Nuclear trafficking of the G-protein-coupled parathyroid hormone receptor.

G-protein-coupled receptors are a family of receptors that signal primarily through heterotrimeric G proteins. However, new evidence has emerged to show that the signaling capabilities of the receptors are beyond those of traditional signaling cascades. One such example is that the parathyroid hormone (PTH) type 1 receptor is found not only at the plasma membrane but also in the nucleus of cells in cell lines and tissues. This review discusses the emerging concepts of nuclear PTH signaling and relates this information to the growing field of nuclear G-protein-coupled receptors. We review recently published studies on the mechanism of PTH nuclear localization, its role in the cell nucleus, and the contrasting roles ligands play in regulating the receptors' nuclear localization. The review also discusses the importance of nuclear G-protein-coupled receptors and future directions for research in this field.