白念珠菌β-葡聚糖的暴露受真菌 CEK1 介导的丝裂原活化蛋白激酶途径的控制,该途径调节通过 dectin-1 触发的免疫反应。

Candida albicans beta-glucan exposure is controlled by the fungal CEK1-mediated mitogen-activated protein kinase pathway that modulates immune responses triggered through dectin-1.

机构信息

Unidad de Biología Molecular, Hospital Universitario de la Princesa, 28006 Madrid, Spain.

出版信息

Infect Immun. 2010 Apr;78(4):1426-36. doi: 10.1128/IAI.00989-09. Epub 2010 Jan 25.

Abstract

Innate immunity to Candida albicans depends upon the recognition of molecular patterns on the fungal cell wall. However, the masking of major components such as beta-glucan seems to be a mechanism that fungi have evolved to avoid immune cell recognition through the dectin-1 receptor. Although the role of C. albicans mitogen-activated protein kinase (MAPK) pathways as virulence determinants has been established previously with animal models, the mechanism involved in this behavior is largely unknown. In this study we demonstrate that a disruption of the C. albicans extracellular signal-regulated kinase (ERK)-like 1 (CEK1)-mediated MAPK pathway causes enhanced cell wall beta-glucan exposure, triggering immune responses more efficiently than the wild type, as measured by dectin-1-mediated specific binding and human dendritic cell (hDC)- and macrophage-mediated phagocytosis, killing, and activation of intracellular signaling pathways. At the molecular level, the disruption of CEK1 resulted in altered spleen tyrosine kinase (Syk), Raf-1, and ERK1/2 activations together with IkappaB degradation on hDCs and increased dectin-1-dependent activator protein 1 (AP-1) activation on transfected cells. In addition, concurring with these altered pathways, we detected increased reactive oxygen species production and cytokine secretion. In conclusion, the CEK1-mediated MAPK pathway is involved in beta-glucan exposure in a fungal pathogen, hence influencing dectin-1-dependent immune cell recognition, thus establishing this fungal intracellular signaling route as a promising novel therapeutic target.

摘要

天然免疫系统对白念珠菌的防御依赖于对真菌细胞壁上分子模式的识别。然而,真菌似乎通过 dectin-1 受体来进化出一种机制,以避免主要成分(如β-葡聚糖)被免疫细胞识别。虽然先前的动物模型已经证实了白念珠菌丝裂原激活蛋白激酶(MAPK)途径作为毒力决定因素的作用,但这种行为的机制在很大程度上尚不清楚。在这项研究中,我们证明了白念珠菌细胞外信号调节激酶(ERK)样 1(CEK1)介导的 MAPK 途径的中断导致细胞壁β-葡聚糖暴露增加,与野生型相比,更有效地触发免疫反应,如通过 dectin-1 介导的特异性结合以及人树突状细胞(hDC)和巨噬细胞介导的吞噬、杀伤和细胞内信号通路的激活来衡量。在分子水平上,CEK1 的中断导致脾酪氨酸激酶(Syk)、Raf-1 和 ERK1/2 的激活以及 hDC 上的 IkappaB 降解改变,并增加了转染细胞上依赖 dectin-1 的激活蛋白 1(AP-1)的激活。此外,与这些改变的途径一致,我们检测到活性氧物质产生和细胞因子分泌的增加。总之,CEK1 介导的 MAPK 途径参与真菌病原体中β-葡聚糖的暴露,从而影响依赖 dectin-1 的免疫细胞识别,从而确立这种真菌细胞内信号通路作为一种有前途的新型治疗靶标。

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