To explore the molecular basis of ligand binding and receptor activation of human motlin receptor

背景和目的：胃动素是胃肠运动功能的重要内源性调节因子，由胃动素受体的G类蛋白偶联受体胃动素和红霉素介导。胃动素受体是两种完全不同的化学激动剂，它们与胃动素受体的不同区域结合，是基于先前对这两种受体作用的胞外区的系统性突变。虽然糖尿病患者存在胃肠道运动障碍，但该受体的作用尚不清楚。在目前的工作中，我们已经研究了该受体的预测细胞内环域对胃动素和红霉素刺激活性的影响，并探索了该受体在糖尿病患者胃肠道中的分布。方法：我们研究了预测的胃动素受体第一、第二和第三细胞内环结构域中残基的顺序缺失，并利用丙氨酸、苯丙氨酸和组氨酸…更多的替代毛皮，每个残基都在功能上很重要的片段内。有糖尿病和无糖尿病的受试者的身体和外科手术标本均取自下段食道、胃、十二指肠、空肠、回肠、结肠和直肠，无出血、坏死或肿瘤。分析胃动素和GHS受体的基因表达和免疫反应性。结果：Tyr66、Arg136和Val299对胃动素和红霉素的生物活性起关键作用。这些数据表明，不同化学类别的激动剂的作用可能会产生该受体胞浆表面的共同激活状态，该状态负责与其G蛋白相互作用。在糖尿病患者中，胃动素受体在肌肉层的表达是粘膜层的10-100倍，与非糖尿病患者相似。提示胃动素激动剂，如胃动素激动剂、非肽基红霉素和Ghrelin激动剂可能是治疗糖尿病患者胃肠道运动障碍的有效药物。较少

Background and Aims: Motilin is an important endogenous regulator of gastrointestinal motor function, mediated by the class I G protein-coupled motilin receptor Motilin and erythromycin, two chemically distinct full agonists of the motilin receptor, are known to bind to distinct regions of this receptor, based on previous systematic mutagenesis of extracellular regions that dissociated the effects on these two agents. While there has been dysmotility of GI tract in patients with diabetes mellitus, roles of this receptor is not yet clear. In the current work, we have examined the predicted intracellular loop domains of this receptor for effects on motilin- and erythromycin-stimulated activity, and explored the distribution of this receptor along the GI tract in diabetic patients. Methods: We have studied sequential deletions of residues within the predicted first, second, and third intracellular loop domains of the motilin receptor and have utilized alanine, phenylalanine, and histidine … More replacement fur each residue within functionally important segments. Post-mortem and surgical human tissue specimens with no hemorrhage, necrosis, or tumor were obtained from lower esophagus, stomach, duodenum, jejunum, ileum, colon, and rectum in subjects with and without diabetes mellitus. We analyzed expression of mRNA and immunoreactivity of motilin and GHS receptors. Results: Tyr66, Arg136, and Val299 were critical on motilin and erythromycin biological activity. These data suggested that action by different chemical classes of agonists likely yield a common activation state of the cytosolic face of this receptor that is responsible for interaction with its G protein. In diabetic patients, motilin receptor was expressed 10 to 100 times more in the muscle layer than in mucosal layer, similar to non-diabetic subjects. These data suggested that motilin agonists such as peptide motilide and non-peptidyl erythromycin and ghrelin agonists may be useful drugs for dysmotility of GI tract in diabetic patients. Less