLS; CRYSTAL-STRUCTURE; PHARMACOLOGICAL-PROPERTIES; STRUCTURAL INSTABILITY; CONSTITUTIVE ACTIVITY; GPCR STRUCTURE; AGONIST; LIGANDS; BINDING; Histamine H-4 receptor; Sf9 insect cells; Chimeric receptors; Extracellular loops; Steady-state GTPase assay; JNJ7777120 |
| Subjects: | 600 Technology > 615 Pharmacy |
| Divisions: | Chemistry and Pharmacy > Institute of Pharmacy > Alumni or Retired Professors > Pharmaceutical/Medicinal Chemistry II (Prof. Buschauer) |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 02 Jun 2020 07:50 |
| Last Modified: | 02 Jun 2020 07:50 |
| URI: | https://pred.uni-regensburg.de/id/eprint/20358 |
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