Submitted on January 19, 2008
Accepted on June 19, 2008
Eliminating phosphorylation sites of the parathyroid hormone receptor type 1 differentially affects stimulation of phospholipase C and receptor internalization
Susanne Ursula Miedlich1* and Abdul Badi Abou-Samra2
1 Endocrine Unit, Massachusetts General Hospital and Harvard Medical School, Boston, Massachusetts, United States
2 Internal Medicine/Division Endocrinology, Wayne State University School of Medicine, Detroit, Michigan, United States
* To whom correspondence should be addressed. E-mail: smiedlich{at}partners.org.
The parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (PTH/PTHrP receptor or PTH1R) belongs to family B of seven-transmembrane spanning receptors and is activated by PTH and PTHrP. Upon PTH stimulation, the rat PTH1R becomes phosphorylated at seven serine residues. Elimination of all PTH1R phosphorylation sites results in prolonged cAMP accumulation and impaired internalization in stably transfected LLC-PK1 cells. The current study explores the role of individual PTH1R phosphorylation sites in PTH1R signaling through phospholipase C, agonist-dependent receptor internalization, and regulation by GRKs.
By means of transiently transfected COS-7 cells we demonstrate that the phosphorylation-deficient (pd) PTH1R confers dramatically enhanced coupling to Gq/11 proteins upon PTH stimulation predominantly caused by elimination of residues Ser491/492/493, Ser501 or Ser504. Reportedly impaired internalization of the pd PTH1R however, is not dependent on a specific phosphorylation site. In addition, we show that GRK 2 interferes with pd PTH1R signaling to Gq/11 proteins at least partially by direct binding to Gq/11.
