Key Laboratory of Cell Proliferation and Regulation Biology, College of Life Sciences, Beijing Normal University, Beijing, China.
Agency for Science, Technology and Research, Institute of Molecular and Cell Biology, Singapore, Singapore.
Mol Microbiol. 2019 Mar;111(3):604-620. doi: 10.1111/mmi.14176. Epub 2019 Jan 8.
β-1,6-glucan is an important component of the fungal cell wall. The β-1,6-glucan synthase gene KRE6 was thought to be essential in the fungal pathogen Candida albicans because it could not be deleted in previous efforts. Also, the role of its homolog SKN1 was unclear because its deletion caused no defects. Here, we report the construction and characterization of kre6Δ/Δ, skn1Δ/Δ and kre6Δ/Δ skn1Δ/Δ mutants in C. albicans. While deleting KRE6 or SKN1 had no obvious phenotypic consequence, deleting both caused slow growth, cell separation failure, cell wall abnormalities, diminished hyphal growth, poor biofilm formation and loss of virulence in mice. Furthermore, the GPI-linked cell surface proteins Hwp1 and the invasin Als3 or Ssa1 were not detected in kre6Δ/Δ skn1Δ/Δ mutant. In GMM medium, RT-qPCR and western blotting revealed a constitutive expression of KRE6 and growth conditions-associated activation of SKN1. Like many hypha-specific genes, SKN1 is repressed by Nrg1, but its activation does not involve the transcription factor Efg1. Dysregulation of SKN1 reduces C. albicans ability to damage epithelial and endothelial cells and attenuates its virulence. Given the vital role of β-1,6-glucan synthesis in C. albicans physiology and virulence, Kre6 and Skn1 are worthy targets for developing antifungal agents.
β-1,6-葡聚糖是真菌细胞壁的重要组成部分。β-1,6-葡聚糖合酶基因 KRE6 被认为在真菌病原体白色念珠菌中是必需的，因为之前的研究无法删除该基因。此外，其同源物 SKN1 的作用尚不清楚，因为其缺失不会造成缺陷。在这里，我们报告了白色念珠菌中 kre6Δ/Δ、skn1Δ/Δ 和 kre6Δ/Δ skn1Δ/Δ 突变体的构建和特征。虽然删除 KRE6 或 SKN1 没有明显的表型后果，但删除两者都会导致生长缓慢、细胞分离失败、细胞壁异常、菌丝生长减弱、生物膜形成不良以及在小鼠中丧失毒力。此外，kre6Δ/Δ skn1Δ/Δ 突变体中未检测到 GPI 连接的细胞表面蛋白 Hwp1 和侵袭素 Als3 或 Ssa1。在 GMM 培养基中，RT-qPCR 和 Western blot 显示 KRE6 的组成型表达和与生长条件相关的 SKN1 的激活。像许多菌丝特异性基因一样，SKN1 被 Nrg1 抑制，但它的激活不涉及转录因子 Efg1。SKN1 的失调降低了白色念珠菌损伤上皮和内皮细胞的能力，并减弱了其毒力。鉴于 β-1,6-葡聚糖合成在白色念珠菌生理学和毒力中的重要作用，Kre6 和 Skn1 是开发抗真菌药物的有价值的靶标。
