The G Protein-Coupled Receptor Family C Group 6 Subtype A (GPRC6A) Receptor Is Involved in Amino Acid-Induced Glucagon-Like peptide-1 Secretion From GLUTag Cells

J Biol Chem. 2013 Feb 15;288(7):4513-21. doi: 10.1074/jbc.M112.402677. Epub 2012 Dec 26.

Abstract

Although amino acids are dietary nutrients that evoke the secretion of glucagon-like peptide 1 (GLP-1) from intestinal L cells, the precise molecular mechanism(s) by which amino acids regulate GLP-1 secretion from intestinal L cells remains unknown. Here, we show that the G protein-coupled receptor (GPCR), family C group 6 subtype A (GPRC6A), is involved in amino acid-induced GLP-1 secretion from the intestinal L cell line GLUTag. Application of l-ornithine caused an increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) in GLUTag cells. Application of a GPRC6A receptor antagonist, a phospholipase C inhibitor, or an IP(3) receptor antagonist significantly suppressed the l-ornithine-induced [Ca(2+)](i) increase. We found that the increase in [Ca(2+)](i) stimulated by l-ornithine correlated with GLP-1 secretion and that l-ornithine stimulation increased exocytosis in a dose-dependent manner. Furthermore, depletion of endogenous GPRC6A by a specific small interfering RNA (siRNA) inhibited the l-ornithine-induced [Ca(2+)](i) increase and GLP-1 secretion. Taken together, these findings suggest that the GPRC6A receptor functions as an amino acid sensor in GLUTag cells that promotes GLP-1 secretion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acids / metabolism
  • Animals
  • Calcium / metabolism
  • Enteroendocrine Cells / metabolism*
  • GTP-Binding Proteins / metabolism*
  • Gene Expression Regulation*
  • Genetic Vectors
  • Glucagon-Like Peptide 1 / metabolism*
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Immunohistochemistry / methods
  • Ligands
  • Mice
  • Mice, Transgenic
  • Models, Biological
  • Ornithine / pharmacology
  • RNA, Small Interfering / metabolism
  • Receptors, G-Protein-Coupled / metabolism*
  • Spectroscopy, Fourier Transform Infrared
  • Time Factors
  • Transfection

Substances

  • Amino Acids
  • GPRC6A protein, human
  • GPRC6A protein, mouse
  • Ligands
  • RNA, Small Interfering
  • Receptors, G-Protein-Coupled
  • Green Fluorescent Proteins
  • Glucagon-Like Peptide 1
  • Ornithine
  • GTP-Binding Proteins
  • Calcium