Agonist-regulated Cleavage of the Extracellular Domain of Parathyroid Hormone Receptor Type 1

Abstract

The receptor for parathyroid hormone (PTHR) is a main regulator of calcium homeostasis and bone maintenance. As a member of class B of G protein-coupled receptors, it harbors a large extracellular domain, which is required for ligand binding. Here, we demonstrate that the PTHR extracellular domain is cleaved by a protease belonging to the family of extracellular metalloproteinases. We show that the cleavage takes place in a region of the extracellular domain that belongs to an unstructured loop connecting the ligand-binding parts and that the N-terminal 10-kDa fragment is connected to the receptor core by a disulfide bond. Cleaved receptor revealed reduced protein stability compared with noncleaved receptor, suggesting degradation of the whole receptor. In the presence of the agonistic peptides PTH (1-34), PTH(1-14), or PTH(1-31), the processing of the PTHR extracellular domain was inhibited, and receptor protein levels were stabilized. A processed form of the PTHR was also detected in human kidney. These findings suggest a new model of PTHR processing and regulation of its stability.

Ubiquitination-deubiquitination balance dictates ligand-stimulated PTHR sorting

“…Moreover, we show a significant decrease in total receptor abundance within 1 hour of exposure to PTH(7‐34) that was sustained for up 8 hours. Complementary findings show a difference in PTHR half‐life in the absence of ligand (12 hours) or decreasing receptor half‐life in the presence of PTH(7‐34) (7 hours) 56. Although it has been shown that 24 to 48‐hour PTH(1‐34) treatment downregulates total PTHR in opossum kidney cells,57 we did not observe significant effects of PTH(1‐34) on PTHR protein levels.…”

GPR37 is processed in the N‐terminal ectodomain by ADAM10 and furin

“…Metalloproteases have also been associated with the proteolytic processing of a few other class A GPCRs but the responsible enzymes have remained unknown. These receptors include the β 1 ‐adrenergic receptor, 35,48 V2 vasopressin receptor, 49 C5a receptor, 50 sphingosine 1‐phosphate receptor, 51 parathyroid hormone 1 receptor 52 as well as the endothelin B receptor 21 and GPR37LI 22 . This prevalent role of metalloproteases in the cleavage of GPCRs suggests that these enzymes, including ADAMs, might be more generally involved in the processing and functional regulation of GPCRs.…”

The Parkinson's-disease-associated receptor GPR37 undergoes metalloproteinase-mediated N-terminal cleavage and ectodomain shedding

“…A similar mechanism has been implicated for TSHR (Latif et al, 2004;Kaczur et al, 2007), although conflicting information exists (Chazenbalk et al, 2004). In the case of the parathyroid hormone receptor, the cleavage leads to reduced protein stability and possible degradation of the receptor protein (Klenk et al, 2010), whereas the exposed new N-termini of the cleaved protease-activated receptors and adhesion family receptors act as tethered agonists for the cognate receptors (Soh et al, 2010;Stoveken et al, 2015). In the case of GPR37, the question about the functional significance of the proteolytic processing is further complicated by the fact that very little is known about the natural physiological function of the receptor.…”