Development of a Substrate-Based Cyclic Phosphopeptide Inhibitor of Protein Phosphatase 2C, Wip1

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• 作者：Hiroshi Yamaguchi ; Stewart R. Durell ; Hanqiao Feng ; Yawen Bai ; Carl W. Anderson ; Ettore Appella
• 刊名：Biochemistry
• 出版年：2006
• 出版时间：November 7, 2006
• 年：2006
• 卷：45
• 期：44
• 页码：13193 - 13202
• 全文大小：432K
• 年卷期：v.45,no.44(November 7, 2006)
• ISSN：1520-4995

文摘

The wild-type p53-induced phosphatase, Wip1 (PP2C or PPM1D) is a member of the proteinphosphatase 2C (PP2C) family and functions as a negative regulator of the p38 MAP kinase-p53 signalingpathway. PPM1D is amplified or Wip1 is overexpressed in several human cancers, and it acts as a weakoncogene. Although inhibition of Wip1 may have therapeutic value, no specific inhibitors are available.In this study, we designed phosphopeptide inhibitors for Wip1 on the basis of its optimal substrate sequence.We found that phosphoserine-containing diphosphorylated peptides with the sequence pSXpY inhibitedWip1 phosphatase activity, whereas phosphothreonine-containing peptides with the sequence pTXpY werephysiological substrates. Moreover, the X residue in the pSXpY sequence modulated inhibitor activity,and -branched amino acid-substituted (Ile or Val) phosphopeptides showed high inhibitory potencies. Athioether cyclic phosphopeptide c(MpSIpYVA) had a K_i <1.0 M. Two serine/threonine phosphatases,PP2C and PP2A, were not significantly inhibited by the cyclic phosphopeptide with a nonhydrolyzablephosphoserine mimetic. A homology model of Wip1 bound to a cyclic phosphopeptide and site-directedmutagenesis helped to identify residues important for Wip1 inhibitor selectivity among the PP2C family.These results provide the first proof of concept of a specific inhibitor of the catalytic site of Wip1 andshould be useful for developing potential anti-cancer drugs.