RESUMEN
Parathyroid hormone (PTH) is an anabolic agent that mediates bone formation through activation of the Gα(s)-, Gα(q)- and ß-arrestin-coupled parathyroid hormone receptor type 1 (PTH1R). Pharmacological evidence based on the effect of PTH(7-34), a PTH derivative that is said to preferentially activate ß-arrestin signaling through PTH1R, suggests that PTH1R-activated ß-arrestin signaling mediates anabolic effects on bone. Here, we performed a thorough evaluation of PTH(7-34) signaling behaviour using quantitative assays for ß-arrestin recruitment, Gα(s)- and Gα(q)-signaling. We found that PTH(7-34) inhibited PTH-induced cAMP accumulation, but was unable to induce ß-arrestin recruitment, PTH1R internalization and ERK1/2 phosphorylation in HEK293, CHO and U2OS cells. Thus, the ß-arrestin bias of PTH(7-34) is not apparent in every cell type examined, suggesting that correlating in vivo effects of PTH(7-34) to in vitro pharmacology should be done with caution.