Division of Gastroenterology and Hepatology, University Hospital Zurich, Zurich, Switzerland.
Inflamm Bowel Dis. 2012 Jul;18(7):1287-302. doi: 10.1002/ibd.21891. Epub 2011 Oct 10.
Autophagy is a process of central importance for maintaining cell homeostasis, survival, and the regulation of inflammation. Recent studies associated variants within the gene loci, encoding protein tyrosine phosphatase nonreceptor type 2 (PTPN2), and autophagy genes, such as autophagy-related 16-like 1 (ATG16L1), with chronic inflammatory disorders, such as Crohn's disease (CD). We show that PTPN2 regulates autophagy in human intestinal epithelial cells (IEC) and primary colonic lamina propria fibroblasts (CLPF).
Protein analysis in IEC and CLPF was performed by western blotting. Autophagososme formation was assessed by LC3B immunofluorescence or immunohistochemistry. Human intestinal tissue samples were obtained from noninflammatory bowel disease (IBD) control or from CD patients and genotyped for disease-associated PTPN2 or ATG16L1 variations.
Knockdown of PTPN2 causes impaired autophagosome formation and dysfunctional autophagy resulted in increased levels of intracellular Listeria monocytogenes (LM) and elevated IEC apoptosis in response to tumor necrosis factor (TNF) and interferon gamma (IFN-γ). Similar findings were observed in primary CLPF derived from CD patients carrying the CD-associated PTPN2 variant. Presence of the ATG16L1 variant prevented the cytokine-induced rise in PTPN2 protein, finally resulting in impaired LC3B-II levels in IEC. Actively inflamed intestinal biopsies from CD patients carrying either ATG16L1 or PTPN2 genetic variants revealed aberrant LC3B expression patterns when compared with samples from non-IBD control patients.
Our results demonstrate that PTPN2 regulates autophagosome formation in human intestinal cells. We provide a model of how a dysfunction of the CD susceptibility genes, PTPN2 and/or ATG16L1, may contribute to the onset and perpetuation of chronic intestinal inflammation.
自噬是维持细胞内稳态、存活和炎症调节的核心过程。最近的研究将编码蛋白酪氨酸磷酸酶非受体型 2（PTPN2）和自噬相关基因，如自噬相关 16 样 1（ATG16L1）的基因座内的变异与克罗恩病（CD）等慢性炎症性疾病相关联。我们表明 PTPN2 可调节人肠上皮细胞（IEC）和原代结肠固有层成纤维细胞（CLPF）中的自噬。
通过 Western blot 分析 IEC 和 CLPF 中的蛋白。通过 LC3B 免疫荧光或免疫组化评估自噬体形成。从非炎症性肠病（IBD）对照或 CD 患者获得人肠组织样本，并对与疾病相关的 PTPN2 或 ATG16L1 变异进行基因分型。
PTPN2 敲低导致自噬体形成受损，功能失调的自噬导致细胞内李斯特菌（LM）水平升高，以及对肿瘤坏死因子（TNF）和干扰素γ（IFN-γ）的反应中 IEC 凋亡增加。在来自携带 CD 相关 PTPN2 变异的 CD 患者的原代 CLPF 中也观察到类似的发现。ATG16L1 变异的存在阻止了细胞因子诱导的 PTPN2 蛋白升高，最终导致 IEC 中 LC3B-II 水平受损。与非 IBD 对照患者的样本相比，来自携带 ATG16L1 或 PTPN2 遗传变异的 CD 患者的活动性炎症性肠活检显示异常的 LC3B 表达模式。
我们的结果表明 PTPN2 调节人肠细胞中的自噬体形成。我们提供了一个模型，说明 CD 易感性基因 PTPN2 和/或 ATG16L1 的功能障碍如何导致慢性肠道炎症的发生和持续。
