Melanin deposition in two Cryptococcus species depends on cell-wall composition and flexibility.

Journal Article (Journal Article)

Cryptococcus neoformans and Cryptococcus gattii are two species complexes in the large fungal genus Cryptococcus and are responsible for potentially lethal disseminated infections. These two complexes share several phenotypic traits, such as production of the protective compound melanin. In C. neoformans, the pigment associates with key cellular constituents that are essential for melanin deposition within the cell wall. Consequently, melanization is modulated by changes in cell-wall composition or ultrastructure. However, whether similar factors influence melanization in C. gattii is unknown. Herein, we used transmission EM, biochemical assays, and solid-state NMR spectroscopy of representative isolates and "leaky melanin" mutant strains from each species complex to examine the compositional and structural factors governing cell-wall pigment deposition in C. neoformans and C. gattii. The principal findings were the following. 1) C. gattii R265 had an exceptionally high chitosan content compared with C. neoformans H99; a rich chitosan composition promoted homogeneous melanin distribution throughout the cell wall but did not increase the propensity of pigment deposition. 2) Strains from both species manifesting the leaky melanin phenotype had reduced chitosan content, which was compensated for by the production of lipids and other nonpolysaccharide constituents that depended on the species or mutation. 3) Changes in the relative rigidity of cell-wall chitin were associated with aberrant pigment retention, implicating cell-wall flexibility as an independent variable in cryptococcal melanin assembly. Overall, our results indicate that cell-wall composition and molecular architecture are critical factors for the anchoring and arrangement of melanin pigments in both C. neoformans and C. gattii species complexes.

Full Text

Duke Authors

Cited Authors

  • Chrissian, C; Camacho, E; Fu, MS; Prados-Rosales, R; Chatterjee, S; Cordero, RJB; Lodge, JK; Casadevall, A; Stark, RE

Published Date

  • February 14, 2020

Published In

Volume / Issue

  • 295 / 7

Start / End Page

  • 1815 - 1828

PubMed ID

  • 31896575

Pubmed Central ID

  • PMC7029119

Electronic International Standard Serial Number (EISSN)

  • 1083-351X

Digital Object Identifier (DOI)

  • 10.1074/jbc.RA119.011949

Language

  • eng

Conference Location

  • United States