Eukaryotic Cell
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Eukaryotic Cell, February 2007, p. 222-234, Vol. 6, No. 2
1535-9778/07/$08.00+0     doi:10.1128/EC.00182-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.

Role of Protein O-Mannosyltransferase Pmt4 in the Morphogenesis and Virulence of Cryptococcus neoformans{triangledown}

Gillian M. Olson,1,4* Deborah S. Fox,1,2,3,4 Ping Wang,1,2,3,4 J. Andrew Alspaugh,5,6 and Kent L. Buchanan1,{dagger}

Department of Microbiology and Immunology, Tulane University Health Sciences Center,1 Departments of Pediatrics,2 Microbiology, Immunology, and Parasitology, Louisiana State University Health Sciences Center,3 Research Institute for Children, New Orleans, Louisiana,4 Departments of Molecular Genetics and Microbiology,5 Medicine, Duke University Medical Center, Durham, North Carolina6

Received 14 June 2006/ Accepted 17 November 2006

Protein O mannosylation is initiated in the endoplasmic reticulum by protein O-mannosyltransferases (Pmt proteins) and plays an important role in the secretion, localization, and function of many proteins, as well as in cell wall integrity and morphogenesis in fungi. Three Pmt proteins, each belonging to one of the three respective Pmt subfamilies, are encoded in the genome of the human fungal pathogen Cryptococcus neoformans. Disruption of the C. neoformans PMT4 gene resulted in abnormal growth morphology and defective cell separation. Transmission electron microscopy revealed defective cell wall septum degradation during mother-daughter cell separation in the pmt4 mutant compared to wild-type cells. The pmt4 mutant also demonstrated sensitivity to elevated temperature, sodium dodecyl sulfate, and amphotericin B, suggesting cell wall defects. Further analysis of cell wall protein composition revealed a cell wall proteome defect in the pmt4 mutant, as well as a global decrease in protein mannosylation. Heterologous expression of C. neoformans PMT4 in a Saccharomyces cerevisiae pmt1pmt4 mutant strain functionally complemented the deficient Pmt activity. Furthermore, Pmt4 activity in C. neoformans was required for full virulence in two murine models of disseminated cryptococcal infection. Taken together, these results indicate a central role for Pmt4-mediated protein O mannosylation in growth, cell wall integrity, and virulence of C. neoformans.

* Corresponding author. Mailing address: Research Institute for Children, Children's Hospital, 200 Henry Clay Ave., New Orleans, LA 70118. Phone: (504) 896-2767. Fax: (504) 894-5379. E-mail: golson{at}chnola-Research.org.

{triangledown} Published ahead of print on 1 December 2006.

{dagger} Present address: Department of Biology, Oklahoma City University, 2501 N. Blackwelder, Oklahoma City, OK 73106.

Eukaryotic Cell, February 2007, p. 222-234, Vol. 6, No. 2
1535-9778/07/$08.00+0     doi:10.1128/EC.00182-06
Copyright © 2007, American Society for Microbiology. All Rights Reserved.





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