Jong Ambrose Y, Chen Steven H M, Stins Monique F, Kim Kwang Sik, Tuan Tan-Lan, Huang Sheng-He
Division of Hematology-Oncology, Mailstop 57, Childrens Hospital Los Angeles, Los Angeles, CA 90027, USA 2Division of Infectious Diseases, Johns Hopkins University School of Medicine, Baltimore, MD, USA 3,4Division of Infectious Diseases3 and Department of Surgery4, Childrens Hospital Los Angeles, Los Angeles, CA 90027, USA.
J Med Microbiol. 2003 Aug;52(Pt 8):615-622. doi: 10.1099/jmm.0.05060-0.
Infection by the human opportunistic fungal pathogen Candida albicans has been increasing over recent years. In an attempt to understand the molecular mechanism of Candida invasion across host tissues, the relationship of C. albicans enolase to human plasminogen/plasmin was investigated. C. albicans enolase is a cell-surface protein and an immunodominant antigen in infected patients' sera. Plasminogen is an abundant plasma protein. Several lines of evidence support the binding of C. albicans enolase to human plasminogen. Firstly, it was found that various Candida strains were able to bind to plasminogen and its active form, plasmin. Secondly, recombinant Candida enolase was retained in a nickel-chelating affinity column matrix that can bind (125)I-labelled plasminogen or plasmin in a dose-dependent manner. Plasmin(ogen)-specific inhibitors, such as epsilon -aminocaproic acid and aprotinin, can effectively block plasmin-binding activity. Thirdly, as with many plasminogen receptors, binding of Candida enolase to plasmin(ogen) is lysine-dependent, whereas little inhibition occurred with arginine, aspartate and glutamate. Fourthly, immobilized enolase enhanced plasminogen's affinity for streptokinase at least tenfold, as demonstrated by its activation of plasmin activity. To elucidate the biological significance of this result, it was demonstrated that the plasmin(ogen)-bound Candida cells were able to induce fibrinolysis activity in a matrix-gel assay. Furthermore, plasmin-bound Candida cells had an increased ability to cross an in vitro blood-brain barrier system. The results given here indicate that Candida enolase is a plasminogen- and plasmin-binding protein and that the interaction of C. albicans enolase with the plasminogen system may contribute to invasion of the tissue barrier.
近年来，人类机会性真菌病原体白色念珠菌的感染率一直在上升。为了了解白色念珠菌侵袭宿主组织的分子机制，研究了白色念珠菌烯醇化酶与人纤溶酶原/纤溶酶的关系。白色念珠菌烯醇化酶是一种细胞表面蛋白，也是感染患者血清中的免疫显性抗原。纤溶酶原是一种丰富的血浆蛋白。多条证据支持白色念珠菌烯醇化酶与人纤溶酶原的结合。首先，发现各种念珠菌菌株能够与纤溶酶原及其活性形式纤溶酶结合。其次，重组念珠菌烯醇化酶保留在镍螯合亲和柱基质中，该基质能以剂量依赖的方式结合（125）I标记的纤溶酶原或纤溶酶。纤溶酶（原）特异性抑制剂，如ε-氨基己酸和抑肽酶，可有效阻断纤溶酶结合活性。第三，与许多纤溶酶原受体一样，念珠菌烯醇化酶与纤溶酶（原）的结合是赖氨酸依赖性的，而精氨酸、天冬氨酸和谷氨酸的抑制作用很小。第四，固定化烯醇化酶增强了纤溶酶原对链激酶的亲和力至少十倍，这通过其对纤溶酶活性的激活得以证明。为了阐明这一结果的生物学意义，证明了结合纤溶酶（原）的念珠菌细胞在基质凝胶试验中能够诱导纤维蛋白溶解活性。此外，结合纤溶酶的念珠菌细胞穿过体外血脑屏障系统的能力增强。此处给出的结果表明，念珠菌烯醇化酶是一种纤溶酶原和纤溶酶结合蛋白，白色念珠菌烯醇化酶与纤溶酶原系统的相互作用可能有助于组织屏障的侵袭。
