Department of Molecular Genetics, The Rappaport Family Institute for Research in the Medical Sciences, Technion - Israel Institute of Technology, Bat-Galim, Haifa, Israel.
Biochem J. 2011 Nov 1;439(3):381-90. doi: 10.1042/BJ20110284.
JNK (c-Jun N-terminal kinase) is part of a MAPK (mitogen-activated protein kinase) signalling cascade. Scaffold proteins simultaneously associate with various components of the MAPK signalling pathway and play a crucial role in signal transmission and MAPK regulation. WDR62 (WD repeat domain 62) is a JNK scaffold protein. Recessive mutations within WDR62 result in severe cerebral cortical malformation. In the present study we demonstrate the association of WDR62 with endogenous and overexpressed proteins of both JNK2 and the JNK2-activating kinase MKK7 (MAPK kinase 7). Association of WDR62 with JNK2 and MKK7 occurs via direct protein-protein interactions. We mapped the docking domain of WDR62 responsible for the association with JNK. WDR62 interacts with all JNK isoforms through a D domain motif located at the C-terminus. A WDR62 mutant lacking the putative JNK-binding domain fails to activate and recruit JNK to cellular granules. Furthermore, a synthetic peptide composed of the WDR62 docking domain inhibits JNK2 activity in vitro. WDR62 association with JNK2 requires both the JNK CD and ED domains, and the binding requisite is distinct from that of the previously described JNK2 association with JIP1 (JNK-interacting protein 1). Next, we characterized the association between WDR62 and MKK7. WDR62 associates directly with the MKK7β1 isoform independently of JNK binding, but fails to interact with MKK7α1. Furthermore, MKK7β1 recruits a protein phosphatase that dephosphorylates WDR62. Interestingly, a premature termination mutation in WDR62 that results in severe brain developmental defects does not abrogate WDR62 association with either JNK or MKK7. Therefore such mutations represent a loss of WDR62 function independent of JNK signalling.
JNK（c-Jun N-末端激酶）是 MAPK（丝裂原活化蛋白激酶）信号级联反应的一部分。支架蛋白同时与 MAPK 信号通路的各种成分结合，并在信号转导和 MAPK 调节中发挥关键作用。WDR62（WD 重复结构域 62）是 JNK 的支架蛋白。WDR62 中的隐性突变导致严重的大脑皮质畸形。在本研究中，我们证明了 WDR62 与内源性和过表达的 JNK2 及其激活激酶 MKK7（MAPK 激酶 7）的蛋白结合。WDR62 与 JNK2 和 MKK7 的结合是通过直接的蛋白-蛋白相互作用实现的。我们绘制了 WDR62 与 JNK 结合的对接结构域。WDR62 通过位于 C 端的 D 结构域基序与所有 JNK 同工型相互作用。一个缺乏假定的 JNK 结合结构域的 WDR62 突变体不能激活 JNK 并将其募集到细胞颗粒中。此外，由 WDR62 对接结构域组成的合成肽在体外抑制 JNK2 活性。WDR62 与 JNK2 的结合需要 JNK 的 CD 和 ED 结构域，结合要求与先前描述的 JNK2 与 JIP1（JNK 相互作用蛋白 1）的结合要求不同。接下来，我们描述了 WDR62 与 MKK7 之间的关联。WDR62 与 MKK7β1 独立于 JNK 结合直接结合，但不与 MKK7α1 相互作用。此外，MKK7β1 募集一种蛋白磷酸酶，使 WDR62 去磷酸化。有趣的是，WDR62 中的一个提前终止突变导致严重的脑发育缺陷，但不会使 WDR62 与 JNK 或 MKK7 失去结合。因此，这种突变代表了一种独立于 JNK 信号的 WDR62 功能丧失。
