The signalling profile of recombinant human orexin-2 receptor

Cell Signal. 2008 Sep;20(9):1651-61. doi: 10.1016/j.cellsig.2008.05.010. Epub 2008 May 27.


Orexin-A and orexin-B orchestrate their diverse central and peripheral effects via two G-protein coupled receptors, OX1R and OX2R, which activate multiple G-proteins. In many tissues, orexins activate extracellular signal-regulated kinase (ERK(1/2)) and p38 mitogen-activated protein kinase (MAPK); however, the mechanism by which OX2R alone mediates MAPK activation is not understood. This study describes the intracellular signalling pathways involved in OX2R-mediated ERK(1/2) and p38 MAPK activation. In HEK-293 cells stably over-expressing recombinant human OX2R, orexin-A/B resulted in a rapid, dose and time dependent increase in activation of ERK(1/2) and p38 MAPK, with maximal activation at 10 min for ERK(1/2) and 30 min for p38 MAPK. Using dominant-negative G-proteins and selective inhibitors of intracellular signalling cascades, we determined that orexin-A and orexin-B induced ERK(1/2) and p38 MAPK activation through multiple G-proteins and different intracellular signalling pathways. ERK(1/2) activation involves Gq/phospholipase C (PLC)/protein kinase C (PKC), Gs/adenylyl cyclase (AC)/cAMP/protein kinase A (PKA) and Gi cascades; however, the Gq/PLC/PKC pathway, as well as PKA is not required for OX2R-mediated p38 MAPK activation. Interestingly, orexin-B-induced ERK(1/2) activation is predominantly mediated through the Gq/PLC/PKC pathway. In conclusion, this is the first comprehensive signalling study of the human OX2R recombinant receptor, showing ERK(1/2) and p38 MAPK activation are regulated by differential signalling pathways in HEK-293 cells, and that the ERK(1/2) activation is severely affected by naturally occurring mutants associated with narcolepsy. Moreover, it is evident that the human OX2R has ligand specific effects, with orexin-B being more potent in this transfected system and this distinct modulation of the MAPKs through OX2R, may translate to the regulation of diverse biological actions of orexins.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Cell Line
  • Cell Proliferation / drug effects
  • Cyclic AMP / metabolism
  • Cyclic AMP-Dependent Protein Kinases / metabolism
  • Enzyme Activation / drug effects
  • GTP-Binding Protein alpha Subunits / metabolism
  • Gene Expression Regulation / drug effects
  • Green Fluorescent Proteins / metabolism
  • Humans
  • Inositol Phosphates / metabolism
  • Intracellular Signaling Peptides and Proteins / pharmacology
  • Mitogen-Activated Protein Kinase 1 / metabolism
  • Mitogen-Activated Protein Kinase 3 / metabolism
  • Mutant Proteins / metabolism
  • Mutation / genetics
  • Neuropeptides / pharmacology
  • Orexin Receptors
  • Orexins
  • Protein Kinase C / metabolism
  • Protein Transport / drug effects
  • Receptors, G-Protein-Coupled / genetics
  • Receptors, G-Protein-Coupled / metabolism*
  • Receptors, Neuropeptide / genetics
  • Receptors, Neuropeptide / metabolism*
  • Recombinant Proteins / metabolism*
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction* / drug effects
  • Type C Phospholipases / metabolism
  • p38 Mitogen-Activated Protein Kinases / metabolism


  • GTP-Binding Protein alpha Subunits
  • HCRT protein, human
  • HCRTR2 protein, human
  • Inositol Phosphates
  • Intracellular Signaling Peptides and Proteins
  • Mutant Proteins
  • Neuropeptides
  • Orexin Receptors
  • Orexins
  • Receptors, G-Protein-Coupled
  • Receptors, Neuropeptide
  • Recombinant Proteins
  • Green Fluorescent Proteins
  • Cyclic AMP
  • Cyclic AMP-Dependent Protein Kinases
  • Protein Kinase C
  • Mitogen-Activated Protein Kinase 1
  • Mitogen-Activated Protein Kinase 3
  • p38 Mitogen-Activated Protein Kinases
  • Type C Phospholipases