Identification of novel MAP kinase pathway signaling targets by functionalproteomics and mass spectrometry

Functional proteomics provides a powerful method for monitoring global mole cular responses following activation of signal transduction pathways, repor ting altered protein posttranslational modification and expression. Here we combine functional proteomics with selective activation and inhibition of MKK1/2, in order to identify cellular targets regulated by the MKK/ERK casc ade. Twenty-five targets of this signaling pathway were identified, of whic h only five were previously characterized as MKK/ERK effecters. The remaini ng targets suggest novel roles for this signaling cascade in cellular proce sses of nuclear transport, nucleotide excision repair, nucleosome assembly, membrane trafficking, and cytoskeletal regulation. This study represents a n application of functional proteomics toward identifying regulated targets of a discrete signal transduction pathway and demonstrates the utility of this discovery-based strategy in elucidating novel MAP kinase pathway effec ters.