Cell Biology

Intracellular Signal Transduction

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Science  19 Apr 2002:
Vol. 296, Issue 5567, pp. 433
DOI: 10.1126/science.296.5567.433a

The classical pathway of signal transduction starts with an extracellular ligand binding to a cell surface receptor that undergoes a conformational change, activating an intracellular cascade that generates diffusible second messengers and culminates in a physiological readout. However, much of the machinery for generating second messengers is not localized exclusively to the cell surface, but can also be found on intracellular membranes; for example, on the Golgi complex or endosomes. Chiu et al. developed a fluorescent probe to examine exactly where one of the key membrane-associated signal transducers, Ras, is activated. Ras proteins localized to the Golgi responded to external signals, and when they were were engineered to relocate to the endoplasmic reticulum, they were similarly responsive. The consequences of localized Ras activation were distinct; thus, by restricting and controlling the distribution of signal transduction machinery, cells may be able to tailor their responses to external stimuli.—SMH

Nature Cell Biol. 10.1038/ncb783 (2002).

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