Oncogenic inhibition by a deleted in liver cancer gene requires cooperation between tensin binding and Rho-specific GTPase-activating protein activities
Oncogenic inhibition by a deleted in liver cancer gene requires cooperation between tensin binding and Rho-specific GTPase-activating protein activities
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DOI：
10.1073/pnas.0703033104
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发表时间：
2007-05-22
影响因子：
11.1
通讯作者：
Lowy, Douglas R.
中科院分区：
文献类型：
--
作者：
Qian, Xiaolan;Li, Guorong;Lowy, Douglas R.
这三个缺失的肝癌基因（DLC 1 -3）编码RhoGTP酶激活蛋白（RhoGAP），其表达在多种人类恶性肿瘤中经常下调或沉默。RhoGAP活性是完全DLC依赖性肿瘤抑制活性所必需的。在这里，我们报告，DLC 1和DLC 3结合人tensin 1和它的鸡同源物。结合已被映射到张力蛋白的C末端的张力蛋白Src同源2（SH 2）和磷酸酪氨酸结合（PTB）结构域。SH 2和PTB结合需要不同的DLC 1序列。在基础条件下，DCL与两个结构域的结合是组成性的。SH 2结合依赖于DCL 1（Y 442）中的酪氨酸，但不依赖于磷酸酪氨酸，这是SH 2结合的一个非常不寻常的特征。DLC 1与其他蛋白质竞争结合到张力蛋白C末端，包括β 3-整联蛋白结合到PTB结构域。DLC 1中一个关键的酪氨酸残基（Y 442 F）的点突变使蛋白质缺乏结合张力蛋白SH 2结构域和结合全长张力蛋白。与野生型DLC 1定位于局灶性粘连相反，Y 442 F蛋白是弥漫性的细胞质，但它保留了降低细胞内Rho-GTP水平的能力。Y 442 F突变体显示出明显降低的生物活性，RhoGAP缺陷的突变体也是如此。结果表明，DLC 1是一种多功能蛋白质，其生物活性取决于其张力蛋白结合和RhoGAP活性之间的合作，尽管两种活性都不依赖于另一种。
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 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.