Li Yang, Roberts Julie, AkhavanAghdam Zohreh, Hao Nan
From the Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093.
From the Section of Molecular Biology, Division of Biological Sciences, University of California San Diego, La Jolla, California 92093
J Biol Chem. 2017 Dec 15;292(50):20354-20361. doi: 10.1074/jbc.AC117.000548. Epub 2017 Nov 9.
In the yeast , the exposure to mating pheromone activates a prototypic mitogen-activated protein kinase (MAPK) cascade and triggers a dose-dependent differentiation response. Whereas a high pheromone dose induces growth arrest and formation of a shmoo-like morphology in yeast cells, lower pheromone doses elicit elongated cell growth. Previous population-level analysis has revealed that the MAPK Fus3 plays an important role in mediating this differentiation switch. To further investigate how Fus3 controls the fate decision process at the single-cell level, we developed a specific translocation-based reporter for monitoring Fus3 activity in individual live cells. Using this reporter, we observed strikingly different dynamic patterns of Fus3 activation in single cells differentiated into distinct fates. Cells committed to growth arrest and shmoo formation exhibited sustained Fus3 activation. In contrast, most cells undergoing elongated growth showed either a delayed gradual increase or pulsatile dynamics of Fus3 activity. Furthermore, we found that chemically perturbing Fus3 dynamics with a specific inhibitor could effectively redirect the mating differentiation, confirming the causative role of Fus3 dynamics in driving cell fate decisions. MAPKs mediate proliferation and differentiation signals in mammals and are therapeutic targets in many cancers. Our results highlight the importance of MAPK dynamics in regulating single-cell responses and open up the possibility that MAPK signaling dynamics could be a pharmacological target in therapeutic interventions.
在酵母中，暴露于交配信息素会激活一个典型的丝裂原活化蛋白激酶（MAPK）级联反应，并引发剂量依赖性的分化反应。高剂量的信息素会诱导酵母细胞生长停滞并形成类似shmoo的形态，而低剂量的信息素则会引发细胞伸长生长。先前的群体水平分析表明，MAPK Fus3在介导这种分化转换中起重要作用。为了进一步研究Fus3如何在单细胞水平上控制命运决定过程，我们开发了一种基于特定易位的报告基因，用于监测单个活细胞中的Fus3活性。使用该报告基因，我们在分化为不同命运的单个细胞中观察到了Fus3激活的显著不同的动态模式。致力于生长停滞和shmoo形成的细胞表现出持续的Fus3激活。相比之下，大多数经历伸长生长的细胞显示出Fus3活性的延迟逐渐增加或搏动动态。此外，我们发现用特定抑制剂化学干扰Fus3动态可以有效地重新引导交配分化，证实了Fus3动态在驱动细胞命运决定中的因果作用。MAPK在哺乳动物中介导增殖和分化信号，并且是许多癌症的治疗靶点。我们的结果强调了MAPK动态在调节单细胞反应中的重要性，并开辟了MAPK信号动态可能成为治疗干预中药理学靶点的可能性。
