To explore the role of the protein tyrosine phosphatase Syp in insulin signaling, a catalytically inert mutant Syp protein was expressed under an inducible promoter in cells transfected with the human insulin receptor. Expression of the mutant phosphatase significantly reduced the stimulation of mitogenesis by insulin, indicating that the mutation produced a dominant negative phenotype. Tyrosin...

It has long been postulated that protein tyrosine phosphatases may act as tumor suppressors because of their ability to counteract the oncogenic actions of protein tyrosine kinases. Here we report the cloning and characterization of a novel human protein tyrosine phosphatase, TEP1. TEP1 contains the protein tyrosine phosphatase signature motif, and we show that it possesses an intrinsic protein...

Activation of the thiol protease calpain results in proteolysis of focal adhesion-associated proteins and severing of cytoskeletal-integrin links. We employed a commonly used inhibitor of calpain, calpeptin, to examine a role for this protease in the reorganization of the cytoskeleton under a variety of conditions. Calpeptin induced stress fiber formation in both forskolin-treated REF-52 fibrob...