Signal transduction pathways comprise the cell's communications system; they transmit cues--from hormones, growth factors, or cytokines, for instance--that tell the cell to proliferate, differentiate, activate (or deactivate) a gene, or even die. As with any critical communications network, problems can arise when the lines go down or the signals get crossed, and studies have linked perturbations in signal transduction pathways with illnesses such as cancer and diabetes. Researchers therefore need reliable ways to monitor signaling cascades.
The most widely studied signaling event is phosphorylation, a sort of protein on/off switch, as it were. Addition (by kinases) or removal (by phosphatases) of one or more phosphate groups to serine, threonine, or tyrosine residues can profoundly change a protein's function, modulating its activity, for instance, or causing it to interact with other proteins. But Joe Duffy, assistant professor of biology, Indiana University, Bloomington, cautions that protein phosphorylation does not automatically imply function. ...
