Deleted in Liver Cancer 1 (DLC1) Utilizes a Novel Binding Site for Tensin2 PTB Domain Interaction and Is Required for Tumor-Suppressive Function
Deleted in Liver Cancer 1 (DLC1) Utilizes a Novel Binding Site for Tensin2 PTB Domain Interaction and Is Required for Tumor-Suppressive Function
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DOI：
10.1371/journal.pone.0005572
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发表时间：
2009-05-15
期刊：
影响因子：
3.7
通讯作者：
Yam, Judy Wai Ping
中科院分区：
文献类型：
--
作者：
Chan, Lo-Kong;Ko, Frankie Chi Fat;Yam, Judy Wai Ping
背景：肝癌 1 (DLC1) 中缺失的是一种 Rho GTP 酶激活蛋白 (RhoGAP)，在肝细胞癌 (HCC) 以及其他癌症中经常缺失且表达不足。最近的独立研究表明，DLC1 与张力蛋白粘着斑蛋白家族成员以 Src 同源性 2 (SH2) 结构域依赖性机制相互作用。 DLC1 和张力蛋白相互作用并共定位于粘着斑处的点状结构。然而，DLC1 和各种张力蛋白之间相互作用的机制仍然存在争议。 方法/主要发现：我们使用免疫共沉淀测定来鉴定 DLC1 375-385 处先前未记录的结合位点，该位点主要与张力蛋白 2 的磷酸酪氨酸结合 (PTB) 结构域相互作用。在缺乏这种新的 PTB 结合位点（DLC1 Delta PTB）的 DLC1 突变体中，DLC1-tensin2 相互作用被完全消除。然而，正如免疫荧光和免疫共沉淀所证明的那样，粘着斑定位以及与tensin1和C末端张力蛋白样(cten)的相互作用均未受到影响。有趣的是，这个新位点的功能意义是通过 RhoGAP 活性的部分降低来体现的，从 DLC1 中去除后，RhoGAP 活性的部分降低反过来又减弱了 DLC1 的生长抑制活性。结论/意义：这项研究提供了新的证据，表明 DLC1 也以 PTB 结构域依赖性方式与张力蛋白 2 相互作用。除了正确定位粘着斑和保留 RhoGAP 活性之外，DLC1 通过这种新型粘着斑结合位点与张力蛋白 2 相互作用，有助于 DLC1 的生长抑制活性。
Background: Deleted in liver cancer 1 (DLC1) is a Rho GTPase-activating protein (RhoGAP) frequently deleted and underexpressed in hepatocellular carcinoma (HCC) as well as in other cancers. Recent independent studies have shown interaction of DLC1 with members of the tensin focal adhesion protein family in a Src Homology 2 (SH2) domain-dependent mechanism. DLC1 and tensins interact and co-localize to punctate structures at focal adhesions. However, the mechanisms underlying the interaction between DLC1 and various tensins remain controversial.Methodology/Principal Findings: We used a co-immunoprecipitation assay to identify a previously undocumented binding site at 375-385 of DLC1 that predominantly interacted with the phosphotyrosine binding (PTB) domain of tensin2. DLC1-tensin2 interaction is completely abolished in a DLC1 mutant lacking this novel PTB binding site (DLC1 Delta PTB). However, as demonstrated by immunofluorescence and co-immunoprecipitation, neither the focal adhesion localization nor the interaction with tensin1 and C-terminal tensin-like (cten) were affected. Interestingly, the functional significance of this novel site was exhibited by the partial reduction of the RhoGAP activity, which, in turn, attenuated the growth-suppressive activity of DLC1 upon its removal from DLC1.Conclusions/Significance: This study has provided new evidence that DLC1 also interacts with tensin2 in a PTB domain-dependent manner. In addition to properly localizing focal adhesions and preserving RhoGAP activity, DLC1 interaction with tensin2 through this novel focal adhesion binding site contributes to the growth-suppressive activity of DLC1.