Effect of sterol side chain on ion channel formation by amphotericin B in lipid bilayers.
Effect of sterol side chain on ion channel formation by amphotericin B in lipid bilayers.
复制标题
甾醇侧链对两性霉素 B 在脂质双层中形成离子通道的影响。
作者：
Nakagawa;Y.;Umegawa;Y.;Takano;T.;Tsuchikawa;H.;Matsumori;N.;and Murata;M.
两性霉素B(Amb)是临床上使用最有效的抗真菌药物之一。AMB与膜甾醇相互作用增加了真菌膜的通透性；然而，AMB如何选择性地识别细胞膜中的真菌甾醇--麦角甾醇(Erg)--仍不清楚。在这项研究中，我们通过K+内流实验测试了一系列与Erg具有相同脂环结构但侧链结构不同的Erg类似物，研究了Erg侧链对Amb活性的影响。结果清楚地表明，甾醇侧链对于Amb对Erg的选择性和AmB-甾醇离子通道的活性是必不可少的。与我们之前发现药物与ERG之间直接相互作用的结果一致，这些数据表明Amb直接识别甾醇侧链结构，从而促进Amb形成离子通道。此外，ERG侧链上的C24甲基和Δ22双键对与Amb的相互作用同样重要。构象分析表明，C24甲基增加了侧链的范德华接触面积，而Δ22双键限制了侧链的构象，使侧链与刚性AMB苷元的范德华接触面积最大。本研究为AMB对真菌ERG的选择性作用机制提供了直接的实验证据。
Amphotericin B (AmB) is one of the most efficient antimycotic drugs used in clinical practice. AmB interacts with membrane sterols increasing permeability of fungal membranes; however, it is still unclear how AmB selectively recognizes the fungal sterol, ergosterol (Erg), over other sterols in cell membranes. In this study, we investigated the effect of an Erg side chain on AmB activity by testing a series of Erg analogues that shared the same alicyclic structure as Erg but varied in the side chain structure by using the K+influx assay. The results clearly showed that the sterol side chain is essential for AmB selectivity toward Erg and for the activity of AmB-sterol ion channels. In agreement with our previous findings showing the direct interaction between the drug and Erg, these data suggested that AmB directly recognizes the sterol side chain structure, consequently promoting the formation of ion channels by AmB. Furthermore, the C24 methyl group and Δ22 double bond in the side chain of Erg are equally important for the interaction with AmB. Conformational analysis revealed that the C24 methyl group contributes to the interaction by increasing the van der Waals (VDW) contact area of the side chain, while the Δ22 double bond restricts the side chain conformation to maximize the VDW contact with the rigid AmB aglycone. This study provides direct experimental evidence of the mechanism of AmB selectivity toward fungal Erg.