ANALYSIS OF THE BINDING OF THE SRC HOMOLOGY-2 DOMAIN OF CSK TO TYROSINE-PHOSPHORYLATED PROTEINS IN THE SUPPRESSION AND MITOTIC ACTIVATION OF C-SRC
ANALYSIS OF THE BINDING OF THE SRC HOMOLOGY-2 DOMAIN OF CSK TO TYROSINE-PHOSPHORYLATED PROTEINS IN THE SUPPRESSION AND MITOTIC ACTIVATION OF C-SRC
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DOI：
10.1073/pnas.91.9.3984
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发表时间：
1994-04-26
影响因子：
11.1
通讯作者：
HANAFUSA, H
中科院分区：
文献类型：
--
作者：
SABE, H;HATA, A;HANAFUSA, H
Csk（C-末端Src激酶）是一种蛋白酪氨酸激酶，具有Src同源2和3（SH 2和SH 3）结构域，与c-Src Tyr-527的磷酸化有关，导致c-Src激酶活性抑制。我们发现，在Csk的SH 2或SH 3结构域的突变，虽然他们不影响其激酶活性，导致在成纤维细胞中的c-Src活性抑制的损失。在正常成纤维细胞中，共定位于粘着斑的酪氨酸磷酸化桩蛋白和粘着斑激酶pp 125（FAK）是Csk SH 2结构域结合的主要蛋白质。Csk SH 2突变体与这些蛋白结合的损失与抑制c-Src的活性的损失相关。与此观察结果一致，桩蛋白和pp 125（FAK）的酪氨酸磷酸化水平大大降低有丝分裂过程中，而c-Src的激酶活性升高。我们建议，所需的SH 2域的Csk抑制c-Src，也许结合SH 3域，通过锚定Csk到一个特定的亚细胞位置，其中c-Src可能存在。我们的数据还表明，一定比例的Csk和Src家族激酶的功能在粘着斑。位于粘着斑的c-Src激酶的活性似乎受细胞粘附于细胞外基质的调节。
Csk (C-terminal Src kinase), a protein-tyrosine kinase, bearing the Src homology 2 and 3 (SH2 and SH3) domains, has been implicated in phosphorylation of c-Src Tyr-527, resulting in suppression of c-Src kinase activity. We found that mutations in the SH2 or SH3 domain of Csk, though they did not affect its kinase activity, resulted in a loss of suppression of c-Src activity in fibroblasts. In normal fibroblasts, tyrosine-phosphorylated paxillin and focal adhesion kinase pp125(FAK), which colocalize at focal adhesion plaques, were the major proteins to which the Csk SH2 domain bound. Loss of binding to these proteins by the Csk SH2 mutants correlated with loss of the activity to suppress c-Src. Consistent with this observation, the levels of tyrosine phosphorylation of paxillin and pp125(FAK) were greatly reduced during mitosis, whereas the kinase activity of c-Src was elevated. We suggest that the SH2 domain is required for Csk to suppress c-Src, perhaps in combination with the SH3 domain, by anchoring Csk to a particular subcellular location where c-Src may exist. Our data also indicate that a certain fraction of the Csk and Src family kinases function at the focal adhesion plaques. The activity of the c-Src kinase localized at the focal adhesion plaques appears to be regulated by cell adhesion to the extracellular matrix.