Two Distinct Pathways for Histamine H Receptor Down-regulation

• Published in: The Journal of biological chemistry Vol. 271; no. 13; p. 7574
• Main Authors: Martine J. Smit, Edwin Roovers, Henk Timmerman, Yvonne van de Vrede, Astrid E. Alewijnse, Rob Leurs
• Format: Journal Article
• Language: English
• Published: American Society for Biochemistry and Molecular Biology 29.03.1996
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1074/jbc.271.13.7574

Pretreatment of Chinese hamster ovary cells expressing the histamine H receptor (CHOrH cells) with histamine resulted in a time-dependent ( t ≈ 7 h) and dose-dependent (EC = 18 nM) H receptor down-regulation measured as [ I]iodoaminopotentidine binding (44 ± 10% down-regulation). Pretreatment of CHOrH cells with cholera toxin or forskolin also led to H receptor down-regulation. Forskolin time-dependently ( t ≈ 7 h) and dose-dependently (EC = 0.3 μM) induced H receptor down-regulation. Both histamine and forskolin induced rapid down-regulation of H receptor mRNA levels, probably caused by mRNA destabilization. Recently, Moro et al. (Moro, O., Lameh, J., Hogger, P., and Sadée, W.(1993) J. Biol. Chem. 268, 22273-22276) showed that hydrophobic amino acids in a conserved G-protein-coupled receptor motif in the second intracellular loop are implicated in G-protein coupling. To uncouple the H receptor from the G -protein, we introduced the Leu Ala mutation in the second intracellular loop of the H receptor. The H Leu Ala mutant showed altered agonist-binding parameters, attenuated histamine-induced cAMP production, and was down-regulated by concentrations of histamine that did not give rise to cAMP production. Taken together, in CHOrH cells, H receptor down-regulation appears to be induced by two distinct pathways, a cAMP-dependent and cAMP-independent pathway.