Vandeputte Patrick, Tronchin Guy, Larcher Gérald, Ernoult Emilie, Bergès Thierry, Chabasse Dominique, Bouchara Jean-Philippe
Groupe d'Etude des Interactions Hôte-Pathogène, UPRES-EA 3142, Laboratoire de Parasitologie-Mycologie, Centre Hospitalier Universitaire, 4 rue Larrey, Angers Cedex 9 49933, France.
Antimicrob Agents Chemother. 2008 Oct;52(10):3701-9. doi: 10.1128/AAC.00423-08. Epub 2008 Aug 11.
Unlike the molecular mechanisms that lead to azole drug resistance, the molecular mechanisms that lead to polyene resistance are poorly documented, especially in pathogenic yeasts. We investigated the molecular mechanisms responsible for the reduced susceptibility to polyenes of a clinical isolate of Candida glabrata. Sterol content was analyzed by gas-phase chromatography, and we determined the sequences and levels of expression of several genes involved in ergosterol biosynthesis. We also investigated the effects of the mutation harbored by this isolate on the morphology and ultrastructure of the cell, cell viability, and vitality and susceptibility to cell wall-perturbing agents. The isolate had a lower ergosterol content in its membranes than the wild type, and the lower ergosterol content was found to be associated with a nonsense mutation in the ERG6 gene and induction of the ergosterol biosynthesis pathway. Modifications of the cell wall were also seen, accompanied by increased susceptibility to cell wall-perturbing agents. Finally, this mutation, which resulted in a marked fitness cost, was associated with a higher rate of cell mortality. Wild-type properties were restored by complementation of the isolate with a centromeric plasmid containing a wild-type copy of the ERG6 gene. In conclusion, we have identified the molecular event responsible for decreased susceptibility to polyenes in a clinical isolate of C. glabrata. The nonsense mutation detected in the ERG6 gene of this isolate led to a decrease in ergosterol content. This isolate may constitute a useful tool for analysis of the relevance of protein trafficking in the phenomena of azole resistance and pseudohyphal growth.
与导致唑类药物耐药性的分子机制不同，导致多烯耐药性的分子机制鲜有文献记载，尤其是在致病性酵母中。我们研究了光滑念珠菌临床分离株对多烯类药物敏感性降低的分子机制。通过气相色谱法分析了甾醇含量，并确定了参与麦角甾醇生物合成的几个基因的序列和表达水平。我们还研究了该分离株所携带的突变对细胞形态和超微结构、细胞活力以及对细胞壁干扰剂的活力和敏感性的影响。该分离株细胞膜中的麦角甾醇含量低于野生型，且发现较低的麦角甾醇含量与ERG6基因中的无义突变以及麦角甾醇生物合成途径的诱导有关。还观察到细胞壁的修饰，同时对细胞壁干扰剂的敏感性增加。最后，这种导致明显适应性代价的突变与更高的细胞死亡率相关。通过用含有野生型ERG6基因拷贝的着丝粒质粒对该分离株进行互补，恢复了野生型特性。总之，我们已经确定了光滑念珠菌临床分离株对多烯类药物敏感性降低的分子事件。在该分离株的ERG6基因中检测到的无义突变导致麦角甾醇含量降低。该分离株可能构成一个有用的工具，用于分析蛋白质转运在唑类耐药性和假菌丝生长现象中的相关性。
