PHOSPHORYLATION DEPENDENT AND INDEPENDENT MECHANISMS IN REGULATION OF HISTAMINE H2 RECEPTOR BY GRK2

ALONSO N; GOTTARDO F; MONCZOR F; DAVIO C; FERNANDEZ N; SHAYO C

Los Cocos-Cordoba

Simposio; The First South American spring Symposium in Signal Trasducction and Molecular Medicine. (SISTAM 2010); 2010

GRK2 mediated specific inhibition of GPCRs response usually involves receptor phosphorylation followed by  arrestin binding and uncoupling from the G protein. However, GRK2-mediated GPCRs regulation also involves phosphorylation independent mechanisms. Here, we investigated whether the histamine H2 receptor (H2R), known to be desensitized by GRK2, needs to be phosphorylated for its desensitization, internalization and resensitization. We evaluated the effect of phosphorylating deficient GRK2K220R mutant on H2R signaling. We found that although this mutant functioned as dominant negative concerning receptor internalization and resensitization, it desensitized H2R signaling in the same degree as the GRK2 wild type. In order to identify the domains responsible for the kinase independent receptor desensitization, we cotransfected the receptor with constructions encoding the GRK2 RGS-homology domain (RH), and the RH or the kinase domain fused to the plekstrin homology domain. Only RH containing constructions desensitized the H2R. Overall, these results indicate that GRK2 induced desensitization of H2R through a phosphorylation independent, RGS dependent mechanism, although kinase activity proved to be necessary for receptor internalization and the resulting resensitization.