Manchester Fungal Infection Group, Division of Infection, Immunity and Respiratory Medicine, University of Manchester, Manchester, United Kingdom.
Division of Pediatric Infectious Diseases, Department of Pediatrics, Duke University Medical Center, Durham, North Carolina, USA.
Antimicrob Agents Chemother. 2017 Sep 22;61(10). doi: 10.1128/AAC.00710-17. Print 2017 Oct.
Caspofungin targets cell wall β-1,3-glucan synthesis and is the international consensus guideline-recommended salvage therapy for invasive aspergillosis. Although caspofungin is inhibitory at low concentrations, it exhibits a paradoxical effect (reversal of growth inhibition) at high concentrations by an undetermined mechanism. Treatment with caspofungin at either the growth-inhibitory concentration (0.5 μg/ml) or paradoxical growth-inducing concentration (4 μg/ml) for 24 h caused similar abnormalities, including wider, hyperbranched hyphae, increased septation, and repeated hyphal tip lysis, followed by regenerative intrahyphal growth. By 48 h, only hyphae at the colony periphery treated with the high caspofungin concentration displayed paradoxical growth. A similar high concentration of caspofungin also induced the paradoxical growth of during human A549 alveolar cell invasion. Localization of the β-1,3-glucan synthase complex (Fks1 and Rho1) revealed significant differences between cells exposed to the growth-inhibitory and paradoxical growth-inducing concentrations of caspofungin. At both concentrations, Fks1 initially mislocalized from the hyphal tips to vacuoles. However, only continuous exposure to 4 μg/ml of caspofungin for 48 h led to recovery of the normal hyphal morphology with renewed localization of Fks1 to hyphal tips. Rho1 remained at the hyphal tip after treatment with both caspofungin concentrations but was required for paradoxical growth. Farnesol blocked paradoxical growth and relocalized Fks1 and Rho1 to vacuoles. Our results highlight the importance of regenerative intrahyphal growth as a rapid adaptation to the fungicidal lytic effects of caspofungin on hyphal tips and the dynamic localization of Fks1 as part of the mechanism for the caspofungin-mediated paradoxical response in .
卡泊芬净靶向细胞壁β-1,3-葡聚糖合成，是侵袭性曲霉病国际共识指南推荐的补救治疗药物。尽管卡泊芬净在低浓度时具有抑制作用，但在高浓度时通过未知机制表现出反常效应（生长抑制的逆转）。用卡泊芬净在生长抑制浓度（0.5μg/ml）或反常生长诱导浓度（4μg/ml）处理 24 小时会引起类似的异常，包括更宽、分支更多的菌丝，增加的分隔和反复的菌丝尖端裂解，随后是菌丝内的再生生长。到 48 小时时，只有用高浓度卡泊芬净处理的菌落边缘的菌丝显示反常生长。类似的高浓度卡泊芬净也诱导了 during 对人 A549 肺泡细胞侵袭的反常生长。β-1,3-葡聚糖合酶复合物（Fks1 和 Rho1）的定位显示，暴露于卡泊芬净生长抑制和反常生长诱导浓度的细胞之间存在显著差异。在这两种浓度下，Fks1 最初从菌丝尖端错误定位到液泡。然而，只有连续暴露于 4μg/ml 的卡泊芬净 48 小时，才导致正常菌丝形态的恢复，Fks1 重新定位于菌丝尖端。Rho1 在两种卡泊芬净浓度处理后仍保留在菌丝尖端，但对反常生长是必需的。法呢醇阻断了反常生长，并将 Fks1 和 Rho1 重新定位到液泡。我们的研究结果强调了再生菌丝内生长作为对菌丝尖端杀真菌裂解作用的快速适应的重要性，以及 Fks1 的动态定位作为卡泊芬净介导的菌丝反常反应机制的一部分。
