Translational Regulation of Candida glabrata Azole Resistance

点击翻译按钮获取中文摘要

PROJECT SUMMARY/ABSTRACT Candida glabrata is an important human fungal pathogen capable of causing both systemic and mucosal infections in a wide variety of immunocompromised individuals, including organ transplant recipients, cancer patients on chemotherapy and AIDS patients. C. glabrata is the second most frequently isolated Candida species in invasive bloodstream infections, has a high crude mortality rate (~40-60%), and has been classified as a “serious” threat to public health by the Centers for Disease Control (CDC). While resistance of C. glabrata clinical isolates to multiple antifungals, particularly azoles, is on the rise only three major drug classes are available for treatment. Previous studies have shown that C. glabrata antifungal resistance can be attributed to a variety of genetic point mutations, chromosomal rearrangements as well as increased transcription of certain drug efflux pumps. In contrast to genetic and transcriptional mechanisms, very little is known about translational mechanisms that control antifungal resistance in C. glabrata or other human fungal pathogens. However, we and others have shown that long 5’ UTR-mediated translational efficiency mechanisms play an important role in controlling the expression of several key regulators of virulence-related processes in Candida albicans and, based on RNA-seq data, many C. glabrata genes specifically involved in azole resistance also possess long 5’ UTRs that could be involved in translational regulation. Using genome-wide ribosome profiling, we have recently demonstrated that the C. albicans yeast-filament transition is under widespread translational control and several genes associated with antifungal resistance also showed altered translational efficiency during this transition. A similar ribosome profiling analysis in Saccharomyces cerevisiae, which is more closely related to C. glabrata, also showed significant translational expression changes in response to oxidative stress. Many C. glabrata genes important for protein synthesis are significantly down-regulated in response to azole treatment. In addition, only a small fraction of C. glabrata genes showing altered protein expression in azole resistant vs. susceptible isolates also showed changes at the transcript level and evidence suggests that C. glabrata ERG11, encoding the azole target lanosterol 14-demethylase, could be under translational control. Based on these observations, we hypothesize that translational mechanisms play an important role in controlling azole resistance in C. glabrata. In order to test this hypothesis, we will: 1) determine the genome- wide translational profile of C. glabrata in response to treatment with fluconazole, the most commonly used azole drug, 2) identify and characterize translational mechanisms important for driving C. glabrata azole resistance. Ultimately, this study will provide a better understanding of global regulatory circuits and pathways that control C. glabrata azole resistance at the translational level. In addition, this study will identify and characterize several key translationally regulated factors important for C. glabrata drug resistance that could potentially serve as targets for the development of novel antifungal strategies.