LOCALIZED ACTIVATION OF RTK MAPK PATHWAYS DURING DROSOPHILA DEVELOPMENT/

Receptor tyrosine kinase (RTK) signaling is mediated by a signaling ca scade culminating in activation of mitogen-activated protein kinase (M APK) by double phosphorylation on threonine and tyrosine residues, The pattern of MAPK activation can now be directly visualized in situ dur ing embryonic and adult development using an antiserum is specific for the double phosphorylated form of MAPK (db-P MAPK).(1,2) The pattern of MAPK activation detected by this antiserum in developing embryos an d larval imaginal discs conforms remarkably well to the inferred patte rn of known RTK function. In addition, db-P MARK staining directly rev eals features of signaling such as the range of signal spreading and t he kinetics of RTK activation, which would be difficult to measure by other methods. The ability to visualize the output of RTK signaling al so permits detailed establishment of epistatic relationships between s ignaling components of RTK cascades. BioEssays 20: 189-194, 1998. (C) 1998 John Wiley & Sons, Inc.