Hunan Provincial Key Laboratory of Nutrition and Quality Control of Aquatic Animals, Department of Biological and Environmental Engineering, Changsha University, Changsha, China.
Front Immunol. 2022 Jun 10;13:925168. doi: 10.3389/fimmu.2022.925168. eCollection 2022.
Myeloid differentiation factor 88 (MyD88) is a key adapter molecule in Toll-like receptor signal transduction that triggers downstream immune cascades involved in the host defense response to exogenous pathogens. However, the function of MyD88s in mollusks, especially in freshwater shellfish, remains poorly understood. In this study, a novel freshwater shellfish MyD88 (denoted MyD88) was characterized from . The present MyD88 protein consists of 474 amino acids and contains a conserved a typical death domain (DD) and a conservative Toll/IL-1R (TIR) domain with three typical boxes. Quantitative real-time PCR (qRT-PCR) analysis showed that MyD88 was broadly expressed in all the examined tissues, and the highest expression level was observed in hemocytes of . When challenged with and lipopolysaccharide (LPS), the mRNA expression levels of MyD88 were significantly induced in hemocytes of and . In addition, injection experiments revealed that MyD88 signaling pathway genes showed strong responsiveness to challenge, and their expression levels were significantly upregulated in hemocytes. Knockdown of MyD88 reduced the transcript levels of immune related transcription factors (NF-κB and AP-1) and effectors (TNF, LYZ, Defense and AIF) during infection. Moreover, subcellular localization analysis indicated that MyD88 was mainly localized to the cytoplasm in HEK293T cells. Finally, luciferase reporter assays revealed that MyD88 associates with TLR to activate the NF-κB and AP-1 signaling pathways in HEK293T cells. These results suggested that MyD88 might be involved in the host defense response to bacterial challenge, providing new insight into the immune function of the MyD88 signaling pathway in freshwater shellfish.
髓样分化因子 88（MyD88）是 Toll 样受体信号转导中的关键衔接分子，它触发下游免疫级联反应，参与宿主对外源病原体的防御反应。然而，MyD88 在软体动物中的功能，特别是在淡水贝类中的功能，仍知之甚少。本研究从 中鉴定了一种新型淡水贝类 MyD88（命名为 MyD88）。本研究中的 MyD88 蛋白由 474 个氨基酸组成，包含一个保守的典型死亡结构域（DD）和一个保守的 Toll/IL-1R（TIR）结构域，具有三个典型的框。定量实时 PCR（qRT-PCR）分析表明，MyD88 在所有检测组织中广泛表达，在 中的血细胞中表达水平最高。当受到 和脂多糖（LPS）的刺激时， 血细胞中的 MyD88 mRNA 表达水平显著上调。此外， 注射实验表明，MyD88 信号通路基因对 刺激表现出强烈的反应性，其在血细胞中的表达水平显著上调。MyD88 的敲低降低了 感染期间免疫相关转录因子（NF-κB 和 AP-1）和效应因子（TNF、LYZ、Defense 和 AIF）的转录水平。此外，亚细胞定位分析表明，MyD88 主要定位于 HEK293T 细胞的细胞质中。最后，荧光素酶报告基因分析显示，MyD88 与 TLR 结合，在 HEK293T 细胞中激活 NF-κB 和 AP-1 信号通路。这些结果表明，MyD88 可能参与了宿主对细菌挑战的防御反应，为淡水贝类中 MyD88 信号通路的免疫功能提供了新的见解。
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