麻豆淫院

C. elegans听as 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听颁.听别濒别驳补苍蝉听as an animal model to study the mechanisms of HBV-induced cell degeneration. We found that expression of the HBV X protein (HBx) in听C.elegans听induces mostly necrosis and some apoptosis, mimicking the early event of liver infection by HBV.听The mechanisms of action of听HBx听are unknown, but听in vitro听it can activate multiple signaling pathways and interact with many different proteins. Transgenic mice expressing听HBx听in the liver display widespread liver cell deaths and later develop liver听cirrhosis and HCC.听听To identify听in vivo听targets and signaling pathways of听HBx,听we carried out genetic screens to isolate suppressors of听HBx-induced cell death and obtained 31 mutations, which define at least ten genes (hids-1听迟辞听hids-10;听贬叠虫-颈苍诲耻肠别诲听诲别补迟丑听蝉耻辫辫谤别蝉蝉辞谤蝉).

In parallel to the genetic suppressor screens, we performed genetic and biochemical analyses of听HBx-induced cell death in听颁.听别濒别驳补苍蝉听and found unexpectedly thatHBx听interacts 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 and听Bcl-xL, also interact with听HBx听through the same BH3 motif in human hepatocytes. Importantly, mutations in the BH3-like motif that prevent听HBx听binding to the Bcl-2 proteins abrogate cytosolic calcium elevation and cell death induced by听HBx听expression in hepatocytes and severely impair HBV viral replication.听RNAi听knockdown of Bcl-2 or听Bcl-xL听also results in decreased viral replication in hepatocytes. The听颁.听别濒别驳补苍蝉听and the human studies together听indicate that听HBx听targets 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 also听validate the use of听颁.听别濒别驳补苍蝉听as an animal model of HBV.听

We are in the process of mapping and cloning the听hids听genes.听听We also initiated a large-scale drug screen in听颁.听别濒别驳补苍蝉听to isolate compounds that inhibit听HBx-induced cell death using a new drug screen strategy that we developed (Kokel听et al. Nature Chemical Biology 2006). These studies will provide important insights into what听HBx听host targets and signaling pathways are and how听HBx听causes cell death and promotes viral replication and pathogenesis in hepatocytes.

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Publications

听1.听Geng, X., Harry, B.L., Zhou, Q.H., Skeen-Gaar, R.B.,听Ge, X., Lee, E.S.,听Mitani, S., and Xue, D. (2012). Hepatitis B Virus X protein targets the Bcl-2 protein CED-9 to induce intracellular Ca2+听increase and cell death in听颁.听别濒别驳补苍蝉.听Proc. Natl. Acad. Sci. USA听109: 18465-18470. (听and听PDF)

2. Geng, X., Huang, C.H., Qin, Y.,听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.听Proc. Natl. Acad. Sci. USA听109, 18471-18476. (听and听PDF)

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.听Nature Communications听10: 3192 (and听). *Equal contribution. #Co-corresponding authors

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Patents

Ding Xue and Xin Geng, US patent 9518090 (Approved 12/13/2016). Entitled 鈥淐OMPOSITIONS AND METHODS FOR TREATING HEPATITIS B.鈥�

Ding Xue and Xin Geng, US Patent 10155020 (Approved 12/18/2018). Entitled 鈥淐OMPOSITIONS AND METHODS FOR TREATING HEPATITIS B.鈥�