Doan Alexander G, Schafer Jessica E, Douglas Casey M, Quintanilla Matthew S, Morse Meredith E, Edwards Harley, Huso Walker D, Gray Kelsey J, Lee JungHun, Dayie Joshua K, Harris Steven D, Marten Mark R
Department of Chemical, Biochemical, and Environmental Engineering, University of Maryland, Baltimore County, Baltimore, Maryland, USA.
Department of Plant Pathology, Entomology, and Microbiology, Iowa State University, Ames, Iowa, USA.
mSphere. 2025 Jan 28;10(1):e0064124. doi: 10.1128/msphere.00641-24. Epub 2024 Dec 13.
This study investigates a previously unreported stress signal transduced as crosstalk between the cell wall integrity (CWI) pathway and the septation initiation network (SIN). Echinocandins, which target cell wall synthesis, are widely used to treat mycoses. Their efficacy, however, is species specific. Our findings suggest that this is due largely to CWI-SIN crosstalk and the ability of filamentous species to fortify with septa in response to echinocandin stress. To better understand this crosstalk, we used a microscopy-based assay to measure septum density, aiming to understand the septation response to cell wall stress. The echinocandin micafungin, an inhibitor of β-(1,3)-glucan synthase, was employed to induce this stress. We observed a strong positive correlation between micafungin treatment and septum density in wild-type strains. This finding suggests that CWI activates SIN under cell wall stress, increasing septum density to protect against cell wall failure. More detailed investigations, with targeted knockouts of CWI and SIN signaling proteins, enabled us to identify crosstalk occurring between the CWI kinase, MpkA, and the SIN kinase, SepH. This discovery of the previously unknown crosstalk between the CWI and SIN pathways not only reshapes our understanding of fungal stress responses, but also unveils a promising new target pathway for the development of novel antifungal strategies.
Echinocandin-resistant species pose a major challenge in clinical mycology by rendering one of only four lines of treatment, notably one of the two that are well-tolerated, ineffective in treating systemic mycoses of these species. Previous studies have demonstrated that echinocandins fail against highly polarized fungi because they target only apical septal compartments. It is known that many filamentous species respond to cell wall stress with hyperseptation. In this work, we show that echinocandin resistance hinges on this dynamic response, rather than on innate septation alone. We also describe, for the first time, the signaling pathway used to deploy the hyperseptation response. By disabling this pathway, we were able to render mycelia susceptible to echinocandin stress. This work enhances our microbiological understanding of filamentous fungi and introduces a potential target to overcome echinocandin-resistant species.
本研究调查了一种先前未报道的应激信号，该信号作为细胞壁完整性（CWI）途径和隔膜起始网络（SIN）之间的串扰进行转导。靶向细胞壁合成的棘白菌素被广泛用于治疗真菌病。然而，它们的疗效具有物种特异性。我们的研究结果表明，这在很大程度上是由于CWI-SIN串扰以及丝状物种在棘白菌素应激下用隔膜强化自身的能力。为了更好地理解这种串扰，我们使用了基于显微镜的检测方法来测量隔膜密度，旨在了解对细胞壁应激的隔膜形成反应。使用β-(1,3)-葡聚糖合酶抑制剂棘白菌素米卡芬净来诱导这种应激。我们在野生型菌株中观察到米卡芬净处理与隔膜密度之间存在很强的正相关。这一发现表明，在细胞壁应激下，CWI会激活SIN，增加隔膜密度以防止细胞壁破裂。通过对CWI和SIN信号蛋白进行靶向敲除进行更详细的研究，使我们能够确定CWI激酶MpkA和SIN激酶SepH之间发生的串扰。这一先前未知的CWI和SIN途径之间串扰的发现不仅重塑了我们对真菌应激反应的理解，还揭示了一条有前景的新靶标途径，可用于开发新型抗真菌策略。
耐棘白菌素的物种在临床真菌学中构成了重大挑战，因为它们使仅有的四条治疗线之一，尤其是两条耐受性良好的治疗线之一，在治疗这些物种的系统性真菌病时无效。先前的研究表明，棘白菌素对高度极化的真菌无效，因为它们仅靶向顶端隔膜隔室。已知许多丝状物种会通过过度形成隔膜来应对细胞壁应激。在这项工作中，我们表明棘白菌素耐药性取决于这种动态反应，而不仅仅取决于先天的隔膜形成。我们还首次描述了用于部署过度隔膜形成反应的信号通路。通过阻断这条通路，我们能够使菌丝体对棘白菌素应激敏感。这项工作增强了我们对丝状真菌的微生物学理解，并引入了一个潜在的靶点来克服耐棘白菌素的物种。
