文摘
To identify phosphoproteins regulated by thephosphoprotein phosphatase (PPP) family of S/T phosphatases, we performed a large-scale characterization ofchanges in protein phosphorylation on extracts from HeLacells treated with or without calyculin A, a potent PPPenzyme inhibitor. A label-free comparative phosphoproteomics approach using immobilized metal ion affinitychromatography and targeted tandem mass spectrometrywas employed to discover and identify signatures basedupon distinctive changes in abundance. Overall, 232proteins were identified as either direct or indirect targetsfor PPP enzyme regulation. Most of the present identifications represent novel PPP enzyme targets at the level ofboth phosphorylation site and protein. These includephosphorylation sites within signaling proteins such asp120 Catenin, A Kinase Anchoring Protein 8, JunB, andType II Phosphatidyl Inositol 4 Kinase. These data can beused to define underlying signaling pathways and eventsregulated by the PPP family of S/T phosphatases.