Interaction between the Btk PH domain and phosphatidylinositol-3,4,5-trisphosphate directly regulates Btk
Interaction between the Btk PH domain and phosphatidylinositol-3,4,5-trisphosphate directly regulates Btk
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DOI：
10.1074/jbc.m100873200
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发表时间：
2001-05-11
影响因子：
4.8
通讯作者：
Kinet, JP
中科院分区：
文献类型：
--
作者：
Saito, K;Scharenberg, AM;Kinet, JP
布鲁顿酪氨酸激酶（Btk）通过Btk pleckstrin同源（PH）结构域与磷脂酰肌醇-3,4,5-三磷酸（ptdins -3,4,5- p -3）结合，这种相互作用被认为是B细胞受体信号传导过程中Btk膜易位所必需的。在这里，我们报道了在体外激酶试验中，ptdins -3,4,5- p -3与Btk的PH结构域的相互作用直接诱导Btk酶的激活。一个点突变减少了ptdins -3,4,5- b与Btk PH结构域的相互作用，在体外阻断了ptdins -3,4,5- p -3依赖的Btk激活，而PH结构域的缺失增强了Btk的基础活性，但消除了ptdins -3,4,5- p -3依赖的刺激。Btk激酶活性和Btk激活环磷酸化位点都是ptdins -3,4,5- p -3介导的Btk激酶活性刺激所必需的。总之，这些结果表明Btk PH结构域的定位使得它通常抑制Btk激酶活性和对底物的获取；当与ptdins -3,4,5- p -3相互作用时，这种抑制被缓解，产生明显的Btk激活。此外，使用Src家族激酶抑制剂和Btk催化失活突变体，我们证明在体内，Btk的激活是由于Lyn磷酸化和ptdins -3,4,5- p -3介导的直接激活。因此，Btk- ptdins -3,4,5- p -3相互作用可将Btk转运到膜上并直接调节其信号功能。
Bruton's tyrosine kinase (Btk) binds to phosphatidylinositol-3,4,5-trisphosphate (PtdIns-3,4,5-P-3) through the Btk pleckstrin homology (PH) domain, an interaction thought to be required for Btk membrane translocation during B cell receptor signaling. Here, we report that interaction of PtdIns-3,4,5-P-3, with the PH domain of Btk directly induces Btk enzymatic activation in an in vitro kinase assay. A point mutation that reduces interaction of PtdIns-3,4,5-B, with the Btk PH domain blocks in vitro PtdIns-3,4,5-P-3-dependent Btk activation, whereas the PH domain deletion enhances Btk basal activity but eliminates the PtdIns-3,4,5-P-3-dependent stimulation. Btk kinase activity and the Btk activation loop phosphorylation site are both required for the PtdIns-3,4,5-P-3-mediated stimulation of Btk kinase activity. Together, these results suggest that the Btk PH domain is positioned such that it normally suppresses both Btk kinase activity and access to substrates; when interacting with PtdIns-3,4,5-P-3, this suppression is relieved, producing apparent Btk activation. In addition, using Src family kinase inhibitors and Btk catalytically inactive mutants, we demonstrate that in vivo, the activation of Btk is due to both Lyn phosphorylation and PtdIns-3,4,5-P-3-mediated direct activation. Thus, the Btk-PtdIns-3,4,5-P-3 interaction serves to translocate Btk to the membrane and directly regulate its signaling function.