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 RhoGTPase-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 ␤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. DLC1 ͉ Src homology 2 and phosphotyrosine binding domains ͉ tumor suppressor gene

DLC-1 Expression Levels in Breast Cancer Assessed by qRT-PCR are Negatively Associated with Malignancy

“…Liver cancer cell lines without endogenous DLC-1 gene expression was transfected by DLC-1 cDNA, confirmed DLC-1 gene expression has an inhibitory effect on liver cancer cells growth (Zhou et al, 2004). In addition, the same results were also obtained from the lung cancer, breast cancer cell lines and nasopharyngeal carcinoma (NPC) (Yuan et al, 2004;Plaumann et al, 2003;Qian et al, 2007;Seng et al, 2007). transfected DLC-1 into two DLC-1 negative breast cancer cell lines, and found cell proliferation rate declined obviously, and further the DLC-1 negative cells and DLC-1 trasfected cells were injected into the nude mouse for 3 weeks, respectively, the former gradually developed into tumor, its histopathological was same as mammary gland adenocarcinoma, the latter had no tumor formation, therefore, DLC-1 play an important inhibition role in the breast cancer formation.…”

PKA-induced dimerization of the RhoGAP DLC1 promotes its inhibition of tumorigenesis and metastasis

“…DLC is a nucleocytoplasmic shuttling protein 20,23 , although this shuttling function was not affected by Ser549 phosphorylation. DLC1 interaction with tensin has been well established and is crucial for proper function of DLC1 12,[24][25][26] . Thus, we investigated whether Ser549 phosphorylation regulates the association between DLC1 and tensins.…”

“…However, the activation of Rho proteins contributes to tumorigenesis and metastasis in many cancers 10 , and RhoGAP activity has a predominant role in the tumour suppressor functions of DLC1 11 . In different cell line models, ectopic expression of the RhoGAP mutant of DLC1 fails to suppress cell growth and motility 12,13 , and functional studies have shown that RhoGAP and the growth inhibitory activities of DLC1 are impaired as a result of T301K and S308I mutations, which were identified in prostate and colon cancer patients 14 . These studies suggest that RhoGAP activity and growth suppression activity are tightly associated.…”

H2O2Inhibits Proliferation and Mediates Suppression of Migration via DLC1/RhoA Signaling in Cancer Cells

“…As a new member of GAP family, deleted in liver cancer 1 (DLC1) has been proved to possess RhoGAP activity (Yuan et al, 1998;Wong et al, 2003). Our previous studies show that DLC1 suppresses cancer cell migration by its RhoGAP activity (Qian et al, 2007;Li et al, 2011). In this paper, we investigated effects of H 2 O 2 on proliferation by checking cell cycle and apoptosis-related genes and explored H 2 O 2 -mediated suppression of migration via DLC1/RhoA signaling pathway.…”