Beta-adrenergic receptor kinase-1 acutely regulates PTH/PTHrP receptor signalling in human osteoblastlike cells.

To investigate whether G protein-coupled receptor kinases (GRKs) are involved in the regulation of the PTH/PTHrPR, we have established mutant SaOS-2 cells which stably overexpress (> 10-20-fold) a dominant negative form of the beta-adrenergic receptor kinase-1 (beta ARK-1). Acute (< or = 2 h) incubation with hPTH (1-34) induced significantly less (by up to 50%) downregulation of the PTH/PTHrPR in beta ARK-1 mutant SaOS-2 cells than observed in wild-type cells. Pretreatment of wild-type cells with PTH for 2 h induced homologous cAMP desensitisation to a second challenge with PTH, while the effect was blunted by up to 60% in beta ARK-1 mutant cells. We conclude that activation of beta ARK-1 (or a closely related GRK) is a critical component of the acute phase (< or = 2 h) of PTH-induced receptor downregulation and homologous cAMP desensitisation of the PTH/PTHrPR.