Opioid inhibition of adenylyl cyclase in membranes from pertussis toxin-treated NG108-15 cells

J Recept Signal Transduct Res. 1998 Jan;18(1):25-49. doi: 10.3109/10799899809039163.


Gi/Go proteins are uncoupled from receptors by ADP-ribosylation with pertussis toxin (PTX). However, PTX treatment of delta opioid receptor-containing NG108-15 cells reduces, but does not eliminate, opioid inhibition of adenylyl cyclase. The present study explored potential mechanisms of this residual inhibition. Overnight treatment of NG108-15 cells with 100 ng/ml PTX eliminated both PTX-catalyzed [adenylyl-32P]NAD+-labeling of G proteins and agonist stimulation of low Km GTPase in membranes. Although PTX-treatment decreased the maximal opioid inhibition of adenylyl cyclase by 50-65%, the inhibition that remained was concentration-dependent and antagonist-reversible. This inhibition persisted in the absence of GTP (even though opioid inhibition of adenylyl cyclase in untreated membranes was GTP-dependent), but was eliminated by hydrolysis-resistant guanine nucleotide analogs, indicating that G-proteins were still involved in the coupling mechanism. However, assays of agonist-stimulated [35S]GTPgammaS binding in the presence of excess GDP indicated that PTX pretreatment eliminated stimulation of guanine nucleotide exchange by opioid agonists. These results suggest that in membranes from PTX-treated NG108-15 cells, a subpopulation of G proteins may transduce an inhibitory signal from agonist-bound opioid receptors without involvement of guanine nucleotide exchange.

Publication types

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

MeSH terms

  • Adenosine Diphosphate Ribose / metabolism
  • Adenylate Cyclase Toxin*
  • Adenylyl Cyclase Inhibitors*
  • Animals
  • Catalysis
  • Cell Membrane / drug effects
  • Cell Membrane / enzymology
  • Enzyme Activation
  • GTP Phosphohydrolases / metabolism
  • GTP-Binding Proteins / drug effects
  • GTP-Binding Proteins / metabolism
  • Guanine Nucleotides / metabolism
  • Guanosine 5'-O-(3-Thiotriphosphate) / metabolism
  • Hydrolysis
  • Kinetics
  • Mice
  • Naltrexone / analogs & derivatives
  • Naltrexone / pharmacology
  • Narcotics / agonists
  • Narcotics / pharmacology*
  • Neuroblastoma
  • Pertussis Toxin*
  • Tumor Cells, Cultured
  • Virulence Factors, Bordetella / pharmacology*


  • Adenylate Cyclase Toxin
  • Adenylyl Cyclase Inhibitors
  • Guanine Nucleotides
  • Narcotics
  • Virulence Factors, Bordetella
  • Adenosine Diphosphate Ribose
  • Guanosine 5'-O-(3-Thiotriphosphate)
  • Naltrexone
  • Pertussis Toxin
  • GTP Phosphohydrolases
  • GTP-Binding Proteins
  • naltrindole