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Eukaryotic Cell, October 2008, p. 1640-1648, Vol. 7, No. 10
1535-9778/08/$08.00+0     doi:10.1128/EC.00129-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

Identification of the Putative Protein Phosphatase Gene PTC1 as a Virulence-Related Gene Using a Silkworm Model of Candida albicans Infection ^,

Nozomu Hanaoka,^1,2 Yukie Takano,¹ Kazutoshi Shibuya,³ Hajime Fugo,² Yoshimasa Uehara,^1, and Masakazu Niimi^1*

Department of Bioactive Molecules, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640,¹ United Graduate School of Agricultural Science, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu-City, Tokyo 183-8509,² Department of Pathology, Toho University School of Medicine, 6-11-1 Omori Nishi, Ota-ku, Tokyo, Japan³

Received 11 April 2008/ Accepted 31 July 2008

Protein phosphatases are critical for the regulation of many cellular processes. Null mutants of 21 putative protein phosphatases of Candida albicans were constructed by consecutive allele replacement using the URA3 and ARG4 marker genes. A simple silkworm model of C. albicans infection was used to screen the panel of mutants. Four null mutant (cmp1, yvh1, sit4, and ptc1) strains showed attenuated virulence in the silkworm model relative to that of control and parental strains. Three of the mutants, the cmp1, yvh1, and sit4 mutants, had previously been identified as affecting virulence in a conventional mouse model, indicating the validity of the silkworm model screen. Disruption of the putative protein phosphatase gene PTC1 of C. albicans, which has 52% identity to the Saccharomyces cerevisiae type 2C protein phosphatase PTC1, significantly reduced virulence in the silkworm model. The mutant was also avirulent in a mouse model of disseminated candidiasis. Reintroducing either of the C. albicans PTC1 alleles into the disruptant strain, using a cassette containing either allele under the control of a constitutive ACT1 promoter, restored virulence in both infection models. Characterization of ptc1 revealed other phenotypic traits, including reduced hyphal growth in vitro and in vivo, and reduced extracellular proteolytic activity. We conclude that PTC1 may contribute to pathogenicity in C. albicans.

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* Corresponding author. Mailing address: Department of Bioactive Molecules, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan. Phone: 81 3 5285 1111. Fax: 81 3 5285 1272. E-mail: niimi{at}nih.go.jp

Published ahead of print on 15 August 2008.

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

Present address: Department of Microbial Chemical Biology and Drug Discovery, Iwate Medical University School of Pharmacy, 2-1-1 Nishitokuda, Yahabacho, Shiwa-gun, Iwate 028-3694, Japan.

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Eukaryotic Cell, October 2008, p. 1640-1648, Vol. 7, No. 10
1535-9778/08/$08.00+0     doi:10.1128/EC.00129-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.