Src酪氨酸激酶在吗啡依赖中的调节作用及机制研究

Recent studies have revealed that under prolonged morphine administration, adenylyl cyclase (AC) superactivation required the recruitment and activation of Src kinases and subsequent Src-mediated phosphorylation of mu opioid receptor at the Tyr336 residue. Since the compensatory AC activation phenomenon has been postulated to be responsible for the development of drug tolerance and dependence. The purpose of the present study will be designed to investigate the role of different Src family kinases in different brain regions on naloxone-precipitated morphine withdrawal behavior and morphine-induced conditioned place preference (CPP). With these behavioral tests, the effects of Src kinases on mu opioid receptor phosphorylation at the Tyr336 residue and AC superactivation will be further examined. Our findings will provide novel evidences for the critical role of Src kinases in the regulation of morphine dependence. More importantly, a specific treatment paradigm for opioid dependence may be attainable, if the Src-mediated mu opioid receptor phosphorylation at the Tyr336 residue can be prevented while still maintaining the overall Src kinases activity.

吗啡长期处理造成的特定脑区内神经系统发生适应性改变是构成耐受，戒断和依赖的基础。研究表明慢性吗啡处理的细胞在纳洛酮诱导下环腺苷酸（cyclic AMP, cAMP）发生的超射与Src酪氨酸激酶依赖性的mu阿片受体酪氨酸残基336位点（Tyr336）发生磷酸化有关。本课题将进一步研究慢性吗啡处理后Src酪氨酸激酶通过对mu阿片受体Tyr336位点磷酸化和cAMP水平的调节进而影响吗啡躯体依赖和精神依赖的过程。我们将检测不同脑区不同Src酪氨酸激酶家族成员对慢性吗啡依赖小鼠纳洛酮戒断症状和吗啡条件性位置偏爱的调节作用，并且深入研究该过程中Src酪氨酸激酶对mu阿片受体磷酸化及cAMP水平的影响。本研究不但能进一步阐明阿片类物质成瘾的神经生物学机制，更可能为成瘾的治疗提供理论依据：若能在不影响Src激酶活性情况下特异性阻断对mu阿片受体的磷酸化作用，将可能为成瘾的治疗提供新的靶点。

药物戒断是引起阿片类物质成瘾的关键因素，成瘾相关假说认为特定神经环路中胞内cAMP的增多和PKA活性增强是介导成瘾的关键因素。长期吗啡处理通过Src蛋白激活μ阿片受体酪氨酸336位点（Tyr336）磷酸化引起cAMP增多和PKA活性增强。本研究发现吗啡急性戒断招募Src蛋白引起μ受体Tyr336位点磷酸化。脑室和蓝斑给予Src抑制剂AZD0530及病毒干扰Src表达可以降低Tyr336磷酸化水平及躯体依赖戒断症状。Fyn敲除鼠也表现较低的Tyr336磷酸化水平及躯体依赖戒断症状。μ阿片受体敲除小鼠蓝斑表达野生型而非Tyr336突变型μ阿片受体可以恢复吗啡戒断引起的躯体依赖戒断症状。综上，μ阿片受体Y336位点磷酸化是控制躯体依赖戒断症状的关键靶标。本研究在分子生物学水平揭示了阿片类物质成瘾的机制，并为开发抗成瘾药物提供了新的靶点。