Purification of a 72-kDa protein-tyrosine kinase from rat liver and its identification as Syk: Involvement of Syk in signaling events of hepatocytes
Purification of a 72-kDa protein-tyrosine kinase from rat liver and its identification as Syk: Involvement of Syk in signaling events of hepatocytes
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DOI：
10.1093/oxfordjournals.jbchem.a022610
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发表时间：
2000-02-01
影响因子：
2.7
通讯作者：
Yamamura, H
中科院分区：
文献类型：
--
作者：
Tsuchida, S;Yanagi, S;Yamamura, H
Syk蛋白酪氨酸激酶（PTK）参与了多种造血细胞反应，包括免疫受体信号传导。然而，到目前为止，没有证据表明Syk或Syk相关的PTK在非造血组织中表达。本研究从去血细胞的大鼠肝中纯化了一个72-kDa的PTK，它与抗Syk抗体具有交叉反应性，部分氨基酸序列分析表明，该72-kDa的PTK与Syk相同。免疫组织化学和RT-PCR分析表明，Syk在人肝细胞和两个大鼠肝源性细胞系JTC-27和RLC-16中表达。此外，Syk在JTC-27细胞中对血管紧张素II的反应是显著的酪氨酸磷酸化，并且血管紧张素II诱导的MAP激酶活化通过用Syk选择性抑制剂piceatannol处理细胞而被阻断。这些结果表明Syk在肝细胞的信号事件中起重要作用，例如导致G蛋白偶联受体激活MAP激酶的信号步骤。这是Syk在非造血组织中表达的首次报道。
Syk protein-tyrosine kinase (PTK) has been implicated in a variety of hematopoietic cell responses including immunoreceptor signaling. However, so far, there has been no evidence of the expression of Syk or Syk-related PTK in non-hematopoietic tissues. In this study, we have purified from blood cell-depleted rat liver a 72-kDa cytoplasmic PTK which shows cross-reactivity with anti-Syk antibody, Partial amino acid sequence analysis revealed that this 72-kDa PTK is identical to Syk, Immunohistochemical and RT-PCR analyses demonstrated that Syk is expressed in human hepatocytes and two rat liver-derived cell lines, JTC-27 and RLC-16. Furthermore, Syk is significantly tyrosine-phosphorylated in response to angiotensin II in JTC-27 cells, and angiotensin II-induced MAP kinase activation is blocked by the treatment of cells with a Syk-selective inhibitor piceatannol. These results suggest that Syk plays an important role in signaling events of hepatocytes, such as signaling steps leading to MAP kinase activation by G-protein-coupled receptors, This is the first report of the expression of Syk in non-hematopoietic tissue.