Bray D
MRC Cell Biophysics Unit, London, U.K.
J Theor Biol. 1990 Mar 22;143(2):215-31. doi: 10.1016/s0022-5193(05)80268-1.
Living cells respond to their environment by means of an interconnected network of receptors, second messengers, protein kinases and other signalling molecules. This article suggests that the performance of cell signalling pathways taken as a whole has similarities to that of the parallel distributed process networks (PDP networks) used in computer-based pattern recognition. Using the response of hepatocytes to glucagon as an example, a procedure is described by which a PDP network could simulate a cell signalling pathway. This procedure involves the following steps: (a) a bounded set of molecules is defined that carry the signals of interest; (b) each of these molecules is represented by a PDP-type of unit, with input and output functions and connection weights corresponding to specific biochemical parameters; (c) a "learning algorithm" is applied in which small random changes are made in the parameters of the cell signalling units and the new network is then tested by a selection procedure in favour of a specific input-output relationship. The analogy with PDP networks shows how living cells can recognize combinations of environmental influences, how cell responses can be stabilized and made resistant to damage, and how novel cell signalling pathways might appear during evolution.
活细胞通过由受体、第二信使、蛋白激酶和其他信号分子组成的相互连接的网络对其环境做出反应。本文表明，作为一个整体的细胞信号通路的性能与基于计算机的模式识别中使用的并行分布式处理网络（PDP网络）的性能相似。以肝细胞对胰高血糖素的反应为例，描述了一种PDP网络模拟细胞信号通路的程序。该程序包括以下步骤：（a）定义一组携带感兴趣信号的有界分子；（b）这些分子中的每一个都由一个PDP类型的单元表示，其输入和输出函数以及连接权重对应于特定的生化参数；（c）应用一种“学习算法”，其中对细胞信号单元的参数进行小的随机变化，然后通过有利于特定输入-输出关系的选择程序对新网络进行测试。与PDP网络的类比展示了活细胞如何识别环境影响的组合、细胞反应如何得以稳定并抵抗损伤，以及新的细胞信号通路在进化过程中可能如何出现。
