Structures of Amphotericin-Sterol Complexes

描述（由申请人提供）：本项目旨在促进对临床上重要但也具有高毒性的抗真菌药物阿朴霉素B（AmB）的作用方式的理解。替代经典的离子通道模型，在这个建议的初步研究表明，AmB形成大的膜外聚集体，从脂质双层提取甾醇，从而杀死细胞。这种新的“甾醇海绵”模型阐明了一种新的和更可行的路线图，以改善治疗指数，即，最大化AmB甾醇海绵对真菌中发现的甾醇（麦角甾醇）与人中发现的甾醇（胆固醇）的相对结合亲和力。目的1是确定AmB甾醇海绵的结构，在生理相关的脂质双层的存在下组装。目的二是确定AmB海绵与麦角甾醇、胆固醇的配合物的结构。目的3是确定甾醇海绵和相应的麦角甾醇复合物的结构，该复合物衍生自一种新的AmB衍生物AmBMU，其最近被发现并显示结合麦角甾醇但不结合胆固醇，对人细胞无毒，并在体外和小鼠中保留有效的抗真菌活性。总的来说，这些研究将提供一个高分辨率的原子相互作用的图片，基础上的生物活性的AmB，从而有力地使这种临床上至关重要的天然产品的毒性较低的衍生物的合理开发。这些研究还将进一步阐明如何实现临床验证的耐药性难治性抗菌作用的基本特征，并为其他生物学相关小分子-小分子的前沿追求奠定基础。 分子相互作用 与人类健康的相关性。两性霉素B是治疗全身性真菌感染的强效但不幸的是高毒性的金标准疗法，尽管该药物已被广泛应用于临床超过半个世纪，但其独特地避免了微生物耐药性的出现。因此，更好地了解AmB如何发挥其生物活性对于指导具有改善的治疗指数的衍生物以及其他耐药难治性抗菌药物的合理开发至关重要。

DESCRIPTION (provided by applicant): This project aims to advance understanding of the mode of action of the clinically vital but also highly toxic antifungal drug amphotericin B (AmB). Alternative to the classic ion channel model, preliminary studies in this proposal show that AmB forms large extramembranous aggregates that extract sterols from lipid bilayers and thereby kill cells. This novel "sterol sponge" model illuminates a new and more actionable roadmap to an improved therapeutic index, i.e., maximize the relative binding affinity of the AmB sterol sponge for the sterol found in fungi (ergosterol) vs. humans (cholesterol). Aim 1 is to determine the structure of the AmB sterol sponge, assembled in the presence of physiologically relevant lipid bilayers. Aim 2 is to determine the structures of the complexes of the AmB sponge with ergosterol and cholesterol. Aim 3 is to determine the structure of the sterol sponge and corresponding ergosterol complex derived from a new derivative of AmB, AmBMU, which was recently discovered and shown to bind ergosterol but not cholesterol, to be non-toxic to human cells, and to retain potent antifungal activity in vitro and in mice. Collectively, these studies wll provide a high-resolution picture of the atomistic interactions that underlie the biological activities of AmB and thus powerfully enable the rational development of less toxic derivatives of this clinically vital natural product. These studies will also further illuminate the fundamental features of how clinically validated resistance-refractory antimicrobial action can be achieved and lay the foundation for the frontier pursuit of other biologically relevant small molecule-small molecule interactions. Relevance to Human Health. Amphotericin B is the powerful but unfortunately highly toxic gold standard therapy for treatment of systemic fungal infections, and this drug has uniquely evaded the emergence of microbial resistance despite more than half a century of widespread clinical utilization. Better understanding how AmB exerts its biological activities is thus critical for guiding the rational development of derivatives with an improved therapeutic index as well as other resistance-refractory antimicrobial agents.