Spatio-logical processes in intracellular signalling

Classical models of intracellular signalling describe how small changes in a cell's external environment can bring about major changes in cellular act ivity. Recent findings from experimental biology indicate that many intrace llular signalling systems show a high level of spatial organisation, This p ermits the modification, by protein kinase or protein phosphatase action, o f specific subsets of intracellular proteins - an attribute that is not add ressed in classical signalling models. Here we use ideas and concepts from computer science to describe the information processing nature of intracell ular signalling pathways and the impact of spatial heterogeneity of their c omponents (e.g, protein kinases and protein phosphatases) on signalling act ivity. We argue that it is useful to view the signalling ecology as a vast parallel distributed processing network of agents operating in heterogeneou s microenvironments, and we conclude with an overview of the mathematical a nd semantic methodologies that might help clarify this analogy between biol ogical and computational systems. (C) 2000 Elsevier Science Ireland Ltd. Al l rights reserved.