Cyclic marinopyrrole derivatives as disruptors of Mcl-1 and Bcl-x(L) binding to Bim.
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ABSTRACT:
SUBMITTER: Cheng C
PROVIDER: S-EPMC3967213 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:A series of novel marinopyrroles with sulfide and sulphone spacers were designed and synthesized. Their activity to disrupt the binding of the pro-apoptotic protein, Bim, to the pro-survival proteins, Mcl-1 and Bcl-xL, was evaluated using ELISA assays. Fluorescence-quenching (FQ) assays confirmed the direct binding of marinopyrroles to Mcl-1. Benzyl- and benzyl methoxy-containing sulfide derivatives 4 and 5 were highly potent dual Mcl-1/Bim and Bcl-xL/Bim disruptors (IC50 values of 600 and 700 nM), whereas carboxylate-containing sulfide derivative 9 exhibited 16.4-fold more selectivity for disrupting Mcl-1/Bim over Bcl-xL/Bim binding. In addition, a nonsymmetrical marinopyrrole 12 is as equally potent as the parent marinopyrrole A (1) for disrupting both Mcl-1/Bim and Bcl-xL/Bim binding. Some of the derivatives were also active in intact human breast cancer cells where they reduced the levels of Mcl-1, induced programd cell death (apoptosis) and inhibited cell proliferation.
| S-EPMC4145318 | biostudies-literature
Project description:Inhibition of anti-apoptotic Mcl-1 is a promising anticancer strategy to overcome the survival and chemoresistance of a broad spectrum of human cancers. We previously reported on the identification of a natural product marinopyrrole A (1) that induces apoptosis in Mcl-1-dependent cells through Mcl-1 degradation. Here, we report the design and synthesis of novel marinopyrrole-based analogs and their evaluation as selective inhibitors of Mcl-1 as well as dual Mcl-1/Bcl-xL inhibitors. The most selective Mcl-1 antagonists were 34, 36 and 37 with 16-, 13- and 9-fold more selectivity for disrupting Mcl-1/Bim over Bcl-xL/Bim binding, respectively. Among the most potent dual inhibitors is 42 which inhibited Mcl-1/Bim and Bcl-xL/Bim binding 15-fold (IC50 = 600 nM) and 33-fold (500 nM) more potently than (±)-marinopyrrole A (1), respectively. Fluorescence quenching, NMR analysis and molecular docking indicated binding of marinopyrroles to the BH3 binding site of Mcl-1. Several marinopyrroles potently decreased Mcl-1 cellular levels and induced caspase 3 activation in human breast cancer cells. Our studies provide novel "lead" marinopyrroles for further optimization as selective Mcl-1 inhibitors and dual Mcl-1 and Bcl-xL inhibitors.
| S-EPMC4445146 | biostudies-literature
Project description:Dependence on Bcl-2 proteins is a common feature of cancer cells and provides a therapeutic opportunity. ABT-737 is an antagonist of antiapoptotic Bcl-2 proteins and therefore is a good predictor of Bcl-x(L)/Bcl-2 dependence. Surprisingly, analysis of Mcl-1-dependent multiple myeloma cell lines revealed codependence on Bcl-2/Bcl-x(L) in half the cells tested. Codependence is not predicted by the expression level of antiapoptotic proteins, rather through interactions with Bim. Consistent with these findings, acquired resistance to ABT-737 results in loss of codependence through redistribution of Bim to Mcl-1. Overall, these results suggest that complex interactions, and not simply expression patterns of Bcl-2 proteins, need to be investigated to understand Bcl-2 dependence and how to better use agents, such as ABT-737.
| S-EPMC3152498 | biostudies-literature
Project description:To elucidate the roles of metalloproteinases and the Bcl-2 family of proteins in Trichovaginalis. vaginalis-induced apoptosis in human cervical cancer cells (SiHa cells) and vaginal epithelial cells (MS74 cells), SiHa cells and MS74 cells were incubated with live T. vaginalis, T. vaginalis excretory and secretory products (ESP), and T. vaginalis lysates, either with or without the specific metalloproteinase inhibitor 1,10-phenanthroline (1,10-PT), and examined apoptotic events and Bcl-2 signaling. The live T. vaginalis and the T. vaginalis ESP induced the release of cytochrome c into the cytosol, the activation of caspase-3 and caspase-9, and the cleavage of PARP. Additionally, the live T. vaginalis, but not the T. vaginalis lysate, induced the cleavage of the proapoptotic Bim protein. The live T. vaginalis and the T. vaginalis ESP, but not the T. vaginalis lysate, induced the dose-dependent cleavage of the antiapoptotic Bcl-xL and Mcl-1 proteins and decreased the association levels of Bcl-xL/Bim and Mcl-1/Bim complexes. We performed gelatin zymography and casein-hydrolysis assays on the live T. vaginalis and the T. vaginalis ESP to identify the apoptosis-inducing factor. Both the live T. vaginalis and the ESP contained high levels of metalloproteinases, of which activities were significantly inhibited by 1,10-PT treatment. Furthermore, the 1,10-PT blocked the cleavage of Bcl-xL, Mcl-1, PARP, caspase-3, and caspase-9, as well as the release of cytochrome c into the cytosol, and it significantly increased the association levels of the Bcl-xL/Bim and Mcl-1/Bim protein complexes, returning them to normal levels. Our results demonstrate that T. vaginalis induces mitochondria-dependent apoptosis in SiHa cells through the dissociation of Bcl-xL/Bim and Mcl-1/Bim complexes and that the apoptosis is blocked by the metalloproteinase inhibitor 1,10-PT. These results expand our understanding of the role of metalloproteinases in T. vaginalis-induced apoptosis and the signaling pathway in trichomoniasis of the cervicovaginal epithelial cells.
| S-EPMC4208800 | biostudies-literature
Project description:The Bcl-2 antagonist ABT-737 kills transformed cells in association with displacement of Bim from Bcl-2. The histone deactetylase (HDAC) inhibitor suberoyl bis-hydroxamic acid (SBHA) was employed to determine whether and by what mechanism ABT-737 might interact with agents that upregulate Bim. Expression profiling of BH3-only proteins indicated that SBHA increased Bim, Puma, and Noxa expression, while SBHA concentrations that upregulated Bim significantly potentiated ABT-737 lethality. Concordance between SBHA-mediated Bim upregulation and interactions with ABT-737 was observed in various human leukemia and myeloma cells. SBHA-induced Bim was largely sequestered by Bcl-2 and Bcl-x(L), rather than Mcl-1; ABT-737 attenuated these interactions, thereby triggering Bak/Bax activation and mitochondrial outer membrane permeabilization. Knockdown of Bim (but not Puma or Noxa) by shRNA or ectopic overexpression of Bcl-2, Bcl-x(L), or Mcl-1 diminished Bax/Bak activation and apoptosis. Notably, ectopic expression of these antiapoptotic proteins disabled death signaling by sequestering different proapoptotic proteins, i.e., Bim by Bcl-2, both Bim and Bak by Bcl-x(L), and Bak by Mcl-1. Together, these findings indicate that HDAC inhibitor-inducible Bim is primarily neutralized by Bcl-2 and Bcl-x(L), thus providing a mechanistic framework by which Bcl-2 antagonists potentiate the lethality of agents, such as HDAC inhibitors, which upregulate Bim.
| S-EPMC2786688 | biostudies-literature
Project description:The anti-apoptotic Bcl-2 family of proteins, including Bcl-2, Bcl-X(L) and Mcl-1, are well-validated drug targets for cancer treatment. Several small molecules have been designed to interfere with Bcl-2 and its fellow pro-survival family members. While ABT-737 and its orally active analog ABT-263 are the most potent and specific inhibitors to date that bind Bcl-2 and Bcl-X(L) with high affinity but have a much lower affinity for Mcl-1, they are not very effective as single agents in certain cancer types because of elevated levels of Mcl-1. Accordingly, compounds that specifically target Mcl-1 may overcome this resistance. In this study, we identified and characterized the natural product marinopyrrole A as a novel Mcl-1-specific inhibitor and named it maritoclax. We found that maritoclax binds to Mcl-1, but not Bcl-X(L), and is able to disrupt the interaction between Bim and Mcl-1. Moreover, maritoclax induces Mcl-1 degradation via the proteasome system, which is associated with the pro-apoptotic activity of maritoclax. Importantly, maritoclax selectively kills Mcl-1-dependent, but not Bcl-2- or Bcl-X(L)-dependent, leukemia cells and markedly enhances the efficacy of ABT-737 against hematologic malignancies, including K562, Raji, and multidrug-resistant HL60/VCR, by ?60- to 2000-fold at 1-2 ?M. Taken together, these results suggest that maritoclax represents a new class of Mcl-1 inhibitors, which antagonizes Mcl-1 and overcomes ABT-737 resistance by targeting Mcl-1 for degradation.
| S-EPMC3323047 | biostudies-literature
Project description:Interactions among Bcl-2 family proteins are important for regulating apoptosis. Prosurvival members of the family interact with proapoptotic BH3 (Bcl-2-homology-3)-only members, inhibiting execution of cell death through the mitochondrial pathway. Structurally, this interaction is mediated by binding of the alpha-helical BH3 region of the proapoptotic proteins to a conserved hydrophobic groove on the prosurvival proteins. Native BH3-only proteins exhibit selectivity in binding prosurvival members, as do small molecules that block these interactions. Understanding the sequence and structural basis of interaction specificity in this family is important, as it may allow the prediction of new Bcl-2 family associations and/or the design of new classes of selective inhibitors to serve as reagents or therapeutics. In this work, we used two complementary techniques--yeast surface display screening from combinatorial peptide libraries and SPOT peptide array analysis--to elucidate specificity determinants for binding to Bcl-x(L)versus Mcl-1, two prominent prosurvival proteins. We screened a randomized library and identified BH3 peptides that bound to either Mcl-1 or Bcl-x(L) selectively or to both with high affinity. The peptides competed with native ligands for binding into the conserved hydrophobic groove, as illustrated in detail by a crystal structure of a specific peptide bound to Mcl-1. Mcl-1-selective peptides from the screen were highly specific for binding Mcl-1 in preference to Bcl-x(L), Bcl-2, Bcl-w, and Bfl-1, whereas Bcl-x(L)-selective peptides showed some cross-interaction with related proteins Bcl-2 and Bcl-w. Mutational analyses using SPOT arrays revealed the effects of 170 point mutations made in the background of a peptide derived from the BH3 region of Bim, and a simple predictive model constructed using these data explained much of the specificity observed in our Mcl-1 versus Bcl-x(L) binders.
| S-EPMC2896288 | biostudies-literature
Project description:A critical hallmark of cancer cell survival is evasion of apoptosis. This is commonly due to overexpression of anti-apoptotic proteins such as Bcl-2, Bcl-X(L), and Mcl-1, which bind to the BH3 ?-helical domain of pro-apoptotic proteins such as Bax, Bak, Bad, and Bim, and inhibit their function. We designed a BH3 ?-helical mimetic BH3-M6 that binds to Bcl-X(L) and Mcl-1 and prevents their binding to fluorescently labeled Bak- or Bim-BH3 peptides in vitro. Using several approaches, we demonstrate that BH3-M6 is a pan-Bcl-2 antagonist that inhibits the binding of Bcl-X(L), Bcl-2, and Mcl-1 to multi-domain Bax or Bak, or BH3-only Bim or Bad in cell-free systems and in intact human cancer cells, freeing up pro-apoptotic proteins to induce apoptosis. BH3-M6 disruption of these protein-protein interactions is associated with cytochrome c release from mitochondria, caspase-3 activation and PARP cleavage. Using caspase inhibitors and Bax and Bak siRNAs, we demonstrate that BH3-M6-induced apoptosis is caspase- and Bax-, but not Bak-dependent. Furthermore, BH3-M6 disrupts Bcl-X(L)/Bim, Bcl-2/Bim, and Mcl-1/Bim protein-protein interactions and frees up Bim to induce apoptosis in human cancer cells that depend for tumor survival on the neutralization of Bim with Bcl-X(L), Bcl-2, or Mcl-1. Finally, BH3-M6 sensitizes cells to apoptosis induced by the proteasome inhibitor CEP-1612.
| S-EPMC3059047 | biostudies-literature
Project description:B-cell lymphoma-2 (Bcl-2) proteins mediate intrinsic-, or mitochondrial-, initiated apoptosis. We have investigated the structure and function of the least characterized Bcl-2 family member, Bcl-B, solving the crystal structure of a Bcl-B:Bim complex to 1.9?Å resolution. Bcl-B is distinguished from other Bcl-2 family members through an insertion of an unstructured loop between helices ?5 and ?6. Probing Bcl-B interactions with Bcl-2 homology (BH)3 motifs using a combination of biophysical- and cell-based assays revealed a unique BH3-only protein binding profile. Bcl-B has high-affinity interactions with Bim and Bik only. Our results not only delineate the mode of action of Bcl-B but also complete our understanding of the specific interactions between BH3-only proteins and their prosurvival Bcl-2 counterparts. Notably, we conclude that Bim is the universal prosurvival antagonist as no other BH3-only protein binds all six prosurvival proteins and that Mcl-1 and Bcl-x(L) form a distinct prosurvival dyad.
| S-EPMC3542614 | biostudies-literature
Project description:Neutrophil granulocyte (neutrophil) apoptosis plays a key role in determining inflammation in infectious and non-infectious settings. Recent work has shown that inhibitors of cyclin-dependent kinases (cdk) such as roscovitine can potently induce neutrophil apoptosis and reduce inflammation. Using a conditional Hoxb8-expression system we tested the participation of Bcl-2-family proteins to roscovitine-induced apoptosis in mouse neutrophils and in neutrophil progenitor cells. Bcl-2 strongly protected against roscovitine-induced apoptosis in neutrophils. The isolated loss of either Bim or noxa provided significant, partial protection while protection through combined loss of Bim and noxa or Bim and Puma was only slightly greater than this individual loss. The only substantial change in protein levels observed was the loss of Mcl-1, which was not transcriptional and was inhibited by proteasome blockade. In progenitor cells there was no protection by the loss of Bim alone but substantial protection by the loss of both Bim and Puma; surprisingly, strongest protection was seen by the isolated loss of noxa. The pattern of protein expression and Mcl-1-regulation in progenitor cells was very similar to the one observed in differentiated neutrophils. In addition, roscovitine strongly inhibited proliferation in progenitor cells, associated with an accumulation of cells in G2/M-phase.
| S-EPMC3815126 | biostudies-literature