Li Fang, Palecek Sean P
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
Eukaryot Cell. 2003 Dec;2(6):1266-73. doi: 10.1128/EC.2.6.1266-1273.2003.
Candida albicans adhesion to host tissues contributes to its virulence and adhesion to medical devices permits biofilm formation, but we know relatively little about the molecular mechanisms governing C. albicans adhesion to materials or mammalian cells. Saccharomyces cerevisiae provides an attractive model system for studying adhesion in yeast because of its well-characterized genetics and gene expression systems and the conservation of signal transduction pathways among the yeasts. In this study, we used a parallel plate flow chamber to screen and characterize attachment of a flo8Delta S. cerevisiae strain expressing a C. albicans genomic library to a polystyrene surface. The gene EAP1 was isolated as a putative cell wall adhesin. Sequence analysis of EAP1 shows that it contains a signal peptide, a glycosylphosphatidylinositol anchor site, and possesses homology to many other yeast genes encoding cell wall proteins. In addition to increasing adhesion to polystyrene, heterologous expression of EAP1 in S. cerevisiae and autonomous expression of EAP1 in a C. albicans efg1 homozygous null mutant significantly enhanced attachment to HEK293 kidney epithelial cells. EAP1 expression also restored invasive growth to haploid flo8Delta and flo11Delta strains as well as filamentous growth to diploid flo8/flo8 and flo11/flo11 strains. Transcription of EAP1 in C. albicans is regulated by the transcription factor Efg1p, suggesting that EAP1 expression is activated by the cyclic AMP-dependent protein kinase pathway.
白色念珠菌对宿主组织的黏附有助于其致病，而对医疗器械的黏附则会导致生物膜形成，但我们对白色念珠菌黏附材料或哺乳动物细胞的分子机制了解相对较少。酿酒酵母因其具有特征明确的遗传学和基因表达系统，且酵母间信号转导途径具有保守性，为研究酵母黏附提供了一个有吸引力的模型系统。在本研究中，我们使用平行平板流动腔筛选并表征表达白色念珠菌基因组文库的flo8Δ酿酒酵母菌株对聚苯乙烯表面的附着情况。基因EAP1被分离出来作为一种假定的细胞壁黏附素。EAP1的序列分析表明它含有一个信号肽、一个糖基磷脂酰肌醇锚定位点，并且与许多其他编码细胞壁蛋白的酵母基因具有同源性。除了增加对聚苯乙烯的黏附外，EAP1在酿酒酵母中的异源表达以及在白色念珠菌efg1纯合缺失突变体中的自主表达显著增强了对HEK293肾上皮细胞的附着。EAP1的表达还恢复了单倍体flo8Δ和flo11Δ菌株的侵袭性生长以及二倍体flo8/flo8和flo11/flo11菌株的丝状生长。白色念珠菌中EAP1的转录受转录因子Efg1p调控，这表明EAP1的表达由环磷酸腺苷依赖性蛋白激酶途径激活。
