Histamine H 1 receptor-mediated CREB phosphorylation via G q protein signaling and arrestin modulation

Histamine H ₁ receptors mediate multiple physiological and pathophysiological processes, including inflammation and allergy, by regulating downstream gene expression via transcription factors. Agonist binding activates G _q proteins, increasing intracellular Ca²⁺ and activating protein kinase C (PKC) and stimulating G protein-coupled receptor kinases (ERK) and c-Jun N-terminal kinase (JNK) to promote cytokine production and H ₁ receptor upregulation. G protein-coupled receptor kinase (GRK)-mediated phosphorylation and arrestin-dependent internalization enable alternative signaling. cAMP response element-binding protein (CREB) is a major transcription factor whose phosphorylation is regulated by multiple signaling pathways. Therefore, we investigated the roles of G _q proteins and arrestins in H ₁ receptor-mediated CREB phosphorylation in Chinese hamster ovary (CHO) cells expressing wild-type (WT) human H ₁ receptors and C-terminal mutants, namely S487TR (G _q protein-biased) and S487A (arrestin-biased), in which the Ser487 residue was truncated and substituted with alanine, respectively. Histamine promoted CREB phosphorylation in CHO cells expressing WT or S487TR receptors, but not in cells expressing S487A, suggesting that H ₁ receptor-mediated CREB phosphorylation occurs via G _q protein-dependent but arrestin-independent mechanisms. Inhibitors of PKC, ERK, or JNK, and intracellular Ca ²⁺ chelator suppressed histamine-induced CREB phosphorylation in CHO cells expressing WT or S487TR receptors. Basal CREB phosphorylation levels increased after β-arrestin1 or β-arrestin2 overexpression and decreased after their siRNA-mediated knockdown, modulating histamine-stimulated CREB phosphorylation in WT CHO cells. Collectively, H ₁ receptor-mediated CREB phosphorylation is induced through G _q protein/Ca ²⁺ /PKC-dependent ERK and JNK activation; arrestins can modulate this process by regulating basal CREB phosphorylation.