cGMP Metabolism in Resistance to Bacterial Infection

描述（由申请人提供）：鸟苷素和尿鸟苷素是在粘膜表面表达并与跨膜受体鸟苷酸环化酶C（GC-C）结合的肽。与GC-C结合的配体也在粘膜上皮细胞上表达，通过囊性纤维化跨膜传导调节因子和Na +/H+交换器3升高细胞内cGMP和elevate跨膜离子运动。该信号通路在由肠致病性大肠杆菌菌株引起的急性疾病中具有直接的临床相关性。杆菌 通常由热稳定毒素STa介导，STa是GC-C的超级激动剂。 使用基因缺失小鼠作为我们的模型系统，我们的初步数据表明，通过GC-C信号传导在调节粘膜免疫稳态中具有重要作用。我们进一步表明，cGMP水平在肠上皮细胞所需的调节，良好控制NF-？B和删除 GC-C的降低以及随后cGMP水平的下降导致高度致敏的粘膜表面。在粘膜cGMP水平降低的小鼠中，促炎基因表达升高，并且在脂多糖攻击期间进一步加剧。 此外，我们证明了通过GC-C的信号传导在胃肠道病原体如啮齿柠檬酸杆菌感染期间的宿主防御中是重要的。本申请的首要假设是，GC-C，通过配体诱导的cGMP生成，是上皮NF-？B活性和GC-C功能这一方面的丧失使粘膜先天免疫稳态失调。我们将在以下目标中解决这一问题。具体目标1将确定GC-C信号在NF-？B信号转导和基因表达。具体目标2将定义GC-C在细菌病原体感染中的作用。本提案中的研究将确定GC-C调节的cGMP产生与维持粘膜免疫稳态之间的新的重要联系。

DESCRIPTION (provided by applicant): Guanylin and uroguanylin are peptides that are expressed at mucosal surfaces and bind to the transmembrane receptor guanylate cyclase C (GC-C). Ligand binding to GC-C, also expressed on mucosal epithelial cells, elevates intracellular cGMP and elicits transmembrane ion movement via the cystic fibrosis transmembrane conductance regulator and the Na+/H+ Exchanger 3. This signaling pathway has direct clinical relevance in that acute illness caused by enterotoxigenic strains of E. coli is often mediated by the heat stable toxin STa, a super-agonist of GC-C. Using gene deleted mice as our model system, our preliminary data indicate that signaling through GC-C has an important role in regulating mucosal immune homeostasis. We further show that cGMP levels in the epithelial of the intestine are required for regulated, well-controlled NF-?B and that deletion of GC-C, and a subsequent drop in cGMP levels, results in a highly sensitized mucosal surface. Proinflammatory gene expression is elevated in mice with diminished mucosal cGMP levels and this is further exacerbated during lipopolysaccharide challenge. Further, we demonstrate that signaling through GC-C is important in host defense during infection by gastrointestinal pathogens such as Citrobacter rodentium. The overarching hypothesis of this application is that GC-C, via ligand-induced cGMP generation, is an essential regulator of epithelial NF-?B activity and that loss of this aspect of GC-C function deregulate mucosal innate immune homeostasis. We will address this in the following aims. Specific Aim 1 will determine the role of GC- C signaling in NF-?B signal transduction and gene expression. Specific Aim 2 will define the role of GC-C in bacterial pathogen infection. The studies in this proposal will define a novel and important link between GC-C regulated cGMP production and maintenance of mucosal immune homeostasis.