Biology of Fungal Melanin

描述（由申请人提供）：黑色素与大多数机会性真菌病原体的毒力相关，这些病原体可导致免疫功能低下患者（包括艾滋病患者）发生危及生命的疾病。黑色素通过降低对宿主免疫机制的敏感性和破坏免疫应答的组合来增加微生物在宿主中的适应性，从而有助于毒力。此外，黑色素降低真菌对多烯和棘白菌素型抗真菌剂的敏感性，因此代表了获得性耐药性的重要组成部分。鉴于黑色素在毒力和耐药性中的重要性，控制黑色素合成和在细胞壁中组装的机制是药物发现的潜在重要靶点。最近，细胞壁黑化与暴露于γ射线照射后真菌细胞生长效应增加有关，这表明这种神秘的色素在能量转导中具有新的作用。本申请建议通过解剖人类致病真菌新型隐球菌中的黑化过程来继续我们对真菌黑色素生物学的研究。这种生物体是艾滋病患者的主要病原体，并为黑色素生物学的研究提供了一个独特的系统，因为它只在外源性底物存在的情况下才会变黑，并具有广泛的遗传工具箱。黑化过程中对外源性底物的需求为利用同位素代谢标记和核磁共振波谱研究黑色素结构提供了独特的机会。这项研究计划的目标是进一步了解黑色素的生物学，功能和结构的病原真菌。本文提出了三个具体的目标：1）确定C. neoformans与囊泡相关; 2）建立胞外囊泡、黑素体与毒力的关系;黑色素生物合成。公共卫生相关性：该项目与NIH的使命相关，因为黑色素的研究可以导致治疗真菌疾病的新疗法。此外，该研究还与人类色素组织疾病如黑色素瘤有关。在这方面，作为该研究计划的一部分，针对真菌黑色素的单克隆抗体已经在临床评估中用于治疗黑色素瘤。

DESCRIPTION (provided by applicant): Melanin pigments have been associated with virulence for most opportunistic fungal pathogens that cause life-threatening diseases in immunocompromised patients, including those with AIDS. Melanins contribute to virulence by increasing the fitness of the microbe in the host through a combination of reduced susceptibility to host immune mechanisms and subversion of the immune response. In addition, melanins reduce the susceptibility of fungi to polyene and echinocandin type antifungal agents and thus represent an important component of acquired drug resistance. Given the importance of melanin in virulence and drug resistance, the mechanisms that govern melanin synthesis and assembly in cell walls are potentially important targets for drug discovery. Recently, cell wall melanization was associated with increased fungal cell growth effects after exposure to gamma irradiation suggesting a novel role for this enigmatic pigment in energy transduction. This application proposes to continue our studies of the biology of fungal melanin by dissecting the process of melanization in the human pathogenic fungus Cryptococcus neoformans. This organism is a major pathogen for patients with AIDS and provides a unique system for the study of melanin biology because it melanizes only in the presence of an exogenous substrate and has an extensive genetic toolbox. The requirement for exogenous substrates in melanization provides a unique opportunity for studying melanin structure by using isotopic metabolic labeling and nuclear magnetic resonance spectroscopy. The goal of this research program is to further our understanding of melanin biology, function, and structure in pathogenic fungi. Three specific aims are proposed: 1) To establish that melanization in C. neoformans is vesicle-associated; 2) To establish the relationship between extracellular vesicles, melanosomes, and virulence; 3) To investigate the molecular events of C. neoformans melanin biosynthesis. PUBLIC HEALTH RELEVANCE: This project is relevant to the mission of the NIH because studies of melanin can lead to new therapies for the treatment of fungal diseases. Furthermore, the research is also relevant to human diseases of pigmented tissues such as melanoma. In this regard, a monoclonal antibody to fungal melanin made as part of this research program is already in clinical evaluation for the therapy of melanoma.