Zhang Xibo, Fang Yue, Jaiseng Wurentuya, Hu Lingling, Lu Yabin, Ma Yan, Furuyashiki Tomoyuki
Division of Pharmacology, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.
Department of Biopharmaceutics, School of Pharmacy, China Medical University, Shenyang 110001, China.
Kobe J Med Sci. 2015 Oct 9;61(2):E54-63.
Tamoxifen, a selective estrogen receptor modulator used for managing breast cancer, is known to have antifungal activity. However, its molecular mechanism remains unknown. Using the fission yeast Schizosaccharomyces pombe as a model organism, we have explored the mechanism involved in antifungal action of tamoxifen. Since tamoxifen was shown to inhibit the binding of calmodulin to calcineurin in fungi, we first examined involvement of these molecules and found that overexpression of a catalytic subunit of calcineurin and its constitutively active mutant as well as calmodulin increases tamoxifen sensitivity. Since terbinafine and azoles inhibit enzymes for ergosterol biosynthesis, Erg1 and Erg11, for their antifungal actions, we also examined involvement of these molecules. Overexpression of Erg1 and Erg11 reduced the sensitivity to terbinafine and azoles, respectively, but increased tamoxifen sensitivity, suggesting that ergosterol biosynthesis is differently related to the action of tamoxifen and those of terbinafine and azoles. To elucidate molecules involved in tamoxifen action, we performed a genome-wide screen for altered sensitivity to tamoxifen using a fission yeast gene deletion library, and identified various hypersensitive and resistant mutants to this drug. Notably, these mutants are rarely overlapped with those identified in similar genetic screens with currently used antifungals, suggesting a novel mode of antifungal action. Furthermore, tamoxifen augmented antifungal actions of terbinafine and azoles, suggesting synergetic actions between these drugs. Therefore, our findings suggest that calmodulin-calcineurin pathway and ergosterol biosynthesis are related to antifungal action of tamoxifen, and propose novel targets for antifungal development as well as combined therapy with tamoxifen for fungal diseases.
他莫昔芬是一种用于治疗乳腺癌的选择性雌激素受体调节剂，已知具有抗真菌活性。然而，其分子机制尚不清楚。我们以裂殖酵母粟酒裂殖酵母作为模式生物，探索了他莫昔芬抗真菌作用的机制。由于他莫昔芬在真菌中显示出抑制钙调蛋白与钙调神经磷酸酶的结合，我们首先研究了这些分子的作用，发现钙调神经磷酸酶催化亚基及其组成型活性突变体以及钙调蛋白的过表达会增加对他莫昔芬的敏感性。由于特比萘芬和唑类通过抑制麦角甾醇生物合成酶Erg1和Erg11发挥抗真菌作用，我们也研究了这些分子的作用。Erg1和Erg11的过表达分别降低了对特比萘芬和唑类的敏感性，但增加了对他莫昔芬的敏感性，这表明麦角甾醇生物合成与他莫昔芬以及特比萘芬和唑类的作用存在不同的关系。为了阐明参与他莫昔芬作用的分子，我们使用裂殖酵母基因缺失文库对他莫昔芬敏感性改变进行了全基因组筛选，并鉴定出了对该药物的各种高敏和抗性突变体。值得注意的是，这些突变体很少与目前使用的抗真菌药物在类似遗传筛选中鉴定出的突变体重叠，这表明存在一种新的抗真菌作用模式。此外，他莫昔芬增强了特比萘芬和唑类的抗真菌作用，表明这些药物之间存在协同作用。因此，我们的研究结果表明，钙调蛋白 - 钙调神经磷酸酶途径和麦角甾醇生物合成与他莫昔芬的抗真菌作用有关，并提出了抗真菌药物开发的新靶点以及他莫昔芬与抗真菌药物联合治疗真菌疾病的方案。
