Related Experiment Video
Updated: Jul 4, 2026

Characterizing Modulators of Protease-Activated Receptors with a Calcium Mobilization Assay Using a Plate Reader
Published on: May 24, 2024
Eliminating phosphorylation sites of the parathyroid hormone receptor type 1 differentially affects stimulation of
Susanne U Miedlich1, Abdul B Abou-Samra
1Massachusetts General Hospital/Harvard Medical School, Boston, MA 02114, USA. smiedlich@partners.org
Abstract:
The parathyroid hormone (PTH)/PTH-related peptide (PTHrP) receptor (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 present study explores the role of individual PTH1R phosphorylation sites in PTH1R signaling through phospholipase C, agonist-dependent receptor internalization, and regulation by G protein-coupled receptor kinases. By means of transiently transfected COS-7 cells, we demonstrate that the phosphorylation-deficient (pd) PTH1R confers dramatically enhanced coupling to G(q/11) proteins upon PTH stimulation predominantly caused by elimination of Ser(491/492/493), Ser(501), or Ser(504). Reportedly, impaired internalization of the pd PTH1R, however, is not dependent on a specific phosphorylation site. In addition, we show that G protein-coupled receptor kinase 2 interferes with pd PTH1R signaling to G(q/11) proteins at least partially by direct binding to G(q/11) proteins.
Related Concept Videos
Amplifying Signals via Enzymatic Cascade
Calmodulin-dependent Signaling
The Ca2+-CaM complex does not have enzymatic activity by itself. Instead, the complex binds downstream target proteins, including membrane proteins or enzymes,...
Protein Kinases and Phosphatases
Protein kinases
Many proteins in the cell are regulated by phosphorylation, the addition of a phosphate group. A family of enzymes called kinases...
cAMP-dependent Protein Kinase Pathways
Transducer Mechanism: Enzyme-Linked Receptors
Major types that are helpful drug targets include:
GPCR Desensitization

