Format

Send to

Choose Destination
Proc Natl Acad Sci U S A. 2019 Feb 19;116(8):3294-3299. doi: 10.1073/pnas.1814670116. Epub 2019 Feb 4.

Ca2+ allostery in PTH-receptor signaling.

Author information

1
Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261.
2
Graduate Program in Molecular Pharmacology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261.
3
Graduate Program in Molecular Biophysics and Structural Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261.
4
Department of Internal Medicine and Laboratory of Molecular Endocrinology, Gachon University School of Medicine, Incheon 21565, South Korea.
5
Department of Pharmacology and Chemical Biology, School of Medicine, University of Pittsburgh, Pittsburgh, PA 15261; khxiao@pitt.edu ies4@pitt.edu jpv@pitt.edu.
6
Vascular Medicine Institute, University of Pittsburgh, School of Medicine, Pittsburgh, PA 15261.

Abstract

The parathyroid hormone (PTH) and its related peptide (PTHrP) activate PTH receptor (PTHR) signaling, but only the PTH sustains GS-mediated adenosine 3',5'-cyclic monophosphate (cAMP) production after PTHR internalization into early endosomes. The mechanism of this unexpected behavior for a G-protein-coupled receptor is not fully understood. Here, we show that extracellular Ca2+ acts as a positive allosteric modulator of PTHR signaling that regulates sustained cAMP production. Equilibrium and kinetic studies of ligand-binding and receptor activation reveal that Ca2+ prolongs the residence time of ligands on the receptor, thus, increasing both the duration of the receptor activation and the cAMP signaling. We further find that Ca2+ allostery in the PTHR is strongly affected by the point mutation recently identified in the PTH (PTHR25C) as a new cause of hypocalcemia in humans. Using high-resolution and mass accuracy mass spectrometry approaches, we identified acidic clusters in the receptor's first extracellular loop as key determinants for Ca2+ allosterism and endosomal cAMP signaling. These findings coupled to defective Ca2+ allostery and cAMP signaling in the PTHR by hypocalcemia-causing PTHR25C suggest that Ca2+ allostery in PTHR signaling may be involved in primary signaling processes regulating calcium homeostasis.

KEYWORDS:

Ca2+ allosterism; GPCR signaling; PTH; PTH receptor; endosomal cAMP signaling

PMID:
30718391
PMCID:
PMC6386702
[Available on 2019-08-19]
DOI:
10.1073/pnas.1814670116

Supplemental Content

Full text links

Icon for HighWire
Loading ...
Support Center