Uropathogenic Escherichia coli (UPEC) are the primary cause of urinary tract infections (UTIs) in humans. P-fimbriae are key players for bacterial adherence to the uroepithelium through the Galα1–4Gal-binding PapG adhesin. The three identified classes I, II and III of PapG are supposed to adhere differently to host cell glycosphingolipids (GSLs) of the uroepithelial tract harboring a distal or internal Galα1–4Gal sequence. In this study, GSL binding characteristics were obtained in a nonradioactive adhesion assay using biotinylated E. coli UTI and urine isolates combined with enzyme-linked NeutrAvidin for detection. Initial experiments with reference globotriaosylceramide (Gb3Cer, Galα1–4Galβ1–4Glcβ1–1Cer), globotetraosylceramide (Gb4Cer, GalNAcβ1–3Galα1–4Galβ1–4Glcβ1–1Cer) and Forssman GSL (GalNAcα1–3GalNAcβ1–3Galα1–4Galβ1–4Glcβ1–1Cer) revealed balanced adhesion toward the three GSLs for PapG I–mediated attachment. In contrast, E. coli carrying PapG II or PapG III increasingly adhered to growing oligosaccharide chain lengths of Gb3Cer, Gb4Cer and Forssman GSL. Binding studies with GSLs from human A498 kidney and human T24 bladder epithelial cells, both being negative for the Forssman GSL, revealed the less abundant Gb4Cer vs. Gb3Cer as the prevalent receptor in A498 cells of E. coli expressing PapG II or PapG III. On the other hand, T24 cells exhibited a higher relative content of Gb4Cer vs. Gb3Cer alongside dominant binding of PapG II- or PapG III–harboring E. coli toward Gb4Cer and vastly lowered attachment to minor Gb3Cer. Further studies on PapG-mediated interaction with cell surface–exposed GSLs will improve our knowledge on the molecular mechanisms of P-fimbriae-mediated adhesion and may contribute to the development of antiadhesion therapeutics to combat UTIs.

中文翻译：

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大肠杆菌对人肾和膀胱尿道上皮细胞球系列糖鞘脂的PapG亚型特异性结合特征

尿毒原性大肠杆菌（UPEC）是人类尿路感染（UTI）的主要原因。P-菌毛是细菌通过结合Galα1-4Gal的PapG粘附素粘附于尿道上皮的关键因素。PapG的三个鉴定出的I，II和III类假定以不同的方式粘附于带有远端或内部Galα1-4Gal序列的尿道上皮道的宿主细胞糖鞘脂（GSL）。在这项研究中，GSL结合特性是使用生物素化大肠杆菌通过非放射性粘附试验获得的。UTI和尿液分离物结合酶联NeutrAvidin进行检测。初始实验使用参比globotriaosylceramide（Gb3Cer，Galα1-4Galβ1-4Glcβ1-1Cer），globotetraosylceramide（Gb4Cer，GalNAcβ1-3Galα1-4Galβ1-4Glcβ1-1Cer）和ForssmanGSLGalGal4-Cal1-Cal1-3Cal1-Galβ4-Galβ1-4Gal面向PapG I介导的附件的三个GSL。相反，携带PapG II或PapG III的大肠杆菌越来越多地粘附在Gb3Cer，Gb4Cer和Forssman GSL的低聚糖链长度上。与人类A498肾脏的GSL和人类T24膀胱上皮细胞的GSL结合研究均对Forssman GSL阴性，揭示了Gb4Cer比Gb3Cer丰富程度低，是大肠杆菌A498细胞中的普遍受体。表达PapG II或PapG III。另一方面，T24细胞表现出相对于Gb3Cer更高的Gb4Cer相对含量，同时带有PapG II或PapG III的大肠埃希氏菌与Gb4Cer的显性结合以及与次要Gb3Cer的附着力大大降低。对PapG介导的与细胞表面接触的GSL相互作用的进一步研究将改善我们对P菌毛介导的粘附的分子机制的了解，并可能有助于开发对抗UTI的抗粘附疗法。