A Chitin Synthase and Its Regulator Protein Are Critical for Chitosan Production and Growth.pdf

EUKARYOTIC CELL, Nov. 2005, p. 1902–1912 Vol. 4, No. 11
1535-9778/05/$ doi:.–
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
us neoformans†
Isaac R. Banks,1*‡ Charles A. Specht,3‡ 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 Biology1 and Department of Molecular Microbiology
and Immunology,2 Saint Louis University School of Medicine, 1402 S. Grand Boulevard,
Saint Louis, Missouri 63104, and Department of Medicine, Boston University, 650 Albany Street,
Boston, Massachusetts 021183
Received 9 August 2005/Accepted 7 September 2005
Chitin is an ponent of the cell wall of many fungi. Chitin also can be enzymatically deacetylated
to chitosan, a more flexible and soluble polymer. us neoformans is a fungal pathogen that causes
al meningoencephalitis, particularly in promised 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 haromyces 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⌬ and the csr2⌬ mutants are de