Pancholi Vijay, Fontan Patricia, Jin Hong
Laboratory of Bacterial Pathogenesis, Public Health Research Institute, The International Center for Public Health, 225 Warren Street, W450T, Newark, NJ 07103-3535, USA.
Microb Pathog. 2003 Dec;35(6):293-303. doi: 10.1016/j.micpath.2003.08.004.
Alpha-enolase (SEN) is a strong plasminogen-binding protein on the surface of group A streptococci (GAS). By flow cytometry and immunofluorescence analyses and using human enolase-specific antibody, human pharyngeal cells (Detroit 562) also were found to express enolase on their surface. Detroit 562 cells preferentially bound to Lys-plasminogen and this binding was inhibited in the presence of a lysine analog, epsilon-aminocaproic acid and by carboxypeptidase-B treatment suggesting that the C-terminal lysine residue of the putative pharyngeal cell receptor(s) may play an important role in plasminogen-binding. The increased plasminogen-binding in the presence of free enolase indicated the presence of an enolase/SEN-specific receptor on the pharyngeal cell surface. GAS, when precoated with Lys-plasminogen, adhered to pharyngeal cells significantly more in numbers than when precoated with fibronectin or laminin. Similarly, GAS adhered also significantly more in numbers to pharyngeal cells which were precoated with Lys-plasminogen. GAS adhered similarly in high numbers when incubated with pharyngeal cells in the presence of soluble plasminogen. The de novo pharyngeal cell-bound protease activity, created as a result of activation of bound plasminogen by t-PA, indicated its potential role in pericellular fibrinolytic activity. Further GAS with tPA-activated plasminogen bound on their surface penetrated through Transwell-grown pharyngeal cells in significantly higher numbers. Together, the results presented in this study highlight a novel function of plasminogen in streptococcal adherence to pharyngeal cells and a newly discovered streptococcal ability to pericellularly invade pharyngeal cells as a result of tPA/endogenous plasminogen activator-mediated proteolytic activity.
α-烯醇化酶（SEN）是A组链球菌（GAS）表面一种强大的纤溶酶原结合蛋白。通过流式细胞术和免疫荧光分析，并使用人烯醇化酶特异性抗体，还发现人咽细胞（底特律562）在其表面表达烯醇化酶。底特律562细胞优先结合赖氨酸纤溶酶原，并且在赖氨酸类似物ε-氨基己酸存在下以及经羧肽酶B处理后这种结合受到抑制，这表明假定的咽细胞受体的C末端赖氨酸残基可能在纤溶酶原结合中起重要作用。在游离烯醇化酶存在下纤溶酶原结合增加表明咽细胞表面存在烯醇化酶/SEN特异性受体。当预先包被赖氨酸纤溶酶原时，GAS黏附到咽细胞上的数量明显多于预先包被纤连蛋白或层粘连蛋白时。同样，预先包被赖氨酸纤溶酶原的GAS黏附到咽细胞上的数量也明显更多。当在可溶性纤溶酶原存在下与咽细胞一起孵育时，GAS也以大量类似的方式黏附。由于组织型纤溶酶原激活物（t-PA）激活结合的纤溶酶原而产生的新生的咽细胞结合蛋白酶活性表明其在细胞周围纤维蛋白溶解活性中的潜在作用。此外，表面结合有tPA激活的纤溶酶原的GAS穿透Transwell培养的咽细胞的数量明显更多。总之，本研究呈现的结果突出了纤溶酶原在链球菌黏附咽细胞中的新功能，以及新发现的链球菌由于tPA/内源性纤溶酶原激活物介导的蛋白水解活性而在细胞周围侵入咽细胞的能力。
