Modulation of histamine H 2 receptor signalling by G‐protein‐coupled receptor kinase 2 and 3

To evaluate the role of G‐protein‐coupled receptor kinases (GRK) in the desensitization of the histamine H 2 receptor, the H 2 receptor was transiently cotransfected with GRK2, 3, 5 or 6 in COS‐7 cells and the cyclic AMP levels in response to histamine were studied. Coexpression of the H 2 receptor with GRK2 and 3 significantly decreased both the basal cyclic AMP levels and the cyclic AMP response to 100 μ M histamine. Moreover, preincubation with 100 μ M histamine desensitized the H 2 receptor response to 53±8%. Coexpression of GRK2 and 3 increased the H 2 receptor desensitization to 27±4% and 24±4% respectively. No effect on either cyclic AMP response or desensitization was found when GRK5, GRK6 or dominant negative mutants of GRK2 or 3 (GRK2K 220 R and GRK3K 220 R) were coexpressed. To study the role of the C‐terminal tail in the GRK‐mediated desensitization of the H 2 receptor, three truncations of C‐tail were constructed: H 2 T295, H 2 T307 and H 2 T341. H 2 T307 and 341 H 2 T341 expressed and responded normally to 100 μ M histamine. The interaction of the H 2 receptor with GRK2 and 3 was also not altered upon truncation of the C‐terminal tail. These findings strongly suggest a role of GRK2 and 3 in the desensitization of the H 2 receptor. Furthermore, the finding that C‐terminal truncations of the H 2 receptor did not abolish the effect of GRK2 and 3 suggests that the C‐terminus is not involved in the GRK mediated desensitization of the histamine H 2 receptor.British Journal of Pharmacology (2000) 131 , 1707–1715; doi: 10.1038/sj.bjp.0703676