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Eukaryotic Cell, November 2005, p. 1902-1912, Vol. 4, No. 11
1535-9778/05/$08.00+0     doi:10.1128/EC.4.11.1902-1912.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.

A Chitin Synthase and Its Regulator Protein Are Critical for Chitosan Production and Growth of the Fungal Pathogen Cryptococcus neoformans{dagger}

Isaac R. Banks,1*,{ddagger} Charles A. Specht,3,{ddagger} Maureen J. Donlin,1,2 Kimberly J. Gerik,1 Stuart M. Levitz,3 and Jennifer K. Lodge1,2

Edward A. Doisy Department of Biochemistry and Molecular Biology,1 Department of Molecular Microbiology and Immunology, Saint Louis University School of Medicine, 1402 S. Grand Boulevard, Saint Louis, Missouri 63104,2 Department of Medicine, Boston University, 650 Albany Street, Boston, Massachusetts 021183

Received 9 August 2005/ Accepted 7 September 2005

Chitin is an essential component of the cell wall of many fungi. Chitin also can be enzymatically deacetylated to chitosan, a more flexible and soluble polymer. Cryptococcus neoformans is a fungal pathogen that causes cryptococcal meningoencephalitis, particularly in immunocompromised patients. In this work, we show that both chitin and chitosan are present in the cell wall of vegetatively growing C. neoformans yeast cells and that the levels of both rise dramatically as cells grow to higher density in liquid culture. C. neoformans has eight putative chitin synthases, and strains with any one chitin synthase deleted are viable at 30°C. In addition, C. neoformans genes encode three putative regulator proteins, which are homologs of Saccharomyces cerevisiae Skt5p. None of these three is essential for viability. However, one of the chitin synthases (Chs3) and one of the regulators (Csr2) are important for growth. Cells with deletions in either CHS3 or CSR2 have several shared phenotypes, including sensitivity to growth at 37°C. The similarity of their phenotypes also suggests that Csr2 specifically regulates chitin synthesis by Chs3. Lastly, both chs3{Delta} and the csr2{Delta} mutants are defective in chitosan production, predicting that Chs3-Csr2 complex with chitin deacetylases for conversion of chitin to chitosan. These data suggest that chitin synthesis could be an excellent antifungal target.

* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, 1402 S. Grand Blvd., St. Louis, MO 63104. Phone: (314) 977-9217. Fax: (314) 977-9205. E-mail: lodgejk{at}slu.edu.

{dagger} Supplemental material for this article may be found at http://ec.asm.org/.

{ddagger} These authors contributed equally to the manuscript.

Eukaryotic Cell, November 2005, p. 1902-1912, Vol. 4, No. 11
1535-9778/05/$08.00+0     doi:10.1128/EC.4.11.1902-1912.2005
Copyright © 2005, American Society for Microbiology. All Rights Reserved.



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Copyright © 2005 by the American Society for Microbiology.