Research Abstract:
Cryptococcus neoformans is a pathogenic fungus responsible for serious opportunistic infections in immunocompromised individuals. My lab studies unique aspects of cryptococcal biology that are of biological interest and may suggest targets for badly needed antifungal chemotherapy.
The main virulence factor of C. neoformans is its extensive polysaccharide capsule, a unique protective structure that is required for virulence. The chemical structure of the capsule is known, but almost nothing is known about its synthesis and assembly. We are taking several approaches to understanding capsule biosynthesis, and to investigating interactions of this pathogen with host cells.
One approach is biochemical. We develop assays for enzymes involved in capsule construction in order to purify and study them or to identify them genetically. We are also investigating the synthesis and intracellular transport of nucleotide sugar precursors that are required for the sugar transferase reactions that link capsule components. Another approach is genetic: generating and studying mutants with defects in capsule synthesis. In these studies we can take advantage of the well-sequenced cryptococcal genome for reverse genetic studies. (We also exploit this sequence information by using RNA interference to specifically down-regulate gene expression.) Taking a forward genetic strategy, we can also screen for mutants of interest after mutagenesis or exposure of cells to an RNA interference library.
Other experiments employ methods of cell biology to address the question of how new capsular material is incorporated into the existing structure, how capsule matures, and how capsular material associates with the cell. We hope in the future to address the molecular mechanisms of these fascinating processes. These and other studies in the lab will be aided by our recent development of RNA interference in this system and a 70-mer oligonucleotide microarray for studies ofC. neoformans gene expression.
Selected Publications:
Cottrell TR, Griffith CL, Liu H, Nenninger AA, and Doering TL. The pathogenic fungus Cryptococcus neoformans expresses two functional GDP-mannose transporters with distinct expression patterns and roles in capsule synthesis. Eukaryotic Cell 2007 6:776-785. PubMed ID 17351078. [Cover image.]
Klutts JS, Levery SB, and Doering TL. A beta-1,2-xylosyltransferase from Cryptococcus neoformans defines a new family of glycosyltransferases. J Biol Chem 2007 282:17890-17899. PubMed ID 17430900.
Reese AJ, Yoneda A, Breger JA, Beauvais A, Liu H, Griffith CL, Bose I, Kim M-J, Skau C, Yang S, Sefko JA, Osumi M, Latge J-P, Mylonakis E, and Doering TL. Loss of cell wall alpha(1-3) glucan affects Cryptococcus neoformans from ultrastructure to virulence. Molec Microbio 2007 63:1385-1398 2007. PubMed ID 17244196. [Cover image.]
Yoneda A and Doering TL. A eukaryotic capsular polysaccharide is synthesized intracellularly and secreted via exocytosis. Molec Bio of the Cell 2006 17:5131-5140. PubMed ID 17021252.
Bose I, Reese AJ, Ory JJ, Janbon G, and Doering TL. A yeast under cover: The capsule of Cryptococcus neoformans. Eukaryotic Cell 2003 2:655-663. PubMed ID 12912884. [Review article].
Last Updated: 09/07/2007 |