Identity of adenylyl cyclase isoform determines the G protein mediating chronic opioid-induced adenylyl cyclase supersensitivity

J Neurochem. 2002 Nov;83(4):818-27. doi: 10.1046/j.1471-4159.2002.01188.x.


To determine the intracellular signal transduction pathway responsible for the development of tolerance/dependence, the ability of Gzalpha to substitute for pertussis toxin (PTX)-sensitive G proteins in mediating adenylyl cyclase (AC) supersensitivity was examined in the presence of defined AC isoforms. In transiently micro-opioid receptor (OR) transfected COS-7 cells (endogenous inhibitory G proteins: Gialpha2, Gialpha3 and Gzalpha), neither acute (1 micro mol/L) nor chronic morphine treatment (1 micromol/L; 18 h) influenced intracellular cAMP production. Coexpression of the micro -OR together with AC type V and VI fully restored the ability of morphine to acutely inhibit cAMP generation. Chronic morphine treatment further resulted in the development of tolerance/dependence, as assessed by desensitization of the acute inhibitory opioid effect (tolerance) as well as the induction of AC supersensitivity after drug withdrawal (dependence). Specific direction of micro -OR signalling via Gzalpha by both PTX treatment and Gzalpha over-expression had no effect on chronic morphine regulation of AC type V, but completely abolished the development of tolerance/dependence with AC type VI. Similar results were obtained in stably micro -OR-expressing HEK293 cells transiently cotransfected with Gzalpha and either AC type V or VI. Coprecipitation studies further verified that Gzalpha specifically binds to AC type V but not type VI. Taken together, these results demonstrate that in principle each of the OR-activated G proteins per se is able to mediate AC supersensitivity. However, they also indicate that it is the molecular nature of AC isoform that selects and determines the OR-activated G protein mediating tolerance/dependence.

MeSH terms

  • Adenylyl Cyclases / genetics
  • Adenylyl Cyclases / metabolism*
  • Animals
  • COS Cells
  • Colforsin / pharmacology
  • Cyclic AMP / metabolism
  • Dose-Response Relationship, Drug
  • Drug Tolerance / physiology
  • Enzyme Activation / drug effects
  • GTP-Binding Protein alpha Subunits*
  • GTP-Binding Proteins / metabolism*
  • Heterotrimeric GTP-Binding Proteins / genetics
  • Heterotrimeric GTP-Binding Proteins / metabolism
  • Humans
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Kidney / cytology
  • Kidney / drug effects
  • Kidney / metabolism
  • Morphine / pharmacology
  • Narcotics / pharmacology*
  • Protein Binding / physiology
  • Receptors, Opioid, mu / genetics
  • Receptors, Opioid, mu / metabolism*
  • Signal Transduction / drug effects
  • Signal Transduction / physiology
  • Substance-Related Disorders / metabolism
  • Time
  • Transfection


  • GNAZ protein, human
  • GTP-Binding Protein alpha Subunits
  • Isoenzymes
  • Narcotics
  • Receptors, Opioid, mu
  • Colforsin
  • Morphine
  • Cyclic AMP
  • GTP-Binding Proteins
  • Heterotrimeric GTP-Binding Proteins
  • Adenylyl Cyclases
  • adenylyl cyclase 6
  • adenylyl cyclase type V