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Protein phosphatase 2A mediates resensitization of the neurokinin 1 receptor

Jane E Murphy1, Dirk Roosterman, Graeme S Cottrell

  • 1Department of Surgery, University of California, San Francisco, 94143-0660, USA.

American Journal of Physiology. Cell Physiology
|July 29, 2011
PubMed

Insights

A novel mechanism for G protein-coupled receptor (GPCR) resensitization involves protein phosphatase 2A (PP2A) dephosphorylating cell-surface neurokinin 1 receptors (NK1R), requiring β-arrestin1 and endothelin-converting enzyme-1 (ECE-1). This discovery offers new insights into GPCR signaling and regulation.

Area of Science:

  • Molecular and Cellular Biology
  • Neuroscience
  • Pharmacology

Background:

  • Activated G protein-coupled receptors (GPCRs) undergo phosphorylation and interact with β-arrestins, leading to desensitization and endocytosis.
  • While endocytosis, dephosphorylation, and recycling are known resensitization pathways, many desensitized receptors persist at the cell surface.
  • The substance P (SP) neurokinin 1 receptor (NK1R) is a key GPCR involved in various physiological processes.

Purpose of the Study:

  • To investigate a novel mechanism for the resensitization of non-internalized, desensitized neurokinin 1 receptors (NK1R).
  • To determine the role of protein phosphatase 2A (PP2A) in the reactivation of cell-surface retained NK1R.
  • To elucidate the involvement of β-arrestin1 and endothelin-converting enzyme-1 (ECE-1) in NK1R resensitization.

Main Methods:

  • Investigated the resensitization of substance P (SP) neurokinin 1 receptor (NK1R) signaling following desensitization.
  • Utilized β-arrestin1 small interfering RNA (siRNA) knockdown to assess the role of β-arrestin1 in receptor-PP2A interaction.
  • Examined the effect of endothelin-converting enzyme-1 (ECE-1) inhibition on receptor resensitization and associated protein interactions.

Main Results:

  • A significant proportion of desensitized NK1R remained at the cell surface, with SP-induced calcium signals resensitizing before full recovery of binding sites.
  • SP induced the association of β-arrestin1 and protein phosphatase 2A (PP2A) with non-internalized NK1R.
  • Resensitization of NK1R signaling was dependent on both PP2A and ECE-1 activity, with β-arrestin1 mediating PP2A recruitment to cell-surface NK1R.

Conclusions:

  • A novel mechanism of GPCR resensitization involves PP2A dephosphorylation of non-internalized NK1R at the cell surface.
  • β-arrestin1 acts as a scaffold, recruiting PP2A to desensitized NK1R, while ECE-1 facilitates this process by promoting β-arrestin1 release from endosomes.
  • This PP2A- and ECE-1-dependent pathway represents a new paradigm for GPCR resensitization, distinct from traditional internalization-dependent mechanisms.

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