Hepatitis B/C viruses manipulate TNNT1 expression to induce epithelial-mesenchymal transition and hepatocellular carcinogenesis
Infection with hepatitis B and C viruses (HBV and HCV) is a major cause of hepatocellular carcinoma (HCC). While troponin T (TNNT1) is essential for actin thin filament function, little is known about its role in HBV/HCV-associated HCC. Here, we found TNNT1 expression was significantly upregulated in HBV/HCV-infected hepatoma cells, HCC tissues, and mouse models. HBV/HCV-induced c-Myc acts as a transcription factor for TNNT1 induction. HBV/HCV-induced TNNT1 binds metastasis-associated protein 2 (MTA2) and activates the PI3K-AKT-mTOR-TNNT1 loop, causing lysosomal dysfunction and autophagy suppression. This leads to increased proliferation and epithelial-mesenchymal transition (EMT) of liver cancer cells marked by Vimentin and ZEB2. Four amino acid residues (R110A, E112A, R115A, and E119A) within the TNNT1 troponin domain are required for TNNT1-MTA2 binding and mediate TNNT1's suppression of autophagy and promotion of proliferation/EMT. Importantly, liver-specific TNNT1 deficiency in mice attenuates HBV/HCV-induced c-Myc-driven HCC EMT properties in vivo. This study reveals for the first time that hepatitis virus-induced TNNT1 can induce EMT and hepatocellular carcinogenesis. TNNT1 may be a promising target for viral HCC therapy. Overall design: To detect the mechanism of TNNT1 in hepatocellular carcinoma progression, we knocked down TNNT1 in the hepatocellular carcinoma cell line Huh7.5.1 by Crispr-cas9 technology, and then performed RNA-seq sequencing together with wild-type Huh7.5.1.