Recent evidence for the role of laminin in cell adhesion and in the pathogenesis of several bacterial infections has led us to investigate the existence of receptors for this extracellular matrix component in Candida albicans. At first, immunofluorescence demonstrated the presence of laminin-binding sites at the surface of germ tubes. Electron microscopy confirmed this result and permitted precise localization of the binding sites on the outermost fibrillar layer of the germ tube cell wall. By using 125I-radiolabeled laminin, the binding was shown to be saturable and specific, hence demonstrating characteristics of true receptors. Analysis of the data by the Scatchard equation indicated that there were about 8,000 binding sites per cell, with a dissociation constant (Kd) of 1.3 x 10(-9) M. Binding was inhibited by prior heating or trypsinization of cells. Furthermore, of the different proteins and carbohydrates tested in competition experiments, only fibrinogen greatly reduced the laminin binding. Finally, dithiothreitol and iodoacetamide treatment of germ tubes allowed us to identify the laminin receptors through analysis of this extract by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Western immunoblotting. Two components, of 68 kilodaltons and a doublet of 60 and 62 kilodaltons, were detected. Thus, C. albicans possesses germ tube-specific surface receptors for laminin which could mediate its attachment to basement membranes and so contribute to the establishment of candidiasis.
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机译：层粘连蛋白在细胞粘附和几种细菌感染的发病机理中的作用的最新证据使我们研究了白色念珠菌中这种细胞外基质成分的受体的存在。首先，免疫荧光证明胚芽管表面存在层粘连蛋白结合位点。电子显微镜证实了该结果，并允许在胚管细胞壁的最外层原纤维层上精确定位结合位点。通过使用125 I-放射性标记的层粘连蛋白，表明结合是可饱和的和特异性的，因此证明了真实受体的特性。通过Scatchard方程对数据进行的分析表明，每个细胞大约有8,000个结合位点，解离常数（Kd）为1.3 x 10（-9）M。事先加热或胰蛋白酶消化细胞会抑制结合。此外，在竞争实验中测试的不同蛋白质和碳水化合物中，只有纤维蛋白原极大地降低了层粘连蛋白的结合。最后，二硫苏糖醇和碘乙酰胺处理胚芽管使我们能够通过十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和Western免疫印迹分析该提取物来鉴定层粘连蛋白受体。检测到两个成分，分别为68千道尔顿和60和62千道尔顿的双峰。因此，白色念珠菌具有层粘连蛋白的胚管特异性表面受体，可以介导其与基底膜的附着，从而有助于念珠菌病的建立。
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