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This article has been peer reviewed. It is the authors' final version prior to publication in Journal of Biological Chemistry. Volume 284, Issue 51, December 2009, Pages 35273-35277. The published version is available at DOI: 10.1074/jbc.R109.059972. Copyright © American Society for Biochemistry and Molecular Biology


The regulatory circuit controlling cellular protein phosphatase-1 (PP1), an abundant group of Ser/Thr phosphatases, involves phosphorylation of PP1-specific inhibitor proteins. Malfunctions of these inhibitor proteins have been linked to a variety of diseases, including cardiovascular disease and cancer. Upon phosphorylation at Thr(38), the 17-kDa PP1 inhibitor protein, CPI-17, selectively inhibits a specific form of PP1, myosin light chain phosphatase, which transduces multiple kinase signals into the phosphorylation of myosin II and other proteins. Here, the mechanisms underlying PP1 inhibition and the kinase/PP1 cross-talk mediated by CPI-17 and its related proteins, PHI, KEPI, and GBPI, are discussed.

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