A naturally occurring proline-to-alanine amino acid change in Fks1p in Candida parapsilosis, Candida orthopsilosis, and Candida metapsilosis accounts for reduced echinocandin susceptibility
A naturally occurring proline-to-alanine amino acid change in Fks1p in Candida parapsilosis, Candida orthopsilosis, and Candida metapsilosis accounts for reduced echinocandin susceptibility
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DOI：
10.1128/aac.00262-08
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发表时间：
2008-07-01
影响因子：
4.9
通讯作者：
Perlin, David S.
中科院分区：
文献类型：
--
作者：
Garcia-Effron, Guillermo;Katiyar, Santosh K.;Perlin, David S.
近平滑念珠菌已成为侵袭性真菌感染的常见原因，特别是在拉丁美洲和新生儿环境中。近平滑念珠菌是一组密切相关的生物体的一部分，包括正平滑念珠菌和偏平滑念珠菌。相对于其他念珠菌属，所有三个菌种均显示棘白菌素类新药卡泊芬净、米卡芬净和阿尼芬净的MIC升高。尽管对治疗有潜在影响，但这种棘白菌素敏感性降低背后的机制尚未确定。在这份报告中，我们调查了一个自然发生的前丙氨酸取代氨基酸位置660（P660 A），立即远端的高度保守的热点1区Fks 1 p，在减少棘白菌素敏感性表型的作用。动力学抑制研究表明，葡聚糖合成酶从C。近平滑组对棘白菌素药物的敏感性比C.白色念珠菌此外，临床分离的C.白色念珠菌和C.在该等同位置携带突变的glabrata也显示出靶酶敏感性的2-log降低，这与MIC增加相关。这些突变还导致V-max降低2.4- 18.8倍。相对于野生型酶的值，与C.近平滑组酶。最后，P660 A取代内在抗性的重要性通过将等效的P647 A突变工程化到酿酒酵母的Fks 1 p中来证实。突变葡聚糖合酶显示特征性的2-log降低棘白菌素药物的敏感性。总之，这些数据有力地表明，来自C.近平滑组解释了降低的易感性表型。
Candida parapsilosis has emerged as a common cause of invasive fungal infection, especially in Latin America and in the neonatal setting. C parapsilosis is part of a closely related group of organisms that includes the species Candida orthopsilosis and Candida metapsilosis. All three species show elevated MICs for the new echinocandin class drugs caspofungin, micafungin, and anidulafungin relative to other Candida species. Despite potential impacts on therapy, the mechanism behind this reduced echinocandin susceptibility has not been determined. In this report, we investigated the role of a naturally occurring Pro-to-Ala substitution at amino acid position 660 (P660A), immediately distal to the highly conserved hot spot 1 region of Fks1p, in the reduced-echinocandin-susceptibility phenotype. Kinetic inhibition studies demonstrated that glucan synthase from the C. parapsilosis group was 1 to 2 logs less sensitive to echinocandin drugs than the reference enzyme from C. albicans. Furthermore, clinical isolates of C. albicans and C. glabrata which harbor mutations at this equivalent position also showed comparable 2-log decreases in target enzyme sensitivity, which correlated with increased MICs. These mutations also resulted in 2.4- to 18.8-fold-reduced V-max. values relative to those for the wild-type enzyme, consistent with kinetic parameters obtained for C. parapsilosis group enzymes. Finally, the importance of the P660A substitution for intrinsic resistance was confirmed by engineering an equivalent P647A mutation into Fks1p of Saccharomyces cerevisiae. The mutant glucan synthase displayed characteristic 2-log decreases in sensitivity to the echinocandin drugs. Overall, these data firmly indicate that a naturally occurring P660A substitution in Fks1p from the C. parapsilosis group accounts for the reduced susceptibility phenotype.