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Review
. 2003 Aug;2(4):655-63.
doi: 10.1128/EC.2.4.655-663.2003.

A yeast under cover: the capsule of Cryptococcus neoformans

Indrani Bose  1 , Amy J Reese, Jeramia J Ory, Guilhem Janbon, Tamara L Doering
Affiliations
Review

A yeast under cover: the capsule of Cryptococcus neoformans

Indrani Bose et al. Eukaryot Cell. 2003 Aug.
No abstract available

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Figures

FIG. 1.
FIG. 1.
Views of the cryptococcal capsule. (A) Differential interference contrast micrograph of cells that were mixed with India ink after induction of capsule formation by growth in low-iron medium (80). Scale bar, 3 μm. (B) Thin-section micrograph of a budding cell fixed in the presence of ruthenium red dye (80). Scale bar, 1 μm. (C) Quick-freeze, deep-etch image of the edge of a cell, with an arc of cell wall separating the cell interior (lower left) from the abundant capsule fibers emanating upwards. Scale bar, 0.15 μm. All images were obtained as described by Pierini and Doering (80).
FIG. 2.
FIG. 2.
Structures of the cryptococcal capsule components. (A) GXM of serotype B (27); (B) GalXM (96). Linkages between sugars are printed next to the arrows connecting monosaccharides; arrow position is not intended to represent linkage. Blue, mannose; gray, glucuronic acid; red, xylose; green, galactose. 6-O-acetylation of mannose, which modifies the GXM backbone, is not shown.
FIG. 3.
FIG. 3.
Steps in GXM synthesis. Proteins with a role in biosynthesis are indicated by red letters and are discussed further in the text. (A) Phosphomannose isomerase; (B) UDP-glucose dehydrogenase; (C) UDP-glucuronic acid decarboxylase; (D) nucleotide sugar transporters specific for GDP-mannose (D1), UDP-glucuronic acid (D2), and UDP-xylose (D3); (E) mannosyltransferase; (F) xylosyltransferase; (G) glucuronosyltransferase; and (H) acetyltransferase. The color coding is the same as described in the legend to Fig. 2, with the addition of purple to represent glucose.
FIG. 4.
FIG. 4.
Cell wall and newly synthesized capsule overlying nascent buds. Cell walls were tagged with fluorescein (green), and capsules were labeled with fluorophore-linked antibody to GXM (red). Cells were then returned to culture to allow bud emergence. A comparison of differential interference contrast (left) and fluorescence (right) images shows that none of the original label extends beyond the mother-bud neck (arrow), indicating that there is no incorporation of maternal glycans in the new bud. Reprinted with permission from Blackwell Publishing (80).
FIG. 5.
FIG. 5.
cAMP signaling pathway in the regulation of the capsule. See text for explanation. Red symbols, Pkr1p; black circles, Pka1p; blue-gray circles, cAMP.
See this image and copyright information in PMC

References

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    1. Alspaugh, J. A., J. R. Perfect, and J. Heitman. 1997. Cryptococcus neoformans mating and virulence are regulated by the G-protein α subunit GPA1 and cAMP. Genes Dev. 11:3206-3217. - PMC - PubMed
    1. Alspaugh, J. A., R. Pukkila-Worley, T. Harashima, L. M. Cavallo, D. Funnell, G. M. Cox, J. R. Perfect, J. W. Kronstad, and J. Heitman. 2002. Adenylyl cyclase functions downstream of the Gα protein Gpa1 and controls mating and pathogenicity of Cryptococcus neoformans. Eukaryot. Cell 1:75-84. - PMC - PubMed
    1. Altschul, S. F., W. Gish, W. Miller, E. W. Myers, and D. J. Lipman. 1990. Basic local alignment search tool. J. Mol. Biol. 215:403-410. - PubMed
    1. Bar-Peled, M., C. L. Griffith, and T. L. Doering. 2001. Functional cloning and characterization of a UDP-glucuronic acid decarboxylase: the pathogenic fungus Cryptococcus neoformans elucidates UDP-xylose synthesis. Proc. Natl. Acad. Sci. USA 98:12003-12008. - PMC - PubMed

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