Functional characterization of glycine N-methyltransferase and its interactive protein DEPDC6/DEPTOR in hepatocellular carcinoma
Journal
Molecular Medicine
Journal Volume
18
Journal Issue
2
Pages
286-296
Date Issued
2012
Author(s)
Yen C.-H.
Lu Y.-C.
Li C.-H.
Lee C.-M.
Chen C.-Y.
Cheng M.-Y.
Huang S.-F.
Chen K.-F.
Liao L.-Y.
Lee Y.-H.W.
Chen Y.-M.A.
Abstract
Glycine N-methyltransferase (GNMT) is a tumor suppressor for hepatocellular carcinoma (HCC). High rates of Gnmtknockout mice developed HCC. Epigenetic alteration and dysregulation of several pathways including wingless-type MMTV integration site (Wnt), mitogen activated protein kinase (MAPK) and Janus kinase and signal transducer and activator of transcription (JAK-STAT) are associated with HCC development in Gnmtknockout mice. We hypothesized that GNMT may regulate signal transduction through interacting with other proteins directly. In this report, we identified a mammalian target of rapamycin (mTOR) inhibitor (DEP domain containing MTOR-interacting protein [DEPDC6/DEPTOR]) as a GNMT-binding protein by using yeast two-hybrid screening. Fluorescence resonance energy transfer assay demonstrated that the C-terminal half of GNMT interact with the PSD-95/Dlg1/ZO-1 (PDZ) domain of DEPDC6/DEPTOR. Immuno histo chemical staining showed that 27.5% (14/51) of HCC patients had higher expression levels of DEPDC6/DEPTOR in the tumorous tissues than in tumor-adjacent tissues, especially among HCC patients with hepatitis B viral infection (odds ratio 10.3, 95% confidence interval [CI] 1.05-11.3) or patients with poor prognosis (death hazard ratio 4.51, 95% CI 1.60-12.7). In terms of molecular mechanism, knockdown of DEPDC6/DEPTOR expression in HuH-7 cells caused S6K and 4E-BP activation, but suppressed Akt. Over expression of DEPDC6/DEPTOR activated Akt and increased survival of HCC cells. Over expression of GNMT caused activation of mTOR/raptor downstream signaling and delayed G2/M cell cycle progression, which altogether resulted in cellular senescence. Furthermore, GNMT reduced proliferation of HuH-7 cells and sensitized them to rapamycin treatment both in vitro and in vivo. In conclusion, GNMT regulates HCC growth in part through interacting with DEPDC6/DEPTOR and modulating mTOR/raptor signaling pathway. Both GNMT and DEPDC6/DEPTOR are potential targets for developing therapeutics for HCC.
SDGs
Other Subjects
DEP domain containing MTOR interacting protein; everolimus; glycine methyltransferase; initiation factor 4E binding protein; mammalian target of rapamycin; mammalian target of rapamycin inhibitor; membrane protein; placebo; postsynaptic density protein 95; protein Dlg 1; protein kinase B; protein ZO1; S6 kinase; unclassified drug; adult; animal experiment; animal model; article; cancer cell culture; cancer inhibition; cancer prognosis; cancer survival; carboxy terminal sequence; cell cycle G2 phase; cell cycle M phase; cell cycle progression; cell cycle regulation; cell proliferation; cell survival; clinical article; controlled study; disease association; drug targeting; enzyme activation; enzyme inhibition; female; fluorescence resonance energy transfer; gene overexpression; hepatitis B; human; human cell; human tissue; immunohistochemistry; in vitro study; in vivo study; liver cell carcinoma; male; mouse; nonhuman; priority journal; protein analysis; protein expression; protein function; protein localization; protein protein interaction; senescence; signal transduction; tissue distribution; two hybrid system; Adult; Aged; Animals; Carcinoma, Hepatocellular; Cell Line, Tumor; Female; Glycine N-Methyltransferase; HEK293 Cells; Hepatitis B; Hepatitis C; Humans; Immunosuppressive Agents; Liver Neoplasms; Male; Mice; Mice, SCID; Middle Aged; Sirolimus; TOR Serine-Threonine Kinases; Two-Hybrid System Techniques; Xenograft Model Antitumor Assays
Type
journal article