Structures of Amphotericin-Sterol Complexes

描述(由申请人提供)：该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两性霉素B(AMB)的作用模式的了解。与经典的离子通道模型不同，本方案中的初步研究表明，AMB形成大的膜外聚集体，从脂质双层中提取甾醇，从而杀死细胞。这一新颖的“甾醇海绵”模型阐明了一个新的、更具可操作性的路线图，以提高治疗指数，即最大限度地提高AMB甾醇海绵与真菌(麦角甾醇)与人类(胆固醇)中发现的类固醇的相对结合亲和力。目的1是确定AMB甾醇海绵的结构，该海绵是在生理上相关的脂双层存在下组装的。目的2确定AMB海绵与麦角甾醇和胆固醇的络合物的结构。目的3确定由新近发现的Amb的新衍生物AmBMU衍生的甾醇海绵和相应的麦角甾醇复合体的结构，该化合物与麦角固醇结合，但不结合胆固醇，对人体细胞无毒，并在体外和小鼠体内保持较强的抗真菌活性。总而言之，这些研究将提供AMB生物活性基础上的原子相互作用的高分辨率图景，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成为可能。这些研究还将进一步阐明临床验证的耐药耐药抗菌作用的基本特征，并为其他生物相关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是治疗系统性真菌感染的有效但毒性很高的黄金标准疗法，尽管半个多世纪的临床应用广泛，但这种药物唯一地避免了微生物耐药性的出现。因此，更好地了解Amb是如何发挥其生物活性的，对于指导合理开发具有改善治疗指数的衍生物以及其他耐药抗菌剂至关重要。

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.