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Small-molecule Inhibitors (small-molecule + inhibitor)

Distribution by Scientific Domains

Chemistry	79%
Medical Sciences	16%

Distribution within Chemistry

Crystallography	36%

Selected Abstracts

Discovery of a Small-Molecule Inhibitor of the KIX,KID Interaction

CHEMBIOCHEM, Issue 17 2009
Bingbing X. Li Dr.
Are you too small? The small molecule (MW=297) shown here was discovered to be an inhibitor of the KIX,KID interaction by using a novel Renilla luciferase complementation assay. This compound also inhibits CREB-mediated gene transcription in living cells. [source]

Small-Molecule Inhibitors and Probes for Ubiquitin- and Ubiquitin-Like-Specific Proteases

CHEMBIOCHEM, Issue 2 2005
Anna Borodovsky Dr.
There's always a catch. The post-translational modification of proteins with ubiquitin (Ub) or ubiquitin-like (Ubl) modifiers is an important signal in the regulation of a variety of biological processes, such as degradation and regulation of gene expression. Here we report the synthesis of a panel of peptide vinyl sulfones (see scheme) harboring various portions of the Ub C terminus by using a safety-catch linker. Depending on their length, such compounds can efficiently target Ubl-specific proteases. [source]

Small-Molecule Inhibitors of the Hedgehog Signaling Pathway as Cancer Therapeutics

CHEMMEDCHEM, Issue 4 2010
Stefan Peukert Dr.
Abstract Inhibitors of the Hedgehog (Hh) molecular signaling pathway have emerged in recent years as a promising new class of potential therapeutics for cancer treatment. Numerous drug discovery efforts have resulted in the identification of a wide variety of small molecules that target different members of this pathway, including Smoothened (Smo), Sonic hedgehog protein (Shh), and Gli1. Several Smo inhibitors have now entered human clinical trials, and successful proof-of-concept studies have been carried out in patients with defined genetic mutations in the Hh pathway. This review provides a general overview of three main topics in this rapidly expanding area: 1),the various types of biological assays and in,vivo models that have been employed for the identification and optimization of Hh pathway inhibitors; 2),Smo inhibitors reported to date, including recent clinical results where available; and 3),efforts toward the identification and characterization of inhibitors of other members of the Hh pathway. [source]

Small-Molecule Inhibitors of Store-Operated Calcium Entry

CHEMMEDCHEM, Issue 5 2009
Zachary
Abstract Molecules that inhibit store-operated calcium entry (SOCE) are potentially useful immunomodulating agents. The identification of proteins involved in this pathway may further enable the identification of selective inhibitors. Herein we document some examples of the small-molecule inhibitors of SOCE that have been reported to date. We also describe methods that were used to characterize the mechanism of action of these inhibitors. Controlled variation in intracellular calcium concentration is a key component of the immune response signaling pathway in lymphocytes. Store-operated calcium entry (SOCE) in these cells provides a prolonged increase in cytoplasmic Ca2+ concentrations and ultimately leads to the production of pro-inflammatory cytokines. Molecules that inhibit SOCE could therefore be useful immunomodulating agents for the treatment of rheumatoid arthritis, psoriasis, inflammatory bowel disease, and other conditions. Although the presence of the SOCE signaling pathway in lymphocytes and other cells involved in the immune response has been known for many years, key proteins involved in SOCE were identified only recently. The identification of these proteins may further enable the identification of agents that inhibit SOCE without affecting other cellular processes. This contribution documents representative examples of the small-molecule inhibitors of SOCE that have been reported to date. Where possible, methods that were used to characterize the mechanism of action of the inhibitors are also described. [source]

Discovery of Potent, Orally Bioavailable Small-Molecule Inhibitors of the Human CCR2 Receptor

CHEMMEDCHEM, Issue 4 2008
Julien Doyon Dr.
Abstract We recently reported the discovery of a series of 2-thioimidazoles as CCR2 antagonists. The most potent molecules of this series, the 4,5-diesters, were rapidly hydrolyzed to the inactive acids and were found to be metabolically unstable. Herein we describe the synthesis of a number of analogues with heterocyclic bioisosteric replacements of the ester group(s). Small 5-membered heterocyclic substituents at the 4-position gave highly potent CCR2 antagonists. Hydrolysis of the 5-ester is diminished, thus imparting these compounds with sufficient stability and systemic exposure after oral administration to warrant further study of the in,vivo pharmacology of these functional CCR2 inhibitors. [source]

ApoG2, a novel inhibitor of antiapoptotic Bcl-2 family proteins, induces apoptosis and suppresses tumor growth in nasopharyngeal carcinoma xenografts

INTERNATIONAL JOURNAL OF CANCER, Issue 10 2008
Zhe-Yu Hu
Abstract Nasopharyngeal carcinoma (NPC) is a common malignant tumor in South China. It has been reported that overexpression of antiapoptotic Bcl-2 family proteins in NPC has caused the lack of long-term efficacy of conventional therapies. Apogossypolone (ApoG2), a novel small-molecule inhibitor of antiapoptotic Bcl-2 family proteins, has been discovered as the optimized derivative of gossypol. In this study, we found that in NPC cells, ApoG2 totally blocked the antiapoptotic function of Bcl-2 family proteins without affecting the expression levels of these proteins. ApoG2 selectively inhibited proliferation of 3 NPC cell lines (C666-1, CNE-1 and CNE-2) that highly expressed the antiapoptotic Bcl-2 proteins. This inhibitory activity was associated with release of cytochrome c, activation of caspase-9 and caspase-3 and apoptosis of sensitive NPC cells. However, ApoG2 had no obvious inhibitory effect on NPC cell line HONE-1, which expressed antiapoptotic Bcl-2 and Bcl-xL at a low level. We further found that ApoG2 effectively suppressed tumor growth of NPC xenografts in nude mice and enhanced the antitumor effect of CDDP (cisplatin) on NPC cells in vitro and in vivo. Immunohistochemical results showed that the expression of CD31 decreased after ApoG2 treatment, which suggested inhibition of angiogenesis in NPC xenografts. Our findings strongly suggest that ApoG2 may serve as a novel inhibitor of Bcl-2 family proteins and, by targeting these proteins, may become a promising drug for the treatment of NPC. © 2008 Wiley-Liss, Inc. [source]

In vivo pharmacology and antidiarrheal efficacy of a thiazolidinone CFTR inhibitor in rodents

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2005
N.D. Sonawane
Abstract A small-molecule inhibitor of the cystic fibrosis transmembrane conductance regulator (CFTR), 3-[(3-trifluoromethyl)phenyl]-5-[(4-carboxyphenyl)methylene]-2-thioxo-4-thiazolidinone (CFTRinh -172), reduces enterotoxin-induced intestinal fluid secretion in rodents. Here, we study CFTRinh -172 pharmacology and antidiarrheal efficacy in rodents using 14C-labeled CFTRinh -172, liquid chromatography/mass spectrometry, and a closed intestinal loop model of fluid secretion. CFTRinh -172 was cleared primarily by renal glomerular filtration without chemical modification. CFTRinh -172 accumulated in liver within 5 min after intravenous infusion in mice, and was concentrated fivefold in bile over blood. At 30,240 min, CFTRinh -172 was found mainly in liver, intestine, and kidney, with little detectable in the brain, heart, skeletal muscle, or lung. Pharmacokinetic analysis in rats following intravenous bolus infusion showed a distribution volume of 770 mL with redistribution and elimination half-times of 0.14 h and 10.3 h, respectively. CFTRinh -172 was stable in hepatic microsomes. Closed-loop studies in mice indicated that a single intraperitoneal injection of 20 ,g CFTRinh -172 inhibited fluid accumulation at 6 h after cholera toxin by >90% in duodenum and jejunum, ,60% in ileum and <10% in colon. No toxicity was seen after high-dose CFTRinh -172 administration (3 mg/kg/day in two daily doses) in mice over the first 6 weeks of life. The metabolic stability, enterohepatic recirculation, slow renal elimination, and intestinal accumulation of CFTRinh -172 account for its efficacy as an antidiarrheal. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 94:134,143, 2005 [source]

ZD6474 induces growth arrest and apoptosis of GIST-T1 cells, which is enhanced by concomitant use of sunitinib

CANCER SCIENCE, Issue 12 2006
Yang Yang
ZD6474 (Zactima, AstraZeneca, Macclesfield, UK) is an orally available, small-molecule inhibitor of vascular endothelial growth factor receptor-2 and epidermal growth factor receptor tyrosine kinases, with additional activity versus rearranged during transfection (RET). This study explored the effect of ZD6474 in gastrointestinal stromal tumor-T1 (GIST-T1) cells that possess a gain of function mutation in exon 11 of the c-KIT gene. ZD6474 induced growth arrest and apoptosis of GIST-T1 cells in association with blockade of c-Kit and its downstream effectors, including Akt and extracellular signal-regulated kinase (ERK). ZD6474 treatment also blocked the mammalian target of rapamycin (mTOR), which lies downstream of Akt and ERK. Interestingly, when ZD6474 was combined with sunitinib (SU11248; Sutent, Pfizer, Kalamazoo, MI, USA), a class III and V receptor tyrosine kinase inhibitor, the ZD6474-mediated growth inhibition was potentiated in association with further down-regulation of the mTOR targets p-p70S6K and p-4E-BP-1. The combination of ZD6474 and sunitinib should be investigated further. (Cancer Sci 2006; 97: 1404,1409) [source]

Indoleamine 2,3-dioxygenase in T-cell tolerance and tumoral immune escape

IMMUNOLOGICAL REVIEWS, Issue 1 2008
Jessica B. Katz
Summary: Indoleamine 2, 3-dioxygenase (IDO) degrades the essential amino acid tryptophan in mammals, catalyzing the initial and rate-limiting step in the de novo biosynthesis nicotinamide adenine dinucleotide (NAD). Broad evidence implicates IDO and the tryptophan catabolic pathway in generation of immune tolerance to foreign antigens in tissue microenvironments. In particular, recent findings have established that IDO is overexpressed in both tumor cells and antigen-presenting cells in tumor-draining lymph nodes, where it promotes the establishment of peripheral immune tolerance to tumor antigens. In the normal physiologic state, IDO is important in creating an environment that limits damage to tissues due to an overactive immune system. However, by fostering immune suppression, IDO can facilitate the survival and growth of tumor cells expressing unique antigens that would be recognized normally as foreign. In preclinical studies, small-molecule inhibitors of IDO can reverse this mechanism of immunosuppression, complementing classical cytotoxic cancer chemotherapeutic agents' ability to trigger regression of treatment-resistant tumors. These results have encouraged the clinical translation of IDO inhibitors, the first of which entered phase I clinical trials in the fall of 2007. In this article, we survey the work defining IDO as an important mediator of peripheral tolerance, review evidence of IDO dysregulation in cancer cells, and provide an overview of the development of IDO inhibitors as a new immunoregulatory treatment modality for clinical trials. [source]

Pharmacological targeting of CDK9 in cardiac hypertrophy

MEDICINAL RESEARCH REVIEWS, Issue 4 2010
Vladimír Kry
Abstract Cardiac hypertrophy allows the heart to adapt to workload, but persistent or unphysiological stimulus can result in pump failure. Cardiac hypertrophy is characterized by an increase in the size of differentiated cardiac myocytes. At the molecular level, growth of cells is linked to intensive transcription and translation. Several cyclin-dependent kinases (CDKs) have been identified as principal regulators of transcription, and among these CDK9 is directly associated with cardiac hypertrophy. CDK9 phosphorylates the C -terminal domain of RNA polymerase II and thus stimulates the elongation phase of transcription. Chronic activation of CDK9 causes not only cardiac myocyte enlargement but also confers predisposition to heart failure. Due to the long interest of molecular oncologists and medicinal chemists in CDKs as potential targets of anticancer drugs, a portfolio of small-molecule inhibitors of CDK9 is available. Recent determination of CDK9's crystal structure now allows the development of selective inhibitors and their further optimization in terms of biochemical potency and selectivity. CDK9 may therefore constitute a novel target for drugs against cardiac hypertrophy. © 2009 Wiley Periodicals, Inc. Med Res Rev 30, No. 4, 646,666, 2010 [source]

Development of anaplastic lymphoma kinase (ALK) small-molecule inhibitors for cancer therapy

MEDICINAL RESEARCH REVIEWS, Issue 3 2008
Rongshi Li
Abstract Anaplastic lymphoma kinase (ALK) is a receptor tyrosine kinase (RTK) involved in the genesis of several human cancers; indeed, ALK was initially identified in constitutively activated and oncogenic fusion forms,the most common being nucleophosmin (NPM)-ALK,in a non-Hodgkin's lymphoma (NHL) known as anaplastic large-cell lymphoma (ALCL) and subsequent studies identified ALK fusions in the human sarcomas called inflammatory myofibroblastic tumors (IMTs). In addition, two recent reports have suggested that the ALK fusion, TPM4-ALK, may be involved in the genesis of a subset of esophageal squamous cell carcinomas. While the cause-effect relationship between ALK fusions and malignancies such as ALCL and IMT is very well established, more circumstantial links implicate the involvement of the full-length, normal ALK receptor in the genesis of additional malignancies including glioblastoma, neuroblastoma, breast cancer, and others; in these instances, ALK is believed to foster tumorigenesis following activation by autocrine and/or paracrine growth loops involving the reported ALK ligands, pleiotrophin (PTN) and midkine (MK). There are no currently available ALK small-molecule inhibitors approved for clinical cancer therapy; however, recognition of the variety of malignancies in which ALK may play a causative role has recently begun to prompt developmental efforts in this area. This review provides a succinct summary of normal ALK biology, the confirmed and putative roles of ALK fusions and the full-length ALK receptor in the development of human cancers, and efforts to target ALK using small-molecule kinase inhibitors. © 2007 Wiley Periodicals, Inc. Med Res Rev, 28, No. 3, 372,412, 2008 [source]

The transcription factor Fra-2 regulates the production of extracellular matrix in systemic sclerosis

ARTHRITIS & RHEUMATISM, Issue 1 2010
Nicole Reich
Objective Fra-2 belongs to the activator protein 1 family of transcription factors. Mice transgenic for Fra-2 develop a systemic fibrotic disease with vascular manifestations similar to those of systemic sclerosis (SSc). The aim of the present study was to investigate whether Fra-2 plays a role in the pathogenesis of SSc and to identify the molecular mechanisms by which Fra-2 induces fibrosis. Methods Dermal thickness and the number of myofibroblasts were determined in skin sections from Fra-2,transgenic and wild-type mice. The expression of Fra-2 in SSc patients and in animal models of SSc was analyzed by real-time polymerase chain reaction and immunohistochemistry. Fra-2, transforming growth factor , (TGF,), and ERK signaling in SSc fibroblasts were inhibited using small interfering RNA, neutralizing antibodies, and small-molecule inhibitors. Results Fra-2,transgenic mice developed a skin fibrosis with increases in dermal thickness and increased myofibroblast differentiation starting at age 12 weeks. The expression of Fra-2 was up-regulated in SSc patients and in different mouse models of SSc. Stimulation with TGF, and platelet-derived growth factor (PDGF) significantly increased the expression of Fra-2 in SSc fibroblasts and induced DNA binding of Fra-2 in an ERK-dependent manner. Knockdown of Fra-2 potently reduced the stimulatory effects of TGF, and PDGF and decreased the release of collagen from SSc fibroblasts. Conclusion We demonstrate that Fra-2 is overexpressed in SSc and acts as a novel downstream mediator of the profibrotic effects of TGF, and PDGF. Since transgenic overexpression of Fra-2 causes not only fibrosis but also vascular disease, Fra-2 might be an interesting novel candidate for molecular-targeted therapies for SSc. [source]

Structures of the PKC-, kinase domain in its ATP-bound and apo forms reveal defined structures of residues 533,551 in the C-terminal tail and their roles in ATP binding

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 5 2010
Tetsuo Takimura
Protein kinase C (PKC) plays an essential role in a wide range of cellular functions. Although crystal structures of the PKC-,, PKC-, and PKC-,II kinase domains have previously been determined in complexes with small-molecule inhibitors, no structure of a PKC,substrate complex has been determined. In the previously determined PKC-, complex, residues 533,551 in the C-terminal tail were disordered. In the present study, crystal structures of the PKC-, kinase domain in its ATP-bound and apo forms were determined at 2.1 and 2.0,Å resolution, respectively. In the ATP complex, the electron density of all of the C-terminal tail residues was well defined. In the structure, the side chain of Phe543 protrudes into the ATP-binding pocket to make van der Waals interactions with the adenine moiety of ATP; this is also observed in other AGC kinase structures such as binary and ternary substrate complexes of PKA and AKT. In addition to this interaction, the newly defined residues around the turn motif make multiple hydrogen bonds to glycine-rich-loop residues. These interactions reduce the flexibility of the glycine-rich loop, which is organized for ATP binding, and the resulting structure promotes an ATP conformation that is suitable for the subsequent phosphoryl transfer. In the case of the apo form, the structure and interaction mode of the C-terminal tail of PKC-, are essentially identical to those of the ATP complex. These results indicate that the protein structure is pre-organized before substrate binding to PKC-,, which is different from the case of the prototypical AGC-branch kinase PKA. [source]

Engineering the catalytic domain of human protein tyrosine phosphatase , for structure-based drug discovery

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2006
Artem G. Evdokimov
Protein tyrosine phosphatases (PTPs) play roles in many biological processes and are considered to be important targets for drug discovery. As inhibitor development has proven challenging, crystal structure-based design will be very helpful to advance inhibitor potency and selectivity. Successful application of protein crystallography to drug discovery heavily relies on high-quality crystal structures of the protein of interest complexed with pharmaceutically interesting ligands. It is very important to be able to produce protein,ligand crystals rapidly and reproducibly for as many ligands as necessary. This study details our efforts to engineer the catalytic domain of human protein tyrosine phosphatase , (HPTP,-CD) with properties suitable for rapid-turnaround crystallography. Structures of apo HPTP,-CD and its complexes with several novel small-molecule inhibitors are presented here for the first time. [source]

Structure of murine angiogenin: features of the substrate- and cell-binding regions and prospects for inhibitor-binding studies

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 12 2005
Daniel E. Holloway
Angiogenin is an unusual member of the pancreatic ribonuclease superfamily that induces blood-vessel formation and is a promising anticancer target. The three-dimensional structure of murine angiogenin (mAng) has been determined by X-ray crystallography. Two structures are presented: one is a complex with sulfate ions (1.5,Å resolution) and the other a complex with phosphate ions (1.6,Å resolution). Residues forming the putative B1, P1 and B2 subsites occupy positions similar to their hAng counterparts and are likely to play similar roles. The anions occupy the P1 subsite, sulfate binding conventionally and phosphate adopting two orientations, one of which is novel. The B1 subsite is obstructed by Glu116 and Phe119, with the latter assuming a less invasive position than its hAng counterpart. Hydrophobic interactions between the C-terminal segment and the main body of the protein are more extensive than in hAng and may underly the lower enzymatic activity of the murine protein. Elsewhere, the structure of the H3,B2 loop supports the view that hAng Asn61 interacts directly with cell-surface molecules and does not merely stabilize adjacent regions of the hAng structure. mAng crystals appear to offer small-molecule inhibitors a clear route to the active site and may even withstand a reorientation of the C-terminal segment that provides access to the cryptic B1 subsite. These features represent considerable advantages over crystalline hAng and bAng. [source]

Mutation of surface residues to promote crystallization of activated factor XI as a complex with benzamidine: an essential step for the iterative structure-based design of factor XI inhibitors

ACTA CRYSTALLOGRAPHICA SECTION D, Issue 10 2005
Pramod Pandey
Activated factor XI (FXIa) is a key enzyme in the amplification phase of the blood-coagulation cascade. Thus, a selective FXIa inhibitor may have lesser bleeding liabilities and provide a safe alternative for antithrombosis therapy to available drugs on the market. In a previous report, the crystal structures of the catalytic domain of FXIa (rhFXI370,607) in complex with various ecotin mutants have been described [Jin et al. (2005), J. Biol. Chem.280, 4704,4712]. However, ecotin forms a matrix-like interaction with rhFXI370,607 and is impossible to displace with small-molecule inhibitors; ecotin crystals are therefore not suitable for iterative structure-based ligand design. In addition, rhFXI370,607 did not crystallize in the presence of small-molecule ligands. In order to obtain the crystal structure of rhFXI370,607 with a weak small-molecule ligand, namely benzamidine, several rounds of surface-residue mutation were implemented to promote crystal formation of rhFXI370,607. A quadruple mutant of rhFXI370,607 (rhFXI370,607 -S434A,T475A,C482S,K437A) readily crystallized in the presence of benzamidine. The benzamidine in the preformed crystals was easily exchanged with other FXIa small-molecule inhibitors. These crystals have facilitated the structure-based design of small-molecule FXIa inhibitors. [source]

Structure of the adenylation domain of NAD+ -dependent DNA ligase from Staphylococcus aureus

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 11 2009
Seungil Han
DNA ligase catalyzes phosphodiester-bond formation between immediately adjacent 5,-phosphate and 3,-hydroxyl groups in double-stranded DNA and plays a central role in many cellular and biochemical processes, including DNA replication, repair and recombination. Bacterial NAD+ -dependent DNA ligases have been extensively characterized as potential antibacterial targets because of their essentiality and their structural distinction from human ATP-dependent DNA ligases. The high-resolution structure of the adenylation domain of Staphylococcus aureus NAD+ -dependent DNA ligase establishes the conserved domain architecture with other bacterial adenylation domains. Two apo crystal structures revealed that the active site possesses the preformed NAD+ -binding pocket and the `C2 tunnel' lined with hydrophobic residues: Leu80, Phe224, Leu287, Phe295 and Trp302. The C2 tunnel is unique to bacterial DNA ligases and the Leu80 side chain at the mouth of the tunnel points inside the tunnel and forms a narrow funnel in the S. aureus DNA ligase structure. Taken together with other DNA ligase structures, the S. aureus DNA ligase structure provides a basis for a more integrated understanding of substrate recognition and catalysis and will be also be of help in the development of small-molecule inhibitors. [source]

Structural analysis of caspase-1 inhibitors derived from Tethering

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 5 2005
Bruce T. Fahr
Caspase-1 is a key endopeptidase responsible for the post-translational processing of the IL-1, and IL-18 cytokines and small-molecule inhibitors that modulate the activity of this enzyme are predicted to be important therapeutic treatments for many inflammatory diseases. A fragment-assembly approach, accompanied by structural analysis, was employed to generate caspase-1 inhibitors. With the aid of Tethering® with extenders (small molecules that bind to the active-site cysteine and contain a free thiol), two novel fragments that bound to the active site and made a disulfide bond with the extender were identified by mass spectrometry. Direct linking of each fragment to the extender generated submicromolar reversible inhibitors that significantly reduced secretion of IL-1, but not IL-6 from human peripheral blood mononuclear cells. Thus, Tethering with extenders facilitated rapid identification and synthesis of caspase-1 inhibitors with cell-based activity and subsequent structural analyses provided insights into the enzyme's ability to accommodate different inhibitor-binding modes in the active site. [source]

Signal Transducers and Activators of Transcription as Targets for Small Organic Molecules

CHEMBIOCHEM, Issue 13 2008
Thorsten Berg Dr.
Abstract Signal transducers and activators of transcription (STATs) are a family of transcription factors that are of central importance for cellular signaling and have therefore emerged as attractive target proteins for cell-permeable small molecules. This review outlines the basic concept of STAT signaling, the relevance of individual members of the STAT family for cellular signaling and human disease, and generally applicable approaches taken to the identification of small-molecule inhibitors of STATs. [source]

Molecular Characterization of the NCoA-1,STAT,6 Interaction

CHEMBIOCHEM, Issue 8 2008
Markus Seitz
Abstract Many protein,protein interactions involved in cell signalling, cell adhesion and regulation of transcription are mediated by short ,-helical recognition motifs with the sequence Leu-Xaa-Xaa-Leu-Leu (LXXLL, where Xaa is any amino acid). Originally observed in cofactors that interact with hormone-activated nuclear receptors, LXXLL motifs are now known to occur in many transcription factors, including the STAT family, which transmit signals from activated cytokine receptors at the cell surface to target genes in the nucleus. STAT,6 becomes activated in response to IL-4 and IL-13, which regulate immune and anti-inflammatory responses. Structural studies have revealed how an LXXLL motif located in 2.5 turns of an ,-helical peptide derived from STAT,6 provide contacts through the leucine side chains to the coactivator of transcription, NCoA-1. However, since many protein,protein interactions are mediated by LXXLL motifs, it is important to understand how specificity is achieved in this and other signalling pathways. Here, we show that energetically important contacts between STAT,6 and NCoA-1 are made in residues that flank the LXXLL motif, including the underlined residues in the sequence LLPPTEQDLTKLL. We also demonstrate how the affinity for NCoA-1 of peptides derived from this region of STAT,6 can be significantly improved by optimising knobs-into-holes contacts on the surface of the protein. The results provide important new insights into the origins of binding specificity, and might be of practical value in the design of novel small-molecule inhibitors of this important protein,protein interaction. [source]

Research Article: Effective and Specific Inhibition of the CD40,CD154 Costimulatory Interaction by a Naphthalenesulphonic Acid Derivative

CHEMICAL BIOLOGY & DRUG DESIGN, Issue 4 2010
Emilio Margolles-Clark
Costimulatory interactions are important regulators of T-cell activation and, hence, promising therapeutic targets in autoimmune diseases as well as in transplant recipients. Following our recent identification of the first small-molecule inhibitors of the CD40,CD154 costimulatory protein,protein interaction (J Mol Med 87, 2009, 1133), we continued our search within the chemical space of organic dyes, and we now report the identification of the naphthalenesulphonic acid derivative mordant brown 1 as a more active, more effective, and more specific inhibitor. Flow cytometry experiments confirmed its ability to concentration-dependently inhibit the CD154(CD40L)-induced cellular responses in human THP-1 cells at concentrations well below cytotoxic levels. Binding experiments showed that it not only inhibits the CD40,CD154 interaction with sub-micromolar activity, but it also has considerably more than 100-fold selectivity toward this interaction even when compared to other members of the tumor necrosis factor superfamily pairs such as TNF-R1,TNF-,, BAFF-R(CD268),BAFF(CD257/BLys), OX40(CD134),OX40L(CD252), RANK(CD265),RANKL(CD254/TRANCE), or 4-1BB(CD137),4-1BBL. There is now sufficient structure-activity relationship information to serve as the basis of a drug discovery initiative targeting this important costimulatory interaction. [source]