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Our increasingly sophisticated understanding of the molecular mechanisms of cell signalling networks in eukaryotes has revealed a remarkably modular organization. Synthetic biologists are exploring how this can be exploited to engineer cells with novel signalling behaviours that are useful in medicine and biotechnology.
Complex organisms rely on a fairly small number of signalling pathways to regulate all of their responses to developmental and environmental cues. Traditionally, it has been assumed that signalling pathways are linear, but, as exemplified by the Wnt and Hippo pathways, they are now known to achieve considerable levels of diversity and selectivity through extensive integration and crosstalk.
The discovery of molecular signalling machines such as Ras nanoclusters, spatial activity gradients and flexible network circuitries involving transcriptional feedback, are beginning to reveal the design principles of spatiotemporal organization that are crucial for signalling network function and cell fate decisions.
Signalling networks regulate the biology of cells and organisms in normal and disease states. Large-scale 'precision proteomics' based on mass spectrometry now enables the system-wide characterization of signalling events, including the quantitative changes of thousands of proteins and their post-translational modifications, in response to any perturbation.
Microscopic approaches that image protein mobility and reactivity have been integral in understanding the spatial organization of signalling molecules. Data from imaging studies, combined with computational and theoretical models, have given us great insight into how cells process information to elicit morphological changes.
Current descriptions of eukaryotic chemotaxis focus on how extracellular signals (chemoattractants) cause new pseudopods to form. However, reinterpretation of recent data suggests a 'pseudopod-centred' explanation, whereby most pseudopods form without exogenous signals and chemoattractants only bias the position and rate of pseudopod growth.
