A contribution to further understand the molecular mechanisms of antifungal resistance in Candida glabrata mediated by the transcription factor CgPdr1

Rita Silva Ramos Madureira Simões

Informações chave

Autores:

Rita Silva Ramos Madureira Simões (Rita Silva Ramos Madureira Simões)

Orientadores:

Nuno Gonçalo Pereira Mira (Nuno Gonçalo Pereira Mira)

Publicado em

14/11/2018

Resumo

Recently, Candida glabrata has emerged as a human pathogen, partly due to its high resilience to azoles which results, generally, from the acquisition of point mutations in the transcriptional regulator CgPdr1 that render the protein constitutively active, even in the absence of any drug. In this work three non-characterized mutations in CgPDR1 – E5K, R35K and I392M – were identified in azole-resistant clinical isolates. Expression profiling of CgCDR1 and CgPUP1, two hallmarks of CgPdr1 hyper-activity, and site-directed mutagenesis strongly suggested that E5K and I392M are new gain-of-function CgPdr1 substitutions resulting in azole resistance. Additionally, it was investigated how gain-of-function substitutions modulate the biochemical activity of CgPdr1, specially, its transactivation potential. The increasing emergence of azole-resistant C. glabrata strains and the recently shown anti-C.glabrata efficacy of Ag(I)-camphorimine complexes outlined this work’s remaining objectives: i) characterize how these complexes affect the physiology of C. glabrata; ii) search for new Ag(I)-derived compounds showing anti-C.glabrata potential, including against azole-resistant strains. DNA microarrays revealed that exposure to compound A results in up-regulation of genes involved in oxidative stress response and methionine metabolism, simultaneously leading to down-regulation of genes involved in glucose and iron uptake. Although further studies are required, the results obtained show that the effects of Ag(I)-camphorimine complexes are similar to those already described for silver. Two novel compounds, B and C, were also herein characterized as robust anti-C.glabrata agents, against both laboratory (MIC=62,5 mg/L) and azole-resistant (MIC between 125-500 mg/L) strains, reinforcing the usefulness of these chemicals as new antifungals.