Prohibitin 1 (PHB1) is a highly conserved, ubiquitously expressed protein that participates in diverse processes including mitochondrial chaperone, growth and apoptosis. The role of PHB1 in vivo is unclear as embryonic deletion is lethal. We reported that mice lacking methionine adenosyltransferase 1A (MAT1A) have reduced PHB1 expression at the protein level, impaired mitochondrial function, and spontaneously develop steatohepatitis and hepatocellular carcinoma (HCC). To see if reduced PHB1 expression can contribute to the Mat1a knockout (KO) phenotype, we generated liver-specific Phb1 KO mice. At 3 weeks, liver-specific Phb1 KO mice exhibit biochemical and histologic liver injury. Immunohistochemistry revealed oxidative stress, fibrosis, hepatocyte dysplasia, and increased staining of preneoplastic markers. Mitochondrial function is impaired. Phb1 KO mice are sensitized to multiple forms of liver injury but the key mechanism appears to be independent of its role as a mitochondrial chaperone. Our preliminary data show PHB1 deficiency leads to higher total and nuclear histone deacetylase 4 (HDAC4) expression and activity. Interestingly, inhibiting HDAC activity prevented increased cell death in Phb1 KO hepatocytes induced by a variety of toxicants. We also found PHB1 protein level falls in cholestatic liver injury in mouse and humans, suggesting this could further perpetuate liver damage. Many Phb1 KO mice develop multifocal HCC by 35 weeks. Our preliminary data also support PHB1 can directly influence genes implicated in hepatocarcinogenesis. Two genes highly up-regulated in 4-week-old male KO mice livers are H19 and insulin-like growth factor 2 (IGF2). Acute knockdown of PHB1 in murine non-transformed AML12 cells raised cyclin D1, H19 and IGF2 expression, increased E2F binding to the cyclin D1 promoter, and proliferation. The opposite occurred with PHB1 overexpression. These results support PHB1 as a tumor suppressor in hepatocytes. The current application is to examine these highly novel areas and define the role of PHB1 in liver injury and HCC.
Three specific aims are proposed: 1) examine the role of PHB1 in liver injury, 2) examine how PHB1 influences HCC development, and 3) determine if PHB1 down-regulation contributes to mitochondrial dysfunction, liver injury and HCC formation in the Mat1a KO mice. Our main hypotheses are 1) PHB1 protein stability falls during cholestatic liver injury and this is part of the mechanism of injury, 2) PHB1 regulates hepatocyte death via HDAC-mediated epigenetic changes, 3) PHB1 regulates HDAC4, H19 and IGF2 expression directly and their induction contribute to HCC formation in the liver-specific Phb1 KO mice, and 4) decreased PHB1 expression contributes to impaired mitochondrial function and HCC formation in the Mat1a KO mice. The application is hypothesis-driven and mechanistic and represents a new area of investigation as little is known of the biological functions of PHB in the liver. The ultimate goal is to translate results from the laboratory to bedside to optimize PHB1 function, which is essential to prevent liver injury and HCC, topics that are highly relevant to public health.

Public Health Relevance

Prohibitin 1 (PHB1) is a highly conserved, ubiquitously expressed protein that participates in diverse processes including protecting mitochondrial proteins, growth and cell death. Most studies on the functions of PHB1 were conducted in yeast and cells growing in Petri dishes. The role of PHB1 in intact animal is unclear as embryonic deletion is lethal. We have developed a mouse model of liver-specific deletion of PHB1 and demonstrated that deficiency in PHB1 resulted in significant liver injury, inflammation, fibrosis, cell death, and liver cancer formation. Using this highly novel model, we can gain for the first time, important insights into the role that this protein plays in maintaining liver health. This isan area largely unknown and our project should pave the way to improve our understanding of the roles of PHB1 in liver health and cancer. Successful completion of this project may identify decreased PHB1 expression as a risk factor for the development of liver injury and cancer and provide rationale for design of therapy targeting PHB1.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
7R01CA172086-02
Application #
8791012
Study Section
Xenobiotic and Nutrient Disposition and Action Study Section (XNDA)
Program Officer
Salnikow, Konstantin
Project Start
2014-01-10
Project End
2018-12-31
Budget Start
2015-01-01
Budget End
2015-12-31
Support Year
2
Fiscal Year
2015
Total Cost
$327,234
Indirect Cost
$113,678
Name
Cedars-Sinai Medical Center
Department
Type
DUNS #
075307785
City
Los Angeles
State
CA
Country
United States
Zip Code
90048
Yang, Jin Won; Murray, Ben; Barbier-Torres, Lucia et al. (2018) The mitochondrial chaperone Prohibitin 1 negatively regulates interleukin-8 in human liver cancers. J Biol Chem :
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Liu, Ting; Yang, Heping; Fan, Wei et al. (2018) Mechanisms of MAFG Dysregulation in Cholestatic Liver Injury and Development of Liver Cancer. Gastroenterology 155:557-571.e14
De Las Heras, Javier; Aldámiz-Echevarría, Luis; Martínez-Chantar, María-Luz et al. (2017) An update on the use of benzoate, phenylacetate and phenylbutyrate ammonia scavengers for interrogating and modifying liver nitrogen metabolism and its implications in urea cycle disorders and liver disease. Expert Opin Drug Metab Toxicol 13:439-448
Barbier-Torres, Lucía; Iruzubieta, Paula; Fernández-Ramos, David et al. (2017) The mitochondrial negative regulator MCJ is a therapeutic target for acetaminophen-induced liver injury. Nat Commun 8:2068
Zubiete-Franco, Imanol; Fernández-Tussy, Pablo; Barbier-Torres, Lucía et al. (2017) Deregulated neddylation in liver fibrosis. Hepatology 65:694-709
Fan, Wei; Yang, Heping; Liu, Ting et al. (2017) Prohibitin 1 suppresses liver cancer tumorigenesis in mice and human hepatocellular and cholangiocarcinoma cells. Hepatology 65:1249-1266
Ramani, Komal; Mavila, Nirmala; Ko, Kwang Suk et al. (2016) Prohibitin 1 Regulates the H19-Igf2 Axis and Proliferation in Hepatocytes. J Biol Chem 291:24148-24159
Barbier-Torres, Lucía; Delgado, Teresa C; García-Rodríguez, Juan L et al. (2015) Stabilization of LKB1 and Akt by neddylation regulates energy metabolism in liver cancer. Oncotarget 6:2509-23
Liu, Ting; Zhou, Yu; Ko, Kwang Suk et al. (2015) Interactions between Myc and Mediators of Inflammation in Chronic Liver Diseases. Mediators Inflamm 2015:276850

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