Phosphorylation Sites of the Gastric Inhibitory Polypeptide Receptor (GIPR) Revealed by Trapped-Ion-Mobility Spectrometry Coupled to Time-of-Flight Mass Spectrometry (TIMS-TOF MS)

The gastric inhibitory polypeptide receptor (GIPR), a G protein-coupled receptor (GPCR) that regulates glucose metabolism and insulin secretion, is a target for the development of therapeutic agents to address type 2 diabetes and obesity. Signal transduction processes mediated by GPCR activation typically result in receptor phosphorylation, but very little is known about GIPR phosphorylation. Mass spectrometry (MS) is a powerful tool for detecting phosphorylation and other post-translational modifications of proteins and for identifying modification sites. However, applying MS methods to GPCRs is challenging because the native expression levels are low and the hydrophobicity of these proteins complicates isolation and enrichment. Here we use a widely available technique, trapped-ion-mobility spectrometry coupled to time-of-flight mass spectrometry (TIMS-TOF MS), to characterize the phosphorylation status of the GIPR. We identified eight serine residues that are phosphorylated, one in an intracellular loop and the remainder in the C-terminal domain. Stimulation with the native agonist GIP enhanced phosphorylation at four of these sites. For comparison, we evaluated tirzepatide (TZP), a dual agonist of the glucagon-like peptide-1 (GLP-1) receptor and the GIPR that has recently been approved for the treatment of type 2 diabetes. Stimulation with TZP enhanced phosphorylation at the same four sites that were enhanced with GIP; however, TZP also enhanced phosphorylation at a fifth site that is unique to this synthetic agonist. This work establishes an important and accessible tool for the characterization of signal transduction via the GIPR and reveals an unanticipated functional difference between GIP and TZP.

Medienart:

E-Artikel

Erscheinungsjahr:

2023

Erschienen:

2023

Enthalten in:

Zur Gesamtaufnahme - volume:145

Enthalten in:

Journal of the American Chemical Society - 145(2023), 51 vom: 27. Dez., Seite 28030-28037

Sprache:

Englisch

Beteiligte Personen:

Brown, Kyle A [VerfasserIn]
Morris, Rylie K [VerfasserIn]
Eckhardt, Samantha J [VerfasserIn]
Ge, Ying [VerfasserIn]
Gellman, Samuel H [VerfasserIn]

Links:

Volltext

Themen:

59392-49-3
D6H00MV7K8
Gastric Inhibitory Polypeptide
Gastric inhibitory polypeptide receptor
Glucagon-Like Peptide-1 Receptor
Journal Article
Receptors, G-Protein-Coupled
Research Support, N.I.H., Extramural

Anmerkungen:

Date Completed 28.12.2023

Date Revised 14.02.2024

published: Print-Electronic

Citation Status MEDLINE

doi:

10.1021/jacs.3c09078

funding:

Förderinstitution / Projekttitel:

PPN (Katalog-ID):

NLM365821888