Distinct stress responses of two functional laccases in Cryptococcus neoformans are revealed in the absence of the thiol-specific antioxidant Tsa1. Eukaryot Cell 2005 Jan;4(1):202-8
Date
01/12/2005Pubmed ID
15643075Pubmed Central ID
PMC544170DOI
10.1128/EC.4.1.202-208.2005Scopus ID
2-s2.0-13744260680 (requires institutional sign-in at Scopus site) 106 CitationsAbstract
Laccases are thought to be important to the virulence of many fungal pathogens by producing melanin, a presumed oxygen radical scavenger. A laccase in Cryptococcus neoformans has been shown to synthesize melanin and contributes to the virulence and the survival in macrophages of this fungal pathogen. One C. neoformans laccase gene, LAC1, previously called CNLAC1, has been extensively studied, and we describe a homologous gene, LAC2, that is found 8 kb away from LAC1 in the genome. In this study we report a role for both laccases, in addition to the thiol peroxidase, Tsa1, in oxidative and nitrosative stress resistance mechanisms of C. neoformans. With use of real-time PCR, similar changes in expression of the two laccase genes occur in response to oxidative and nitrosative stresses, but only the regulation of the LAC2 gene during stress is influenced by Tsa1. Both laccases contribute to melanin production using L-dopa as a substrate and are differentially localized in the cell based on green fluorescent protein fusions. A single deletion of either LAC1 or LAC2 alone had no effect on sensitivity to H2O2 or nitric oxide. However, deletion of either LAC1 or LAC2 in combination with a TSA1 deletion resulted in a slight peroxide sensitivity, and a lac2Delta tsa1Delta deletion strain was sensitive to nitric oxide stress. In addition, the deletion of both laccases reduces survival of C. neoformans in primary macrophages. Based on our expression and functional analysis, we propose a novel model for the interaction of these two systems, which are both important for virulence.
Author List
Missall TA, Moran JM, Corbett JA, Lodge JKAuthor
John A. Corbett PhD Professor in the Biochemistry department at Medical College of WisconsinMESH terms used to index this publication - Major topics in bold
AnimalsBlotting, Southern
Cell Survival
Cryptococcosis
Cryptococcus neoformans
DNA
Free Radicals
Green Fluorescent Proteins
Hydrogen Peroxide
Laccase
Macrophages
Melanins
Mice
Models, Biological
Models, Genetic
Mutation
Nitric Oxide
Nitrogen
Oxidative Stress
Oxygen
Peritoneum
Peroxidases
Peroxiredoxins
Protein Structure, Tertiary
Reverse Transcriptase Polymerase Chain Reaction
Substrate Specificity
Sulfhydryl Compounds
Temperature
