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Deleted in liver cancer 1 (DLC1) utilizes a novel binding site for Tensin2 PTB domain interaction and is required for

Lo-Kong Chan1, Frankie Chi Fat Ko, Irene Oi-Lin Ng

  • 1Department of Pathology, Liver Cancer and Hepatitis Research Laboratory and SH Ho Foundation Research Laboratories, The University of Hong Kong, Pokfulam, Hong Kong, China.

Plos One
|May 15, 2009
PubMed
Abstract

Insights

Deleted in liver cancer 1 (DLC1) interacts with tensin2 via a novel PTB domain binding site, impacting its RhoGAP activity and growth-suppressive functions in cancer. This clarifies DLC1-tensin interactions.

Area of Science:

  • Cell Biology
  • Molecular Oncology
  • Protein Interactions

Background:

  • Deleted in liver cancer 1 (DLC1) is a Rho GTPase-activating protein (RhoGAP) frequently lost in hepatocellular carcinoma (HCC) and other cancers.
  • DLC1 interacts with tensin proteins at focal adhesions, but the precise mechanisms remain unclear.
  • Previous studies suggested a Src Homology 2 (SH2) domain-dependent interaction mechanism.

Purpose of the Study:

  • To elucidate the molecular mechanisms underlying DLC1 interactions with tensin family members.
  • To identify novel binding sites and domains involved in DLC1-tensin interactions.
  • To investigate the functional consequences of these interactions on DLC1 activity and cellular processes.

Main Methods:

  • Co-immunoprecipitation assays were employed to identify protein-protein interactions.
  • Site-directed mutagenesis was used to create DLC1 mutants lacking specific binding domains (DLC1DeltaPTB).
  • Immunofluorescence microscopy was utilized to assess protein localization at focal adhesions.

Main Results:

  • A novel binding site (375-385) on DLC1 was identified, primarily interacting with the phosphotyrosine binding (PTB) domain of tensin2.
  • Disruption of this PTB binding site abolished DLC1-tensin2 interaction but did not affect interactions with tensin1 or cten.
  • Loss of the PTB binding site partially reduced DLC1's RhoGAP activity and attenuated its growth-suppressive function.

Conclusions:

  • DLC1 interacts with tensin2 in a PTB domain-dependent manner, distinct from previously described SH2-dependent interactions.
  • This novel interaction site is crucial for maintaining DLC1's RhoGAP activity and its role in suppressing tumor cell growth.
  • The findings provide new insights into the complex regulatory network of DLC1 in cancer progression.

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