Song Xiufeng, Coffa Sergio, Fu Haian, Gurevich Vsevolod V
Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232 and the Department of Pharmacology, Emory University, Atlanta, Georgia 30322.
Department of Pharmacology, Vanderbilt University, Nashville, Tennessee 37232 and the Department of Pharmacology, Emory University, Atlanta, Georgia 30322.
J Biol Chem. 2009 Jan 2;284(1):685-695. doi: 10.1074/jbc.M806124200. Epub 2008 Nov 10.
Arrestins bind active phosphorylated G protein-coupled receptors, precluding G protein activation and channeling signaling to alternative pathways. Arrestins also function as mitogen-activated protein kinase (MAPK) scaffolds, bringing together three components of MAPK signaling modules. Here we have demonstrated that all four vertebrate arrestins interact with JNK3, MKK4, and ASK1, but only arrestin3 facilitates JNK3 activation. Thus, the functional specificity of arrestins is not determined by differential binding of the kinases. Using receptor binding-impaired mutant, we have shown that free arrestin3 readily promotes JNK3 phosphorylation. We identified key arrestin-binding elements in JNK3 and ASK1 and investigated the molecular interactions of arrestin2 and arrestin3 and their individual domains with the components of the two MAPK cascades, ASK1-MKK4-JNK3 and c-Raf-1-MEK1-ERK2. We found that both arrestin domains interact with all six kinases. These findings shed new light on the mechanism of arrestin-mediated MAPK activation and the spatial arrangement of the three kinases on arrestin molecule.
抑制蛋白结合活性磷酸化的G蛋白偶联受体，阻止G蛋白激活并将信号传导至替代途径。抑制蛋白还作为丝裂原活化蛋白激酶（MAPK）支架，将MAPK信号模块的三个组分聚集在一起。在这里，我们已经证明所有四种脊椎动物抑制蛋白都与JNK3、MKK4和ASK1相互作用，但只有抑制蛋白3促进JNK3激活。因此，抑制蛋白的功能特异性不是由激酶的差异结合决定的。使用受体结合受损的突变体，我们已经表明游离的抑制蛋白3很容易促进JNK3磷酸化。我们在JNK3和ASK1中鉴定了关键的抑制蛋白结合元件，并研究了抑制蛋白2和抑制蛋白3及其各个结构域与两个MAPK级联反应ASK1-MKK4-JNK3和c-Raf-1-MEK1-ERK2的组分之间的分子相互作用。我们发现两个抑制蛋白结构域都与所有六种激酶相互作用。这些发现为抑制蛋白介导的MAPK激活机制以及三种激酶在抑制蛋白分子上的空间排列提供了新的线索。
