Mu opioid receptor function in the enteric nervous system

描述（由申请人提供）：配体诱导的G蛋白偶联受体的运输及其与相关蛋白的相互作用是调节受体介导的信号转导和细胞反应性的关键步骤。?阿片受体（？OR）介导阿片类药物（用于疼痛控制的强效药物）的镇痛作用及其副作用，包括阿片类肠综合征（严重便秘和腹痛）和耐受性。我们之前已经证明了a）？或肠神经元对内源性阿片类药物和大多数阿片类药物的内吞反应，但对吗啡无反应，B）慢性？OR激活能让吗啡触发？或内吞作用，并诱导过表达和易位的发动蛋白，细胞内的蛋白质，是重要的受体内化，c）的幅度？或内吞诱导的高效阿片类药物不改变阿片类药物耐受的条件下，d）激活？OR与内化激动剂刺激培养的肌间神经元中的丝裂原活化蛋白激酶（MAPK）磷酸化。这个应用程序将测试的假设，延长？或激活诱导细胞内机制的变化，调节激动剂诱导？OR运输和肠道神经元中的受体后信号传导，这是耐受发展的潜在机制。具体目标1将确定哪些细胞内蛋白质调节？或贩运后，急性和慢性激活体外使用神经元转染的天然细胞表达？OR，并将其表达与受体内吞作用和体内肠耐受状态相关联。具体目标2将确定急性和慢性的影响？OR刺激对肠神经元MAPK激活的影响，MAPK抑制剂对激动剂诱导的肠神经元MAPK激活的影响？或脱敏和内化，以及慢性阿片类药物治疗是否导致肠道耐受状态诱导回肠完整节段持续MAPK活化。这些研究将提供一个更好的知识阿片诱导适应肠神经元自然表达？或，这将增加我们对阿片类肠综合征的理解，阿片类肠综合征是一种影响接受慢性阿片类药物治疗疼痛的患者的疾病，耐受性阻碍了这些药物的使用。

DESCRIPTION (provided by applicant): Ligand-induced trafficking of G protein-coupled receptors and their interaction with associated proteins are key steps regulating receptor-mediated signal transduction and cellular responsiveness. ? opioid receptor (?OR) mediates the analgesic effects of opiates, potent drugs used for pain control, and their side effects, including opioid bowel syndrome (profound constipation and abdominal pain), and tolerance. We previously showed that a) ?OR endocytoses in enteric neurons in response to endogenously opioids and to most opiates, but not to morphine, b) chronic ?OR activation confers morphine the ability to trigger ?OR endocytosis and induces over expression and translocation of dynamin, an intracellular protein that is important for receptor internalization, c) the magnitude of ?OR endocytosis induced by high efficacy opiates does not change in a condition of opioid tolerance, d) activation of ?OR with an internalizing agonist stimulates mitogen-activated protein kinase (MAPK) phosphorylation in cultured myenteric neurons. This application will test the hypothesis that prolonged ?OR activation induces alterations in the intracellular machinery that regulates agonist-induced ?OR trafficking and post-receptor signaling in enteric neurons, which are possible mechanisms underlying the development of tolerance. Specific Aim 1 will establish which intracellular proteins regulate ?OR trafficking following acute and chronic activation in vitro using neuronal transfection of native cells expressing ?OR and correlate their expression with receptor endocytosis and state of gut tolerance in vivo. Specific Aim 2 will determine the effects of acute and chronic ?OR stimulation on MAPK activation in enteric neurons, the effects of MAPK inhibitors on agonist- induced ?OR desensitization and internalization, and whether chronic opiate treatment resulting in a state of tolerance in the gut induces sustained MAPK activation in intact segments of the ileum. These studies will provide a better knowledge of opiate-induced adaptations in enteric neurons naturally expressing ?OR, which will increase our understanding of opioid bowel syndrome, a condition affecting patients receiving chronic opiates for pain, and tolerance, which hamper the use of these drugs.