A newly identified amino acid substitution T123I in the 14α-demethylase (Erg11p) of Candida albicans confers azole resistance.
The increasing prevalence of azole resistance in Candida albicans poses a growing problem for clinical treatment. Amino acid substitution of the 14α-demethylase (Erg11p) encoded by the ERG11 gene is one of the most common mechanisms involved in azole resistance. Although amino acid substitutions of Erg11p have been observed in many clinical isolates, only a few amino acid substitutions have been confirmed to be related to azole resistance. In this study, by amplifying and sequencing the open reading frame of the ERG11 gene from 55 clinical isolates, we identified 27 fluconazole-resistant isolates that harbor a novel amino acid substitution, T123I, in Erg11p, in addition to the previously described homozygous substitution Y132H. We investigated both the contribution of this novel substitution T123I and its synergistic effect with substitution Y132H to azole resistance by heterogeneously expressing the C. albicans Erg11p with different substitution forms in Saccharomyces cerevisiae. Results showed that S. cerevisiae cells harboring the substitution T123I displayed higher (4-fold) minimum inhibitory concentration values to both fluconazole and voriconazole than the cells expressing the wild-type version of C. albicans Erg11p, but this was not true for itraconazolele. More importantly, a synergistic effect of substitutions T123I and Y132H was observed in an assay of voriconazole resistance. These results indicate that amino acid substitutions of Erg11p are prevalent among azole-resistant isolates and that the substitution T123I confers resistance to both fluconazole and voriconazole.
Department of Clinical Laboratory, Obstetrics and Gynecology Hospital of Fudan University, 419 Fangxie Road, Shanghai 200011, China.
YongQin
Y
Wu
Unit of Pathogenic Fungal Infection and Host Immunity, CAS Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Chinese Academy of Sciences, 320 Yueyang Road, Shanghai 200031, China.
Ning
N
Gao
Department of Clinical Laboratory, Obstetrics and Gynecology Hospital of Fudan University, 419 Fangxie Road, Shanghai 200011, China.
Cui
C
Li
Department of Clinical Laboratory, Obstetrics and Gynecology Hospital of Fudan University, 419 Fangxie Road, Shanghai 200011, China.
Jing
J
Gao
Department of Clinical Laboratory, Obstetrics and Gynecology Hospital of Fudan University, 419 Fangxie Road, Shanghai 200011, China.
ChunMei
C
Ying
D019943:Amino Acid Substitution; D000935:Antifungal Agents / Q000737:chemistry / Q000494:pharmacology*; D001665:Binding Sites; D002176:Candida albicans / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D025141:Drug Resistance, Fungal / Q000235:genetics*; D015725:Fluconazole / Q000737:chemistry / Q000494:pharmacology; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D007532:Isoleucine / Q000737:chemistry / Q000378:metabolism; D017964:Itraconazole / Q000737:chemistry / Q000494:pharmacology; D008826:Microbial Sensitivity Tests; D008958:Models, Molecular; D016366:Open Reading Frames; D010766:Phosphorylation; D011485:Protein Binding; D000072756:Protein Conformation, alpha-Helical; D054730:Protein Interaction Domains and Motifs; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics; D013912:Threonine / Q000737:chemistry / Q000378:metabolism; D065819:Voriconazole / Q000737:chemistry / Q000494:pharmacology
D000935:Antifungal Agents; D005656:Fungal Proteins; C465525:cytochrome P-450 CYP51, Candida albicans; D007532:Isoleucine; D013912:Threonine; D017964:Itraconazole; D015725:Fluconazole; D003577:Cytochrome P-450 Enzyme System; D065819:Voriconazole
Candida albicans; azole resistance; heterologous expression; homology modeling; the amino acid substitution T123I