Project description:Cryptococcus neoformans is an invasive human fungal pathogen, which causes pneumonia and meningoencephalitis in both healthy and immunodeficient individuals, resulting 181,100 deaths each year. Studies have demonstrated that copper detoxification machineries play critical functions in modulating C. neoformans fitness and pathogenicity in the host lung tissue. Pulmonary C. neoformans infection provokes the generation of toxic copper bombardment, which in return activate detoxification process in fungal cells. However, the molecular mechanism on how Cu inhibits C. neoformans in proliferation remains unclear. Here, using Cu detoxification gene knockout strains we demonstrated that exogenous Cu ions inhibit cell growth of the metallothionein mutant, which was significantly rescue when supplementing with the ROS scavenger, N-acetylcysteine. To future characterize the molecular mechanism of C. neoformans response to Cu toxicity, we employ iTRAQ with LC-MS/MS analysis, in the presence of exogenous Cu or NAC. Our data showed that an increased Cu level repressed expression of factors involved in protein translation but activates expression of important players in ubiquitin-degradation process. We proposed that the downregulation of protein synthesis and the upregulation of protein degradation were the main strategy of Cu toxicity. The metallothionein mutant showed a higher ubiquitination level under Cu treatment. In addition, MG132 could partially restore the Cu toxicity effect on metallothionein mutant. These results shed new light on the Cu antifungal mechanisms from proteomic profile.
Project description:Purpose: To examine the comparative transcriptional profiles of WT and rim101 mutant cells in host-mimicking in vitro conditions to determine genes that are responsible for the increased virulence of the rim101 strain. The rim101 mutant is able to trigger an overactive inflammatory response, presumably by exposing an antigenic trigger. Using transcriptional profiling, we determined that many genes involved in cell wall processes were differentially transcribed between the wild type and the mutant strain.
Project description:Purpose: To examine the comparative transcriptional profiles of WT and rim101 mutant cells in host-mimicking in vitro conditions to determine genes that are responsible for the increased virulence of the rim101 strain. The rim101 mutant is able to trigger an overactive inflammatory response, presumably by exposing an antigenic trigger. Using transcriptional profiling, we determined that many genes involved in cell wall processes were differentially transcribed between the wild type and the mutant strain. Whole mRNA profiles of WT and rim101 cells were generated by deep sequencing using Illumina GAII.
Project description:To investigate the pleiotropic roles of Lkh1 in stress response and virulence, we constructed lkh1∆ mutant strains. In this study, we found that Tor1 was an upstream regulator of Lkh1 in C. neoformans. We then performed gene expression profiling analysis to elucidate signaling circuitry downstream of CnLkh1 in the TOR1-Lkh1 pathway using data obtained from RNA seq of 2 different strains (WT of lkh1∆ mutant) with or without rapamycin treatment.
Project description:Cryptococcus spp. are environmental fungi that first must adapt to the host environment before they can cause life-threatening meningitis in immunocompromised patients. Host CO2 concentrations are 100-fold higher than the external environment and strains unable to grow at host CO2 concentrations are not pathogenic. Using a genetic screening and transcriptional profiling approach, we found that the TOR pathway is critical for C. neoformans adaptation to host CO2 partly through Ypk1-dependent remodeling of phosphatidylserine asymmetry at the plasma membrane. We also identified a C. neoformans ABC/PDR transporter (PDR9) that is highly expressed in CO2-sensitive environmental strains, suppresses CO2-induced phosphatidylserine remodeling, and increases susceptibility to host concentrations of CO2. Interestingly, regulation of plasma membrane lipid asymmetry by the TOR-Ypk1 axis is distinct in C. neoformans compared to S. cerevisiae. Finally, host CO2 concentrations suppress the C. neoformans pathways that respond to host temperature (Mpk1) and pH (Rim101), indicating that host adaptation requires a stringent balance among distinct stress responses.
Project description:We investigated the effects of the hypoxia-mimetic CoCl2 on the gene expression of pathogenic fungus Cryptococcus neoformans. Keywords: compound treatment design
Project description:Cryptococcus neoformans is a prevalent human fungal pathogen that must survive within various tissues in order to establish a human infection. We have identified the C. neoformans Rim101 transcription factor, a highly conserved pH-response regulator in many fungal species. The rim101- mutant strain displays growth defects similar to other fungal species in the presence of alkaline pH, increased salt concentrations, and iron limitation. However, the rim101- strain is also characterized by a striking defect in capsule, an important virulence-associated phenotype. This capsular defect is likely due to alterations in polysaccharide attachment to the cell surface, not in polysaccharide biosynthesis. In contrast to many other C. neoformans capsule-defective strains, the rim101- mutant is hypervirulent in animal models of cryptococcosis. Whereas Rim101 activation in other fungal species occurs through the conserved Rim pathway, we demonstrate that C. neoformans Rim101 is also activated by the cAMP/PKA pathway. We report here that C. neoformans uses PKA and the Rim pathway to regulate the localization, activation, and processing of the Rim101 transcription factor. We also demonstrate specific host- relevant activating conditions for Rim101 cleavage, showing that C. neoformans has co-opted conserved signaling pathways to respond to the specific niche within the infected host. These results establish a novel mechanism for Rim101 activation and the integration of two conserved signaling cascades in response to host environmental conditions.