Caspase enzymology and activation mechanisms

Calmodulin Binding Activates Chromobacterium CopC Effector to ADP-Riboxanate Host Apoptotic Caspases

Blocking host cell death is an important virulence strategy employed by many bacterial pathogens. We recently reported that Shigella flexneri inhibits host pyroptosis by delivering a type III secretion system (T3SS) effector OspC3 that catalyzes a novel arginine ADP-riboxanation modification on caspase-4/11. Here, we investigated the OspC3 homologue CopC from Chromobacterium violaceum, an opportunistic but sometimes deadly bacterial pathogen. CopC bears the same arginine ADP-riboxanase activity as OspC3, but with a different substrate specificity. Through proteomic analysis, we first identified host calmodulin (CaM) as a binding partner of CopC. The analyses additionally revealed that CopC preferably modifies apoptotic caspases including caspase-7, -8 and -9. This results in suppression of both extrinsic and intrinsic apoptosis programs in C. violaceum-infected cells. Biochemical reconstitution showed that CopC requires binding to CaM, specifically in the calcium-free state, to achieve efficient ADP-riboxanation of the caspases. We determined crystal structure of the CaM-CopC-CASP7 ternary complex, which illustrates the caspase recognition mechanism and a unique CaM-binding mode in CopC. Structure-directed mutagenesis validated the functional significance of CaM binding for stimulating CopC modification of its caspase substrates. CopC adopts an ADP-ribosyltransferase-like fold with a unique His-Phe-Glu catalytic triad, featuring two acidic residues critical for site-specific arginine ADP-riboxanation. Our study expands and deepens our understanding of the OspC family of ADP-riboxanase effectors.

miRNA-19b-3p Stimulates Cardiomyocyte Apoptosis Induced by Myocardial Ischemia Reperfusion via Downregulating PTEN

Objective

To clarify the function of miRNA-19b-3p in accelerating myocardial ischemia-reperfusion injury- (MIRI-) induced cardiomyocyte apoptosis by downregulating gene of phosphate and tension homology deleted on chromsome ten (PTEN), thus influencing the progression of acute myocardial infarction.

Materials and Methods

miRNA-19b-3p and PTEN levels in HCM cells undergoing hypoxia/reoxygenation (H/R) were determined. Meanwhile, activities of myocardium injury markers [lactate dehydrogenase (LDH), malondialdehyde; malonic dialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GSH-PX)] in H/R-induced HCM cells were tested. Through dual-luciferase reporter gene assay, the binding between miRNA-19b-3p and PTEN was verified. Regulatory effects of miRNA-19b-3p and PTEN on apoptotic rate and apoptosis-associated gene expressions (proapoptotic protein Bcl-2 associated X protein (Bax), antiapoptotic protein B-cell lymphoma-2 (Bcl-2), and cytochrome C) in H/R-induced human cardiac myocytes (HCM) cells were examined.

Results

miRNA-19b-3p was upregulated, while PTEN was downregulated in H/R-induced HCM cells. Knockdown of miRNA-19b-3p decreased activities of LDH, MDA, and GSH-PX, but increased SOD level in H/R-induced HCM cells. The binding between miRNA-19b-3p and PTEN was confirmed. More importantly, knockdown of miRNA-19b-3p reduced apoptotic rate, downregulated proapoptosis gene expressions (Bax and cytochrome C), and upregulated antiapoptosis gene expression (Bcl-2), which were reversed by silence of PTEN.

Conclusions

miRNA-19b-3p is upregulated in HCM cells undergoing hypoxia and reoxygenation, which accelerates MIRI-induced cardiomyocyte apoptosis through downregulating PTEN.

Insight into OroxylinA-7-O-β-d-Glucuronide-Enriched Oroxylum indicum Bark Extract in Oral Cancer HSC-3 Cell Apoptotic Mechanism: Role of Mitochondrial Microenvironment

Oroxylum indicum, of the Bignoniaceae family, has various ethnomedical uses such as an astringent, anti-inflammatory, anti-bronchitis, anti-helminthic and anti-microbial, including anticancer properties. The druggability of OI stem bark extract was determined by its molecular docking interactions with PARP and Caspase-3, two proteins involved in cell survival and death. Note that 50 µg/mL of Oroxylum indicum extract (OIE) showed a significant (p < 0.05%) toxicity to HSC-3 cells. MTT aided cell viability and proliferation assay demonstrated that 50 µg/mL of OIE displayed significant (p < 0.5%) reduction in cell number at 4 h of incubation time. Cell elongation and spindle formation was noticed when HSC-3 cells were treated with 50 µg/mL of OIE. OIE initiated DNA breakage and apoptosis in HSC-3 cells, as evident from DNA ladder assay and calcein/EB staining. Apoptosis potential of OIE is confirmed by flow cytometer and triple-staining (live cell/apoptosis/necrosis) assay. Caspase-3/7 fluorescence quenching (LANCE) assay demonstrated that 50 µg/mL of OIE significantly enhanced the RFU of caspases-3/7, indicating that the apoptosis potential of OIE is probably through the activation of caspases. Immuno-cytochemistry of HSC-3 cells treated with 50 µg/mL of OIE showed a significant reduction in mitochondrial bodies as well as a reduction in RFU in 60 min of incubation time. Immunoblotting studies clearly showed that treatment of HSC-3 cells with OI extract caused caspase-3 activation and PARP deactivation, resulting in apoptotic cell death. Overall, our data indicate that OIE is an effective apoptotic agent for human squamous carcinoma cells and it could be a future cancer chemotherapeutic target.

Chrysophanol Induced Glioma Cells Apoptosis via Activation of Mitochondrial Apoptosis Pathway

Glioma is a common intracranial tumor originated from neuroglia cell. Chrysophanol is an anthraquinone derivative proved to exert anticancer effects in various cancers. This paper investigated the effect and mechanism of chrysophanol in glioma. Glioma cell lines U251 and SHG-44 were adopted in the experiments. The cells were treated with chrysophanol at different concentrations (0, 10, 20 50, 100 and 200 μM) for 48 h in the study, and then processed with MitoTempo. Mitochondria and cytosol were isolated to investigate the role of mitochondria during chrysophanol functioning on glioma cells. Cell viability was detected through 3-(4,5-Dimethyl-2-Thiazolyl)-2,5-Diphenyl Tetrazolium Bromide (MTT) assay, and cell apoptosis, cell cycle as well as relative reactive oxygen species (ROS) were assessed by flow cytometry. Expressions of Cytosol Cyt C, cleaved caspase-3, cleaved caspase-9, Cyclin D1 and Cyclin E were evaluated by western blot. In U251 and SHG-44 cells, with chrysophanol concentration rising, cell viability, expressions of Cyclin D1 and Cyclin E were decreased while cell apoptosis, levels of cleaved caspase-3, cleaved caspase-9 and Cytosol Cyt C as well as ROS accumulation were increased with cell cycle arrested in G1 phase. Besides, chrysophanol promoted ROS accumulation, cell apoptosis and transfer of Cyt C from mitochondria to cytosol in cells while MitoTempo partly reversed the effect of chrysophanol. Chrysophanol promoted cell apoptosis via activating mitochondrial apoptosis pathway in glioma.

Tilianin inhibits the human ovarian cancer (PA-1) cell proliferation via blocking cell cycle, inducing apoptosis and inhibiting JAK2/STAT3 signaling pathway

Ovarian cancer is one of the deadliest gynecologic malignancies and is the seventh leading cause of mortalities and morbidities globally. Although there are various therapeutic strategies, a major challenge for scientific community is to come up with effective strategy to treat ovarian cancer. Tilianin, a polyphenol flavonoid is well known for its extensive biological actions like cardioprotective, neuroprotective, anti-oxidant, anti-inflammatory, anti-diabetic and anti-tumor properties. The current study is designed to investigate the anti-cancer action of Tilianin in ovarian cancer (PA-1) cells. The findings of this study revealed that Tilianin treatment results in significant and concentration dependent decrease in cell viability. The growth inhibiting action of Tilianin is associated with apoptosis which was confirmed by DAPI and AO/EtBr staining. The Tilianin-triggered apoptosis in PA-1 cells was correlated with elevated generation of ROS, loss of mitochondrial membrane potential, alterations in pro-apoptotic (upregulated mRNA expression of Bax) and anti-apoptotic (downregulated mRNA expression of Bcl2) factors and activation of caspase-8, −9 and −3. Cell cycle analysis revealed that Tilianin treatment prevented G1/S transition through reduced mRNA expression of cyclin D1. Additionally, the findings of this study also showed Tilianin inhibited JAK2/STAT3 signaling (downregulated expression of pJAK2, JAK2, pSTAT3, and STAT3) with no change in mRNA expression level of ERK indicating its non-involvement in the apoptotic and/or growth inhibition of ovarian cancer cells. In conclusion, the findings of this exploration provided clear evidence of anti-cancer effects of Tilianin in PA-1 cells through its anti-proliferative action, ability to induce apoptosis both through extrinsic and intrinsic pathways, cell cycle (G1/S) arrest and JAK2/STAT3 signaling inhibition.

New pyridine and chromene scaffolds as potent vasorelaxant and anticancer agents

Based on studies that have reported the association between cancer and cardiovascular diseases, new series of pyridine- (3a–o) and/or chromene- (4a–e) carbonitrile analogous were designed, synthesized and screened for their vasodilation and cytotoxic properties. The majority of the new chemical entities demonstrated significant vasodilation efficacies, compounds 3a, 3h, 3j, 3m, 3o, 4d and 4e exhibited the most promising potency with IC₅₀ = 437.9, 481.0, 484.5, 444.8, 312.1, 427.6 and 417.2 μM, respectively, exceeding prazosin hydrochloride (IC₅₀ = 487.3 μM). Compounds 3b–e, 3k and 3l also, revealed moderate vasodilation activity with IC₅₀ values ranging from 489.7 to 584.5 μM. In addition, the anti-proliferative activity evaluation of the experimental compounds at 10 μM on the MCF-7 and MDA-MB 231 breast cancer cell lines illustrated the excellent anti-proliferative properties of derivatives 3d, 3g and 3i. Compound 3d was the most potent analogue with IC₅₀ = 4.55 ± 0.88 and 9.87 ± 0.89 μM against MCF-7 and MDA-MB 231, respectively. Moreover, compound 3d stimulated apoptosis and cell cycle arrest at the S phase in MCF-7 cells in addition to its capability in accumulation of cells in pre-G1 phase and activating caspase-3. Furthermore, the molecular docking of 3d was performed to discover the binding modes within the active site of caspase-3. 3d, as the only common bi-functional agent among the tested hits, demonstrated that new pyridine-3-carbonitrile derivatives bearing cycloheptyl ring systems offer potential as new therapeutic candidates with combined vasodilation and anticancer properties.

Series of pyridine- (3a–o) and/or chromene- (4a–e) carbonitrile scaffolds have been designed, synthesized and evaluated for their bi-function activities, 3d was the only common derivative having combined vasodilation and anticancer properties.

Design, Synthesis, Anticancer Evaluation, Enzymatic Assays, and a Molecular Modeling Study of Novel Pyrazole-Indole Hybrids

The molecular hybridization concept has recently emerged as a powerful approach in drug discovery. A series of novel indole derivatives linked to the pyrazole moiety were designed and developed via a molecular hybridization protocol as antitumor agents. The target compounds (5a-j and 7a-e) were prepared by the reaction of 5-aminopyrazoles (1a-e) with N-substituted isatin (4a,b) and 1H-indole-3-carbaldehyde (6), respectively. All products were characterized via several analytical and spectroscopic techniques. Compounds (5a-j and 7a-e) were screened for their cytotoxicity activities in vitro against four human cancer types [human colorectal carcinoma (HCT-116), human breast adenocarcinoma (MCF-7), human liver carcinoma (HepG2), and human lung carcinoma (A549)] using the MTT assay. The obtained results showed that the newly synthesized compounds displayed good-to-excellent antitumor activity. For example, 5-((1H-indol-3-yl)methyleneamino)-N-phenyl-3-(phenylamino)-1H-pyrazole-4-carboxamide (7a) and 5-((1H-indol-3-yl)methyleneamino)-3-(phenylamino)-N-(4-methylphenyl)-1H-pyrazole-4-carboxamide (7b) provided excellent anticancer inhibition performance against the HepG2 cancer cell line with IC₅₀ values of 6.1 ± 1.9 and 7.9 ± 1.9 μM, respectively, compared to the standard reference drug, doxorubicin (IC₅₀ = 24.7 ± 3.2 μM). The two powerful anticancer compounds (7a and 7b) were further subjected to cell cycle analysis and apoptosis investigation in HepG2 using flow cytometry. We have also studied the enzymatic assay of these two compounds against some enzymes, namely, caspase-3, Bcl-2, Bax, and CDK-2. Interestingly, the molecular docking study revealed that compounds 7a and 7b could well embed in the active pocket of the CDK-2 enzyme via different interactions. Overall, the prepared pyrazole-indole hybrids (7a and 7b) can be proposed as strong anticancer candidate drugs against various cancer cell lines.

Anti-Myocardial Ischemia Reperfusion Injury Mechanism of Dried Ginger-Aconite Decoction Based on Network Pharmacology

Dried ginger-aconite decoction (DAD) is a traditional Chinese medicine (TCM) formula that has been extensively used in the treatment of myocardial ischemia reperfusion injury (MI/RI). However, its specific mechanism against MI/RI has not been reported yet. Therefore, this paper studies the potential active components and mechanism of DAD against MI/RI based on network pharmacology and experimental verification. Sixteen active components of DAD were screened according to oral bioavailability and drug similarity indices. Through Cytoscape 3.7.0, a component-target network diagram was drawn, and potential active components of DAD against MI/RI were determined. Protein-protein interaction (PPI) and compound-target-pathway (C-T-P) networks were established through the software to discover the biological processes, core targets and core pathways of DAD against MI/RI. High Performance Liquid Chromatography (HPLC) analysis identified the presence of potentially active core components for network pharmacological prediction in DAD. It was found that DAD might have played a therapeutic role in anti-MI/RI by activating the PI3K/Akt/GSK-3β signaling pathway in order to reduce mitochondrial hypoxia injury and myocardial cell apoptosis. The network pharmacological prediction was validated by Hypoxia/reoxygenation(H/R) model in vitro and ligation model of the ligation of the left anterior descending branch in vivo. It was verified that DAD had activated PI3K/AKT/GSK-3β to reduce myocardial apoptosis and play a therapeutic function in MI/RI.

Piscidin-1 Induces Apoptosis via Mitochondrial Reactive Oxygen Species-Regulated Mitochondrial Dysfunction in Human Osteosarcoma Cells

Osteosarcoma (OSA) is the most common type of cancer that originates in the bone and usually occurs in young children. OSA patients were treated with neoadjuvant chemotherapy and surgery, and the results were disappointing. Marine antimicrobial peptides (AMPs) have been the focus of antibiotic research because they are resistant to pathogen infection. Piscidin-1 is an AMP from the hybrid striped bass (Morone saxatilis × M. chrysops) and has approximately 22 amino acids. Research has shown that piscidin-1 can inhibit bacterial infections and has antinociception and anti-cancer properties; however, the regulatory effects of piscidin-1 on mitochondrial dysfunction in cancer cells are still unknown. We aimed to identify the effects of piscidin-1 on mitochondrial reactive oxygen species (mtROS) and apoptosis in OSA cells. Our analyses indicated that piscidin-1 has more cytotoxic effects against OSA cells than against lung and ovarian cancer cells; however, it has no effect on non-cancer cells. Piscidin-1 induces apoptosis in OSA cells, regulates mtROS, reduces mitochondrial antioxidant manganese superoxide dismutase and mitochondrial transmembrane potential, and decreases adenosine 5′-triphosphate production, thus leading to mitochondrial dysfunction and apoptosis. The mitochondrial antioxidant, mitoTempo, reduces the apoptosis induced by piscidin-1. Results suggest that piscidin-1 has potential for use in OSA treatment.

Prognostic significance of mRNA expression of CASPs in gastric cancer

Current studies suggest that the cysteinyl aspartate specific proteinase (caspase/CASP) family may be closely associated with apoptosis. Scientists have suggested that caspases may be a key to the development of more effective anti-cancer therapies. However, the prognostic value of CASP expression in gastric cancer (GC) remains unclear. Using a Kaplan-Meier plotter online database, the predictive prognostic significance of the expression of 12 CASPs genes (CASP1, CASP2, CASP3, CASP4, CASP5, CASP6, CASP7, CASP8, CASP9, CASP10, CASP12 and CASP14) to overall survival (OS) in different clinicopathological features, including Lauren classification, pathological stages, therapies employed and differentiation in gastric cancer patients was explored. The present study revealed that higher CASP1, 2, 3, 4, 5, 6, 7 and 8 mRNA expression was associated with better OS, whereas higher expression of CASP9, 10, 12 and 14 showed an unfavorable OS in all GC patients. Moreover, CASP1 to 8 were all associated with favorable OS in intestinal type and diffuse type classified by Lauren classification. Therefore, the results of the present study suggested that the CASP family may function as new prognostic indicators in GC and may be helpful in making treatment decisions.

BA6 Induces Apoptosis via Stimulation of Reactive Oxygen Species and Inhibition of Oxidative Phosphorylation in Human Lung Cancer Cells

Lung cancer is the leading cause of cancer deaths in the world, with a five-year survival rate of less than 30%. Clinically effective chemotherapeutic treatments at the initial stage may eventually face the dilemma of no drug being effective due to drug resistance; therefore, finding new effective drugs for lung cancer treatment is a necessary and important issue. Compounds capable of further increasing the oxidative stress of cancer cells are considered to have anticancer potential because they possessed the ability to induce apoptosis. This study mainly investigated the effects of BA6 (heteronemin), the marine sponge sesterterpene, on lung cancer cell apoptosis, via modulation of mitochondrial reactive oxygen species (mtROS) and oxidative phosphorylation (OXPHOS). BA6 has cellular cytotoxic activities against a variety of cancer cell lines, but it has no effect on nontumor cells. The BA6-treated lung cancer cells show a significant increase in both cellular ROS and mtROS, which in turn caused the loss of mitochondrial membrane potential (MMP). The increase of oxidative stress in lung cancer cells treated with BA6 was accompanied by a decrease in the expression of antioxidant enzymes Cu/Zn SOD, MnSOD, and catalase. In addition, OXPHOS performed in the mitochondria and glycolysis in the cytoplasm were inhibited, which subsequently reduced downstream ATP production. Pretreatment with mitochondria-targeted antioxidant MitoTEMPO reduced BA6-induced apoptosis through the mitochondria-dependent apoptotic pathway, which was accompanied by increased cell viability, decreased mtROS, enhanced MMP, and suppressed expression of cleaved caspase-3 and caspase-9 proteins. In conclusion, the results of this study clarify the mechanism of BA6-induced apoptosis in lung cancer cells via the mitochondrial apoptotic pathway, suggesting that it is a potentially innovative alternative to the treatment of human lung cancer.

New thiazol-hydrazono-coumarin hybrids targeting human cervical cancer cells: Synthesis, CDK2 inhibition, QSAR and molecular docking studies

Motivated by the potential anticancer activity of both coumarin and 2-aminothiazole nuclei, a new set of thiazol-2-yl hydrazono-chromen-2-one analogs were efficiently synthesized aiming to obtain novel hybrids with potential cytotoxic activity. MTT assay investigated the significant potency of all the target compounds against the human cervical cancer cell lines (HeLa cells). Cell cycle analysis showed that the representative compound 8a led to cell cycle cessation at G0/G1 phase indicating that CDK2/E1complex could be the plausible biological target for these newly synthesized compounds. Thus, the most active compounds (7c and 8a-c) were tested for their CDK2 inhibitory activity. The biological results revealed their significant CDK2 inhibitory activity with IC₅₀ range of 0.022-1.629 nM. Moreover, RT-PCR gene expression assay showed that compound 8a increased the levels of the nuclear CDK2 regulators P21 and P27 by 2.30 and 5.7 folds, respectively. ELISA tequnique showed also that compound 8a led to remarkable activation of caspases-9 and -3 inducing cell apoptosis. QSAR study showed that the charge distribution and molecular hydrophobicity are the structural features affecting cytotoxic activity in this series. Molecular docking study for the most potent cytotoxic compounds (7c and 8a-c) rationalized their superior CDK2 inhibitory activity through their hydrogen bonding and hydrophobic interactions with the key amino acids in the CDK2 binding site. Pharmacokinetic properties prediction of the most potent compounds showed that the newly synthesized compounds are not only with promising antitumor activity but also possess promising pharmacokinetic properties.

Parkinson disease-induced upregulation of apoptotic mediators could be attenuated in the skeletal muscle following chronic exercise training

BACKGROUND

We have shown elevated levels of p53 and active caspase-3 in gastrocnemius skeletal muscle with Parkinson's disease (PD). The main aim of this study is to examine the impact of endurance exercise training on the expression of p53 and active caspase-3 in the skeletal muscle of mouse with induced Parkinsonism.

METHODS

Sedentary control (SC), sedentary Parkinson diseased (SPD), and exercised Parkinson diseased (EPD) groups were formed; each consisting of 10 randomly selected normal albino mice. Chronic Parkinson disease was induced in the SPD and EPD animals using 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and probenecid (MPTP/p). The expression of p53 and active caspase-3 was investigated, using immunohistochemistry, in the gastrocnemius muscle in each animal group.

RESULTS

Both p53 and active caspase-3 expression was significantly (p value < 0.05) reduced in the PD gastrocnemius skeletal muscle following endurance exercise training.

CONCLUSION

Our present data suggest that chronic exercise training reduced Parkinson disease-induced upregulation of p53 and active caspase-3 in gastrocnemius skeletal muscle. Thus, our study suggests that inhibiting p53 and/or active caspase-3 may be considered as a therapeutic approach to ameliorate PD skeletal muscle abnormalities.

MSP-4, an Antimicrobial Peptide, Induces Apoptosis via Activation of Extrinsic Fas/FasL- and Intrinsic Mitochondria-Mediated Pathways in One Osteosarcoma Cell Line

Osteosarcoma (OS) is a common malignant bone cancer. The relatively high density of a person's bone structure means low permeability for drugs, and so finding drugs that can be more effective is important and should not be delayed. MSPs are marine antimicrobial peptides (AMP) and natural compounds extracted from Nile tilapia (Oreochromis niloticus). MSP-4 is a part of the AMPs series, with the advantage of having a molecular weight of about 2.7-kDa and anticancer effects, although the responsible anticancer mechanism is not very clear. The goal of this study is to determine the workings of the mechanism associated with apoptosis resulting from MSP-4 in osteosarcoma MG63 cells. The study showed that MSP-4 significantly induced apoptosis in MG63 cells, with Western blot indicating that MSP-4 induced this apoptosis through an intrinsic pathway and an extrinsic pathway. Thus, a pretreatment system with a particular inhibitor of Z-IETD-FMK (caspase-8 inhibitor) and Z-LEHD-FMK (caspase-9 inhibitor) significantly attenuated the cleavage of caspase-3 and prevented apoptosis. These observations indicate that low concentrations of MSP-4 can help induce the apoptosis of MG63 through a Fas/FasL- and mitochondria-mediated pathway and suggest a potentially innovative alternative to the treatment of human osteosarcoma.

Limited activation of the intrinsic apoptotic pathway plays a main role in amyloid-β-induced apoptosis without eliciting the activation of the extrinsic apoptotic pathway

Amyloid-β (Aβ), a main pathogenic factor of Alzheimer's disease (AD), induces apoptosis accompanied by caspase activation. However, limited caspase activation and the suppression of the intrinsic apoptotic pathway (IAPW) are frequently observed upon Aβ treatment. In this study, we investigated whether these suppressive effects of Aβ can be overcome; we also examined the death-related pathways. Single treatments of cells with Aβ42 for up to 48 h barely induced caspase activation. In cells treated with Aβ42 twice for 2 h followed by 22 h (2+22 h) or for longer durations, the apoptotic protease activating factor-1 (Apaf-1) apoptosome was formed and caspases-3 and -9 were activated to a certain extent, suggesting the activation of the IAPW. However, the Aβ42-induced activation of the IAPW differed from that induced by treatment with other agents, such as staurosporine (STS) in that lower amounts of cytochrome c were released from the mitochondria, the majority of procaspase-9 in the Apaf-1 complex was not processed and caspase-3 was activated to a lesser extent in the peptide-treated cells. Thus, it seemed that the IAPW was not fully activated by Aβ42. The 30- and 41/43-kDa fragments derived from procaspase-8 were detected, which appear to be produced through the IAPW without death-inducing signaling-complex (DISC) formation, a key feature of the extrinsic apoptotic pathway (EAPW). Bid cleavage was observed only after caspase-3 activity reached its maximal levels, suggesting that the cleavage may contribute in a limited capacity to the amplification process of the IAPW in the Aβ-treated cells. Taken together, our data suggest that the IAPW, albeit functional only to a limited extent, plays a major role in Aβ42-induced apoptosis without the EAPW.

Regulatory effects of COL1A1 on apoptosis induced by radiation in cervical cancer cells

Background

Cervical cancer is a common cancer of women in developing countries, and radiotherapy still remains its predominant therapeutic treatment. Collagen type I alpha 1 (COL1A1) has been shown to have a radioresistance effect in previous studies. However, such effect of COL1A1 has not yet been revealed in cervical cancer.

Methods

Expression of COL1A1 in cervical cancer tissues and normal tissues was assessed by qRT-PCR and immunohistochemistry. The effect of COL1A1 on radioresistance of human cervical cancer cell lines HeLa and CaSki was assessed using the colony formation assay. Apoptosis alterations were analyzed by flow cytometry. In addition, western blotting was used assessed the alterations of several critical apoptosis and signaling pathway related proteins.

Results

The expression of COL1A1 was significantly increased in cervical cancer tissues compared with normal tissues at the mRNA and protein level. Further, based on COL1A1 knock down and COL1A1 activation cell models, a negative correlation was observed between COL1A1 expression level and radiosensitivity. Moreover, the findings are further supported by apoptosis analysis that COL1A1 activation could inhibit the apoptosis of cervical cancer cells. Subsequently, a significantly decreased expression of p-AKT and Bcl-2, increased expression of Caspase-3 were observed in the LY294002 plus radiation group compared with radiation alone group, while these influences caused by LY294002 or X-ray radiation were reversed after COL1A1 activation.

Conclusions

To our knowledge, this is the only study to profile the mechanisms that COL1A1 plays a crucial role in cervical cells anti-apoptosis induced by radiation. Therefore, our identification of radioresistance-related COL1A1 in cervical cancer could be a starting point to explore the function of collagens, adding a new dimension to our understanding of the cervical cancer, assisting cancer biologists and clinical oncologists in novel therapeutic strategies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-017-0443-5) contains supplementary material, which is available to authorized users.

EGFR tyrosine kinase inhibitors promote pro-caspase-8 dimerization that sensitizes cancer cells to DNA-damaging therapy

The combination of time and order-dependent chemotherapeutic strategies has demonstrated enhanced efficacy in killing cancer cells while minimizing adverse effects. However, the precise mechanism remains elusive. Our results showed that pre-treatment of MCF-7 and MDA-MB-468 cells with epidermal growth factor receptor (EGFR) tyrosine kinase inhibitor erlotinib or lapatinib significantly enhanced the cytotoxic effects of DNA-damaging agents compared to coadministration of the EGFR inhibitor and DNA-damaging agent. Sequential application of erlotinib and doxorubicin increased activated caspase-8 by promoting pro-caspase-8 homodimerization and autocatalytical cleavage, whereas coadministration did not. We found that EGFR inhibitors promoted pro-caspase-8 homodimerization by inhibiting ERK pathway signaling, while doxorubicin promoted it. Our data highlight that ERK has the potential to inhibit the formation of pro-caspase-8 homodimers by phosphorylating pro-caspase-8 at S387. In conclusion, the pretreatment of EGFR tyrosine kinase inhibitors promote pro-caspase-8 dimerization that sensitizes cancer cells to DNA-damaging agents. Our findings provide rationale for novel strategies for the implementation of combined targeted and cytotoxic chemotherapy within a new framework of time and order-dependent therapy.

Structural Insights into Separase Architecture and Substrate Recognition through Computational Modelling of Caspase-Like and Death Domains

Separases are large proteins that mediate sister chromatid disjunction in all eukaryotes. They belong to clan CD of cysteine peptidases and contain a well-conserved C-terminal catalytic protease domain similar to caspases and gingipains. However, unlike other well-characterized groups of clan CD peptidases, there are no high-resolution structures of separases and the details of their regulation and substrate recognition are poorly understood. Here we undertook an in-depth bioinformatical analysis of separases from different species with respect to their similarity in amino acid sequence and protein fold in comparison to caspases, MALT-1 proteins (mucosa-associated lymphoidtissue lymphoma translocation protein 1) and gingipain-R. A comparative model of the single C-terminal caspase-like domain in separase from C. elegans suggests similar binding modes of substrate peptides between these protein subfamilies, and enables differences in substrate specificity of separase proteins to be rationalised. We also modelled a newly identified putative death domain, located N-terminal to the caspase-like domain. The surface features of this domain identify potential sites of protein-protein interactions. Notably, we identified a novel conserved region with the consensus sequence WWxxRxxLD predicted to be exposed on the surface of the death domain, which we termed the WR motif. We envisage that findings from our study will guide structural and functional studies of this important protein family.

The separation of sister chromatids is a crucial step in cell division and is triggered by the activation of separase, a protease that cleaves the proteins that maintain the cohesion between sister chromatids. Knowledge of the molecular structure and activation mechanism of separase is limited by the difficulty of obtaining structural information on this large and flexible protein. Sequence conservation between separase homologues from diverse species is limited to the C-terminal region that contains the catalytically active protease domain. We conducted an in-depth bioinformatical analysis of separase and generated structural models of the two conserved domains that comprise the C-terminal region: a caspase-like domain and a putative death domain. This analysis provided insights into substrate recognition and identified potential sites of protein-protein interactions. Both the death domain and caspase-like domain are well-conserved in separases, which suggests an evolutionary pressure to keep these two domains together, perhaps to enable separase activity and/or provide stability. Insights into the molecular structures of separase gained in this study may provide a starting point for experimental structural studies on this protein and may aid therapeutic development against cancers where chromosomes are improperly segregated.

Caspases: therapeutic targets in neurologic disease

Specific therapies for neurologic diseases such as Alzheimer's disease provide the potential for better clinical outcomes. Expression of caspases in the brain is developmentally regulated, and dysregulated in neurologic disease, supporting that caspases may be therapeutic targets. The activity of caspases is carefully regulated via binding partners, cleavage, or endogenous inhibitors to prevent spontaneous activation, which could lead to aberrant cell death. This review serves as a brief examination of the current understanding of the regulation and function of caspases, and approaches to specifically target aberrant caspase activity. The use of proper tools to investigate individual caspases is addressed. Moreover, it summarizes the reports of various caspases in Alzheimer's disease studies. A better understanding of specific caspase pathways in heath and neurodegenerative disease is crucial for identifying specific targets for the development of therapeutic interventions.