Identity of adenylyl cyclase isoform determines the G protein mediating chronic opioid-induced adenylyl cyclase supersensitivity
Identity of adenylyl cyclase isoform determines the G protein mediating chronic opioid-induced adenylyl cyclase supersensitivity
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DOI：
10.1046/j.1471-4159.2002.01188.x
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发表时间：
2002-11-01
影响因子：
4.7
通讯作者：
Christ, TE
中科院分区：
文献类型：
--
作者：
Ammer, H;Christ, TE
为了确定导致耐受性/依赖性发展的细胞内信号转导途径，在存在确定的腺苷酸环化酶（AC）亚型的情况下，检查了G（z）α替代百日咳毒素（PTX）敏感性G蛋白介导AC超敏性的能力。在瞬时μ阿片受体（OR）转染的COS- 7细胞（内源性抑制性G蛋白：G（i）α 2、G（i）α 3和G（z）α）中，急性（1 μ mol/L）和慢性吗啡处理（1 μ mol/L; 18 h）均不影响细胞内cAMP的产生。mu-OR与AC V型和VI型的共表达完全恢复了吗啡急性抑制cAMP生成的能力。慢性吗啡治疗进一步导致耐受性/依赖性的发展，如通过急性抑制性阿片样物质作用的脱敏（耐受性）以及停药后AC超敏性的诱导（依赖性）所评估的。通过PTX处理和G（z）α过表达经由G（z）α的mu-OR信号传导的特定方向对AC V型的慢性吗啡调节没有影响，但完全消除了AC VI型的耐受/依赖的发展。在用G（z）α和AC V型或VI型瞬时共转染的稳定表达mu-OR的HEK 293细胞中获得了类似的结果。共沉淀研究进一步证实Gza特异性结合AC V型，但不结合VI型。综上所述，这些结果表明，原则上每一个OR激活的G蛋白本身能够介导AC超敏性。然而，他们也表明，这是AC亚型的分子性质，选择和确定的OR-活化的G蛋白介导的耐受性/依赖性。
To determine the intracellular signal transduction pathway responsible for the development of tolerance/dependence, the ability of G(z)alpha 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 mu-opioid receptor (OR) transfected COS- 7 cells (endogenous inhibitory G proteins: G(i)alpha2, G(i)alpha3 and G(z)alpha), neither acute (1 mumol/L) nor chronic morphine treatment (1 mumol/L; 18 h) influenced intracellular cAMP production. Coexpression of the mu-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 mu-OR signalling via G(z)alpha by both PTX treatment and G(z)alpha 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 mu-OR-expressing HEK293 cells transiently cotransfected with G(z)alpha and either AC type V or VI. Coprecipitation studies further verified that Gza 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.