Cryptococcus neoformans melanization incorporates multiple catecholamines to produce polytypic melanin

Area of Science:

• Mycology
• Biochemistry
• Immunology

Background:

• Melanin is a critical virulence factor in pathogenic fungi, aiding resistance to immune clearance.
• Cryptococcus neoformans synthesizes melanin from catecholamine precursors during human infections, but the specific melanin type in meningoencephalitis remains unknown.

Purpose of the Study:

• To investigate the types of melanin produced by Cryptococcus neoformans using catecholamines found in brain tissue.
• To determine if fungal melanin synthesized in vivo is composed of a single precursor or a mixture.

Main Methods:

• Analysis of melanization using animal brain tissue and synthetic catecholamine mixtures.
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy to characterize melanin pigment.
• Use of radiolabeled catecholamines to probe melanin biosynthesis.

Main Results:

• Melanin production exceeded expectations for dopamine alone, indicating incorporation of additional catecholamines.
• Cryptococcus neoformans simultaneously incorporated multiple catecholamines, resulting in polytypic melanin.
• Melanin derived from individual or mixed catecholamines offered comparable protection against UV light and oxidants.

Conclusions:

• Fungal melanin synthesized in vivo is likely a polymer of mixed catecholamine precursors, varying with tissue composition.
• Melanin produced using dopamine as a precursor yields pigment comparable to that formed during infection.
• This study reveals greater structural complexity in natural cryptococcal melanin than previously understood.