β-Arrestin-biased signaling of PTH analogs of the type 1 parathyroid hormone receptor

Parathyroid hormone (PTH) is an anabolic agent that mediates bone formation through activation of the G alpha(s)-, G alpha(q)- and beta-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 beta-arrestin signaling through PTH1R, suggests that PTH1R-activated beta-arrestin signaling mediates anabolic effects on bone. Here, we performed a thorough evaluation of PTH(7-34) signaling behaviour using quantitative assays for beta-arrestin recruitment, G alpha(s)- and G alpha(q)- signaling. We found that PTH(7-34) inhibited PTH-induced CAMP accumulation, but was unable to induce beta-arrestin recruitment, PTH1R internalization and ERK1/2 phosphorylation in HEK293, CHO and U2OS cells. Thus, the beta-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. (C) 2012 Elsevier Inc. All rights reserved.