ABSTRACT
A central challenge of chemical biology is the development of small-molecule tools for controlling protein activity in a target-specific manner. Such tools are particularly useful if they can be systematically applied to the members of large protein families. Here we report that protein tyrosine phosphatases can be systematically 'sensitized' to target-specific inhibition by a cell-permeable small molecule, Fluorescein Arsenical Hairpin Binder (FlAsH), which does not inhibit any wild-type PTP investigated to date. We show that insertion of a FlAsH-binding peptide at a conserved position in the PTP catalytic-domain's WPD loop confers novel FlAsH sensitivity upon divergent PTPs. The position of the sensitizing insertion is readily identifiable from primary-sequence alignments, and we have generated FlAsH-sensitive mutants for seven different classical PTPs from six distinct subfamilies of receptor and non-receptor PTPs, including one phosphatase (PTP-PEST) whose three-dimensional catalytic-domain structure is not known. In all cases, FlAsH-mediated PTP inhibition was target specific and potent, with inhibition constants for the seven sensitized PTPs ranging from 17 to 370 nM. Our results suggest that a substantial fraction of the PTP superfamily will be likewise sensitizable to allele-specific inhibition; FlAsH-based PTP targeting thus potentially provides a rapid, general means for selectively targeting PTP activity in cell-culture- or model-organism-based signaling studies.
Subject(s)
Enzyme Inhibitors/pharmacology , Oligopeptides/pharmacology , Protein Tyrosine Phosphatases/antagonists & inhibitors , Alleles , Amino Acid Sequence , Dose-Response Relationship, Drug , Drug Design , Drug Evaluation, Preclinical , Enzyme Inhibitors/chemistry , Models, Molecular , Molecular Structure , Molecular Weight , Mutagenesis, Insertional , Oligopeptides/chemistry , Oligopeptides/isolation & purification , Protein Tyrosine Phosphatases/classification , Protein Tyrosine Phosphatases/genetics , Sequence Alignment , Structure-Activity Relationship , Substrate Specificity , Time FactorsABSTRACT
Allele-specific enzyme inhibitors are powerful tools in chemical biology. However, few general approaches for the discovery of such inhibitors have been described. Herein is reported a method for the sensitization of protein tyrosine phosphatases (PTPs) to small-molecule inhibition. It is shown that mutation of an active-site isoleucine to alanine (I219A) sensitizes PTP1B to inhibition by a class of thiophene-based inhibitors. This sensitization strategy succeeds for both 'orthogonal' inhibitors, designed to be incompatible with wild-type PTP active sites, and previously optimized wild-type PTP inhibitors. The finding that the I219A mutation sensitizes phosphatase domains to a variety of compounds suggests that isoleucine 219 may act as a 'gatekeeper' residue that can be widely exploited for the chemical-genetic analysis of PTP function.
Subject(s)
Enzyme Inhibitors/pharmacology , Protein Tyrosine Phosphatases/antagonists & inhibitors , Enzyme Inhibitors/chemistry , Models, MolecularABSTRACT
Protein tyrosine phosphatase H1, a member of the ubiquitous protein tyrosine phosphatase (PTP) superfamily of enzymes, is an important signaling molecule, mutant forms of which have been found in human colorectal cancers. Selective PTPH1 inhibitors would be valuable tools for investigating PTPH1's roles in cellular regulation. However, no PTPH1-specific inhibitors are known. To identify target-selective inhibitors of human PTPH1, we have redesigned a PTPH1/inhibitor interface. Structure-based protein design was used to identify two amino-acid residues, isoleucine 846 and methionine 883, that control PTPH1's sensitivity to oxalylaminoindole PTP inhibitors. Mutation of residues 846 and 883 to alanine and glycine, respectively, conferred novel inhibitor sensitivity onto PTPH1. From a small panel of putative inhibitors, compounds that potently and selectively target the inhibitor-sensitized PTPH1 mutants were identified.
Subject(s)
Enzyme Inhibitors/pharmacology , Protein Engineering , Protein Tyrosine Phosphatases/antagonists & inhibitors , Amino Acid Sequence , Amino Acid Substitution , Base Sequence , Binding Sites , DNA Primers , Kinetics , Molecular Sequence Data , Mutation , Protein Tyrosine Phosphatases/chemistry , Protein Tyrosine Phosphatases/geneticsABSTRACT
Protein tyrosine phosphatases (PTPs) are critical cell-signaling molecules. Inhibitors that are selective for individual PTPs would be valuable tools for dissecting complicated phosphorylation networks. However, the common architecture of PTP active sites impedes the discovery of such compounds. To achieve target selectivity, we have redesigned a PTP/inhibitor interface. Site-directed mutagenesis of a prototypical phosphatase, PTP1B, was used to generate "inhibitor-sensitized" PTPs. The PTP1B mutants were targeted by modifying a broad specificity PTP inhibitor with chemical groups that are sterically incompatible with wild-type PTP active sites. From a small panel of putative inhibitors, compounds that selectively inhibit Ile219Ala PTP1B over the wild-type enzyme were identified. Importantly, the corresponding mutation also conferred novel inhibitor sensitivity to T-cell PTP, suggesting that a readily identifiable point mutation can be used to generate a variety of inhibitor-sensitive PTPs.
