Oncogenic inhibition by a deleted in liver cancer gene requires cooperation between tensin binding and Rho-specific GTPase-activating protein activities

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 104; no. 21; pp. 9012 - 9017
• Main Authors: Qian, Xiaolan, Li, Guorong, Asmussen, Holly K, Asnaghi, Laura, Vass, William C, Braverman, Richard, Yamada, Kenneth M, Popescu, Nicholas C, Papageorge, Alex G, Lowy, Douglas R
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 22.05.2007; National Acad Sciences
• Subjects: Amino acids; Animals; Antibodies; Binding sites; Biochemistry; Biological Sciences; Cancer; Cell Line; Cell lines; Cellular immunity; Enzymes; Genes; GTPase-Activating Proteins - metabolism; HEK293 cells; Humans; Integrins - metabolism; Ligands; Liver diseases; Mice; Microfilament Proteins - metabolism; Mutation - genetics; NIH 3T3 cells; Oncogene Proteins - genetics; Oncogene Proteins - metabolism; Phosphotyrosine - metabolism; Protein Binding; Proteins; Pulmonary tuberculosis; src Homology Domains; Tensins; Tumor Suppressor Proteins - genetics; Tumor Suppressor Proteins - metabolism; Tumors; Tyrosine - genetics; Tyrosine - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0703033104

The three deleted in liver cancer genes (DLC1-3) encode Rho-GTPase-activating proteins (RhoGAPs) whose expression is frequently down-regulated or silenced in a variety of human malignancies. The RhoGAP activity is required for full DLC-dependent tumor suppressor activity. Here we report that DLC1 and DLC3 bind to human tensin1 and its chicken homolog. The binding has been mapped to the tensin Src homology 2 (SH2) and phosphotyrosine binding (PTB) domains at the C terminus of tensin proteins. Distinct DLC1 sequences are required for SH2 and PTB binding. DCL binding to both domains is constitutive under basal conditions. The SH2 binding depends on a tyrosine in DCL1 (Y442) but is phosphotyrosine-independent, a highly unusual feature for SH2 binding. DLC1 competed with the binding of other proteins to the tensin C terminus, including β3-integrin binding to the PTB domain. Point mutation of a critical tyrosine residue (Y442F) in DLC1 rendered the protein deficient for binding the tensin SH2 domain and binding full-length tensin. The Y442F protein was diffusely cytoplasmic, in contrast to the localization of wild-type DLC1 to focal adhesions, but it retained the ability to reduce the intracellular levels of Rho-GTP. The Y442F mutant displayed markedly reduced biological activity, as did a mutant that was RhoGAP-deficient. The results suggest that DLC1 is a multifunctional protein whose biological activity depends on cooperation between its tensin binding and RhoGAP activities, although neither activity depends on the other.