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Eukaryotic Cell, October 2009, p. 1543-1553, Vol. 8, No. 10
1535-9778/09/$08.00+0     doi:10.1128/EC.00142-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Role for Chitin and Chitooligomers in the Capsular Architecture of Cryptococcus neoformans{triangledown}

Fernanda L. Fonseca,1 Leonardo Nimrichter,1 Radames J. B. Cordero,2 Susana Frases,2 Jessica Rodrigues,1 David L. Goldman,2,3 Ryszard Andruszkiewicz,4 Slawomir Milewski,4 Luiz R. Travassos,5 Arturo Casadevall,2,6 and Marcio L. Rodrigues1*

Laboratório de Estudos Integrados em Bioquímica Microbiana, Instituto de Microbiologia Professor Paulo de Góes, Universidade Federal do Rio de Janeiro, Rio de Janeiro 21941-902, Brazil,1 Department of Microbiology and Immunology,2 Department of Pediatrics,3 Division of Infectious Diseases of the Department of Medicine, Albert Einstein College of Medicine, 1300 Morris Park Avenue, Bronx, New York 10461,6 Department of Pharmaceutical Technology and Biochemistry, Gdansk University of Technology, 11/12 Narutowicza Street, 80-952 Gdansk, Poland,4 Disciplina de Biologia Celular, Universidade Federal de São Paulo, São Paulo, SP 04023-062, Brazil5

Received 15 May 2009/ Accepted 8 July 2009

Molecules composed of β-1,4-linked N-acetylglucosamine (GlcNAc) and deacetylated glucosamine units play key roles as surface constituents of the human pathogenic fungus Cryptococcus neoformans. GlcNAc is the monomeric unit of chitin and chitooligomers, which participate in the connection of capsular polysaccharides to the cryptococcal cell wall. In the present study, we evaluated the role of GlcNAc-containing structures in the assembly of the cryptococcal capsule. The in vivo expression of chitooligomers in C. neoformans varied depending on the infected tissue, as inferred from the differential reactivity of yeast forms to the wheat germ agglutinin (WGA) in infected brain and lungs of rats. Chromatographic and dynamic light-scattering analyses demonstrated that glucuronoxylomannan (GXM), the major cryptococcal capsular component, interacts with chitin and chitooligomers. When added to C. neoformans cultures, chitooligomers formed soluble complexes with GXM and interfered in capsular assembly, as manifested by aberrant capsules with defective connections with the cell wall and no reactivity with a monoclonal antibody to GXM. Cultivation of C. neoformans in the presence of an inhibitor of glucosamine 6-phosphate synthase resulted in altered expression of cell wall chitin. These cells formed capsules that were loosely connected to the cryptococcal wall and contained fibers with decreased diameters and altered monosaccharide composition. These results contribute to our understanding of the role played by chitin and chitooligosaccharides on the cryptococcal capsular structure, broadening the functional activities attributed to GlcNAc-containing structures in this biological system.

* Corresponding author. Mailing address: Universidade Federal do Rio de Janeiro, Instituto de Microbiologia, Avenida Carlos Chagas Filho, 373, Cidade Universitária CCS, Bloco I, Rio de Janeiro, RJ 21941-902, Brazil. Phone: 55 21 2562 6740. Fax: 55 21 2560 8344. E-mail: marcio{at}micro.ufrj.br

{triangledown} Published ahead of print on 17 July 2009.

Eukaryotic Cell, October 2009, p. 1543-1553, Vol. 8, No. 10
1535-9778/09/$08.00+0     doi:10.1128/EC.00142-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.





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