A Conserved Gcn2-Gcn4 Axis Links Methionine Utilization and the Oxidative Stress Response in Cryptococcus neoformans

Abstract

The fungal pathogen Cryptococcus neoformans relies on post-transcriptional mechanisms of gene regulation to adapt to stressors it encounters in the human host, such as oxidative stress and nutrient limitation. The kinase Gcn2 regulates translation in response to stress by phosphorylating the initiation factor eIF2, and it is a crucial factor in withstanding oxidative stress in C. neoformans, and amino acid limitation in many fungal species. However, little is known about the role of Gcn2 in nitrogen limitation in C. neoformans. In this study, we demonstrate that Gcn2 is required for C. neoformans to utilize methionine as a source of nitrogen, and that the presence of methionine as a sole nitrogen source induces eIF2 phosphorylation. The stress imposed by methionine leads to an oxidative stress response at both the levels of transcription and translation, as seen through polysome profiling as well as increased abundance of select oxidative stress response transcripts. The transcription factor Gcn4 is also required for methionine utilization and oxidative stress resistance, and RT-qPCR data suggests that it regulates expression of certain transcripts in response to oxidative stress. The results of this study suggest a connection between nitrogen metabolism and oxidative stress in C. neoformans that is mediated by Gcn4, possibly indicating the presence of a compound stress response in this clinically important fungal pathogen.

The RAM signaling pathway links morphology, thermotolerance, and CO2 tolerance in the global fungal pathogen Cryptococcus neoformans

“…Our observation that the natural suppressors do not restore transcript abundances of CO 2 -associated genes in cbk1 Δ to WT levels supports a hypothesis that disruption of Ssd1 and Psc1 suppresses the cbk1 Δ mutant’s defects at a post-transcriptional level. C. neoformans has been demonstrated to use post-transcriptional regulation to adapt to various host stresses ( Bloom et al, 2019 ; Kalem et al, 2021 ; Stovall et al, 2021 ). A temperature-sensitive environmental species of Cryptococcus , Cryptococcus amylolentus , fails to initiate host stress-induced translational reprogramming and is non-pathogenic ( Bloom et al, 2019 ).…”

The interactome of Cryptococcus neoformans Rmt5 reveals multiple regulatory points in fungal cell biology and pathogenesis

“…Nevertheless, our C. neoformans Rmt5 interactome included many translation initiation and elongation factors, implicating Rmt5 in translation regulation. We also know that translatome remodeling in C. neoformans is crucial for tolerance to temperature and compound stress (29, 30, 33, 50). Our work demonstrates that Rmt5 modulates translation under stress by targeting translation initiation and elongation factors, ribosomal proteins, and RBPs.…”

“…The potentially fatal human-pathogenic Cryptococcus neoformans harbors five RMTs, but very little is known about these. Our previous work established the importance of post-transcriptional and translational regulation in the virulence and pathogenicity of C. neoformans as well as antifungal resistance (28)(29)(30)(31)(32)(33). Here, we characterized the functional roles of its RMTs to investigate how they fine-tune those regulatory mechanisms and influence the pathogenicity of C. neoformans.…”

The RAM signaling pathway links morphology, thermotolerance, and CO2 tolerance in the global fungal pathogen Cryptococcus neoformans

“…Our observation that the natural suppressors do not restore transcript abundances of CO 2 -associated genes in cbk1 Δ to WT levels supports a hypothesis that disruption of Ssd1 and Psc1 suppresses cbk1 Δ mutant’s defects at a post-transcriptional level. C. neoformans has been demonstrated to use post-transcriptional regulation to adapt to various host stresses (Bloom et al, 2019; Kalem, Subbiah, Leipheimer, Glazier, & Panepinto, 2021; Stovall, Knowles, Kalem, & Panepinto, 2021). A temperature-sensitive environmental species of Cryptococcus, C. amylolentus , fails to initiate host stress-induced translational reprogramming and is non-pathogenic (Bloom et al, 2019).…”