Phosphorylation of the cytoplasmic tail of the PTH/PTHrP receptor

J Bone Miner Res. 1996 May;11(5):578-86. doi: 10.1002/jbmr.5650110505.

Abstract

Activation of the G protein-coupled receptor for parathyroid hormone (PTH)/PTH-related protein (PTHrP) produces homologous desensitization of receptor signaling. We have shown recently that the opossum PTH/PTHrP receptor stably expressed in human embryonic kidney (HEK) 293 cells is phosphorylated upon agonist binding and upon activation of serine/threonine protein kinases (PKA and PKC), an event which for some G protein-coupled receptors has been linked to desensitization. To locate the sites of phosphorylation, mutated forms of the opossum PTH/PTHrP receptor were stably expressed in HEK 293 cells, and ligand-stimulated receptor phosphorylation was evaluated. The five serine and threonine residues of the third cytoplasmic loop of the receptor were not required for receptor phosphorylation. Basal and ligand-induced phosphorylation were, however, completely abolished upon deletion of all but the 16 juxtamembrane residues of the cytoplasmic C-terminal tail of the receptor, even though this truncated receptor resembled the wild-type receptor in its level of expression based on Western blotting and radioligand binding. To identify further the phosphorylation sites, the 129 amino acid C-terminal tail of the rat PTH/PTHrP receptor was expressed in E. coli as a recombinant glutathione S-transferase fusion protein. Elimination of a single PKA consensus site in the tail (serine 491) resulted in > or = 90% loss of PKA-mediated phosphorylation, identifying this as the preferential site for PKA, with two other sites (serine 473 and/or 475) being minor sites. Phosphorylation by PKC occurred largely in the proximal portion of the tail, whereas beta-adrenergic receptor kinase 1 (beta ARK1) phosphorylated more distally in the tail. The ability of these kinases to phosphorylate the PTH/PTHrP receptor at distinct sites on the cytoplasmic tail may allow differential regulation of receptor signaling and trafficking.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cell Line
  • Humans
  • Molecular Sequence Data
  • Parathyroid Hormone-Related Protein
  • Phosphorylation
  • Proteins / metabolism*
  • Rats
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, Parathyroid Hormone / genetics
  • Receptors, Parathyroid Hormone / metabolism*
  • Recombinant Fusion Proteins / genetics
  • Recombinant Fusion Proteins / metabolism
  • Signal Transduction*

Substances

  • PTHLH protein, human
  • Parathyroid Hormone-Related Protein
  • Proteins
  • Receptor, Parathyroid Hormone, Type 1
  • Receptors, Parathyroid Hormone
  • Recombinant Fusion Proteins