Gutiérrez-Jiménez Javier, Arciniega Ivonne, Navarro-García Fernando
Department of Cell Biology, Centro de Investigación y de Estudios Avanzados (CINVESTAV-IPN), Zacatenco, México, DF, Mexico.
Microb Pathog. 2008 Aug;45(2):115-23. doi: 10.1016/j.micpath.2008.04.006. Epub 2008 May 2.
The pic gene is harbored on the chromosomes of three important pathogens: enteroaggregative Escherichia coli (EAEC), uropathogenic E. coli (UPEC), and Shigella flexneri. Since Pic is secreted into the intestinal lumen during EAEC infection, we sought to identify intestinal-mucosal substrates for Pic. Pic did not damage epithelial cells, cleave fodrin, or degrade host defense proteins embedded in the mucus layer (sIgA, lactoferrin and lysozyme). However, by using a solid-phase assay to evaluate the mucinolytic activity of EAEC Pic, we documented a specific, dose-dependent mucinolytic activity. A serine protease inhibitor and an enzymatically inactive variant of Pic were used to show that the Pic serine protease motif is required for mucinolytic activity. Pic binds mucin, and this binding was blocked in competition assays using monosaccharide constituents of the oligosaccharide side chains of mucin. Moreover, Pic mucinolytic activity decreased when sialic acid was removed from mucin. Thus, Pic is a mucinase with lectin-like activity that can be related to its reported hemagglutinin activity. Our results suggest that EAEC may secrete Pic into the intestinal lumen as a strategy for penetrating the gel-like mucus layer during EAEC colonization.
pic基因存在于三种重要病原体的染色体上：肠集聚性大肠杆菌（EAEC）、尿路致病性大肠杆菌（UPEC）和福氏志贺菌。由于在EAEC感染期间Pic会分泌到肠腔中，我们试图确定Pic的肠黏膜作用底物。Pic不会损伤上皮细胞、切割血影蛋白或降解嵌入黏液层的宿主防御蛋白（分泌型免疫球蛋白A、乳铁蛋白和溶菌酶）。然而，通过使用固相分析来评估EAEC Pic的黏蛋白溶解活性，我们记录到了一种特异性的、剂量依赖性的黏蛋白溶解活性。使用丝氨酸蛋白酶抑制剂和Pic的无酶活性变体来表明Pic丝氨酸蛋白酶基序是黏蛋白溶解活性所必需的。Pic能结合黏蛋白，并且在使用黏蛋白寡糖侧链单糖成分的竞争分析中这种结合被阻断。此外，当从黏蛋白中去除唾液酸时，Pic的黏蛋白溶解活性降低。因此，Pic是一种具有凝集素样活性的黏蛋白酶，这可能与其已报道的血凝素活性有关。我们的结果表明，EAEC可能将Pic分泌到肠腔中，作为其在定植过程中穿透凝胶状黏液层的一种策略。
