title: Oncogenic inhibition by a deleted in liver cancer gene requires cooperation between tensin binding and Rho-specific GTPase-activating protein activities.
abstract: 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 beta 3-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.
authors.affiliation: Laboratory of Cellular Oncology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Qian
authors.forename: Guorong
authors.initials: G
authors.lastname: Li
authors.forename: Holly K
authors.initials: HK
authors.lastname: Asmussen
authors.forename: Laura
authors.initials: L
authors.lastname: Asnaghi
authors.forename: William C
authors.initials: WC
authors.lastname: Vass
authors.forename: Richard
authors.initials: R
authors.lastname: Braverman
authors.forename: Kenneth M
authors.initials: KM
authors.lastname: Yamada
authors.forename: Nicholas C
authors.initials: NC
authors.lastname: Popescu
authors.forename: Alex G
authors.initials: AG
authors.lastname: Papageorge
authors.forename: Douglas R
authors.initials: DR
authors.lastname: Lowy
mesh_terms: D000818:Animals; D002460:Cell Line; D020690:GTPase-Activating Proteins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D015513:Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D019000:Phosphotyrosine / Q000378:metabolism; D011485:Protein Binding; D000070876:Tensins; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D014443:Tyrosine / Q000235:genetics / Q000378:metabolism; D018909:src Homology Domains
chemical_list: D020690:GTPase-Activating Proteins; D016023:Integrins; D008840:Microfilament Proteins; D015513:Oncogene Proteins; C000606740:STARD8 protein, human; C000603369:TNS1 protein, human; D000070876:Tensins; C000603373:Tns1 protein, mouse; D025521:Tumor Suppressor Proteins; C085379:rho GTPase-activating protein; D019000:Phosphotyrosine; D014443:Tyrosine