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Melanin as a potential cryptococcal defence against microbicidal proteins.
T L Doering1, J D Nosanchuk, W K Roberts
1The Department of Pharmacology, Cornell University Medical College, New York, NY 10021, USA. tdoering@mail.med.cornell.edu
Medical Mycology
|July 28, 1999
Summary
Cryptococcus neoformans melanin binds proteins and protects the fungus from microbicidal peptides. This suggests melanin plays a role in fungal virulence by neutralizing host defenses.
Area of Science:
- Medical Mycology
- Biochemistry
Background:
- Cryptococcus neoformans is a significant fungal pathogen.
- Melanin production in C. neoformans is linked to virulence, but its precise role is unknown.
Purpose of the Study:
- To investigate the protein-binding capacity of C. neoformans melanin.
- To determine if melanin protects against microbicidal peptides.
Main Methods:
- Studied melanin-protein interactions under varying pH and concentrations.
- Assessed the susceptibility of melanized C. neoformans cells to defensins, protegrins, and magainins.
- Investigated the effect of melanin on the fungicidal activity of microbicidal peptides.
Main Results:
- C. neoformans melanin binds diverse fungal and mammalian proteins in a pH- and concentration-dependent manner.
- Melanized cells exhibited reduced susceptibility to killing by three distinct microbicidal peptides.
- Pre-incubation of peptides with melanin particles diminished their fungicidal activity.
Conclusions:
- C. neoformans melanin sequesters microbicidal peptides, abrogating their activity.
- Melanin's ability to bind proteins and neutralize antimicrobial peptides suggests a protective role in fungal pathogenesis.