Molecular mechanisms underlying cellular effects of human MEK1 mutations.
Molecular mechanisms underlying cellular effects of human MEK1 mutations.
复制标题
DOI：
10.1091/mbc.e20-10-0625
复制
发表时间：
2021-04-19
影响因子：
3.3
通讯作者：
Shvartsman SY
中科院分区：
文献类型：
--
作者：
Marmion RA;Yang L;Goyal Y;Jindal GA;Wetzel JL;Singh M;Schüpbach T;Shvartsman SY
果蝇胚胎的末端区域通过ERK信号来形成图案，在多种人类疾病中，ERK在基因上是不受调控的。最近，对末端模式的定量研究已被用于研究人类MEK1的功能获得变体，该变体编码通过双重磷酸化直接激活ERK的MEK激酶。出乎意料的是，几个突变减少了细胞外信号对ERK的激活，可能是通过突变突变体的信号无关活性引发的负反馈。在这里，我们提出了支持这一模型的实验证据。使用MEK变异体，将负调节区内的突变与激活环中的丙氨酸取代相结合，我们证明了致病变异体确实获得了信号无关的激酶活性。我们还证明，这些变体的信号依赖性激活不依赖于RAS的激酶抑制因子，RAS是正常MEK激活所必需的保守接头。最后，我们发现，细胞外信号对ERK活性的减弱源于Mkp3的转录诱导，Mkp3是一种通过去磷酸化来使ERK失活的双特异性磷酸酶。这些在果蝇胚胎中的发现突显了它在研究人类疾病突变的各种影响方面的力量。
Terminal regions of Drosophila embryos are patterned by signaling through ERK, which is genetically deregulated in multiple human diseases. Quantitative studies of terminal patterning have been recently used to investigate gain-of-function variants of human MEK1, encoding the MEK kinase that directly activates ERK by dual phosphorylation. Unexpectedly, several mutations reduced ERK activation by extracellular signals, possibly through a negative feedback triggered by signal-independent activity of the mutant variants. Here we present experimental evidence supporting this model. Using a MEK variant that combines a mutation within the negative regulatory region with alanine substitutions in the activation loop, we prove that pathogenic variants indeed acquire signal-independent kinase activity. We also demonstrate that signal-dependent activation of these variants is independent of kinase suppressor of Ras, a conserved adaptor that is indispensable for activation of normal MEK. Finally, we show that attenuation of ERK activation by extracellular signals stems from transcriptional induction of Mkp3, a dual specificity phosphatase that deactivates ERK by dephosphorylation. These findings in the Drosophila embryo highlight its power for investigating diverse effects of human disease mutations.