title: Hepatitis B virus X protein increases the IL-1β-induced NF-κB activation via interaction with evolutionarily conserved signaling intermediate in Toll pathways (ECSIT).
abstract: Hepatitis B virus X protein (HBx) transactivates multiple transcription factors including nuclear factor-kappa B (NF-κB) that regulates inflammatory-related genes. However, the regulatory mechanism of HBx in NF-κB activation remains largely unknown. This study reports that HBx augments the interleukin-1β (IL-1β)-induced NF-κB activation via interaction with a Toll-like receptor (TLR) adapter protein, ECSIT (evolutionarily conserved signaling intermediate in Toll pathways). GST pull-down and co-immunoprecipitation analyses showed that HBx interacted with ECSIT. Deletion analysis of HBx in a CytoTrap two-hybrid system revealed that the interaction region of HBx for ECSIT was attributed to aa 51-80. Co-transfection of HBx and ECSIT in IL-1β-stimulated cells appeared to activate IKK and IκB signaling pathway as phosphorylation of both IKK α/β and IκBα was increased whereas knockdown of ECSIT or HBxΔ51-80 mutant attenuated the phosphorylation. As a consequence of IκBα degradation, NF-κB was activated as evidenced by increases in NF-κB transcriptional activity and the nuclear translocation of p65 and p50 that resulted in the induction of IL-10. In contrast, knockdown of ECSIT by siRNA or treatment with an NF-κB selective inhibitor (helenalin) abolished the NF-κB activation and IL-10 expression. We conclude that ECSIT appears to be a novel HBx-interacting signal molecule and their interaction is mechanistically important in IL-1β induction of NF-κB activation.
authors.affiliation: Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China; Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Fuzhou, China.
authors.forename: Wan-nan
authors.initials: WN
authors.lastname: Chen
authors.affiliation: Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
authors.forename: Ling-ling
authors.initials: LL
authors.lastname: Liu
authors.affiliation: Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
authors.forename: Bo-yan
authors.initials: BY
authors.lastname: Jiao
authors.affiliation: Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China.
authors.forename: Wan-song
authors.initials: WS
authors.lastname: Lin
authors.affiliation: Department of Medicine and UC San Diego Moores Cancer Center, University of California-San Diego, CA, USA. Electronic address: xlin@ucsd.edu.
authors.forename: Xin-jian
authors.initials: XJ
authors.lastname: Lin
authors.affiliation: Key Laboratory of Ministry of Education for Gastrointestinal Cancer, School of Basic Medical Sciences, Fujian Medical University, Fuzhou, China; Key Laboratory of Tumor Microbiology, Department of Medical Microbiology, Fujian Medical University, Fuzhou, China. Electronic address: linxu@mail.fjmu.edu.cn.
authors.forename: Xu
authors.initials: X
authors.lastname: Lin
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D002460:Cell Line; D004252:DNA Mutational Analysis; D006515:Hepatitis B virus / Q000276:immunology*; D054884:Host-Pathogen Interactions; D006801:Humans; D053583:Interleukin-1beta / Q000378:metabolism*; D016328:NF-kappa B / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D015398:Signal Transduction; D015534:Trans-Activators / Q000378:metabolism*; D020798:Two-Hybrid System Techniques; D054334:Viral Regulatory and Accessory Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C518657:Ecsit protein, human; D053583:Interleukin-1beta; D016328:NF-kappa B; D015534:Trans-Activators; D054334:Viral Regulatory and Accessory Proteins; C057628:hepatitis B virus X protein
keywords: ECSIT; Hepatitis B virus X protein; Interleukin-1/Toll-like receptor; Interleukin-10; Nuclear factor-κB