Negative and positive feedback in cell signaling

 描述(申请人提供)：在过去的半个世纪里，科学家们对细胞如何检测其环境中的物理和化学线索了解了很多。通常情况下，细胞信号需要质膜受体、细胞内转导和下游效应器，如蛋白激酶。众所周知，蛋白激酶可以磷酸化下游靶标，如转录因子，从而驱动新的基因转录。大多数激酶也会使上游成分磷酸化，从而产生正反馈或负反馈。通过这种方式，一些信号被放大，而另一些信号被削弱。常见的负反馈例子包括对气味、光线和许多药物的脱敏。鉴于过去的工作集中在反馈抑制导致脱敏，我们的工作将集中在反馈调节的三个额外和重要的结果：i：信号协调；例如限制竞争激酶通路的不适当激活。II：信号调谐；例如，将分级输入转换为开关式输出，反之亦然。III：信号跟踪；用于 例如，允许细胞生长或向梯度刺激迁移。我们的研究将集中在丝裂原激活的蛋白激酶(MAPK)上，它是对包括激素、应激和细胞因子在内的各种(通常是竞争性的)刺激而激活的。在酿酒酵母中发现的最具特性的MAPK通路中，它们有助于细胞交配和渗透胁迫反应。我们的方法将利用最近的突破，包括能够跟踪生物反应的新型荧光传感器，以及能够跟踪单细胞途径活动的新型微流控设备。全面识别MAPK底物，并确定这些磷酸化事件的后果，将为新的预测计算模型提供信息。我们的调查将需要多轮数据收集、模型建立、模型测试和模型改进，因此将从R35拨款机制提供的灵活性和稳定性中受益匪浅。

 DESCRIPTION (provided by applicant): Over the past half century scientists have learned much about how cells detect physical and chemical cues in their environment. Typically, cell signaling requires a plasma membrane receptor, an intracellular transducer and a downstream effector such as a protein kinase. Protein kinases are well known to phosphorylate downstream targets such as transcription factors, which drive new gene transcription. Most kinases also phosphorylate upstream components leading to positive or negative feedback. In this way, some signals become amplified while others become diminished. Familiar examples of negative feedback include desensitization to odors, light, and many pharmaceuticals. Whereas past work has focused on feedback inhibition leading to desensitization, our proposed work will focus on three additional and important consequences of feedback regulation: I: Signal coordination; for example to limit inappropriate activation of a competing kinase pathway. II: Signal tuning; for example to convert a graded input to a switch-like output, or vice versa. III: Signal tracking; for example to allow cell growth or migration towards a gradient stimulus. Our investigation will center on the mitogen activated protein kinases (MAPKs), which are activated in response to diverse (and often competing) stimuli including hormones, stresses and cytokines. Among the best- characterized MAPK pathways are those found in yeast Saccharomyces cerevisiae, where they contribute to cell mating and the osmotic stress response. Our approach will capitalize on recent breakthroughs, including newer fluorescent sensors capable of tracking biological responses, as well as new microfluidics devices capable of tracking pathway activity in single cells. Comprehensive identification of MAPK substrates, and establishing the consequences of those phosphorylation events, will inform new predictive computational models. Our investigations will require multiple rounds of data collection, model building, model testing, and model refinement, and would therefore benefit greatly from the flexibility and stability provided by the R35 grant mechanism.