Mu and kappa opioid receptors activate ERK/MAPK via different protein kinase C isoforms and secondary messengers in astrocytes

J Biol Chem. 2005 Jul 29;280(30):27662-9. doi: 10.1074/jbc.M502593200. Epub 2005 Jun 8.

Abstract

Acute mu and kappa opioids activate the ERK/MAPK phosphorylation cascade that represents an integral part of the signaling pathway of growth factors in astrocytes. By this cross-talk, opioids may impact neural development and plasticity among other basic neurobiological processes in vivo. The mu agonist, [D-ala2,mephe4,glyol5]enkephalin (DAMGO), induces a transient stimulation of ERK phosphorylation, whereas kappa agonist, U69,593, engenders sustained ERK activation. Here we demonstrate that acute U69,593 and DAMGO stimulate ERK phosphorylation by utilization of different secondary messengers and protein kinase C (PKC) isoforms upstream of the growth factor pathway. Immortalized astrocytes transfected with either antisense calmodulin (CaM), a mutant mu opioid receptor that binds CaM poorly or a dominant negative mutant of PKCepsilon were used as a model system to study mu signaling. Evidence was gained to implicate CaM and PKCepsilon in DAMGO stimulation of ERK. DAMGO activation of PKCepsilon and/or ERK was insensitive to selective inhibitors of Ca2+ mobilization, but it was blocked upon phospholipase C inhibition. These results suggest a novel mechanism wherein, upon DAMGO binding, CaM is released from the mu receptor and activates phospholipase C. Subsequently, phospholipase C generates diacylglycerides that activate PKCepsilon. In contrast, U69,593 appears to act via phosphoinositide 3-kinase, PKCzeta, and Ca2+ mobilization. These signaling components were implicated based on studies with specific inhibitors and a dominant negative mutant of PKCzeta. Collectively, our findings on acute opioid effects suggest that differences in their mechanism of signaling may contribute to the distinct outcomes on ERK modulation induced by chronic mu and kappa opioids.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Analgesics / pharmacology
  • Analgesics, Opioid / pharmacology
  • Animals
  • Astrocytes / cytology
  • Astrocytes / metabolism*
  • Benzeneacetamides / pharmacology
  • Calcium / metabolism
  • Calmodulin / metabolism
  • Carbazoles / pharmacology
  • Cell Membrane / metabolism
  • Cells, Cultured
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)- / pharmacology
  • Enzyme Activation
  • ErbB Receptors / metabolism
  • Extracellular Signal-Regulated MAP Kinases / metabolism*
  • Humans
  • Immunoblotting
  • Immunoprecipitation
  • Indoles
  • MAP Kinase Signaling System*
  • Maleimides
  • Neurons / metabolism
  • Phosphatidylinositol 3-Kinases / metabolism
  • Phosphorylation
  • Protein Binding
  • Protein Isoforms
  • Protein Kinase C / chemistry*
  • Protein Kinase C / metabolism
  • Protein Kinase C-epsilon
  • Pyrrolidines / pharmacology
  • Rats
  • Receptors, Opioid, kappa / agonists
  • Receptors, Opioid, kappa / physiology*
  • Receptors, Opioid, mu / physiology*
  • Signal Transduction
  • Transfection
  • Type C Phospholipases / metabolism

Substances

  • 2-(1-(3-dimethylaminopropyl)-5-methoxyindol-3-yl)-3-(1H-indol-3-yl)maleimide
  • Analgesics
  • Analgesics, Opioid
  • Benzeneacetamides
  • Calmodulin
  • Carbazoles
  • Indoles
  • Maleimides
  • Protein Isoforms
  • Pyrrolidines
  • Receptors, Opioid, kappa
  • Receptors, Opioid, mu
  • Enkephalin, Ala(2)-MePhe(4)-Gly(5)-
  • Phosphatidylinositol 3-Kinases
  • Prkce protein, rat
  • ErbB Receptors
  • protein kinase C zeta
  • PRKCE protein, human
  • Protein Kinase C
  • Protein Kinase C-epsilon
  • Extracellular Signal-Regulated MAP Kinases
  • Type C Phospholipases
  • U 69593
  • Calcium