Department of Neuroscience and Center for Neurovirology, Temple University Lewis Katz School of Medicine, Philadelphia, PA, 19140, USA.
Institute of NeuroImmune Pharmacology and Department of Biological Sciences, Seton Hall University, South Orange, NJ, USA.
J Neuroimmune Pharmacol. 2022 Jun;17(1-2):277-288. doi: 10.1007/s11481-021-10009-4. Epub 2021 Aug 21.
Clinically used opioids, such as morphine, activate the mu opioid receptor (MOR) encoded by Opioid Receptor Mu 1 (OPRM1) gene. Examination of the opioid receptor genes showed that the human OPRM1 pre-mRNA undergoes extensive alternative splicing events and capable of expressing 21 isoforms. However, characterization of OPRM1 signaling is generalized, and only one isoform (MOR-1) has been extensively studied. Compounding this issue is the increasing significance of intravenous drug abuse in HIV neuropathogenesis. Here, we investigated the molecular impact of morphine and HIV-1 on regulation of OPRM1 pre-mRNA splicing in in vitro and in vivo models. Our results suggested that morphine treatment specifically induces the alternative splicing of MOR-1X isoform among the other isoforms analyzed in neuronal cells. Interestingly, alternative splicing and expression of MOR-1X isoform was also induced in postmortem brain tissues obtained from people with HIV (PWH). Additionally, treatment of control rats with morphine induced alternative splicing of MOR-1X in the brain regions involved in the reward pathways. More interestingly, HIV-1 transgenic (HIV-1Tg) rats, showed an additive induction of MOR-1X isoform with the exposure to morphine. To further assess the possible role of HIV secretory proteins in alternative splicing of OPRM1 gene, we analyzed the impact of HIV-1 Tat, gp120 and Nef proteins on alternative splicing of MOR-1X isoform. While the Tat and gp120 had no visible effects, treatment of neurons with Nef induced MOR-1X alternative splicing that was comparable to treatment with morphine. Altogether, our results suggest that HIV-1 may alter MOR isoform expression with Nef protein by amplifying the rate of MOR-1X alternative splicing induced by morphine.
临床上使用的阿片类药物，如吗啡，可激活由阿片受体 mu1 (OPRM1)基因编码的 mu 阿片受体 (MOR)。对阿片受体基因的研究表明，人类 OPRM1 前体 mRNA 经历广泛的选择性剪接事件，并能表达 21 种同工型。然而，对阿片受体信号的特征描述是普遍的，只有一种同工型 (MOR-1) 被广泛研究。使问题更加复杂的是静脉药物滥用在 HIV 神经发病机制中的重要性日益增加。在这里，我们研究了吗啡和 HIV-1 对体外和体内模型中 OPRM1 前体 mRNA 剪接调控的分子影响。我们的研究结果表明，吗啡处理特异性地诱导神经元细胞中分析的其他同工型中 MOR-1X 同工型的选择性剪接。有趣的是，在来自 HIV 患者 (PWH) 的尸检脑组织中也诱导了 MOR-1X 同工型的选择性剪接。此外，用吗啡处理对照大鼠可诱导参与奖励途径的大脑区域中 MOR-1X 的选择性剪接。更有趣的是，HIV-1 转基因 (HIV-1Tg) 大鼠在暴露于吗啡时，MOR-1X 同工型的诱导呈叠加趋势。为了进一步评估 HIV 分泌蛋白在 OPRM1 基因选择性剪接中的可能作用，我们分析了 HIV-1 Tat、gp120 和 Nef 蛋白对 MOR-1X 同工型选择性剪接的影响。虽然 Tat 和 gp120 没有明显的影响，但用 Nef 处理神经元可诱导与吗啡处理相当的 MOR-1X 选择性剪接。总之，我们的研究结果表明，HIV-1 可能通过放大吗啡诱导的 MOR-1X 选择性剪接率来改变 Nef 蛋白的 MOR 同工型表达。
