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In Vitro Analysis of E3 Ubiquitin Ligase Function
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In Vitro Analysis of E3 Ubiquitin Ligase Function

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c-FLIP is a target of the E3 ligase deltex1 in gastric cancer

Tzu-Sheng Hsu1, Shu-Ting Mo1, Ping-Ning Hsu2

  • 1Institute of Molecular Biology, Academia Sinica, Taipei, Taiwan.

Cell Death & Disease
|January 28, 2018
PubMed

Insights

The ubiquitin ligase DELTEX1 (DTX1) targets c-FLIP for degradation in gastric cancer, enhancing apoptosis and improving patient survival. Restoring DTX1 levels may sensitize cancer cells to TRAIL therapy.

Area of Science:

  • Oncology
  • Cell Biology
  • Molecular Biology

Background:

  • Gastric cancer exhibits downregulated DELTEX1 (DTX1), a ubiquitin E3 ligase, correlating with poorer prognoses.
  • Cellular FLICE inhibitory protein (c-FLIP) promotes cancer cell survival by inhibiting apoptosis.
  • DTX1's role in gastric cancer progression and its interaction with c-FLIP remain unclear.

Purpose of the Study:

  • To investigate the role of DTX1 as an E3 ligase for c-FLIP in gastric cancer.
  • To determine if DTX1 influences gastric cancer cell sensitivity to apoptosis.
  • To explore the therapeutic potential of modulating DTX1 levels for gastric cancer treatment.

Main Methods:

  • Ubiquitin ligase assays to confirm DTX1's E3 ligase activity towards c-FLIP.
  • Western blotting and immunofluorescence to assess protein levels and localization.
  • Cell viability assays and apoptosis assays (e.g., TRAIL-induced apoptosis).
  • Gene knockdown and overexpression studies in gastric cancer cell lines.

Main Results:

  • DTX1 directly targets c-FLIP for degradation in gastric cancer cells.
  • DTX1 overexpression sensitizes cells to TRAIL-induced apoptosis; DTX1 knockdown reduces sensitivity.
  • DTX1 facilitates c-FLIP degradation via the endosome-lysosomal pathway, independent of the proteasome.
  • Induction of DTX1 by geldanamycin enhances TRAIL-induced apoptosis in AGS cells.

Conclusions:

  • DTX1 functions as a tumor suppressor in gastric cancer by degrading c-FLIP.
  • Elevating DTX1 levels represents a potential therapeutic strategy to enhance TRAIL efficacy in gastric cancer.
  • DTX1 plays a physiological role in regulating c-FLIP stability and apoptosis induction in T cells.

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