Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA.
Division of Cancer Biology, The Cancer Institute of JFCR, Koto-ku, Tokyo 135-8550, Japan.
Genetics. 2021 Jul 14;218(3). doi: 10.1093/genetics/iyab075.
The fungal pathogen Candida albicans is surrounded by a cell wall that is the target of caspofungin and other echinocandin antifungals. Candida albicans can grow in several morphological forms, notably budding yeast and hyphae. Yeast and hyphal forms differ in cell wall composition, leading us to hypothesize that there may be distinct genes required for yeast and hyphal responses to caspofungin. Mutants in 27 genes reported previously to be caspofungin hypersensitive under yeast growth conditions were all caspofungin hypersensitive under hyphal growth conditions as well. However, a screen of mutants defective in transcription factor genes revealed that Cup9 is required for normal caspofungin tolerance under hyphal and not yeast growth conditions. In a hyphal-defective efg1Δ/Δ background, Cup9 is still required for normal caspofungin tolerance. This result argues that Cup9 function is related to growth conditions rather than cell morphology. RNA-seq conducted under hyphal growth conditions indicated that 361 genes were up-regulated and 145 genes were down-regulated in response to caspofungin treatment. Both classes of caspofungin-responsive genes were enriched for cell wall-related proteins, as expected for a response to disruption of cell wall integrity and biosynthesis. The cup9Δ/Δ mutant, treated with caspofungin, had reduced RNA levels of 40 caspofungin up-regulated genes, and had increased RNA levels of 8 caspofungin down-regulated genes, an indication that Cup9 has a narrow rather than global role in the cell wall integrity response. Five Cup9-activated surface-protein genes have roles in cell wall integrity, based on mutant analysis published previously (PGA31 and IFF11) or shown here (ORF19.3499, ORF19.851, or PGA28), and therefore may explain the hypersensitivity of the cup9Δ/Δmutant to caspofungin. Our findings define Cup9 as a new determinant of caspofungin susceptibility.
白色念珠菌是一种真菌病原体，其细胞外被细胞壁所包裹，而卡泊芬净和其他棘白菌素类抗真菌药物的作用靶标就是细胞壁。白色念珠菌可以呈现出几种不同的形态，其中包括芽生酵母和菌丝。酵母和菌丝的形态在细胞壁组成上存在差异，这使我们推测，可能存在特定的基因，这些基因对于酵母和菌丝对卡泊芬净的反应是必需的。在先前的研究中，有 27 个基因被报道在酵母生长条件下对卡泊芬净敏感，在菌丝生长条件下，这些基因的突变体也同样对卡泊芬净敏感。然而，在转录因子基因缺失突变体的筛选中，我们发现 Cup9 对于菌丝和酵母生长条件下正常的卡泊芬净耐受都是必需的。在菌丝缺陷型 efg1Δ/Δ 背景中，Cup9 仍然是正常卡泊芬净耐受所必需的。这一结果表明，Cup9 的功能与生长条件有关，而不是与细胞形态有关。在菌丝生长条件下进行的 RNA-seq 分析表明，有 361 个基因被上调，145 个基因被下调，这是对卡泊芬净处理的响应。这两类对卡泊芬净有反应的基因都富集了细胞壁相关蛋白，这与细胞外被完整性和生物合成受到破坏的反应是一致的。用卡泊芬净处理 cup9Δ/Δ 突变体后，有 40 个上调的卡泊芬净反应基因的 RNA 水平降低，8 个下调的卡泊芬净反应基因的 RNA 水平升高，这表明 Cup9 在细胞外被完整性反应中只起了一个狭窄而非全局的作用。基于先前发表的突变体分析（PGA31 和 IFF11）或此处显示的结果（ORF19.3499、ORF19.851 或 PGA28），有 5 个 Cup9 激活的表面蛋白基因在细胞壁完整性中发挥作用，因此可能解释了 cup9Δ/Δ 突变体对卡泊芬净的敏感性。我们的研究结果将 Cup9 定义为卡泊芬净敏感性的一个新决定因素。
