Jia N, Arthington-Skaggs B, Lee W, Pierson C A, Lees N D, Eckstein J, Barbuch R, Bard M
Department of Biology, Indiana University Purdue University Indianapolis, Indianapolis, Indiana 46202-5132, USA.
Antimicrob Agents Chemother. 2002 Apr;46(4):947-57. doi: 10.1128/AAC.46.4.947-957.2002.
The incidence of fungal infections has increased dramatically, which has necessitated additional and prolonged use of the available antifungal agents. Increased resistance to the commonly used antifungal agents, primarily the azoles, has been reported, thus necessitating the discovery and development of compounds that would be effective against the major human fungal pathogens. The sterol biosynthetic pathway has proved to be a fertile area for antifungal development, and steps which might provide good targets for novel antifungal development remain. The sterol C-14 reductase, encoded by the ERG24 gene, could be an effective target for drug development since the morpholine antifungals, inhibitors of Erg24p, have been successful in agricultural applications. The ERG24 gene of Candida albicans has been isolated by complementation of a Saccharomyces cerevisiae erg24 mutant. Both copies of the C. albicans ERG24 gene have been disrupted by using short homologous regions of the ERG24 gene flanking a selectable marker. Unlike S. cerevisiae, the C. albicans ERG24 gene was not required for growth, but erg24 mutants showed several altered phenotypes. They were demonstrated to be slowly growing, with doubling times at least twice that of the wild type. They were also shown to be significantly more sensitive to an allylamine antifungal and to selected cellular inhibitors including cycloheximide, cerulenin, fluphenazine, and brefeldin A. The erg24 mutants were also slightly resistant to the azoles. Most importantly, erg24 mutants were shown to be significantly less pathogenic in a mouse model system and failed to produce germ tubes upon incubation in human serum. On the basis of these characteristics, inhibitors of Erg24p would be effective against C. albicans.
真菌感染的发生率急剧上升，这使得现有的抗真菌药物需要额外且长期使用。据报道，对常用抗真菌药物（主要是唑类）的耐药性有所增加，因此有必要发现和开发对主要人类真菌病原体有效的化合物。事实证明，甾醇生物合成途径是抗真菌药物开发的一个富有成果的领域，仍然存在可能为新型抗真菌药物开发提供良好靶点的步骤。由ERG24基因编码的甾醇C-14还原酶可能是药物开发的有效靶点，因为吗啉类抗真菌药物（Erg24p的抑制剂）已在农业应用中取得成功。白色念珠菌的ERG24基因已通过酿酒酵母erg24突变体的互补作用分离出来。利用位于选择标记两侧的ERG24基因的短同源区域破坏了白色念珠菌ERG24基因的两个拷贝。与酿酒酵母不同，白色念珠菌的生长不需要ERG24基因，但erg24突变体表现出几种改变的表型。它们被证明生长缓慢，倍增时间至少是野生型的两倍。它们还被证明对烯丙胺类抗真菌药物和选定的细胞抑制剂（包括环己酰亚胺、浅蓝菌素、氟奋乃静和布雷菲德菌素A）更为敏感。erg24突变体对唑类也有轻微耐药性。最重要的是，erg24突变体在小鼠模型系统中显示出致病性显著降低，并且在人血清中孵育时不能产生芽管。基于这些特征，Erg24p的抑制剂将对白色念珠菌有效。
