Distinct kinetic and spatial patterns of protein kinase C (PKC)- and epidermal growth factor receptor (EGFR)-dependent activation of extracellular signal-regulated kinases 1 and 2 by human nicotinic acid receptor GPR109A

J Biol Chem. 2011 Sep 9;286(36):31199-212. doi: 10.1074/jbc.M111.241372. Epub 2011 Jul 18.

Abstract

Nicotinic acid (niacin) has been widely used as a lipid-lowering drug for several decades, and recently, orphan G protein-coupled receptor GPR109A has been identified as a receptor for niacin. Mechanistic investigations have shown that, upon niacin activation, GPR109A couples to a G(i) protein and inhibits adenylate cyclase activity, leading to inhibition of liberation of free fatty acid. However, the underlying molecular mechanisms for GPR109A signaling remain largely unknown. Using CHO-K1 cells stably expressing GPR109A and A431 cells, which are a human epidermoid cell line with high levels of endogenous expression of functional GPR109A receptors, we found that activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) by niacin was rapid, peaking at 5 min, and was significantly blocked by pertussis toxin. Furthermore, time course experiments with different kinase inhibitors demonstrated that GPR109A induced ERK1/2 activation via the matrix metalloproteinase/epidermal growth factor receptor transactivation pathway at both early and later time points (2-5 min); this pathway was distinct from the PKC pathway-mediated ERK1/2 phosphorylation that occurs at early time points (≤2 min) in response to niacin. Overexpression of Gβγ subunit scavengers βARK1-CT and the Gα subunit of transducin led to a significant reduction of ERK1/2 phosphorylation, suggesting a critical role for βγ subunits in GPR109A-activated ERK1/2 phosphorylation. Using arrestin-2/3-specific siRNA and an internalization-deficient GPR109A mutant, we found that arrestin-2 and arrestin-3 were not involved in GPR109A-mediated ERK1/2 activation. In conclusion, our findings demonstrate that upon binding to niacin GPR109A receptors initially activate G(i), leading to dissociation of the Gβγ subunit from activated G(i), and subsequently induce ERK1/2 activation via two distinct pathways, one PKC-dependent pathway occurring at a peak time of ≤2 min and the other matrix metalloproteinase-dependent growth factor receptor transactivation occurring at both early and later time points (2-5 min).

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ErbB Receptors / metabolism*
  • Humans
  • Kinetics
  • Metalloproteases
  • Mitogen-Activated Protein Kinase 1 / metabolism*
  • Mitogen-Activated Protein Kinase 3 / metabolism*
  • Niacin / metabolism
  • Protein Kinase C / metabolism*
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, Nicotinic / metabolism*
  • Signal Transduction
  • Time Factors

Substances

  • HCAR2 protein, human
  • Receptors, G-Protein-Coupled
  • Receptors, Nicotinic
  • Niacin
  • ErbB Receptors
  • Protein Kinase C
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • Metalloproteases