Endosomal parathyroid hormone receptor signaling

Area of Science:

• Cellular Biology
• Endocrinology
• Pharmacology

Background:

• The canonical model posits G protein-coupled receptor (GPCR) signaling occurs transiently at the cell surface, with termination involving receptor phosphorylation and β-arrestin recruitment.
• This leads to receptor internalization into endosomes, followed by recycling or degradation, ceasing signaling.
• Recent findings indicate that some internalized GPCRs, like the parathyroid hormone type 1 receptor (PTHR), can continue signaling from endosomes.

Purpose of the Study:

• To review recent insights into the mechanisms of PTHR endosomal signaling.
• To discuss the physiological impact of sustained PTHR signaling from endosomes.
• To highlight the extended model of GPCR signaling beyond the cell surface.

Main Methods:

• Review of current literature on GPCR signaling, focusing on endosomal pathways.
• Analysis of studies investigating the parathyroid hormone type 1 receptor (PTHR) and its signaling dynamics.
• Discussion of evidence linking signaling location to physiological outcomes.

Main Results:

• The parathyroid hormone type 1 receptor (PTHR) exhibits sustained cAMP signaling from endosomes following parathyroid hormone (PTH) stimulation.
• Endosomal signaling by internalized GPCRs contributes to distinct physiological effects compared to cell-surface signaling.
• The location of GPCR signaling significantly influences its overall physiological impact.

Conclusions:

• The traditional model of GPCR signaling termination is incomplete, as receptors can signal from endosomes.
• Endosomal PTHR signaling represents a crucial mechanism for sustained physiological responses to PTH.
• Understanding GPCRs' spatiotemporal signaling dynamics is vital for comprehending their full physiological roles.