Key Laboratory of Vector Biology and Pathogen Control of Zhejiang Province, Huzhou University, Huzhou Central Hospital, Huzhou, P. R. China.
Center for Global Health, School of Public Health, Nanjing Medical University, 101 Longmian Avenue, Nanjing, 211166, P. R. China.
J Microbiol. 2021 Jan;59(1):64-75. doi: 10.1007/s12275-021-0347-x. Epub 2020 Nov 17.
Aspergillus fumigatus is a well-known opportunistic pathogen that causes invasive aspergillosis (IA) infections with high mortality in immunosuppressed individuals. Morphogenesis, including hyphal growth, conidiation, and cell wall biosynthesis is crucial in A. fumigatus pathogenesis. Based on a previous random insertional mutagenesis library, we identified the putative polysaccharide synthase gene Afcps1 and its para-log Afcps2. Homologs of the cps gene are commonly found in the genomes of most fungal and some bacterial pathogens. Afcps1/cpsA is important in sporulation, cell wall composition, and virulence. However, the precise regulation patterns of cell wall integrity by Afcps1/cpsA and further effects on the immune response are poorly understood. Specifically, our in-depth study revealed that Afcps1 affects cell-wall stability, showing an increased resistance of ΔAfcps1 to the chitinmicrofibril destabilizing compound calcofluor white (CFW) and susceptibility of ΔAfcps1 to the β-(1,3)-glucan synthase inhibitor echinocandin caspofungin (CS). Additionally, deletion of Afcps2 had a normal sporulation phenotype but caused hypersensitivity to Na stress, CFW, and Congo red (CR). Specifically, quantitative analysis of cell wall composition using high-performance anion exchange chromatography-pulsed amperometric detector (HPAEC-PAD) analysis revealed that depletion of Afcps1 reduced cell wall glucan and chitin contents, which was consistent with the down-regulation of expression of the corresponding biosynthesis genes. Moreover, an elevated immune response stimulated by conidia of the ΔAfcps1 mutant in marrow-derived macrophages (BMMs) during phagocytosis was observed. Thus, our study provided new insights into the function of polysaccharide synthase Cps1, which is necessary for the maintenance of cell wall stability and the adaptation of conidia to the immune response of macrophages in A. fumigatus.
烟曲霉是一种众所周知的机会致病菌，可在免疫抑制个体中引起侵袭性曲霉病（IA）感染，死亡率很高。形态发生，包括菌丝生长、分生孢子形成和细胞壁生物合成，在烟曲霉发病机制中至关重要。基于先前的随机插入突变文库，我们鉴定了假定的多糖合成酶基因 Afcps1 及其旁系同源物 Afcps2。cps 基因的同源物通常存在于大多数真菌和一些细菌病原体的基因组中。Afcps1/cpsA 在孢子形成、细胞壁组成和毒力中很重要。然而，Afcps1/cpsA 对细胞壁完整性的精确调节模式以及对免疫反应的进一步影响知之甚少。具体来说，我们的深入研究表明，Afcps1 影响细胞壁稳定性，ΔAfcps1 对几丁质微纤不稳定化合物 Calcofluor White（CFW）的抗性增加，对β-（1,3）-葡聚糖合酶抑制剂棘白菌素 Caspofungin（CS）的敏感性增加。此外，Afcps2 的缺失具有正常的孢子形成表型，但对 Na 应激、CFW 和刚果红（CR）敏感。具体来说，使用高效阴离子交换色谱-脉冲安培检测（HPAEC-PAD）分析对细胞壁成分进行定量分析表明，Afcps1 的缺失降低了细胞壁葡聚糖和几丁质含量，这与相应生物合成基因的下调表达一致。此外，在吞噬作用过程中，观察到 ΔAfcps1 突变体分生孢子在骨髓来源的巨噬细胞（BMMs）中引起的免疫反应增强。因此，我们的研究为多糖合成酶 Cps1 的功能提供了新的见解，Cps1 对于维持细胞壁稳定性和分生孢子适应烟曲霉中巨噬细胞的免疫反应是必要的。
