Institute for Infection and Immunity, Lundquist Institute for Biomedical Innovation at Harbor-UCLA Medical Center, Torrance, California, USA.
David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
mBio. 2021 Dec 21;12(6):e0271621. doi: 10.1128/mBio.02716-21. Epub 2021 Nov 2.
During oropharyngeal candidiasis, Candida albicans activates the epidermal growth factor receptor (EGFR), which induces oral epithelial cells to endocytose the fungus and synthesize proinflammatory mediators. To elucidate EGFR signaling pathways that are stimulated by C. albicans, we used proteomics to identify 1,214 proteins that were associated with EGFR in C. albicans-infected cells. Seven of these proteins were selected for additional study. Among these proteins, WW domain-binding protein 2, Toll-interacting protein, interferon-induced transmembrane protein 3 (IFITM3), and the globular C1q receptor (gC1qR) were found to associate with EGFR in viable oral epithelial cells. Each of these proteins was required for maximal endocytosis of C. albicans, and all regulated fungus-induced production of interleukin-1β (IL-1β) and/or IL-8, either positively or negatively. gC1qR was found to function as a key coreceptor with EGFR. Interacting with the C. albicans Als3 invasin, gC1qR was required for the fungus to induce autophosphorylation of both EGFR and the ephrin type A receptor 2. The combination of gC1qR and EGFR was necessary for maximal endocytosis of C. albicans and secretion of IL-1β, IL-8, and granulocyte-macrophage colony-stimulating factor (GM-CSF) by human oral epithelial cells. In mouse oral epithelial cells, inhibition of gC1qR failed to block C. albicans-induced phosphorylation, and knockdown of IFITM3 did not inhibit C. albicans endocytosis, indicating that gC1qR and IFITM3 function differently in mouse versus human oral epithelial cells. Thus, this work provides an atlas of proteins that associate with EGFR and identifies several that play a central role in the response of human oral epithelial cells to C. albicans infection. Oral epithelial cells play a key role in the pathogenesis of oropharyngeal candidiasis. In addition to being target host cells for C. albicans adherence and invasion, they secrete proinflammatory cytokines and chemokines that recruit T cells and activated phagocytes to foci of infection. It is known that C. albicans activates EGFR on oral epithelial cells, which induces these cells to endocytose the organism and stimulates them to secrete proinflammatory mediators. To elucidate the EGFR signaling pathways that govern these responses, we analyzed the epithelial cell proteins that associate with EGFR in C. albicansinfected epithelial cells. We identified four proteins that physically associate with EGFR and that regulate different aspects of the epithelial response to C. albicans. One of these is gC1qR, which is required for C. albicans to activate EGFR, induce endocytosis, and stimulate the secretion of proinflammatory mediators, indicating that gC1qR functions as a key coreceptor with EGFR.
在口咽念珠菌病期间，白色念珠菌激活表皮生长因子受体（EGFR），诱导口腔上皮细胞内吞真菌并合成促炎介质。为了阐明白色念珠菌激活的 EGFR 信号通路，我们使用蛋白质组学技术鉴定了与白色念珠菌感染细胞中 EGFR 相关的 1214 种蛋白质。选择其中的 7 种蛋白质进行进一步研究。在这些蛋白质中，WW 结构域结合蛋白 2、Toll 相互作用蛋白、干扰素诱导跨膜蛋白 3（IFITM3）和球形 C1q 受体（gC1qR）被发现与活口腔上皮细胞中的 EGFR 相关。这些蛋白质中的每一种都需要最大程度地内吞白色念珠菌，并且都调节真菌诱导的白细胞介素-1β（IL-1β）和/或 IL-8 的产生，无论是正向还是负向调节。发现 gC1qR 作为 EGFR 的关键共受体发挥作用。与白色念珠菌 Als3 入侵素相互作用，gC1qR 对于真菌诱导 EGFR 和 Ephrin 型 A 受体 2 的自身磷酸化是必需的。gC1qR 与 EGFR 的组合对于最大程度地内吞白色念珠菌和人口腔上皮细胞分泌白细胞介素-1β（IL-1β）、白细胞介素-8（IL-8）和粒细胞-巨噬细胞集落刺激因子（GM-CSF）是必需的。在小鼠口腔上皮细胞中，抑制 gC1qR 不能阻断白色念珠菌诱导的磷酸化，而 IFITM3 的敲低不能抑制白色念珠菌的内吞作用，这表明 gC1qR 和 IFITM3 在小鼠和人口腔上皮细胞中的作用不同。因此，这项工作提供了与 EGFR 相关的蛋白质图谱，并确定了几个在人口腔上皮细胞对白色念珠菌感染的反应中起核心作用的蛋白质。口腔上皮细胞在口咽念珠菌病的发病机制中起着关键作用。除了作为白色念珠菌粘附和入侵的靶宿主细胞外，它们还分泌促炎细胞因子和趋化因子，招募 T 细胞和激活的吞噬细胞到感染灶。已知白色念珠菌激活口腔上皮细胞上的 EGFR，诱导这些细胞内吞该生物体并刺激它们分泌促炎介质。为了阐明控制这些反应的 EGFR 信号通路，我们分析了白色念珠菌感染上皮细胞中与 EGFR 相关的上皮细胞蛋白。我们鉴定了 4 种与 EGFR 物理结合并调节上皮细胞对白色念珠菌反应的不同方面的蛋白质。其中一种是 gC1qR，它是白色念珠菌激活 EGFR、诱导内吞作用和刺激促炎介质分泌所必需的，这表明 gC1qR 作为 EGFR 的关键共受体发挥作用。
