Hepatitis Virus B
C. elegansas a new animal model for treating HBV
Hepatitis B Virus (HBV) is the smallest human DNA virus and the major cause of acute and chronic liver disease including hepatocellular carcinoma (HCC) worldwide. There are ~ 400 million HBV chronic carriers and 600,000 deaths every year. Little is known about how HBV infection causes liver injuries and induces the development of liver cancer, partly due to the lack of an effective animal model amenable to genetic analysis. Neither is there an effective treatment for this disease. HBV infection causes liver injuries by inducing liver cell necrosis and apoptosis, which could cause cycles of inflammatory cytokine release, local liver damage, and compensatory regeneration, leading to the continual acquisition of oncogenic mutations and the development of HCC. We tested the possibility of using.Բas an animal model to study the mechanisms of HBV-induced cell degeneration. We found that expression of the HBV X protein (HBx) inC.elegansinduces mostly necrosis and some apoptosis, mimicking the early event of liver infection by HBV.The mechanisms of action ofHBxare unknown, butin vitroit can activate multiple signaling pathways and interact with many different proteins. Transgenic mice expressingHBxin the liver display widespread liver cell deaths and later develop livercirrhosis and HCC.To identifyin vivotargets and signaling pathways ofHBx,we carried out genetic screens to isolate suppressors ofHBx-induced cell death and obtained 31 mutations, which define at least ten genes (hids-1ٴhids-10;-Իܳٳܱǰ).
In parallel to the genetic suppressor screens, we performed genetic and biochemical analyses ofHBx-induced cell death in.Բand found unexpectedly thatHBxinteracts directly with CED-9, a human Bcl-2 homolog, through a Bcl-2 homology 3 (BH3)-like motif and this interaction triggers both cytosolic Ca2+increase and cell death. Similarly, two mammalian Bcl-2 family proteins, Bcl-2 andBcl-xL, also interact withHBxthrough the same BH3 motif in human hepatocytes. Importantly, mutations in the BH3-like motif that preventHBxbinding to the Bcl-2 proteins abrogate cytosolic calcium elevation and cell death induced byHBxexpression in hepatocytes and severely impair HBV viral replication.RNAiknockdown of Bcl-2 orBcl-xLalso results in decreased viral replication in hepatocytes. The.Բand the human studies togetherindicate thatHBxtargets Bcl-2 proteins to promote cytosolic calcium elevation, cell death, and viral replication during HBV infection, which may present an excellent therapeutic intervention point in treating chronic HBV patients. These studies alsovalidate the use of.Բas an animal model of HBV.
We are in the process of mapping and cloning thehidsgenes.We also initiated a large-scale drug screen in.Բto isolate compounds that inhibitHBx-induced cell death using a new drug screen strategy that we developed (Kokelet al. Nature Chemical Biology 2006). These studies will provide important insights into whatHBxhost targets and signaling pathways are and howHBxcauses cell death and promotes viral replication and pathogenesis in hepatocytes.
Publications
1.Geng, X., Harry, B.L., Zhou, Q.H., Skeen-Gaar, R.B.,Ge, X., Lee, E.S.,Mitani, S., and Xue, D. (2012). Hepatitis B Virus X protein targets the Bcl-2 protein CED-9 to induce intracellular Ca2+increase and cell death in.Բ.Proc. Natl. Acad. Sci. USA109: 18465-18470. (andPDF)
2. Geng, X., Huang, C.H., Qin, Y.,McComb, J., Yuan, Q., Harry, B.L., Palmer, A., Xia, N.S., and Xue, D. (2012). Hepatitis B virus X protein targets Bcl-2 proteins to increase cytosolic Ca2+, required for virus replication and cell death induction.Proc. Natl. Acad. Sci. USA109, 18471-18476. (andPDF)
3. Zhang, T.Y.*, Chen, H.Y.*, Cao, J.L.*, Xiong, H.L., Mo, X.B., Li, T.L., KANG, X.Z., Zhao, J.H., Yin, B., Zhao, X., Huang, C.H., Yuan, Q.#, Xue, D.#, Xia, N.S.#, and Yuan, Y.A. (2019). Structural and functional analyses of Hepatitis B virus X protein BH3-like domain and Bcl-xL interaction.Nature Communications10: 3192 (and). *Equal contribution. #Co-corresponding authors
Patents
Ding Xue and Xin Geng, US patent 9518090 (Approved 12/13/2016). Entitled “COMPOSITIONS AND METHODS FOR TREATING HEPATITIS B.”
Ding Xue and Xin Geng, US Patent 10155020 (Approved 12/18/2018). Entitled “COMPOSITIONS AND METHODS FOR TREATING HEPATITIS B.”
Ding Xue and Xin Geng, China Patent 3886093 (Approved 07/14/2020). Entitled “COMPOSITIONS AND METHODS FOR TREATING HEPATITIS B.”