Activated human hydroxy-carboxylic acid receptor-3 signals to MAP kinase cascades via the PLC-dependent PKC and MMP-mediated EGFR pathways

Br J Pharmacol. 2012 Jul;166(6):1756-73. doi: 10.1111/j.1476-5381.2012.01875.x.

Abstract

BACKGROUND AND PURPOSE 3-Hydroxy-octanoate, recently identified as a ligand for, the orphan GPCR, HCA(3), is of particular interest given its ability to treat lipid disorders and atherosclerosis. Here we demonstrate the pathway of HCA(3)-mediated activation of ERK1/2. EXPERIMENTAL APPROACH Using CHO-K1 cells stably expressing HCA(3) receptors and A431 cells, a human epidermoid cell line with high levels of endogenous expression of functional HCA(3) receptors, HCA(3)-mediated activation of ERK1/2 was measured by Western blot. KEY RESULTS HCA(3)-mediated activation of ERK1/2 was rapid, peaking at 5 min, and was Pertussis toxin sensitive. Our data, obtained by time course analyses in combination with different kinase inhibitors, demonstrated that on agonist stimulation, HCA(3) receptors evoked ERK1/2 activation via two distinct pathways, the PLC/PKC pathway at early time points (≤ 2 min) and the MMP/ epidermal growth factor receptor (EGFR) transactivation pathway with a maximum response at 5 min. Furthermore, our present results also indicated that the βγ-subunits of the G(i) protein play a critical role in HCA(3)-activated ERK1/2 phosphorylation, whereas β-arrestins and Src were not required for ERK1/2 activation. CONCLUSIONS AND IMPLICATIONS We have described the molecular mechanisms underlying the coupling of human HCA(3) receptors to the ERK1/2 MAP kinase pathway in CHO-K1 and A431 cells, which implicate the G(i) protein-initiated, PLC/PKC -and platelet-derived growth factor receptor/EGFR transactivation-dependent pathways. These observations may provide new insights into the pharmacological effects and the physiological functions modulated by the HCA(3)-mediated activation of ERK1/2.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Arrestins / metabolism
  • CHO Cells
  • Calcium / metabolism
  • Cricetinae
  • Cricetulus
  • Cyclic AMP / metabolism
  • Dipeptides / pharmacology
  • ErbB Receptors / metabolism*
  • GTP-Binding Protein alpha Subunits, Gi-Go / metabolism
  • HEK293 Cells
  • Humans
  • MAP Kinase Kinase 1 / metabolism
  • MAP Kinase Kinase 2 / metabolism
  • MAP Kinase Signaling System / drug effects
  • Metalloendopeptidases / antagonists & inhibitors
  • Metalloendopeptidases / metabolism
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Mitogen-Activated Protein Kinase 3 / metabolism*
  • Protein Kinase C / metabolism*
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, Nicotinic / metabolism*
  • beta-Arrestins

Substances

  • Arrestins
  • Dipeptides
  • HCAR3 protein, human
  • N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide
  • Receptors, G-Protein-Coupled
  • Receptors, Nicotinic
  • beta-Arrestins
  • Cyclic AMP
  • ErbB Receptors
  • Protein Kinase C
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • MAP Kinase Kinase 1
  • MAP Kinase Kinase 2
  • Metalloendopeptidases
  • GTP-Binding Protein alpha Subunits, Gi-Go
  • Calcium