eEF1Bγ is a positive regulator of NF-кB signaling pathway

Dong Liu  ¹ , Chunjie Sheng  ¹ , Shijuan Gao  ¹ , Wei Jiang  ¹ , Jiandong Li  ¹ , Chen Yao  ¹ , Huiming Chen  ¹ , Jiaoxiang Wu  ¹ , Shuai Chen  ² , Wenlin Huang  ³

• ¹ CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, PR China.
• ² CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, PR China. Electronic address: shuaichen2010@hotmail.com.
• ³ CAS Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, PR China; State Key Laboratory of Oncology in South China, Cancer Center, Sun Yat-Sen University, Guangzhou, Guangdong 510060, PR China; The Key Laboratory of Tumor Targeted Medicine in Guangdong Province, Guangzhou Doublle Bio-product Inc., Guangzhou, Guangdong 510663, PR China. Electronic address: wl_huang@hotmail.com.

Abstract

Mitochondrial antiviral-signaling protein (MAVS), as a critical adaptor of RIG-I signaling, bridges viral RNA recognition and downstream signal activation. However, the regulating mechanisms of MAVS are not well understood. In this study, we demonstrated that eukaryotic elongation factor 1B gamma (eEF1Bγ) activates NF-кB signaling pathway through targeting MAVS. GST-pull down and mass spectrometric analysis suggested that eEF1Bγ binds to the CARD domain of MAVS. The interaction and mitochondrial colocalization of eEF1Bγ and MAVS were further verified by co-immunoprecipitation (co-IP) and immunofluorescence microscopy assays. The dual-luciferase assays showed that ectopic expression of eEF1Bγ significantly promotes the activities of transcription factor NF-кB and promoters of downstream proinflammatory cytokines Interleukin-8 (IL-8) and Interleukin-6 (IL-6). eEF1Bγ increases the abundance of MAVS by promoting its K63-linked polyubiquitination and attenuating its K48-linked polyubiquitination. Besides, proline-rich (Pro) region and CARD domain of MAVS are indispensable for the process of eEF1Bγ mediated ubiquitination. Collectively, these results demonstrated that eEF1Bγ functions as a positive regulator of NF-кB signal by targeting MAVS for activation, which provides a new regulating mechanism of antiviral responses.

Keywords: Eukaryotic elongation factor 1B gamma (eEF1Bγ); Mitochondrial antiviral-signaling protein (MAVS); NF-кB signaling pathway; Ubiquitination.