Abstract：
Porcine deltacoronavirus (PDCoV), an enteropathogenic coronavirus, causes severe watery diarrhoea, dehydration and high mortality in piglets, which has the potential for cross-species transmission in recent years. Growth factor receptor-bound protein 2 (Grb2) is a bridging protein that can couple cell surface receptors with intracellular signal transduction events. Here, we investigated the reciprocal regulation between Grb2 and PDCoV. It is found that Grb2 regulates PDCoV infection and promotes IFN-β production through activating Raf/MEK/ERK/STAT3 pathway signalling in PDCoV-infected swine testis cells to suppress viral replication. PDCoV N is capable of interacting with Grb2. The proline-rich motifs in the N- or C-terminal region of PDCoV N were critical for the interaction between PDCoV-N and Grb2. Except for Deltacoronavirus PDCoV N, the Alphacoronavirus PEDV N protein could interact with Grb2 and affect the regulation of PEDV replication, while the N protein of Betacoronavirus PHEV and Gammacoronavirus AIBV could not interact with Grb2. PDCoV N promotes Grb2 degradation by K48- and K63-linked ubiquitin-proteasome pathways. Overexpression of PDCoV N impaired the Grb2-mediated activated effect on the Raf/MEK/ERK/STAT3 signal pathway. Thus, our study reveals a novel mechanism of how host protein Grb2 protein regulates viral replication and how PDCoV N escaped natural immunity by interacting with Grb2.
摘要：
猪三角洲冠状病毒（PDCoV），一种肠致病性冠状病毒，导致严重的水样腹泻，仔猪脱水和高死亡率，近年来具有跨物种传播的潜力。生长因子受体结合蛋白2（Grb2）是一种桥接蛋白，可以将细胞表面受体与细胞内信号转导事件偶联。这里,我们研究了Grb2和PDCoV之间的相互调节。发现Grb2通过激活PDCoV感染的猪睾丸细胞中的Raf/MEK/ERK/STAT3途径信号传导来抑制病毒复制，从而调节PDCoV感染并促进IFN-β的产生。PDCoVN能够与Grb2相互作用。PDCoVN末端或C末端区域中富含脯氨酸的基序对于PDCoV-N与Grb2之间的相互作用至关重要。除了DeltacronavirusPDCoVN,AlphacoronavirusPEDVN蛋白可以与Grb2相互作用并影响PEDV复制的调节，而BetacoronavirusPHEV和GammacoronavirusAIBV的N蛋白不能与Grb2相互作用。PDCoVN通过K48和K63连接的泛素-蛋白酶体途径促进Grb2降解。PDCoVN的过表达损害了Grb2介导的对Raf/MEK/ERK/STAT3信号通路的激活作用。因此，我们的研究揭示了宿主蛋白Grb2蛋白如何调节病毒复制以及PDCoVN如何通过与Grb2相互作用而逃避天然免疫的新机制。
