Division of Gastroenterology and Hepatology, Department of Internal Medicine, and Molecular Pharmacology Research Center, Molecular Cardiology Research Institute, Tufts Medical Center, Boston, MA 02111, USA.
Proc Natl Acad Sci U S A. 2010 Mar 2;107(9):4293-8. doi: 10.1073/pnas.0905877107. Epub 2010 Feb 16.
Substance P (SP) is a proinflammatory mediator implicated in inflammatory bowel disease (IBD) and other inflammatory states. SP acts by stimulating the neurokinin-1 receptor (NK-1R) on T lymphocytes and other cell types, and regulates these cells in a complex interplay with multiple cytokines. The mechanisms of interaction among these inflammatory mediators are not yet fully understood. Here, we demonstrate that function of the NK-1R, a member of the G protein-coupled receptor (GPCR) superfamily, is modulated by TGF-beta. The latter acts not on a GPCR but via serine-threonine kinase-class receptors. By flow confocal image analysis, we demonstrate that TGF-beta delays SP-induced NK-1R internalization on mucosal T cells isolated from a mouse model of IBD and on granuloma T cells in murine schistosomiasis. Furthermore, luciferase reporter-gene assays revealed that NK-1R stimulation activates the nuclear factor of activated T cell- and activator protein-1-dependent signaling pathways, which are known triggers of effector T-cell cytokine production. TGF-beta markedly increases SP-induced activation of these signaling cascades, suggesting that delayed NK-1R internalization results in enhanced signaling. Providing a link to amplified immune function, SP and TGF-beta, when applied in combination, trigger a strong release of the proinflammatory cytokines IFN-gamma and IL17 from intestinal inflammatory T cells, whereas either agonist alone shows no effect. These observations establish precedent that members of two distinct receptor superfamilies can interact via a previously unrecognized mechanism, and reveal a paradigm of GPCR transregulation that is relevant to IBD and possibly other disease processes.
P 物质（SP）是一种促炎介质，与炎症性肠病（IBD）和其他炎症状态有关。SP 通过刺激 T 淋巴细胞和其他细胞类型上的神经激肽-1 受体（NK-1R）发挥作用，并与多种细胞因子一起调节这些细胞。这些炎症介质之间相互作用的机制尚未完全阐明。在这里，我们证明了 G 蛋白偶联受体（GPCR）超家族成员 NK-1R 的功能受 TGF-β调节。后者不是作用于 GPCR，而是通过丝氨酸-苏氨酸激酶类受体发挥作用。通过流式共聚焦图像分析，我们证明 TGF-β可延迟 IBD 小鼠模型中的粘膜 T 细胞和鼠血吸虫病中的肉芽肿 T 细胞上 SP 诱导的 NK-1R 内化。此外，荧光素酶报告基因分析表明，NK-1R 刺激激活核因子激活的 T 细胞和激活蛋白-1 依赖性信号通路，这是效应 T 细胞细胞因子产生的已知触发因素。TGF-β显著增加了 SP 诱导的这些信号级联的激活，表明 NK-1R 内化的延迟导致信号增强。SP 和 TGF-β提供了放大免疫功能的联系，当联合应用时，会从肠道炎症性 T 细胞中引发强烈的促炎细胞因子 IFN-γ和 IL17 的释放，而单独使用任一激动剂均无效果。这些观察结果确立了两个不同受体超家族的成员可以通过以前未被认识的机制相互作用的先例，并揭示了 GPCR 反调节的范例，这与 IBD 及可能的其他疾病过程有关。
