Current Research Interests
Determination of the homeostatic role of autophagy in the liver
Autophagy function is important for the normal hepatic physiology and structure. Deletion of key autophagy genes leads to hepatomegaly, liver injury, inflammation, fibrosis and liver cancer. The mechanism by which autophagy deficiency leads to these pathophysiological changes are not clear. We have elucidated a key step in liver tumor development, in which HMGB1 secreted by the autophagy-deficient hepatocytes is instrumental. HMGB1 is also required for the ductular reaction, i.e., the expansion of hepatic progenitor cells, which is implicated in liver repair and regeneration. Representative publications are shown below.
- Yin, X.-M. W-X. Ding and W. Gao. Autophagy in the liver. Hepatology 47:1773-1785, 2008.
- Khambu, B., N. Huda, X. Chen, Y. Li, G. Dai, Z. Dong, W-X Zong, S. Waguri, U.A. Kohler, S. Werner, T.D. Oury, and X.-M. Yin. HMGB1 promotes ductular reaction and tumorigenesis in autophagy deficient livers. J. Clin. Invest. 128(6): 2419-2435, 2018.
- Khambu, B., S. Yan, N. Huda, G. Liu and X.-M. Yin. Homeostatic role of autophagy in hepatocytes. Seminar in Liver Research. 38:308-319, 2018.
- Khambu, B., T. Li, S. Yan, C. Yu, X. Chen, M. Goheen, Y. Li, J. Lin, O.W. Cummings, Y. A. Lee, S. Friedman, Z. Dong, G-S. Feng, S. Wu and X.-M. Yin. Hepatic autophagy deficiency compromises FXR functionality and causes cholestatic injury. Hepatology, 69:2196-2213, 2019.
Determination of the role of autophagy in alcohol and non-alcohol fatty liver diseases (AFLD and NAFLFD)
Autophagy is intimately associated with metabolism and in fact is an integrated component of catabolic process. Being the largest metabolic organ in the body, liver has a potent activity of autophagy at the basal physiological level, which can be further enhanced in pathological conditions. We find that alcohol drinking can stimulate hepatic autophagy, which is required to alleviate alcohol-induced liver injury. Autophagy achieves this function by selective autophagy against damaged mitochondria and accumulated lipid droplets. We have extended our finding to non-alcoholic fatty liver diseases and furthermore indicate that pharmacological promotion of autophagy can be an effective way to reduce liver injury and metabolic syndrome in AFLD and NAFLD. The significance of these studies is the revelation of another survival mechanism against AFLD and NAFLD, which may be explored for therapeutic intervention. Some of the representative publications are shown below.
- Ding, W.-X., M. Li, X. Chen, H-M. Ni, W. Gao, B. Lu, D. B. Stolz, D. L. Clemens and X.-M. Yin. Autophagy reduces acute ethanol-induced hepatotoxicity and steatosis in mice. Gastroenterology, 139: 1740-52. 2010.
- Lin, C.-W., H. Zhang, M. Li, X. Xiong, Xi Chen, X. Chen, C. X. Dong, and X.-M. Yin. Pharmacological promotion of autophagy alleviates steatosis and injury in alcoholic and non-alcoholic fatty liver conditions in mice. J. Hepatology, 58: 993-999, 2013.
- Wang, L., J. Zhou, S. Yan, G. Lei, C-H. Lee, and X.-Ming Yin. Ethanol-triggered lipophagy requires SQSTM1 in AML12 cells. Science Reports, 7(1):12307, 2017.
- Zhang, H., B. Khambu, S. Yan, F. Ma, Y. Li, X. Chen, J. A. Martina, R. Puertollano, Y. Li, N. Chalasani, X.-M. Yin. Oscillating TFEB signaling regulates hepatic steatosis and liver injury. Autophagy, 14:1779-1795, 2018.
Development of small molecules for manipulation of autophagy and for cancer therapy
To explore the mechanism of autophagy and potential applications based on manipulation of autophagy, we have established high throughput screening assays based on cellular responses (high content) or chemical reactions (target based). For the formal, cells expression GFP-LC3 were subjected to a library of 200,000 compounds to find out those cause autophagy alterations. For the latter, we focused on Atg4, the only protease in the entire autophagy machinery, which is required for autophagy. There are four Atg4 homologues and at least 8 homologue substrates in the mammalian cells. We have characterized the enzymatic properties of the enzymes for most of the substrates. The screening assays have generated multiple potential targets that are being characterized. However, the usefulness of inhibition of Atg4 in selective typed of cancer has now been demonstrated in collaborative researches. Some of the representative publications are shown below.
- Li, M., Y. Hou, J. Wang, X. Chen, Z.M. Shao and X.-M. Yin. Kinetics comparisons of mammalian Atg4 homologues indicate selective preferences toward diverse Atg8 substrates. J. Bio. Chem. 286:7327-7338, 2011.
- Li, M., Xi Chen, Q.-Z. Ye, A. Vogt and X.-M. Yin. A High-throughput FRET-based Assay for Determination of Atg4 Activity. Autophagy, 8:401-412, 2012.
- Akin, S., K. Wang, P. Habibzadegah-Tari, B. Law, D. Ostrov, M. Li, X.-M. Yin, J.-S. Kim, N. Horenstein, W.A Dunn, Jr. A novel ATG4B antagonist inhibits autophagy and has a negative impact on osteosarcoma tumors. Autophagy, 10 (11): 2021-35, 2014.
- Li, M., Z. Yang, L.L. Vollmer, Y. Gao, Y. Fu, C. Liu, Xiaoyun Chen, P. Liu, A. Vogt, X.-M. Yin. AMDE-1 Is a Dual Function Chemical for Autophagy Activation and Inhibition. PLoS One 10 (3): e0122083, April 20, 2015.
- Huang, T., C.K. Kim, A.A. Alvarez, R.P. Pangeni, X. Wan, X. Song, T. Shi, Y. Yang, N. Sastry, C.M. Horbinski, S. Lu, R. Stupp, J. A. Kessler, R. Nishikawa, I. Nakano, E.P. Sulman, X. Lu, C.D. James, X-M. Yin, B Hu, and S-Y. Cheng. MST4 phosphorylation of ATG4B regulates autophagic activity, tumorigenicity, and radioresistance in glioblastoma. Cancer Cell, 32: 840-855.e8, 2017.
Determination of the multiple functions and molecular effects of Bid
As a pro-death Bcl-2 family molecule, Bid promotes mitochondrial release of cytochrome c. My laboratory also found that Bid can induce the release of other mitochondrial inter-membrane proteins (Kim et al, JBC, 2000), including SMAC, whose significance has been mentioned above. We further find that Bid has multiple effects on mitochondria, including causing mitochondrial permeability transition, mitochondrial cristae reorganization and ROS generation under TNFα or anti-Fas stimulation. Bid interacts with mitochondrial cardiolipin for promoting these effects, which is different from its role in promoting mitochondrial release of cytochrome c and SMAC, for which its interaction with Bax via the BH3 domain is required. What is most interesting is that we find that Bid possesses an entirely different function under non-apoptosis condition. Bid can promote cell proliferation under growth stimulation condition. This is achieved through its control of ER release of calcium. This pro-proliferation explains the paradoxical finding of Bid’s ability to promote hepatic carcinogenesis. Most recently in collaboration we also found that Bid can promote inflammasome activation through its effect at the mitochondria. The significance of these findings is that Bid can have other functions than apoptosis regulation, and that Bid can have multiple molecular targets to exert its activity. Some of the representative publications are shown below.
- Li, B., H.-M. Ni, X. Chen, D. DiFrancesca and X.-M. Yin. Deletion of Bid impedes cell proliferation and hepatic carcinogenesis. American J. Path. 166:1523-1532, 2005.
- Ni, H-M, C. J. Baty, N. Li, W-X. Ding, W. Gao, M. Li, X. Chen, J. Ma, G. K. Michalopoulos and X.-M. Yin. Bid regulates murine hepatocyte proliferation by controlling ER calcium homeostasis. Hepatology, 52: 338-348, 2010.
- Leibowitz, B., W. Qiu, M.E. Buchanan, F. Zou, P. Vernon; M.P. Moyer, X.-M. Yin, R.E. Schoen, J. Yu and L. Zhang. BID mediates selective killing of APC-deficient cells in intestinal tumor suppression by nonsteroidal anti-inflammatory drugs. Proc. Natl. Acad. Sci, 111:16520-16525, 2014.
- Bronner, D.N., B.H. Abuaita, X. Chen, K.A. Fitzgerald, G. Nuñez, Y. He, X.M. Yin, M.X. O'Riordan. Endoplasmic reticulum Stress activates the inflammasome via NLRP3- and caspase-2-driven mitochondrial damage. Immunity. 43:451-462, 2015.
- Yu, C., S. Yan, B. Khambu, Xiaoyun Chen, Z. Dong, J. Luo, G. K. Michalopoulus, S. Wu, and X.-M. Yin. Gene expression analysis indicates divergent mechanisms in DEN-induced carcinogenesis in wild type and Bid-deficient livers. PLoS ONE 11(5): e0155211, 2016.
Research Funding (last 5 years)
Grant Name 1R21 AA021450-01A1
Grant Title: Mechanism and role of selective autophagy in ethanol-induced liver injury
Role in Project: Principal Investigator
Year (Inclusive): June 15, 2014-May 31, 2016 (no cost extension to May 31, 2017)
Source: NIAAA, NIH
Grant Name 1R01 AA021751-01A1
Grant Title: The dynamics and mechanisms of autophagy in ethanol-induced liver pathogenesis
Role in Project: Principal Investigator
Year (Inclusive): Aug 15, 2013-July 31, 2019 (with no cost extension)
Source: NIAAA, NIH
Grant Name 1R01 DK116605-01
Grant Title: The role of HMGB1 in autophagy-deficiency induced liver pathology
Role in Project: Principal Investigator
Year (Inclusive): July 26, 2018-May 31, 2022
Source: NIDDK, NIH
