School of Chemistry, Raymond & Beverly Sackler Faculty of Exact Sciences, Tel Aviv University, Tel Aviv 6997801, Israel.
ACS Chem Biol. 2022 May 20;17(5):1155-1163. doi: 10.1021/acschembio.2c00060. Epub 2022 Apr 11.
Echinocandin antifungal drugs have a broad spectrum of activities and excellent safety profiles. These agents noncompetitively inhibit the formation of the major polysaccharide component of the fungal cell wall, a reaction catalyzed by the membrane-bound β-glucan synthase (GS) protein complex. We have developed fluorescent probes of three echinocandin drugs: caspofungin (CSF), anidulafungin (ANF), and rezafungin (RZF). Fluorescent echinocandins had the same spectrum of activities as the parent echinocandins, supporting the fact that conjugation of the dye did not alter their mode of action. Of the three echinocandins, ANF has the most potent in vitro activity. Investigation of the subcellular distribution of the fluorescent echinocandins in live yeast cells revealed that despite their high structural similarity, each of the drug probes had a unique subcellular distribution pattern. Fluorescent CSF, which is the least potent of the three echinocandins, accumulated in vacuoles; fluorescent ANF localized in the extracellular environment and on the yeast cell surface where the target GS resides; and fluorescent RZF was partitioned between the surface and the vacuole over time. Recovery of fluorescent CSF from cells revealed substantial degradation over time; functional vacuoles were necessary for this degradation. Under the same conditions, fluorescent ANF was not degraded. This study supports the "target-oriented drug subcellular localization" principle. In the case of echinocandins, localization to the cell surface can contribute to improved potency and accumulation in vacuoles induces degradation leading to drug deactivation.
棘白菌素类抗真菌药物具有广谱的活性和出色的安全性。这些药物非竞争性地抑制真菌细胞壁主要多糖成分的形成，这是由膜结合β-葡聚糖合酶（GS）蛋白复合物催化的反应。我们开发了三种棘白菌素类药物的荧光探针：卡泊芬净（CSF）、阿尼芬净（ANF）和瑞他康唑（RZF）。荧光棘白菌素类药物与母体棘白菌素类药物具有相同的活性谱，这支持了染料缀合不会改变其作用模式的事实。在这三种棘白菌素类药物中，ANF 的体外活性最强。对活酵母细胞中荧光棘白菌素类药物的亚细胞分布的研究表明，尽管它们具有很高的结构相似性，但每种药物探针都具有独特的亚细胞分布模式。荧光 CSF 是三种棘白菌素类药物中活性最低的，它在液泡中积累；荧光 ANF 定位于细胞外环境和靶标 GS 所在的酵母细胞表面；而荧光 RZF 则随时间在表面和液泡之间分配。从细胞中回收荧光 CSF 表明随着时间的推移会发生大量降解；功能液泡是这种降解所必需的。在相同条件下，荧光 ANF 不会降解。这项研究支持了“靶向药物亚细胞定位”的原则。在棘白菌素类药物的情况下，定位于细胞表面可以提高药物的效力，而在液泡中的积累则会诱导降解，从而导致药物失活。
