Antiapoptotic Bcl‐2 family proteins, such as Bcl‐xL, Bcl‐2, and Mcl‐1, are often overexpressed in tumor cells, which contributes to tumor cell resistance to chemotherapies and radiotherapies. Inhibitors of these proteins thus have potential applications in cancer treatment. We discovered, through structure‐based virtual screening, a lead compound with micromolar binding affinity to Mcl‐1 (inhibition constant (Ki)=3 μM ). It contains a phenyltetrazole and a hydrazinecarbothioamide moiety, and it represents a structural scaffold not observed among known Bcl‐2 inhibitors. This work presents the structural optimization of this lead compound. By following the scaffold‐hopping strategy, we have designed and synthesized a total of 82 compounds in three sets. All of the compounds were evaluated in a fluorescence‐polarization binding assay to measure their binding affinities to Bcl‐xL, Bcl‐2, and Mcl‐1. Some of the compounds with a 3‐phenylthiophene‐2‐sulfonamide core moiety showed sub‐micromolar binding affinities to Mcl‐1 (Ki=0.3–0.4 μM ) or Bcl‐2 (Ki≈1 μM ). They also showed obvious cytotoxicity on tumor cells (IC50<10 μM ). Two‐dimensional heteronuclear single quantum coherence NMR spectra of three selected compounds, that is, YCW‐E5, YCW‐E10, and YCW‐E11, indicated that they bind to the BH3‐binding groove on Bcl‐xL in a similar mode to ABT‐737. Several apoptotic assays conducted on HL‐60 cells demonstrated that these compounds are able to induce cell apoptosis through the mitochondrial pathway. We propose that the compounds with the 3‐phenylthiophene‐2‐sulfonamide core moiety are worth further optimization as effective apoptosis inducers with an interesting selectivity towards Mcl‐1 and Bcl‐2. 相似文献
Considerable efforts have been made to the development of small‐molecule inhibitors of antiapoptotic B‐cell lymphoma 2 (Bcl‐2) family proteins (such as Bcl‐2, Bcl‐xL, and Mcl‐1) as a new class of anticancer therapies. Unlike general inhibitors of the entire family, selective inhibitors of each member protein can hopefully reduce the adverse side effects in chemotherapy treatments of cancers overexpressing different Bcl‐2 family proteins. In this study, we designed four series of benzylpiperazine derivatives as plausible Bcl‐2 inhibitors based on the outcomes of a computational algorithm. A total of 81 compounds were synthesized, and their binding affinities to Bcl‐2, Bcl‐xL, and Mcl‐1 measured. Encouragingly, 22 compounds exhibited binding affinities in the micromolar range (Ki<20 μM ) to at least one target protein. Moreover, some compounds were observed to be highly selective binders to Mcl‐1 with no detectable binding to Bcl‐2 or Bcl‐xL, among which the most potent one has a Ki value of 0.18 μM for Mcl‐1. Binding modes of four selected compounds to Mcl‐1 and Bcl‐xL were derived through molecular docking and molecular dynamics simulations. It seems that the binding affinity and selectivity of these compounds can be reasonably interpreted with these models. Our study demonstrated the possibility for obtaining selective Mcl‐1 inhibitors with relatively simple chemical scaffolds. The active compounds identified by us could be used as lead compounds for developing even more potent selective Mcl‐1 inhibitors with potential pharmaceutical applications. 相似文献
In a previous study we reported a class of compounds with a 2H‐thiazolo[3,2‐a]pyrimidine core structure as general inhibitors of anti‐apoptotic Bcl‐2 family proteins. However, the absolute stereochemical configuration of one carbon atom on the core structure remained unsolved, and its potential impact on the binding affinities of compounds in this class was unknown. In this study, we obtained pure R and S enantiomers of four selected compounds by HPLC separation and chiral synthesis. The absolute configurations of these enantiomers were determined by comparing their circular dichroism spectra to that of an appropriate reference compound. In addition, a crystal structure of one selected compound revealed the exocyclic double bond in these compounds to be in the Z configuration. The binding affinities of all four pairs of enantiomers to Bcl‐xL, Bcl‐2, and Mcl‐1 proteins were measured in a fluorescence‐polarization‐based binding assay, yielding inhibition constants (Ki values) ranging from 0.24 to 2.20 μM . Interestingly, our results indicate that most R and S enantiomers exhibit similar binding affinities for the three tested proteins. A binding mode for this compound class was derived by molecular docking and molecular dynamics simulations to provide a reasonable interpretation of this observation. 相似文献
The Bcl‐2 family proteins are key regulators of the intrinsic apoptotic pathway and are among the validated targets for developing anticancer drugs. Protein–protein interactions between the pro‐ and antiapoptotic members of this family determine mitochondrial outer‐membrane permeabilization. Elucidating such protein–protein interactions in a quantitative way is helpful for network pharmacology studies on the Bcl‐2 family, which, in turn, will provide valuable guidance for developing new anticancer therapies. In this study, the binding affinities of the BH3 peptides derived from eight proapoptotic BH3‐only proteins (i.e., Bid, Bim, Puma, Noxa, Bad, Bmf, Bik, Hrk) against five well‐studied antiapoptotic proteins (i.e., Bcl‐xL, Bcl‐2, Mcl‐1, Bcl‐w, Bfl‐1) in the Bcl‐2 family have been measured. Three different types of binding assay (i.e., surface plasmon resonance, fluorescence polarization, and homogeneous time‐resolved fluorescence) were employed for cross‐validation. The results confirmed that each proapoptotic BH3 peptide exhibited a distinct binding profile against the five antiapoptotic proteins. The binding data obtained herein serve as a fresh update or correction to existing knowledge. It is expected that such binding data will be helpful for building more accurate mathematical network models for depicting the complex protein–protein interactions within the Bcl‐2 family. 相似文献
We have used computational methods to improve the affinity of a foldamer ligand for its target protein. The effort began with a previously reported α/β‐peptide based on the BH3 domain of the proapoptotic protein Puma; this foldamer binds tightly to Bcl‐xL but weakly to Mcl‐1. The crystal structure of the Puma‐derived α/β‐peptide complexed to Bcl‐xL was used as the basis for computational design of variants intended to display improved binding to Mcl‐1. Molecular modelling suggested modification of three α residues of the original α/β backbone. Individually, each substitution caused only a modest (4‐ to 15‐fold) gain in affinity; however, together the three substitutions led to a 250‐fold increase in binding to Mcl‐1. These modifications had very little effect on affinity for Bcl‐xL. Crystal structures of a number of the new α/β‐peptides bound to either Mcl‐1 or Bcl‐xL validated the selection of each substitution. Overall, our findings demonstrate that structure‐guided rational design can be used to improve affinity and alter partner selectivity of peptidic ligands with unnatural backbones that bind to specific protein partners. 相似文献
The design of a cross‐acridine scaffold mimicking the i, i+3, i+5, and i+7 residues distributed over a two‐face, two‐turn α‐helix is described. Docking studies and 2D 1H,15N HSQC NMR spectroscopy provide compelling evidence that compound 3 d accurately reproduces the arrangement of four hotspots in the Bim BH3 peptide to permit binding to the Mcl‐1 and Bcl‐2 proteins (Ki 0.079 and 0.056 μM , respectively). Furthermore, the hotspot mutation could also be mimicked by individual or multiple deletions of side chains on the scaffold. 相似文献
Bcl‐xL is an antiapoptotic member of the Bcl‐2 protein family and an attractive target for the development of anticancer agents. Here we describe the isolation of binders to Bcl‐xL from a DNA‐encoded chemical library using affinity‐capture selections and massively parallel high‐throughput sequencing of >30 000 sequence tags of library members. The most potent binder identified, compound 19 / 93 [(R)‐3‐(amido indomethacin)‐4‐(naphthalen‐1‐yl)butanoic acid], bound to Bcl‐xL with a dissociation constant (Kd) of 930 nM and was able to compete with a Bak‐derived BH3 peptide, an antagonist of Bcl‐xL function.相似文献
Turn Bak : We present rationally designed scaffolds that mimic the spatial projection of the i, i+4, i+7, and i+11 residues of an α‐helix. A library of biphenyl derivatives was shown by competition fluorescence polarization and ITC to mimic Bak and disrupt the Bak/Bcl‐xL protein–protein interaction. 15N HSQC experiments confirmed that the surface of Bcl‐xL normally occupied by Bak was the target area of our new synthetic inhibitors.
Although the role of Bcl‐2 phosphorylation is still under debate, it has been identified in a resistance mechanism to BH3 mimetics, for example ABT‐737 and S1 . We identified an S1 analogue, S1‐16 , as a small‐molecule inhibitor of pBcl‐2. S1‐16 efficiently kills EEE‐Bcl‐2 (a T69E, S70E, and S87E mutant mimicking phosphorylation)‐expressing HL‐60 cells and high endogenously expressing pBcl‐2 cells, by disrupting EEE‐Bcl‐2 or native pBcl‐2 interactions with Bax and Bak, followed by apoptosis. In vitro binding assays showed that S1‐16 binds to the BH3 binding groove of EEE‐Bcl‐2 (Kd=0.38 μM by ITC; IC50=0.16 μM by ELISA), as well as nonphosphorylated Bcl‐2 (npBcl‐2; Kd=0.38 μM ; IC50=0.12 μM ). However, ABT‐737 and S1 had much weaker affinities to EEE‐Bcl‐2 (IC50=1.43 and >10 μM , respectively), compared with npBcl‐2 (IC50=0.011 and 0.74 μM , respectively). The allosteric effect on BH3 binding groove by Bcl‐2 phosphorylation in the loop region was illustrated for the first time. 相似文献
The development of drug resistance remains a critical problem for current HIV‐1 antiviral therapies, creating a need for new inhibitors of HIV‐1 replication. We previously reported on a novel anti‐HIV‐1 compound, N2‐(phenoxyacetyl)‐N‐[4‐(1‐piperidinylcarbonyl)benzyl]glycinamide ( 14 ), that binds to the highly conserved phosphatidylinositol (4,5)‐bisphosphate (PI(4,5)P2) binding pocket of the HIV‐1 matrix (MA) protein. In this study, we re‐evaluate the hits from the virtual screen used to identify compound 14 and test them directly in an HIV‐1 replication assay using primary human peripheral blood mononuclear cells. This study resulted in the identification of three new compounds with antiviral activity; 2‐(4‐{[3‐(4‐fluorophenyl)‐1,2,4‐oxadiazol‐5‐yl]methyl})‐1‐piperazinyl)‐N‐(4‐methylphenyl)acetamide ( 7 ), 3‐(2‐ethoxyphenyl)‐5‐[[4‐(4‐nitrophenyl)piperazin‐1‐yl]methyl]‐1,2,4‐oxadiazole ( 17 ), and N‐[4‐ethoxy‐3‐(1‐piperidinylsulfonyl)phenyl]‐2‐(imidazo[2,1‐b][1,3]thiazol‐6‐yl)acetamide ( 18 ), with compound 7 being the most potent of these hits. Mechanistic studies on 7 demonstrated that it directly interacts with and functions through HIV‐1 MA. In accordance with our drug target, compound 7 competes with PI(4,5)P2 for MA binding and, as a result, diminishes the production of new virus. Mutation of residues within the PI(4,5)P2 binding site of MA decreased the antiviral effect of compound 7 . Additionally, compound 7 displays a broadly neutralizing anti‐HIV activity, with IC50 values of 7.5–15.6 μM for the group M isolates tested. Taken together, these results point towards a novel chemical probe that can be used to more closely study the biological role of MA and could, through further optimization, lead to a new class of anti‐HIV‐1 therapeutics. 相似文献
Managing protein–protein interactions is essential for resolving unknown biological events at the molecular level and developing drugs. We have designed and synthesized a side‐chain‐crosslinked helical peptides based on the binding domain of a pro‐apoptotic protein (Bad) that induces programed cell death. The peptide showed high helical content and bound to its target, Bcl‐XL, more strongly than its non‐crosslinked counterparts. When HeLa cells were incubated with the crosslinked peptide, the peptide entered the cytosol across the plasma membrane. The peptide formed a stable complex with Bcl‐XL localized at the outer mitochondrial membrane, and this binding event caused the release of cytochrome c from the intermembrane space of mitochondria into the cytosol. This activated the caspase cascade: 70 % of HeLa cells died by the apoptosis pathway (without evidence of necrosis). 相似文献
CuO‐added (LixK0.9?xNa0.1)NbO3 [C(LxK0.9?xN0.1)N] ceramics with 0.0≤x≤0.05 were well‐sintered at 960°C for 6 hours. The lattice parameters of the specimens decreased with the addition of Li2O. Defect polarization (PD) formed between Cu2+ions and oxygen vacancies. Double polarization vs electric field (P‐E) hysteresis and sprout‐shaped strain vs electric field (S‐E) curves were observed in these specimens with a large strain of 0.16% at 7.0 kV/mm, possibly owing to the presence of PD. When the P‐E curve was measured at temperatures higher than 75°C, the C(K0.9N0.1)N ceramic exhibited a normal P‐E hysteresis curve, whereas the C(L0.04K0.86N0.1)N ceramic maintained the double P‐E hysteresis curve up to 125°C, indicating that Li2O increased the thermal stability of PD. The latter specimen also showed the sprout shaped S‐E curve with a strain of 0.15% at 7.0 kV/mm after 104 cycles of a high electric field of 7.0 kV/mm. 相似文献
Piezoelectric ceramics are widely used in sensors, actuators, and ultrasonic transducers due to their ability to achieve efficient conversion between electric and mechanical energy. There is a current drive toward lead‐free material systems capable of achieving comparable piezoelectric performance to environmentally hazardous, but commonly used, lead‐based materials such as lead zirconate titanate. This work constructs an accurate phase diagram for barium calcium titanate (Ba1‐xCaxTiO3 or BCTO). The substitution of Ca2+ on the Ba‐site of BCTO is of much interest due to electric property improvements compared to BaTiO3. In this work, Ba1‐xCaxTiO3 (x =0‐0.30) samples have been made by solid‐state methods and, following initial characterization by X‐ray diffraction (XRD), evaluation of changes in the Raman spectra has allowed accurate determination of the phase transition temperatures and the construction of a phase diagram. 相似文献