McShan Gina D, Zagozdzon Radoslaw, Park Shin-Young, Zrihan-Licht Sheila, Fu Yigong, Avraham Shalom, Avraham Hava
Division of Experimental Medicine, Beth Israel Deaconess Medical Center, Harvard Institutes of Medicine, Boston, MA 02115, USA.
Int J Oncol. 2002 Jul;21(1):197-205.
Our recent observations indicated that RAFTK (also termed Pyk2 and CAK-beta) participated in intracellular signaling upon heregulin (HRG) stimulation and promoted breast carcinoma invasion. Furthermore, studies from our group indicate that the Csk homologous kinase (CHK), a member of the Csk family, directly associates with HER2/Neu and down-regulates HER2/Neu-mediated Src kinase activation in breast cancer cells upon heregulin stimulation. Since activation of RAFTK is associated with the activity of Src family kinases, we analyzed whether CHK is capable of opposing HRG-induced activation of RAFTK. Stimulation of human T47D breast cancer cells with HRG induced the tyrosine phosphorylation of RAFTK and its association with CHK in vitro and in vivo. This interaction was mediated through the Src binding site (amino acid residue at 402) of RAFTK and the SH2 domain of CHK. RAFTK phosphorylation downstream of the activated HER2/Neu was greatly reduced in the presence of CHK. Maximal inhibition of RAFTK phosphorylation by CHK required the kinase activity of CHK. Furthermore, CHK inhibited the tyrosine phosphorylation of the focal adhesion-associated protein, paxillin, and inhibited HRG-induced T47D breast cancer cell migration. These findings indicate the role of CHK as a negative regulator in HRG- and RAFTK-mediated intracellular signaling in breast cancer cells.
我们最近的观察结果表明，RAFTK（也称为Pyk2和CAK-β）在heregulin（HRG）刺激后参与细胞内信号传导，并促进乳腺癌侵袭。此外，我们小组的研究表明，Csk同源激酶（CHK）是Csk家族的成员，在heregulin刺激后，它直接与HER2/Neu结合，并下调乳腺癌细胞中HER2/Neu介导的Src激酶激活。由于RAFTK的激活与Src家族激酶的活性相关，我们分析了CHK是否能够对抗HRG诱导的RAFTK激活。用HRG刺激人T47D乳腺癌细胞，在体外和体内均诱导了RAFTK的酪氨酸磷酸化及其与CHK的结合。这种相互作用是通过RAFTK的Src结合位点（402位氨基酸残基）和CHK的SH2结构域介导的。在存在CHK的情况下，活化的HER2/Neu下游的RAFTK磷酸化大大降低。CHK对RAFTK磷酸化的最大抑制需要CHK的激酶活性。此外，CHK抑制粘着斑相关蛋白桩蛋白的酪氨酸磷酸化，并抑制HRG诱导的T47D乳腺癌细胞迁移。这些发现表明CHK在乳腺癌细胞中作为HRG和RAFTK介导的细胞内信号传导的负调节因子的作用。
