Bistability and trigger waves in cell signaling

项目摘要/摘要 我们一直在研究非洲爪哇卵和提取物中的细胞周期调节，进行了一项组合 的定量实验和建模，以了解这种生物振荡器的工作原理和特点 它与其他监管系统共享。该振荡器电路包括基于正反馈的双稳态 触发器，这开启了CDK1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CDK1扩散一小段距离，并带来 关于通过正反馈激活该体积中不活跃的CDK1，然后扩散 并在本地重复该过程。动作电位是触发波；钙波也是触发波，钙波的传播也是 穿过田野的大火或在网上传播的笑话。我们最近发现，有丝分裂和 细胞凋亡通过触发波通过非洲爪哇细胞质传播。我们计划以此为基础，并确定： ·是什么机制支撑了非洲爪哇间期细胞质自组织成类细胞的能力 建筑？这是我们在细胞凋亡研究过程中意外观察到的，而且它 是一个令人着迷的现象，试图去理解。 ·凋亡控制电路是双稳系统吗？我们对细胞凋亡触发波的发现表明 的确如此，但其他人辩称，情况可能并非如此。我们计划通过直接实验来解决这个问题。 ·有丝分裂波动波与连续有丝分裂波。我们计划观察CDK1的激活是否会以不同的方式传播 靠近中心体，远离中心体，在中心体，各种有丝分裂原蛋白集中。 ·双稳能将信号限制在某些隔间吗？理论告诉我们，触发波可能是 在小管和大管的交界处堵塞的，如树突/轴突交界处或 一种初级纤毛。我们计划在微流控设备中进行细胞凋亡触发波实验 来测试这种情况是否确实发生了。 ·先天免疫反应是否通过触发波传播？先天免疫系统包括阳性 反馈循环，如干扰素诱导的干扰素释放。这可以使细胞防御系统 在感染之前在一张细胞中传播。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？我们发现，当cdk1活性被强迫到 要打分。我们的工作假设是以PP2A-B55为中心的双负反馈环是 对这种双稳态负有责任。我们正在用萃取物中的滞后实验来验证这一假设。 ·共同工作的蛋白质如何在温度变化时保持协调，特别是在冷血中 有机体？协同工作的酶有相似的激活能和Q10值吗？和/或 进化选择了能容忍高度参数变化的特定电路吗？

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?