Comparable Initial Engagement of Intracellular Signaling Pathways by Parathyroid Hormone Receptor Ligands Teriparatide, Abaloparatide, and Long-Acting PTH

Research output: Contribution to journalArticle

Abstract

Multiple analogs of parathyroid hormone, all of which bind to the PTH/PTHrP receptor PTH1R, are used for patients with osteoporosis and hypoparathyroidism. Although ligands such as abaloparatide, teriparatide (hPTH 1-34 [TPTD]), and long-acting PTH (LA-PTH) show distinct biologic effects with respect to skeletal and mineral metabolism endpoints, the mechanistic basis for these clinically-important differences remains incompletely understood. Previous work has revealed that differential signaling kinetics and receptor conformation engagement between different PTH1R peptide ligands. However, whether such acute membrane proximal differences translate into differences in downstream signaling output remains to be determined. Here, we directly compared short-term effects of hPTH (1-34), abaloparatide, and LA-PTH in multiple cell-based PTH1R signaling assays. At the time points and ligand concentrations utilized, no significant differences were observed between these three ligands at the level of receptor internalization, β-arrestin recruitment, intracellular calcium stimulation, and cAMP generation. However, abaloparatide showed significantly quicker PTH1R recycling in washout studies. Downstream of PTH1R-stimulated cAMP generation, protein kinase A regulates gene expression via effects on salt inducible kinases (SIKs) and their substrates. Consistent with no differences between these ligands on cAMP generation, we observed that hPTH (1-34), abaloparatide, and LA-PTH showed comparable effects on SIK2 phosphorylation, SIK substrate dephosphorylation, and downstream gene expression changes. Taken together, these results indicate that these PTH1R peptide agonists engage downstream intracellular signaling pathways to a comparable degree. It is possible that differences observed in vivo in preclinical and clinical models may be related to pharmacokinetic factors. It is also possible that our current in vitro systems are insufficient to perfectly match the complexities of PTH1R signaling in bona fide target cells in bone in vivo.

Details

Authors
  • Tadatoshi Sato
  • Shiv Verma
  • Ashok Khatri
  • Thomas Dean
  • Olga Goransson
  • Thomas J. Gardella
  • Marc N. Wein
Organisations
External organisations
  • Harvard Medical School
Research areas and keywords

Subject classification (UKÄ) – MANDATORY

  • Endocrinology and Diabetes

Keywords

  • ANABOLICS, BONE MODELING AND REMODELING, CELL/TISSUE SIGNALING, CELLS OF BONE, ENDOCRINE PATHWAYS, HORMONE REPLACEMENT/RECEPTOR MODULATORS, MOLECULAR PATHWAYS, OSTEOCYTES, PTH/Vit D/FGF23, REMODELING, THERAPEUTICS
Original languageEnglish
Article numbere10441
JournalJBMR Plus
Volume5
Issue number5
Publication statusPublished - 2021 May
Publication categoryResearch
Peer-reviewedYes