Free fatty acids and protein kinase C activation induce GPR120 (free fatty acid receptor 4) phosphorylation

Eur J Pharmacol. 2014 Jan 15:723:368-74. doi: 10.1016/j.ejphar.2013.11.003. Epub 2013 Nov 12.

Abstract

GPR120, free fatty acid receptor 4, is a recently deorphanized G protein-coupled receptor that seems to play cardinal roles in the regulation of metabolism and in the pathophysiology of inflammatory and metabolic disorders. In the present work a GPR120-Venus fusion protein was expressed in HEK293 Flp-In T-REx cells and its function (increase in intracellular calcium) and phosphorylation were studied. It was observed that the fusion protein migrated in sodium dodecyl sulfate-polyacrylamide gels as a band with a mass of ≈70-75kDa, although other bands of higher apparent weight (>130kDa) were also detected. Cell stimulation with docosahexaenoic acid or α-linolenic acid induced concentration-dependent increases in intracellular calcium and GPR120 phosphorylation. Activation of protein kinase C with phorbol esters also induced a marked receptor phosphorylation but did not alter the ability of 1µM docosahexaenoic acid to increase the intracellular calcium concentration. Phorbol ester-induced GPR120 phosphorylation, but not that induced with docosahexaenoic acid, was blocked by protein kinase C inhibitors (bis-indolyl-maleimide I and Gö 6976) suggesting that conventional kinase isoforms mediate this action. The absence of effect of protein kinase C inhibitors on agonist-induced GPR120 phosphorylation indicates that this kinase does not play a major role in agonist-induced receptor phosphorylation. Docosahexaenoic acid action was associated with marked GPR120 internalization whereas that induced with phorbol esters was smaller at early times.

Keywords: Free fatty acid receptor 4; GPR120; Protein kinase C; Receptor phosphorylation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Docosahexaenoic Acids / pharmacology*
  • Fatty Acids, Nonesterified / pharmacology
  • HEK293 Cells
  • Humans
  • Phorbol Esters / pharmacology
  • Phosphorylation
  • Protein Kinase C / metabolism*
  • Receptors, G-Protein-Coupled / metabolism*
  • Recombinant Fusion Proteins / metabolism
  • Tetradecanoylphorbol Acetate / pharmacology
  • alpha-Linolenic Acid / pharmacology*

Substances

  • FFAR4 protein, human
  • Fatty Acids, Nonesterified
  • Phorbol Esters
  • Receptors, G-Protein-Coupled
  • Recombinant Fusion Proteins
  • alpha-Linolenic Acid
  • Docosahexaenoic Acids
  • Protein Kinase C
  • Tetradecanoylphorbol Acetate