A cysteine-rich domain of the Cuf1 transcription factor is required for high copper stress sensing and fungal virulence

The ability to sense, import but also detoxify copper (Cu) has been shown to be crucial for microbial pathogens to survive within the host. Previous studies conducted with the opportunistic human fungal pathogenCryptococcus neoformans(Cn) have revealed two extreme Cu environments encountered during infection: A high Cu environment within the lung and a low Cu environment within the brain. However, howCnsenses these different host Cu microenvironments, and the consequences of a blunted Cu stress adaption for pathogenesis, are not well understood.

In contrast to other fungi,Cnhas a single transcription factor, Cuf1, to regulate adaptive responses to both high- and low-Cu stress. Sequence analysis ofCnCuf1 identified three conserved cysteine (Cys)-rich regions that may play a role in Cu sensing. We mutated the 1^stCys-rich region within theCUF1gene to investigate its role forCnhigh Cu stress sensing. Subsequent analysis of Cuf1 transcriptional activity and target gene promoter binding demonstrated that the 1^stCys-rich region is required for Cuf1 transcriptional activity in high Cu stress. We performed an inhalational murine infection to analyze the effects of a blunted high Cu stress response on pathogenesis. No significant differences in lung fungal burden were observed based on variable Cuf1 activity. However, strains with defective high Cu stress regulation induced a markedly altered immune response in mice. Based on these findings, we hypothesize that Cuf1-driven high Cu responses are not required for initial survival but instead modulate immune recognition and inflammation within the mouse lung.