Role of a CUF1/CTR4 copper regulatory axis in the virulence of Cryptococcus neoformans
Scott R. Waterman, … , Nina Singh, Peter R. Williamson
Scott R. Waterman, … , Nina Singh, Peter R. Williamson
Published March 1, 2007
Citation Information: J Clin Invest. 2007;117(3):794-802. https://doi.org/10.1172/JCI30006.
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Role of a CUF1/CTR4 copper regulatory axis in the virulence of Cryptococcus neoformans

Abstract

The study of regulatory networks in human pathogens such as Cryptococcus neoformans provides insights into host-pathogen interactions that may allow for correlation of gene expression patterns with clinical outcomes. In the present study, deletion of the cryptococcal copper-dependent transcription factor 1 (Cuf1) led to defects in growth and virulence factor expression in low copper conditions. In mouse models, cuf1Δ strains exhibited reduced dissemination to the brain, but no change in lung growth, suggesting copper is limiting in neurologic infections. To examine this further, a biologic probe of available copper was constructed using the cryptococcal CUF1-dependent copper transporter, CTR4. Fungal cells demonstrated high CTR4 expression levels after phagocytosis by macrophage-like J774.16 cells and during infection of mouse brains, but not lungs, consistent with limited copper availability during neurologic infection. This was extended to human brain infections by demonstrating CTR4 expression during C. neoformans infection of an AIDS patient. Moreover, high CTR4 expression by cryptococcal strains from 24 solid organ transplant patients was associated with dissemination to the CNS. Our results suggest that copper acquisition plays a central role in fungal pathogenesis during neurologic infection and that measurement of stable traits such as CTR4 expression may be useful for risk stratification of individuals with cryptococcosis.

Authors

Scott R. Waterman, Moshe Hacham, Guowu Hu, Xudong Zhu, Yoon-Dong Park, Soowan Shin, John Panepinto, Tibor Valyi-Nagy, Craig Beam, Shahid Husain, Nina Singh, Peter R. Williamson

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Figure 4

Expression of CTR4 in macrophages and mouse brain demonstrates low copper availability during infection.

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Expression of CTR4 in macrophages and mouse brain demonstrates low coppe...
(A) WT or cuf1Δ cells expressing equivalent CTR4-GFP constructs under the CTR4 promoter were incubated with the macrophage-like cell line J774.16 for the indicated times; 200 intracellular (Intra) and extracellular (Extra) were scored for the presence of epifluorescence at the indicated time points. (B) Representative intracellular fungal cells from A were visualized by epifluorescence and intracellular colocalization by Tetramethylrhodamine-labeled dextran after phagocytosis as described in Methods. Original magnification, ×1,000. (C) C. neoformans cells expressing either CTR4-GFP (open histogram) or empty plasmid (shaded histogram) were injected (106 cells) by tail vein into Swiss albino mice and after sacrifice, fungal cells were harvested from their brains, and epifluorescence was measured by flow cytometry. (D) Representative cryptococcal cells from C were visualized by microscopy after recovery from the brains and lungs of intranasally injected CBA/J mice. DIC, differential interference contrast. Original magnification, ×1,000.