The family-wide structure and function of human dual-specificity protein phosphatases.

Dual-specificity protein phosphatases (DUSPs), which dephosphorylate both phosphoserine/threonine and phosphotyrosine, play vital roles in immune activation, brain function and cell-growth signalling. A family-wide structural library of human DUSPs was constructed based on experimental structure determination supplemented with homology modelling. The catalytic domain of each individual DUSP has characteristic features in the active site and in surface-charge distribution, indicating substrate-interaction specificity. The active-site loop-to-strand switch occurs in a subtype-specific manner, indicating that the switch process is necessary for characteristic substrate interactions in the corresponding DUSPs. A comprehensive analysis of the activity-inhibition profile and active-site geometry of DUSPs revealed a novel role of the active-pocket structure in the substrate specificity of DUSPs. A structure-based analysis of redox responses indicated that the additional cysteine residues are important for the protection of enzyme activity. The family-wide structures of DUSPs form a basis for the understanding of phosphorylation-mediated signal transduction and the development of therapeutics.

Identification of novel inhibitors of mitogen-activated protein kinase phosphatase-1 with structure-based virtual screening.

Mitogen-activated protein kinase phosphatase-1 (MKP-1) has proved to be an attractive target for the development of therapeutics for the treatment of cancer. We report the first example for a successful application of the structure-based virtual screening to identify the novel inhibitors of MKP-1. It is shown that the efficiency of virtual screening can be enhanced significantly by the incorporation of a new solvation energy term in the scoring function. The newly found inhibitors have desirable physicochemical properties as a drug candidate and reveal a moderate potency with IC(50) values ranging from 20 to 50 µM. Therefore, they deserve a consideration for further development by structure-activity relationship studies to optimize the inhibitory activities. Structural features relevant to the stabilization of the inhibitors in the active site of MKP-1 are discussed in detail.

Discovery of novel Cdc25 phosphatase inhibitors with micromolar activity based on the structure-based virtual screening.

Cdc25 phosphatases have been considered as attractive drug targets for anticancer therapy because of the correlation of their overexpression with a wide variety of cancers. We have been able to identify five novel Cdc25 phosphatase inhibitors with micromolar activity by means of a computer-aided drug design protocol involving the homology modeling of Cdc25A and the virtual screening with the automated AutoDock program implementing the effects of ligand solvation in the scoring function. Because the newly discovered inhibitors are structurally diverse and reveal a significant potency with IC 50 values lower than 10 microM, they can be considered for further development by structure-activity relationship studies or de novo design methods. The differences in binding modes of the identified inhibitors in the active sites of Cdc25A and B are discussed in detail.

Protein tyrosine phosphatase 1B inhibitors from Morus root bark.

An organic layer prepared from the Chinese crude drug 'Sang-Bai-Pi' (Morus root bark) was studied in order to identify the inhibitory compounds for protein tyrosine phosphatase 1B (PTP1B). Bioassay-guided fractionation resulted in the isolation of sanggenon C (1), sanggenon G (2), mulberrofuran C (3) and kuwanon L (4) as PTP1B inhibitors, along with moracin O (5) and moracin P (6). Compounds 1-4 inhibited PTP1B with IC(50) values ranging from 1.6+/-0.3 microM to 16.9+/-1.1 microM.

Structure of human FIH-1 reveals a unique active site pocket and interaction sites for HIF-1 and von Hippel-Lindau.

The master switch of cellular hypoxia responses, hypoxia-inducible factor 1 (HIF-1), is hydroxylated by factor inhibiting HIF-1 (FIH-1) at a conserved asparagine residue under normoxia, which suppresses transcriptional activity of HIF-1 by abrogating its interaction with transcription coactivators. Here we report the crystal structure of human FIH-1 at 2.8-A resolution. The structural core of FIH-1 consists of a jellyroll-like beta-barrel containing the conserved ferrous-binding triad residues, confirming that FIH-1 is a member of the 2-oxoglutarate-dependent dioxygenase family. Except for the core structure and triad residues, FIH-1 has many structural deviations from other family members including N- and C-terminal insertions and various deletions in the middle of the structure. The ferrous-binding triad region is highly exposed to the solvent, which is connected to a prominent groove that may bind to a helix near the hydroxylation site of HIF-1. The structure, which is in a dimeric state, also reveals the putative von Hippel-Lindau-binding site that is distinctive to the putative HIF-1-binding site, supporting the formation of the ternary complex by FIH-1, HIF-1, and von Hippel-Lindau. The unique environment of the active site and cofactor-binding region revealed in the structure should allow design of selective drugs that can be used in ischemic diseases to promote hypoxia responses.