Cutaneous Biology Research Center, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts 02129, USA.
J Biol Chem. 2011 May 20;286(20):17672-81. doi: 10.1074/jbc.M111.236612. Epub 2011 Mar 13.
DDR1 (discoidin domain receptor tyrosine kinase 1) kinase s highly expressed in a variety of human cancers and occasionally mutated in lung cancer and leukemia. It is now clear that aberrant signaling through the DDR1 receptor is closely associated with various steps of tumorigenesis, although little is known about the molecular mechanism(s) underlying the role of DDR1 in cancer. Besides the role of DDR1 in tumorigenesis, we previously identified DDR1 kinase as a transcriptional target of tumor suppressor p53. DDR1 is functionally activated as determined by its tyrosine phosphorylation, in response to p53-dependent DNA damage. In this study, we report the characterization of the Notch1 protein as an interacting partner of DDR1 receptor, as determined by tandem affinity protein purification. Upon ligand-mediated DDR1 kinase activation, Notch1 was activated, bound to DDR1, and activated canonical Notch1 targets, including Hes1 and Hey2. Moreover, DDR1 ligand (collagen I) treatment significantly increased the active form of Notch1 receptor in the nuclear fraction, whereas DDR1 knockdown cells show little or no increase of the active form of Notch1 in the nuclear fraction, suggesting a novel intracellular mechanism underlying autocrine activation of wild-type Notch signaling through DDR1. DDR1 activation suppressed genotoxic-mediated cell death, whereas Notch1 inhibition by a γ-secretase inhibitor, DAPT, enhanced cell death in response to stress. Moreover, the DDR1 knockdown cancer cells showed the reduced transformed phenotypes in vitro and in vivo xenograft studies. The results suggest that DDR1 exerts prosurvival effect, at least in part, through the functional interaction with Notch1.
DDR1（盘状结构域受体酪氨酸激酶 1）激酶在多种人类癌症中高度表达，偶尔在肺癌和白血病中发生突变。现在很清楚，DDR1 受体的异常信号与肿瘤发生的各个步骤密切相关，尽管对于 DDR1 在癌症中的作用的分子机制知之甚少。除了 DDR1 在肿瘤发生中的作用外，我们之前还确定 DDR1 激酶是肿瘤抑制因子 p53 的转录靶标。DDR1 作为其酪氨酸磷酸化的功能被激活，以响应 p53 依赖性 DNA 损伤。在这项研究中，我们报告了 Notch1 蛋白作为 DDR1 受体的相互作用伙伴的特征，这是通过串联亲和蛋白纯化确定的。在配体介导的 DDR1 激酶激活后，Notch1 被激活，与 DDR1 结合，并激活 Notch1 的典型靶标，包括 Hes1 和 Hey2。此外，DDR1 配体（胶原 I）处理显著增加了核部分中 Notch1 受体的活性形式，而 DDR1 敲低细胞中 Notch1 的活性形式几乎没有或没有增加，这表明通过 DDR1 激活野生型 Notch 信号的自分泌激活存在新的细胞内机制。DDR1 激活抑制了遗传毒性介导的细胞死亡，而 Notch1 抑制剂（γ-分泌酶抑制剂，DAPT）抑制 Notch1 增强了应激反应中的细胞死亡。此外，DDR1 敲低的癌细胞在体外和体内异种移植研究中表现出减少的转化表型。结果表明，DDR1 通过与 Notch1 的功能相互作用发挥促生存作用，至少部分如此。
