PKA and ERK1/2 are involved in dopamine D₁ receptor-induced heterologous desensitization of the ¦Ä opioid receptor

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• 作者：Wei Xu ; Chongguang Chen ; Jian-Guo Li ; Kelly DiMattio ; Yujun Wang ; Ellen Unterwald ; Lee-Yuan Liu-Chen ; ^{lliuche@temple.edu}
• 关键词：CHO cells ; Chinese hamster ovary cells ; CHO-FLAG-mDOPR ; clonal CHO cells stably transfected with FLAG-mouse ¦Ä opioid receptor cDNA in pcDNA3 vector ; DPDPE ; [D-Pen2 ; D-Pen5]-Enkephalin ; CHO-FLAG-DOPR/HA-D1R cells ; clonal CHO cells stably transfected with F
• 刊名：Life Sciences
• 出版年：2013
• 出版时间：21 June, 2013
• 年：2013
• 卷：92
• 期：23
• 页码：1101-1109
• 全文大小：665 K

文摘

Aims

Chronic administration of cocaine attenuates delta opioid receptor (DOPR) signaling in the striatum and the desensitization is mediated by the indirect actions of cocaine on dopamine D₁ receptors (D₁R). In addition, DOPR and D₁R co-exist in some rat striatal neurons. In the present study, we examined the underlying mechanism of DOPR desensitization by D₁R activation.

Main methods

NG 108-15 cells stably expressing HA-rat D₁ receptor (HA-D₁R) and Chinese hamster ovary (CHO) cells stably expressing both FLAG-mouse DOPR (FLAG-DOPR) and HA-D₁R were used as the cell models. Receptor binding, [³⁵S]GTP¦ÃS binding, receptor phosphorylation and western blot were conducted to examine DOPR affinity, expression, internalization, downregulation, desensitization, phosphorylation and phosphorylated ERK1/2.

Key findings

Pretreatment with either the DOPR agonist DPDPE or the D₁R agonist SKF-82958 for 30 min attenuated DPDPE-stimulated [³⁵S]GTP¦ÃS binding to G proteins, demonstrating homologous and heterologous desensitization of the DOPR, respectively. SKF-82958 pretreatment did not affect the level of DOPR or affinity of DOPR antagonist or agonists, nor did it induce phosphorylation, internalization or down-regulation of the DOPR in the CHO-FLAG-DOPR/HA-D₁R cells. Pretreatment of cells with inhibitors of PKA, MEK1 and PI3K, but not PKC, attenuated SKF-82958-induced desensitization of the DOPR. The D₁R agonist SKF-82958 enhanced phosphorylation of ERK1/2, and pretreatment with inhibitors of MEK1 and PI3K, but not PKA and PKC, reduced the effect. These results indicate that activation of ERK1/2 and/or PKA, but not PKC, is involved in D₁ receptor-induced heterologous desensitization of the DOPR.

Significance

This study provides possible mechanisms underlying D₁R activation-induced DOPR desensitization.