Rios Carl, Gomes Ivone, Devi Lakshmi A
Department of Pharmacology and Biological Chemistry, Mount Sinai School of Medicine, New York, NY 10029, USA.
Br J Pharmacol. 2006 Jun;148(4):387-95. doi: 10.1038/sj.bjp.0706757. Epub 2006 May 8.
Several studies have described functional interactions between opioid and cannabinoid receptors; the underlying mechanism(s) have not been well explored. One possible mechanism is direct receptor-receptor interactions, as has been demonstrated for a number of G-protein-coupled receptors. In order to investigate interactions between opioid and cannabinoid receptors, we epitope tagged mu, delta and kappa opioid receptors with Renilla luciferase and CB1 cannabinoid or CCR5 chemokine receptors with yellow fluorescent protein and examined the extent of substrate hydrolysis induced bioluminescence resonance energy transfer (BRET) signal. We find that coexpression of opioid receptors with cannabinoid receptors, but not with chemokine receptors, leads to a significant increase in the level of BRET signal, suggesting that the opioid-cannabinoid interactions are receptor specific. In order to examine the implications of these interactions to signaling, we used GTPgammaS binding and mitogen-activated protein kinase (MAPK) phosphorylation assays and examined the effect of receptor activation on signaling. We find that the mu receptor-mediated signaling is attenuated by the CB1 receptor agonist; this effect is reciprocal and is seen in heterologous cells and endogenous tissue expressing both receptors. In order to explore the physiological consequences of this interaction, we examined the effect of receptor activation on the extent of Src and STAT3 phosphorylation and neuritogenesis in Neuro-2A cells. We find that the simultaneous activation of mu opioid and CB1 cannabinoid receptors leads to a significant attenuation of the response seen upon activation of individual receptors, implicating a role for receptor-receptor interactions in modulating neuritogenesis.
多项研究描述了阿片类受体与大麻素受体之间的功能相互作用；但其潜在机制尚未得到充分探索。一种可能的机制是直接的受体 - 受体相互作用，正如许多G蛋白偶联受体所证实的那样。为了研究阿片类受体与大麻素受体之间的相互作用，我们用海肾荧光素酶对μ、δ和κ阿片类受体进行表位标记，并用黄色荧光蛋白对CB1大麻素受体或CCR5趋化因子受体进行标记，然后检测底物水解诱导的生物发光共振能量转移（BRET）信号的程度。我们发现，阿片类受体与大麻素受体共表达，但与趋化因子受体共表达则不然，会导致BRET信号水平显著增加，这表明阿片类 - 大麻素相互作用具有受体特异性。为了研究这些相互作用对信号传导的影响，我们使用了GTPγS结合和丝裂原活化蛋白激酶（MAPK）磷酸化测定法，并检测受体激活对信号传导的影响。我们发现，CB1受体激动剂可减弱μ受体介导的信号传导；这种效应是相互的，在表达这两种受体的异源细胞和内源性组织中均可见到。为了探索这种相互作用的生理后果，我们检测了受体激活对Neuro-2A细胞中Src和STAT3磷酸化程度以及神经突生成的影响。我们发现，同时激活μ阿片类受体和CB1大麻素受体可导致单个受体激活时所观察到的反应显著减弱，这表明受体 - 受体相互作用在调节神经突生成中发挥作用。
