Functional characterization of glycine N-methyltransferase and its interactive protein DEPDC6/DEPTOR in hepatocellular carcinoma

Chia Hung Yen, Yao Cheng Lu, Chung Hsien Li, Cheng Ming Lee, Chia Yen Chen, Ming Yuan Cheng, Shiu Feng Huang, Kuen Feng Chen, Ann Lii Cheng, Li Ying Liao, Yan Hwa Wu Lee, Yi Ming Arthur Chen

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39 Citations (Scopus)

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.

Original languageEnglish
Pages (from-to)286-296
Number of pages11
JournalMolecular Medicine
Volume18
Issue number2
DOIs
Publication statusPublished - Feb 1 2012
Externally publishedYes

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ASJC Scopus subject areas

  • Molecular Medicine
  • Molecular Biology
  • Genetics
  • Genetics(clinical)

Cite this

Yen, C. H., Lu, Y. C., Li, C. H., Lee, C. M., Chen, C. Y., Cheng, M. Y., Huang, S. F., Chen, K. F., Cheng, A. L., Liao, L. Y., Lee, Y. H. W., & Chen, Y. M. A. (2012). Functional characterization of glycine N-methyltransferase and its interactive protein DEPDC6/DEPTOR in hepatocellular carcinoma. Molecular Medicine, 18(2), 286-296. https://doi.org/10.2119/molmed.2011.00331