Tyr728 in the Kinase Domain of the Murine Kinase Suppressor of RAS 1 Regulates Binding and Activation of the Mitogen-activated Protein Kinase Kinase*
Tyr728 in the Kinase Domain of the Murine Kinase Suppressor of RAS 1 Regulates Binding and Activation of the Mitogen-activated Protein Kinase Kinase*
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DOI：
10.1074/jbc.m113.490235
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发表时间：
2013-10
期刊：
影响因子：
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通讯作者：
C. Sibilski;T. Mueller;L. Kollipara;R. Zahedi;U. Rapp;T. Rudel;A. Baljuls
中科院分区：
文献类型：
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作者：
C. Sibilski;T. Mueller;L. Kollipara;R. Zahedi;U. Rapp;T. Rudel;A. Baljuls
背景：KSR 1协调RAF-MEK-ERK复合物的组装并调节信号转导。结果：酪氨酸728上KSR 1的LCK依赖性磷酸化调节MEK结合和活化。结论：Tyr 728磷酸化可以协调KSR 1的支架和催化功能之间的过渡，以微调细胞反应。KSR 1的酪氨酸磷酸化是Src家族激酶与RAF/MEK/ERK信号转导之间的一个新的调节环节。在后生动物中，高度保守的MAPK信号通路调节细胞命运决定。该途径的异常激活与多种人类癌症和一些发育障碍有关。KSR 1作为一个重要的支架，结合级联反应的各个组成部分，并协调其组装成多蛋白信号平台。KSR 1的调控机制非常复杂，尚未完全了解。在这项研究中，我们确定Tyr 728作为一个新的调节磷酸化位点KSR 1。我们发现Tyr 728被LCK磷酸化，揭示了Src激酶和MAPK信号之间额外的和意想不到的联系。为了了解Tyr 728的磷酸化如何调节KSR 1在信号转导中的作用，我们整合了结构建模和生化研究。我们证明，Tyr 728参与维持所需的结合MEK的KSR 1激酶结构域的构象。它还通过RAF激酶影响MEK的磷酸化和活化，从而影响细胞增殖。此外，我们的研究表明，Tyr 728的磷酸化可能会影响KSR 1的内在激酶活性。总之，我们认为Tyr 728的磷酸化可以调节支架和KSR 1的催化功能之间的过渡，KSR 1是用于微调细胞反应的控制点。
Background: KSR1 coordinates the assembly of RAF-MEK-ERK complexes and regulates signal transduction. Results: LCK-dependent phosphorylation of KSR1 on Tyr728 regulates MEK binding and activation. Conclusion: Tyr728 phosphorylation may coordinate the transition between the scaffolding and catalytic function of KSR1 to fine-tune cellular responses. Significance: Tyrosine phosphorylation of KSR1 is a new regulatory link between Src family kinases and RAF/MEK/ERK signaling. In metazoans, the highly conserved MAPK signaling pathway regulates cell fate decision. Aberrant activation of this pathway has been implicated in multiple human cancers and some developmental disorders. KSR1 functions as an essential scaffold that binds the individual components of the cascade and coordinates their assembly into multiprotein signaling platforms. The mechanism of KSR1 regulation is highly complex and not completely understood. In this study, we identified Tyr728 as a novel regulatory phosphorylation site in KSR1. We show that Tyr728 is phosphorylated by LCK, uncovering an additional and unexpected link between Src kinases and MAPK signaling. To understand how phosphorylation of Tyr728 may regulate the role of KSR1 in signal transduction, we integrated structural modeling and biochemical studies. We demonstrate that Tyr728 is involved in maintaining the conformation of the KSR1 kinase domain required for binding to MEK. It also affects phosphorylation and activation of MEK by RAF kinases and consequently influences cell proliferation. Moreover, our studies suggest that phosphorylation of Tyr728 may affect the intrinsic kinase activity of KSR1. Together, we propose that phosphorylation of Tyr728 may regulate the transition between the scaffolding and the catalytic function of KSR1 serving as a control point used to fine-tune cellular responses.