Dual signal transduction through delta opioid receptors in a transfected human T-cell line.
Opiates are known to function as immunomodulators, in part by effects on T cells. However, the signal transduction pathways mediating the effects of opiates on T cells are largely undefined. To determine whether pathways that regulate free intracellular calcium ([Ca2+]i) and/or cAMP are affected by opiates acting through delta-type opioid receptors (DORs), a cDNA encoding the neuronal DOR was expressed in a stably transfected Jurkat T-cell line. The DOR agonists, deltorphin and [D-Ala2, D-Leu5]-enkephalin (DADLE), elevated [Ca2+]i, measured by flow cytofluorometry using the calcium-sensitive dye, Fluo-3. At concentrations from 10(-11)-10(-7) M, both agonists increased [Ca2+]i from 60 nM to peak concentrations of 400 nM in a dose-dependent manner within 30 sec (ED50 of approximately 5 x 10(-9) M). Naltrindole, a selective DOR antagonist, abolished the increase in [Ca2+]i, and pretreatment with pertussis toxin was also effective. To assess the role of extracellular calcium, cells were pretreated with EGTA, which reduced the initial deltorphin-induced elevation of [Ca2+]i by more than 50% and eliminated the second phase of calcium mobilization. Additionally, the effect of DADLE on forskolin-stimulated cAMP production was determined. DADLE reduced cAMP production by 70% (IC50 of approximately equal to 10(-11) M), and pertussis toxin inhibited the action of DADLE. Thus, the DOR expressed by a transfected Jurkat T-cell line is positively coupled to pathways leading to calcium mobilization and negatively coupled to adenylate cyclase. These studies identify two pertussis toxin-sensitive, G protein-mediated signaling pathways through which DOR agonists regulate the levels of intracellular messengers that modulate T-cell activation.
Sharp
B M
BM
Endocrine-Neuroscience Research Laboratory, Minneapolis Medical Research Foundation, MN, USA.
Shahabi
N A
NA
Heagy
W
W
McAllen
K
K
Bell
M
M
Huntoon
C
C
McKean
D J
DJ
D037361:Adenylate Cyclase Toxin; D002118:Calcium / Q000502:physiology; D002614:Chelating Agents / Q000494:pharmacology; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000502:physiology; D004533:Egtazic Acid / Q000494:pharmacology; D016308:Enkephalin, Leucine-2-Alanine / Q000494:pharmacology; D019204:GTP-Binding Proteins / Q000502:physiology; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology; D037342:Pertussis Toxin; D017465:Receptors, Opioid, delta / Q000502:physiology*; D015398:Signal Transduction; D013601:T-Lymphocytes / Q000502:physiology*; D014162:Transfection; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
D037361:Adenylate Cyclase Toxin; D002614:Chelating Agents; D009842:Oligopeptides; D017465:Receptors, Opioid, delta; D010566:Virulence Factors, Bordetella; C059567:deltorphin; D005576:Colforsin; D004533:Egtazic Acid; D016308:Enkephalin, Leucine-2-Alanine; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019204:GTP-Binding Proteins; D002118:Calcium