Regulation of ß(1,3)-glucan exposure in Candida albicans

白色念珠菌中α(1,3)-葡聚糖暴露的调节

基本信息

批准号：
10161731
负责人：
Todd B Reynolds
金额：
$ 49.51万
依托单位：
UNIVERSITY OF TENNESSEE KNOXVILLE
依托单位国家：
美国
项目类别：
财政年份：
2020
资助国家：
美国
起止时间：
2020-05-08 至 2025-04-30
项目状态：
未结题

来源：
https://reporter.nih.gov/project-details/10161731
关键词：
ACE2 Address Alleles Antifungal Agents Antifungal Therapy Architecture Biology Candida Candida albicans Carbohydrates Caspofungin Cell Wall Cells Cellular biology Chitin Cytolysis Decision Making Detection Epitopes Exhibits Feedback Genes Genetic Genetic Epistasis Genetic Transcription Glucans Glycoproteins Goals Health Human Hyperactivity Immune Immune response Immune system Immunologic Receptors In Vitro Infection Life LoxP-flanked allele MAP Kinase Modules Macrophage-1 Antigen Mammals Mannans Masks Mediating Mitogen-Activated Protein Kinases Molecular Mus Mycoses Pathway interactions Patient-Focused Outcomes Pharmaceutical Preparations Polymers Proteins Regulation Research Services Signal Pathway Signal Transduction Stress Systemic infection Techniques Technology Testing Transgenic Mice Virulence cell type dectin 1 experimental study fungus genetic approach glucan synthase macrophage mortality mutant neutrophil novel overexpression receptor tool trait transcription factor upstream kinase

项目摘要

Candida albicans and related Candida spp. are responsible for ~400,000 invasive infections/year, which have an ~50% mortality rate. A crucial virulence trait of C. albicans, and other fungi, is the ability to diminish their detection by their hosts. The cell wall carbohydrate ß(1,3)-glucan is an important epitope that the immune systems of humans and other mammals use to recognize and respond to fungal infections through receptors like Dectin-1 and complement receptor 3 (CR3). Fungi like C. albicans diminish their detection from immune cells through masking ß(1,3)-glucan under an outer layer of mannosylated glycoproteins (mannan). The virulence of C. albicans is compromised in conditions where ß(1,3)-glucan is more exposed (unmasked). For example, echinocandin antifungal drugs, like caspofungin, inhibit ß(1,3)-glucan synthase and cause cell lysis in vitro, but also induce exposure of ß(1,3)-glucan, even at sublethal concentrations. In addition, a number of mutants that exhibit increased exposure of ß(1,3)-glucan have decreased virulence. However, a major research challenge is to understand the impact of ß(1,3)-glucan exposure on virulence during caspofungin treatment. It has been difficult to differentiate between cidal effects of the drug and the impact of ß(1,3)-glucan exposure. A challenge closely related to this is that the mechanism by which caspofungin causes ß(1,3)-glucan exposure is unknown. We have found that we can decouple caspofungin's cidal effects from unmasking, which allows us to address both of these challenges. This can be done by activating caspofungin-responsive signaling pathways using a genetic approach rather than the drug, and we have discovered that at least one of these pathways causes unmasking. The Cek1 MAP kinase (MAPK) pathway is activated by caspofungin treatment, and we have discovered that genetic activation of this cascade causes unmasking when hyperactivated, even in the absence of caspofungin. However, unlike the drug, activation of this pathway does not compromise viability. Thus, we can meet the second challenge by using this pathway to dissect the mechanism through which unmasking occurs. Moreover, we can meet the first challenge by using the Cek1 pathway as tool to probe how the immune system responds to unmasking during mouse systemic infections because, unlike caspofungin, it is not cidal. We will address these challenges in three specific aims. In Aim 1 we will elucidate the mechanisms by which the Cek1 cascade regulates ß(1,3)-glucan exposure. There are two main transcription factors downstream of Cek1 and we will determine how the pathway chooses a particular one (Cph1) using a combination of genetic, epistasis, and cell biology techniques that will identify how Cek1- Cph1 is activated to cause unmasking. In Aim 2 we will determine how transcriptional targets of Cek1-Cph1 alter the cell wall to cause unmasking. In Aim 3, we will elucidate how exposure of ß(1,3)-glucan causes decreased virulence in mice. We will use transgenic mice to define how neutrophils, macrophages, Dectin-1 and/or CR3 participate to reduce the virulence of unmasked C. albicans.

白色念珠菌和相关念珠菌属每年造成约 400,000 例侵袭性感染，其中白色念珠菌和其他真菌的一个重要毒力特征是降低其死亡率的能力，约为 50%。细胞壁碳水化合物β(1,3)-葡聚糖是免疫系统的重要表位。人类和其他哺乳动物的系统用于通过受体识别和应对真菌感染 Dectin-1 和补体受体 3 (CR3) 等真菌会减少免疫检测。通过将 ß(1,3)-葡聚糖掩蔽在甘露糖化糖蛋白（甘露聚糖）外层下来对细胞进行作用。在 ß(1,3)-葡聚糖更多暴露（暴露）的条件下，白色念珠菌的毒力会受到损害。例如，棘白菌素抗真菌药物，如卡泊芬净，可抑制 ß(1,3)-葡聚糖合酶并导致细胞裂解。在体外，甚至在亚致死浓度下也会诱导 ß(1,3)-葡聚糖的暴露。然而，β(1,3)-葡聚糖暴露量增加的突变体的毒力降低。研究挑战是了解 ß(1,3)-葡聚糖暴露对卡泊芬净毒力的影响很难区分药物的杀伤作用和 ß(1,3)-葡聚糖的影响。与此密切相关的一个挑战是卡泊芬净引起β(1,3)-葡聚糖的机制。我们发现我们可以将卡泊芬净的杀伤作用与暴露作用分开，这使我们能够通过激活卡泊芬净响应来解决这两个挑战。使用遗传方法而不是药物来研究信号通路，我们发现至少其中一种这些途径会导致 Cek1 MAP 激酶 (MAPK) 途径被卡泊芬净激活。治疗，我们发现这个级联的基因激活会导致暴露即使在没有卡泊芬净的情况下，该通路也会过度激活。然而，与该药物不同的是，该通路的激活确实会发生。因此，我们可以通过使用这条途径来剖析来应对第二个挑战。此外，我们可以通过使用 Cek1 来应对第一个挑战。通路作为工具来探究免疫系统如何响应小鼠全身感染期间的暴露因为与卡泊芬净不同，它不具有杀灭作用，我们将在目标 1 中解决这些挑战。我们将阐明 Cek1 级联调节 ß(1,3)-葡聚糖暴露的机制有两种。 Cek1 下游的主要转录因子，我们将确定该途径如何选择特定的一个 (Cph1) 使用遗传、上位性和细胞生物学技术的组合来识别 Cek1- Cph1 被激活以导致暴露。在目标 2 中，我们将确定 Cek1-Cph1 的转录靶标如何。在目标 3 中，我们将阐明暴露 ß(1,3)-葡聚糖是如何导致的。我们将使用转基因小鼠来定义中性粒细胞、巨噬细胞、Dectin-1 的毒性。和/或CR3参与降低未掩蔽的白色念珠菌的毒力。