LAUSR

Description Physiological responses to parathyroid hormone depend on the subcellular location of receptor activity. Location matters for GPCR signaling Parathyroid hormone (PTH) receptor (PTHR) is a G protein–coupled receptor (GPCR) that controls vitamin D, Ca2+, and bone homeostasis by stimulating cAMP production at the plasma membrane and at endosomes after β-arrestin–dependent internalization. White et al. generated a synthetic PTH derivative (PTH7d) that inhibited β-arrestin coupling to PTHR, thereby leading to sustained cAMP production at the cell surface. Comparison of cellular and organismal responses to wild-type PTH, PTH7d, or a PTH analog that elicits sustained endosomal signaling demonstrated that the biological outcome was determined by the subcellular location of PTHR activity. These findings suggest that biological responses elicited by other GPCRs that are active at intracellular compartments may show a similar dependence on the location of signaling. The parathyroid hormone (PTH) type 1 receptor (PTHR) is a class B G protein–coupled receptor (GPCR) that regulates mineral ion, vitamin D, and bone homeostasis. Activation of the PTHR by PTH induces both transient cell surface and sustained endosomal cAMP production. To address whether the spatial (location) or temporal (duration) dimension of PTHR-induced cAMP encodes distinct biological outcomes, we engineered a biased PTHR ligand (PTH7d) that elicits cAMP production at the plasma membrane but not at endosomes. PTH7d stabilized a unique active PTHR conformation that mediated sustained cAMP signaling at the plasma membrane due to impaired β-arrestin coupling to the receptor. Experiments in cells and mice revealed that sustained cAMP production by cell surface PTHR failed to mimic the pharmacological effects of sustained endosomal cAMP production on the abundance of the rate-limiting hydroxylase catalyzing the formation of active vitamin D, as well as increases in circulating active vitamin D and Ca2+ and in bone formation in mice. Thus, similar amounts of cAMP generated by PTHR for similar lengths of time in different cellular locations, plasma membrane and endosomes, mediate distinct physiological responses. These results unveil subcellular signaling location as a means to achieve specificity in PTHR-mediated biological outcomes and raise the prospect of rational drug design based upon spatiotemporal manipulation of GPCR signaling.