Systems analysis of the single photon response in invertebrate photoreceptors
Systems analysis of the single photon response in invertebrate photoreceptors
复制标题
DOI：
10.1073/pnas.0711884105
复制
发表时间：
2008-07-29
影响因子：
11.1
通讯作者：
Shraiman, Boris I.
中科院分区：
文献类型：
--
作者：
Pumir, Alain;Graves, Jennifer;Shraiman, Boris I.
果蝇复眼的光感受器采用 G 蛋白介导的信号传导途径，将单个光子转换为称为“量子颠簸”(QB) 的瞬态电响应。尽管该途径的大部分分子成分已为人所知，但对 QB 生成机制的系统级理解仍然难以捉摸。在这里，我们提出了一个定量模型，解释 QB 如何从信号级联的随机非线性动力学中出现。该模型显示级联充当“集成和激发”装置，并解释了光感受器如何在黑暗中保持低背景的情况下实现对光的可靠响应。该模型预测了突变体增强或抑制信号传导的重要行为，并解释了对控制反馈调节的外部钙的依赖性。结果提供了对生理问题的深入了解，例如单光子响应效率和对高入射光水平的响应适应性。通过光转导建模实现的系统级分析为理解不太适合定量方法的 G 蛋白信号通路奠定了基础。
Photoreceptors of Drosophila compound eye employ a G protein-mediated signaling pathway that transduces single photons into transient electrical responses called "quantum bumps" (QB). Although most of the molecular components of this pathway are already known, the system-level understanding of the mechanism of QB generation has remained elusive. Here, we present a quantitative model explaining how QBs emerge from stochastic nonlinear dynamics of the signaling cascade. The model shows that the cascade acts as an "integrate and fire" device and explains how photoreceptors achieve reliable responses to light although keeping low background in the dark. The model predicts the nontrivial behavior of mutants that enhance or suppress signaling and explains the dependence on external calcium, which controls feedback regulation. The results provide insight into physiological questions such as single-photon response efficiency and the adaptation of response to high incident-light level. The system-level analysis enabled by modeling phototransduction provides a foundation for understanding G protein signaling pathways less amenable to quantitative approaches.