Cell Signaling

Testing the Signal

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Science  19 Oct 2012:
Vol. 338, Issue 6105, pp. 307
DOI: 10.1126/science.338.6105.307-c

In many experiments, cell signaling events are measured in cells given a strong and constant stimulus. Though this has been useful in delineating signaling pathways, cells may often receive signals that are more subtle and dynamic. Tomida et al. explored how a common signaling enzyme, the protein kinase known as MAPK-1 (mitogen-activated protein kinase–1), responds to variable input in a sensory neuron of the worm Caenorhabditis elegans. They kept living worms in a microfluidic chamber in which they could accurately control exposure of the animals to changes in salt concentration of varied magnitude and duration. They then monitored activity of the enzyme over time within a single neuron by monitoring a synthetic substrate expressed in the cell that gave a fluorescent signal when phosphorylated. Constant stimulation of the neuron did not activate MAPK-1 much. The strongest response came from pulses of stimulation at a moderate frequency—about 20 s of stimulus followed by a rest of the same duration. The authors propose that this pattern of response might make sense in a signaling system that should be inactive in a constant environment, but activated in response to changes, while at the same time filtering out noise.

Sci. Signal. 5, ra76 (2012).

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