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The GIP receptor displays higher basal activity than the GLP-1 receptor but does not recruit GRK2 or arrestin3

Suleiman Al-Sabah1, Munya Al-Fulaij1, Ghina Shaaban1

  • 1Department of Pharmacology and Toxicology, Faculty of Medicine, Kuwait University, Safat, Kuwait.

Plos One
|September 6, 2014
PubMed
Abstract

Insights

Glucagon-like peptide-1 receptor (GLP-1R) effectively recruits arrestin proteins, unlike the glucose-dependent insulinotropic polypeptide receptor (GIPR). This difference may explain why GLP-1, but not GIP, remains effective in type 2 diabetes mellitus.

Area of Science:

  • Endocrinology
  • Molecular Pharmacology
  • Cell Biology

Background:

  • Glucagon-like peptide-1 (GLP-1) and glucose-dependent insulinotropic polypeptide (GIP) are key regulators of insulin secretion.
  • Loss of their function is an early sign of type 2 diabetes mellitus (T2DM).
  • Pharmacological doses of GLP-1, but not GIP, can restore insulin secretion in T2DM.

Purpose of the Study:

  • To compare the signaling properties of GLP-1 receptor (GLP-1R) and GIP receptor (GIPR).
  • To understand why GLP-1 remains insulinotropic in T2DM while GIP does not.

Main Methods:

  • Transiently expressed GLP-1R and GIPR in HEK-293 cells.
  • Assessed cAMP production using a luciferase reporter gene assay.
  • Investigated arrestin3 (Arr3) recruitment via enzyme fragment complementation, confocal microscopy, and FRET.

Main Results:

  • GIPR showed significantly higher ligand-independent activity than GLP-1R.
  • GLP-1R robustly recruited Arr3 upon stimulation, unlike GIPR.
  • GLP-1 stimulated the recruitment of GRK2 and Arr3 to GLP-1R, which was not reversed upon agonist washout.

Conclusions:

  • GIPR exhibits higher basal activity but fails to recruit GRK2 or Arr3 effectively.
  • GLP-1R's interaction with arrestin suggests it functions as a Class A receptor.
  • Differential arrestin recruitment may explain the distinct therapeutic roles of GLP-1 and GIP in T2DM.

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