An expanded cell wall damage signaling network is comprised of the transcription factors Rlm1 and Sko1 in Candida albicans
An expanded cell wall damage signaling network is comprised of the transcription factors Rlm1 and Sko1 in Candida albicans
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DOI：
10.1371/journal.pgen.1008908
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发表时间：
2020-07-01
期刊：
影响因子：
4.5
通讯作者：
Rauceo, Jason M.
中科院分区：
文献类型：
--
作者：
Heredia, Marienela Y.;Ikeh, Melanie A. C.;Rauceo, Jason M.
人类真菌病原体白色念珠菌不断暴露于影响细胞壁的环境挑战。信号通路协调应激适应，对于共生和毒力至关重要。转录因子 Sko1、Cas5 和 Rlm1 控制抗真菌药物卡泊芬净引起的细胞壁应激反应。在这里，我们扩展了 Sko1 和 Rlm1 转录回路，并证明 Rlm1 激活 Sko1 细胞壁应激信号传导。与处理的野生型菌株相比，卡泊芬净诱导的 SKO1 和几个 Sko1 依赖性细胞壁完整性基因的转录在 rlm1 Delta/Delta 突变菌株中减弱，但在 cas5 Delta/Delta 突变菌株中则不然。全基因组染色质免疫沉淀 (ChIP-seq) 结果显示，在卡泊芬净存在下，许多 Sko1 和 Rlm1 直接结合靶基因，而这在之前的基因表达研究中未检测到。值得注意的目标包括涉及细胞壁完整性、渗透压和细胞聚集的基因，以及一些未表征的基因。有趣的是，我们发现在卡泊芬净存在的情况下，Rlm1 不与 SKO1 的上游基因间区域结合，表明 Rlm1 间接控制卡泊芬净诱导的 SKO1 转录。此外，我们发现卡泊芬净诱导的 SKO1 转录是通过自我激活发生的。根据我们的 ChIP-seq 数据，我们还发现了白色念珠菌特有的 Rlm1 共有基序。对于 Sko1，我们发现了一个与酿酒酵母已知的 Sko1 基序相似的共有基序。生长测定表明，SKO1 过表达可抑制 rlm1 Delta/Delta 突变株中的卡泊芬净超敏反应。此外，甘油磷酸酶 RHR2 的过度表达可抑制卡泊芬净超敏反应，特别是在 sko1 Delta/Delta 突变株中。我们的研究结果将 Sko1 和 Rlm1 信号通路联系起来，确定了 Sko1 和 Rlm1 的新生物学作用，并强调了细胞壁信号传导背后的复杂动态。作者摘要白色念珠菌是临床环境中分离出的最常见的人类真菌病原体。棘白菌素药物卡泊芬净用于治疗侵袭性念珠菌病； however, the emergence of increasing echinocandin resistance underscores the need for new antifungal strategies.阐明控制卡泊芬净诱导耐受的信号机制有可能识别出可作为新治疗靶点的候选蛋白。在这里，我们扩展了 Rlm1 和 Sko1 细胞壁转录网络，发现 Rlm1 间接调节 Sko1 信号传导。此外，我们还确定了 Sko1 和 Rlm1 在卡泊芬净适应中的特异性生物学作用，例如渗透调节和分泌。最后，我们发现甘油在卡泊芬净耐受中具有保护作用。总的来说，这些发现为白色念珠菌细胞壁信号传导的遗传和细胞基础提供了机制上的见解。
The human fungal pathogen Candida albicans is constantly exposed to environmental challenges impacting the cell wall. Signaling pathways coordinate stress adaptation and are essential for commensalism and virulence. The transcription factors Sko1, Cas5, and Rlm1 control the response to cell wall stress caused by the antifungal drug caspofungin. Here, we expand the Sko1 and Rlm1 transcriptional circuit and demonstrate that Rlm1 activates Sko1 cell wall stress signaling. Caspofungin-induced transcription of SKO1 and several Sko1-dependent cell wall integrity genes are attenuated in an rlm1 Delta/Delta mutant strain when compared to the treated wild-type strain but not in a cas5 Delta/Delta mutant strain. Genome-wide chromatin immunoprecipitation (ChIP-seq) results revealed numerous Sko1 and Rlm1 directly bound target genes in the presence of caspofungin that were undetected in previous gene expression studies. Notable targets include genes involved in cell wall integrity, osmolarity, and cellular aggregation, as well as several uncharacterized genes. Interestingly, we found that Rlm1 does not bind to the upstream intergenic region of SKO1 in the presence of caspofungin, indicating that Rlm1 indirectly controls caspofungin-induced SKO1 transcription. In addition, we discovered that caspofungin-induced SKO1 transcription occurs through self-activation. Based on our ChIP-seq data, we also discovered an Rlm1 consensus motif unique to C. albicans. For Sko1, we found a consensus motif similar to the known Sko1 motif for Saccharomyces cerevisiae. Growth assays showed that SKO1 overexpression suppressed caspofungin hypersensitivity in an rlm1 Delta/Delta mutant strain. In addition, overexpression of the glycerol phosphatase, RHR2, suppressed caspofungin hypersensitivity specifically in a sko1 Delta/Delta mutant strain. Our findings link the Sko1 and Rlm1 signaling pathways, identify new biological roles for Sko1 and Rlm1, and highlight the complex dynamics underlying cell wall signaling.Author summaryCandida albicans is the most common human fungal pathogen isolated in clinical settings. The echinocandin drug caspofungin is used to treat invasive candidiasis; however, the emergence of increasing echinocandin resistance underscores the need for new antifungal strategies. Elucidating the signaling mechanisms that govern caspofungin-induced tolerance has the potential to identify candidate proteins that could serve as novel therapeutic targets. Here, we expand the Rlm1 and Sko1 cell wall transcriptional network and find that Rlm1 indirectly regulates Sko1 signaling. Furthermore, we identify Sko1- and Rlm1-specific biological roles in caspofungin adaptation, such as osmoregulation and secretion. Lastly, we discover a protective role for glycerol in caspofungin tolerance. Overall, these findings provide mechanistic insight into the genetic and cellular bases underlying cell wall signaling in C. albicans.