Nitrergic relaxation in the gastrointestinal tract of mice with cell-specific deletion of NO-sensitive guanylyl cyclase

NO-敏感鸟苷酸环化酶（NO-GC）催化细胞内第二信使cGMP的产生。该酶在NO/cGMP信号传导中起关键作用。NO-GC作为信号分子一氧化氮（NO）最重要的受体，参与多种生理功能的调节。这些小鼠患有高血压，患有胃肠动力障碍并过早死亡。负责个体表型的细胞/组织的确切身份仍有待解决。一般GCKO小鼠中GI运动性降低可以通过氮能松弛的丧失来解释。氮能松弛的确切机制尚未被彻底研究。目前在该领域中大量讨论的是神经释放的NO是否直接用于松弛平滑肌细胞（SMC）（类似于血管系统中内皮NO的作用）或是否插入Cajal间质细胞（ICC）以介导氮能松弛。此外，第三种细胞类型被称为“成纤维细胞样细胞”，具有高NO-GC表达。我们已经产生了KO小鼠，其中NO-GC在SMC或ICC中特异性缺失。在两个单敲除中，胃肠道组织的氮能松弛受到中度影响。一个双突变携带缺失的NO-GC在SMC和ICC显示出强烈的减少胃肠道运动和几乎完全缺乏氮能松弛。在这个项目中，我们希望产生在FLC中缺乏NO-GC的小鼠;此外，我们将产生双重和三重突变体。将进行器官浴实验和膜电位测量，包括抑制性连接电位。在这些小鼠的帮助下，在肠道中最重要的NO-GC表达细胞中缺乏NO受体，我们将研究这些细胞的相互作用，并确定氮能松弛的确切机制。

NO-sensitive guanylyl cyclase (NO-GC) catalyzes the generation of the intracellular second messenger cGMP. The enzyme plays a key role within NO/cGMP signalling. Being the most important receptor for the signal molecule nitric oxide, NO-GC participates in the regulation of many different physiological functions.We have generated mice which lack NO-GC ubiquitously. These mice are hypertensive, suffer from gastrointestinal dysmotility and die prematurely. The exact identity of the cells/tissues responsible for the individual phenotypes remains to be resolved.The reduced GI motility in the general GCKO mice can be explained by the loss of nitrergic relaxation. The exact mechanism of nitrergic relaxation has not been investigated thoroughly. It is currently being heavily discussed in the field whether neuronally released NO acts to relax smooth muscle cells (SMC) directly (similar to the action of endothelial NO in the vascular system) or whether interstitial cells of Cajal (ICC) are interposed to mediate nitrergic relaxation. In addition, a third cell type called 'fibroblast-like cell' with high NO-GC expression has been identified.We have already generated KO mice in which NO-GC is deleted specifically in SMC or in ICC. Nitrergic relaxation of GI tissue is moderately affected in the two single knockouts. A double mutant carrying a deletion of NO-GC in both SMC and ICC shows strong reduction of GI motility and an almost total lack of nitrergic relaxation. In this project, we would like to generate mice that lack NO-GC in FLC; in addition, we will generate double and triple mutants. Organ bath experiments and measurements of membrane potential including inhibitory junction potentials will be performed. With the help of these mice lacking the NO receptor in the most important NO-GC expressing cells in the gut, we will investigate the interplay of these cells and identify the exact mechanism of nitrergic relaxation.