Abstract
The σ-1 receptor (Sig-1R) can bind psychostimulants and was shown to be up-regulated in the brain of methamphetamine self-administering rats. Up-regulation of Sig-1Rs has been implicated in neuroplasticity. However, the mechanism(s) whereby Sig-1Rs are up-regulated by psychostimulants is unknown. Here, we employed a neuroblastoma cell line B-104, devoid of dopamine receptors and transporter, and examined the effects of psychostimulants as well as cAMP on the expression of Sig-1Rs in this cell line, with a specific goal to identify signal transduction pathway(s) that may regulate Sig-1R expression. Chronic treatments of B-104 cells with physiological concentrations of cocaine or methamphetamine failed to alter the expression of Sig-1Rs. N6,2′-O-Dibutyryl-cAMP (dB-cAMP), when used at 0.5 mM, caused a down-regulation of Sig-1Rs that could be blocked by a protein kinase A (PKA) inhibitor, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride (H-89). However, dB-cAMP, when used at 2 mM, caused an up-regulation of Sig-1Rs that was insensitive to the H-89 blockade but was partially blocked by an extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase inhibitor PD98059 (2′-amino-3′-methoxyflavone). Furthermore, 2 mM dB-cAMP induced an ERK phosphorylation lasting at least 90 min, at which time the phosphorylation caused by 0.5 mM dB-cAMP had already diminished. PD98059, applied 90 min after addition of 2 mM dB-cAMP, attenuated the Sig-1R up-regulation. Our results indicate that cAMP is bimodal in regulating Sig-1R expression: a down-regulation via PKA and an up-regulation via ERK. Results also suggest that psychostimulants may manipulate the cAMP-PKA-Sig-1R and/or the cAMP-ERK-Sig-1R pathways to achieve a neuroplasticity that favors addictive behaviors.
Footnotes
-
This work was supported by the Intramural Research Program of National Institute on Drug Abuse, National Institutes of Health, Department of Health and Human Services.
-
G.C., T.M., and T.H. contributed equally to this work.
-
Article, publication date, and citation information can be found at http://jpet.aspetjournals.org.
-
doi:10.1124/jpet.106.108415.
-
ABBREVIATIONS: Sig-1R, σ-1 receptor; BMY 14802, α-(4-fluorophenyl)-4-(5-fluoro-2-pyrimidinyl)-1-piperazine; DA, dopamine; PKA, protein kinase A; ERK, extracellular signal-regulated kinase; dB-cAMP, N6,2′-O-dibutyryl-cAMP; NE-100, N,N-dipropyl-2-[4-methoxy-3-(2-phenylethoxy)-phenyl]-ethylamine monohydrochloride; PD98059, 2′-amino-3′-methoxyflavone; FCS, fetal calf serum; DMEM, Dulbecco's modified Eagle's medium; MS-377, ((R)-(+)-1-(4-chlorophenyl)-3-[4-(2-methoxyethyl)piperazin-1-yl]methyl-2-pyrrolidinone l-tartate; H-89, N-[2-(p-bromocinnamylamino)ethyl]-5-isoquinolinesulfonamide dihydrochloride; PAGE, polyacrylamide gel electrophoresis; TBS-T, Tris-buffered saline plus 0.05% Tween 20; ANOVA, analysis of variance; SCH23390, R-(+)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine; Sp-cBIMP, Sp isomer of cyclic-5,6-dichloro-benzimidazol-riboside thiophosphate.
- Received May 24, 2006.
- Accepted October 17, 2006.
- The American Society for Pharmacology and Experimental Therapeutics
JPET articles become freely available 12 months after publication, and remain freely available for 5 years.Non-open access articles that fall outside this five year window are available only to institutional subscribers and current ASPET members, or through the article purchase feature at the bottom of the page.
|