Centre for Host-Microbiome Interactions, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, United Kingdom; Division of Rheumatology and Clinical Immunology, University of Pittsburgh, Pittsburgh Pennsylvania, USA.
Centre for Host-Microbiome Interactions, Faculty of Dentistry, Oral and Craniofacial Sciences, King's College London, London, United Kingdom.
J Biol Chem. 2022 Oct;298(10):102419. doi: 10.1016/j.jbc.2022.102419. Epub 2022 Aug 28.
Candida albicans (C. albicans) is a dimorphic commensal human fungal pathogen that can cause severe oropharyngeal candidiasis (oral thrush) in susceptible hosts. During invasive infection, C. albicans hyphae invade oral epithelial cells (OECs) and secrete candidalysin, a pore-forming cytolytic peptide that is required for C. albicans pathogenesis at mucosal surfaces. Candidalysin is produced in the hyphal invasion pocket and triggers cell damage responses in OECs. Candidalysin also activates multiple MAPK-based signaling events that collectively drive the production of downstream inflammatory mediators that coordinate downstream innate and adaptive immune responses. The activities of candidalysin are dependent on signaling through the epidermal growth factor receptor (EGFR). Here, we interrogated known EGFR-MAPK signaling intermediates for their roles mediating the OEC response to C. albicans infection. Using RNA silencing and pharmacological inhibition, we identified five key adaptors, including growth factor receptor-bound protein 2 (Grb2), Grb2-associated binding protein 1 (Gab1), Src homology and collagen (Shc), SH2-containing protein tyrosine phosphatase-2 (Shp2), and casitas B-lineage lymphoma (c-Cbl). We determined that all of these signaling effectors were inducibly phosphorylated in response to C. albicans. These phosphorylation events occurred in a candidalysin-dependent manner and additionally required EGFR phosphorylation, matrix metalloproteinases (MMPs), and cellular calcium flux to activate a complete OEC response to fungal infection. Of these, Gab1, Grb2, and Shp2 were the dominant drivers of ERK1/2 activation and the subsequent production of downstream innate-acting cytokines. Together, these results identify the key adaptor proteins that drive the EGFR signaling mechanisms that underlie oral epithelial responses to C. albicans.
白色念珠菌（Candida albicans，C. albicans）是一种二相共生的人类真菌病原体，可在易感宿主中引起严重的口腔念珠菌病（口腔鹅口疮）。在侵袭性感染过程中，白色念珠菌菌丝侵入口腔上皮细胞（oral epithelial cells，OECs）并分泌出白色念珠菌溶素（candidalysin），这是一种形成孔的细胞溶解肽，对于白色念珠菌在黏膜表面的发病机制是必需的。白色念珠菌溶素在菌丝侵入囊中产生，并在 OEC 中引发细胞损伤反应。白色念珠菌溶素还激活了多个基于丝裂原活化蛋白激酶（mitogen-activated protein kinase，MAPK）的信号事件，这些信号事件共同驱动下游炎症介质的产生，从而协调下游的先天和适应性免疫反应。白色念珠菌溶素的活性依赖于表皮生长因子受体（epidermal growth factor receptor，EGFR）的信号传递。在这里，我们研究了已知的 EGFR-MAPK 信号转导中间物在介导 OEC 对白色念珠菌感染的反应中的作用。通过 RNA 沉默和药理学抑制，我们鉴定了五个关键的衔接蛋白，包括生长因子受体结合蛋白 2（growth factor receptor-bound protein 2，Grb2）、Grb2 相关结合蛋白 1（Grb2-associated binding protein 1，Gab1）、Src 同源和胶原（Src homology and collagen，Shc）、含 SH2 结构域的蛋白酪氨酸磷酸酶-2（SH2-containing protein tyrosine phosphatase-2，Shp2）和 Casitas B 细胞淋巴瘤（casitas B-lineage lymphoma，c-Cbl）。我们发现这些信号转导效应物都可被白色念珠菌诱导磷酸化。这些磷酸化事件以白色念珠菌溶素依赖性的方式发生，此外还需要 EGFR 磷酸化、基质金属蛋白酶（matrix metalloproteinases，MMPs）和细胞内钙流来激活 OEC 对真菌感染的完整反应。其中，Gab1、Grb2 和 Shp2 是 ERK1/2 激活和随后产生下游先天作用细胞因子的主要驱动因素。综上所述，这些结果确定了驱动 EGFR 信号机制的关键衔接蛋白，这些信号机制是 OEC 对白色念珠菌反应的基础。
