Bistability and trigger waves in cell signaling

项目总结/摘要 我们一直在研究非洲爪蟾卵和提取物中的细胞周期调控， 定量实验和建模，以了解这种生物振荡器是如何工作的， 它与其他监管制度相同。振荡器电路包括基于正反馈的振荡器， 触发器，这开启了Cdk 1活性可能通过所谓的细胞质传播的可能性。 触发波：自我再生的活动波，其中一些活跃的Cdk 1扩散一小段距离， 关于通过正反馈激活该体积中的非活性Cdk 1，然后扩散 本地化并重复该过程。动作电位是触发波;钙波也是， 田野里的一场大火，或者互联网上的一个笑话。我们最近发现有丝分裂和 细胞凋亡通过触发波在非洲爪蟾细胞质中扩散。我们计划以此为基础，并确定： ·什么机制支持相间爪蟾细胞质自我组织成细胞样细胞的能力？ 结构？这是我们在细胞凋亡研究过程中意外发现的， 这是一个很有趣的现象 ·细胞凋亡控制回路是一个神经系统吗？我们发现的凋亡触发波表明 是的，但其他人认为可能不是。我们计划通过直接实验来解决这个问题。 ·跳跃式与连续有丝分裂波。我们计划看看Cdk 1激活是否以不同的方式传播 靠近中心体和远离中心体，在中心体中各种促有丝分裂蛋白质聚集。 ·双稳态可以将信号限制在某些隔间吗？理论告诉我们触发波可能 阻塞在小管和大管之间的连接处，如树突/轴突连接处或 初级纤毛我们计划在微流体装置中进行凋亡触发波的实验 以测试是否会发生这种情况。 先天免疫反应通过触发波传播吗？先天免疫系统包括阳性 反馈回路，如干扰素诱导的干扰素释放。这可以让细胞防御系统 在感染之前以细胞片的形式传播。我们计划通过实验来测试这种可能性。 ·是否存在第二个有丝分裂开关？我们已经发现，当Cdk 1活性被强迫时， 被评分。我们的工作假设是，以PP 2A-B55为中心的双负反馈回路是 对这种双稳态性负责。我们正在测试这一假设与滞后实验提取物。 ·如何使蛋白质在温度变化时保持协调，特别是在冷血动物中 有机体？一起工作的酶是否具有相似的活化能和Q10值？和/或 进化是否选择了能够容忍高度参数变化的特定电路？

PROJECT SUMMARY/ABSTRACT We have been studying cell cycle regulation in Xenopus laevis eggs and extracts, carrying out a combination of quantitative experiments and modeling to understand how this biological oscillator works and what features it shares with other regulatory systems. The oscillator circuit includes a positive feedback-based bistable trigger, which opens the possibility that Cdk1 activity might spread through cytoplasm by what are termed trigger waves: self-regenerating activity waves, where some active Cdk1 diffuses a small distance and brings about the activation of the inactive Cdk1 in that volume through the positive feedback, which then diffuses locally and repeats the process. Action potentials are trigger waves; so are calcium waves, as is the spread of a fire through a field or the spread of a joke on the internet. We recently showed that both mitosis and apoptosis spread through Xenopus cytoplasm via trigger waves. We plan to build upon this, and determine: · What mechanism underpins the ability of interphase Xenopus cytoplasm to self-organize into cell-like structures? This was an unexpected observation we made in the course of our apoptosis studies, and it is a fascinating phenomenon to try to understand. · Is the apoptotic control circuit a bistable system? Our discovery of apoptotic trigger waves suggests that it is, but others have argued that it may not be. We plan to settle the issue with direct experiments. · Saltatory vs. continuous mitotic waves. We plan to see whether Cdk1 activation propagates differently close to vs. far from the centrosome, where various pro-mitotic proteins concentrate. · Can bistability restrict signals to certain compartments? Theory tells us that a trigger wave may be blocked at the junction between a small tube and a big tube, like a dendrite/axon junction or the base of a primary cilium. We plan to carry out experiments with apoptotic trigger waves in microfluidics devices to test whether this does occur. · Do innate immune responses spread via trigger waves? The innate immune system includes positive feedback loops, such as interferon-induced interferon release. This could allow cellular defenses to spread ahead of an infection in a sheet of cells. We plan to test this possibility experimentally. · Is there a second mitotic switch? We have found that bistability persists when Cdk1 activity is forced to be graded. Our working hypothesis is that double-negative feedback loops centered on PP2A-B55 are responsible for this bistability. We are testing this hypothesis with hysteresis experiments in extracts. · How to proteins that work together stay coordinated as temperature changes, especially in cold-blood organisms? Do enzymes that work together have similar activation energies and Q10 values? And/or has evolution selected particular circuits that tolerate high degrees of parameter variation?