HDAC inhibitor and proteasome inhibitor induce cleavage and exosome-mediated secretion of HSP90 in mouse pluripotent stem cells.

Heat shock protein 90 (HSP90), one of the molecular chaperones, stabilizes several proteins necessary to maintain pluripotency of embryonic stem (ES) cells. Recently, we reported that HDAC inhibitors and proteasome inhibitors down-regulate HSP90 activity through HSP90 cleavage induced by reactive oxygen species (ROS) generation and caspase 10 activation in various cancer cells. In this study, we investigated HSP90 cleavage in mouse ES cells. HDAC inhibitors and proteasome inhibitors induced HSP90 cleavage in the mouse ES cell line R1, and the cleaved HSP90 was barely found in the cells and instead secreted out of the cells through the exosome. The HSP90 cleavage was associated with ROS generation and caspase 10 activation. In addition, HDAC inhibitor and proteasome inhibitor induced Fas expression, and the inhibition of caspase 8, a downstream molecule of Fas, blocked HSP90 cleavage. Therefore, HDAC inhibitor- and proteasome inhibitor-mediated HSP90 cleavage was induced by ROS generation and Fas expression. We observed similar results in mouse induced pluripotent stem (iPS) cells. Taken together, HSP90 cleavage was induced in mouse pluripotent cells similarly to cancer cells but differently regulated through Fas expression and exosomal secretion. These findings will be helpful in elucidating the regulation of HSP90 upon stress in pluripotent stem cells.

Proteome-wide covalent ligand discovery in native biological systems.

Small molecules are powerful tools for investigating protein function and can serve as leads for new therapeutics. Most human proteins, however, lack small-molecule ligands, and entire protein classes are considered 'undruggable'. Fragment-based ligand discovery can identify small-molecule probes for proteins that have proven difficult to target using high-throughput screening of complex compound libraries. Although reversibly binding ligands are commonly pursued, covalent fragments provide an alternative route to small-molecule probes, including those that can access regions of proteins that are difficult to target through binding affinity alone. Here we report a quantitative analysis of cysteine-reactive small-molecule fragments screened against thousands of proteins in human proteomes and cells. Covalent ligands were identified for >700 cysteines found in both druggable proteins and proteins deficient in chemical probes, including transcription factors, adaptor/scaffolding proteins, and uncharacterized proteins. Among the atypical ligand-protein interactions discovered were compounds that react preferentially with pro- (inactive) caspases. We used these ligands to distinguish extrinsic apoptosis pathways in human cell lines versus primary human T cells, showing that the former is largely mediated by caspase-8 while the latter depends on both caspase-8 and -10. Fragment-based covalent ligand discovery provides a greatly expanded portrait of the ligandable proteome and furnishes compounds that can illuminate protein functions in native biological systems.

Neochamaejasmin B extracted from Stellera chamaejasme L. induces apoptosis through caspase-10-dependent way in insect neuronal cells.

To explore the toxicity mechanisms of neochamaejasmin B (NCB) extracted from Stellera chamaejasme L., we first evaluated its cytotoxicity in neuronal cells of Helicoverpa zea (AW1 cells). NCB inhibited cell growth and was cytotoxic to AW1 cells in a dose-dependent manner. Further, transmission electron microscopy (TEM) was used to analyze the microstructure, and typical apoptotic characteristics were observed in AW1 cells treated with NCB. Moreover, the NCB-induced apoptosis was dose dependent. Subsequently, we explored the mechanism of apoptosis. A decline in the mitochondrial membrane potential (MMP) was found. Also, the levels of Bax were increased with increases in drug concentration, but there was no statistical difference in Bcl-2 levels at different NCB doses. Caspase-3 and caspase-10 activity was increased. These findings confirmed that NCB induced apoptosis in AW1 cells through a caspase-10-dependent mechanism. The results provide the basic information needed for understanding the toxicity and mechanisms of action of NCB, which could potentially be used to develop NCB as a new insecticide.

Long noncoding RNA PVT1 facilitates high glucose-induced cardiomyocyte death through the miR-23a-3p/CASP10 axis.

Dilated cardiomyopathy (DCM) is the leading cause of morbidity and mortality in diabetic patients. Long noncoding RNA plasmacytoma variant translocation 1 (PVT1) has been shown to be related to the pathogenesis of DCM. However, the mechanism by which PVT1 regulates DCM pathogenesis is unclear. High glucose level was employed to construct a DCM cell model in vitro. Cell viability was determined via cell counting kit-8 assay. The level of lactate dehydrogenase (LDH) was measured with the corresponding kit. Expression levels of PVT1, miR-23a-3p, and caspase-10 (CASP10) messenger RNA were evaluated with a quantitative real-time polymerase chain reaction. Cell apoptosis was assessed by flow cytometry assay. Protein levels of B-cell lymphoma 2-associated X (Bax), cleaved-caspase-3 (cleaved-casp-3), and CASP10 were examined via western blot analysis. The relationship between PVT1 or CASP10 and miR-23a-3p was verified with dual-luciferase reporter assay. We observed that PVT1 and CASP10 were upregulated while miR-23a-3p was downregulated in high glucose-induced cardiomyocytes. High glucose levels repressed cardiomyocyte activity and induced cardiomyocyte apoptosis, but this influence was antagonized by PVT1 knockdown or miR-23a-3p overexpression. Furthermore, PVT1 acted as a sponge for miR-23a-3p, and miR-23a-3p inhibition counterbalanced the influence of PVT1 silencing on viability and apoptosis of cardiomyocytes under high glucose level treatment. PVT1 could increase CASP10 expression via sponging miR-23a-3p. In conclusion, PVT1 acted as a deleterious lncRNA in DCM. PVT1 facilitated cardiomyocyte death by regulating the miR-23a-3p/CASP10, which offered a new mechanism to comprehend the pathogenesis of DCM.

Stoichiometry of the CD95 death-inducing signaling complex: experimental and modeling evidence for a death effector domain chain model.

The CD95 (Fas/APO-1) death-inducing signaling complex (DISC) is essential for the initiation of CD95-mediated apoptotic and nonapoptotic responses. The CD95 DISC comprises CD95, FADD, procaspase-8, procaspase-10, and c-FLIP proteins. Procaspase-8 and procaspase-10 are activated at the DISC, leading to the formation of active caspases and apoptosis initiation. In this study we analyzed the stoichiometry of the CD95 DISC. Using quantitative western blots, mass spectrometry, and mathematical modeling, we reveal that the amount of DED proteins procaspase-8/procaspase-10 and c-FLIP at the DISC exceeds that of FADD by several-fold. Furthermore, our findings imply that procaspase-8, procaspase-10, and c-FLIP could form DED chains at the DISC, enabling the formation of dimers and efficient activation of caspase-8. Taken together, our findings provide an enhanced understanding of caspase-8 activation and initiation of apoptosis at the DISC.

SVMQA: support-vector-machine-based protein single-model quality assessment.

MOTIVATION: The accurate ranking of predicted structural models and selecting the best model from a given candidate pool remain as open problems in the field of structural bioinformatics. The quality assessment (QA) methods used to address these problems can be grouped into two categories: consensus methods and single-model methods. Consensus methods in general perform better and attain higher correlation between predicted and true quality measures. However, these methods frequently fail to generate proper quality scores for native-like structures which are distinct from the rest of the pool. Conversely, single-model methods do not suffer from this drawback and are better suited for real-life applications where many models from various sources may not be readily available. RESULTS: In this study, we developed a support-vector-machine-based single-model global quality assessment (SVMQA) method. For a given protein model, the SVMQA method predicts TM-score and GDT_TS score based on a feature vector containing statistical potential energy terms and consistency-based terms between the actual structural features (extracted from the three-dimensional coordinates) and predicted values (from primary sequence). We trained SVMQA using CASP8, CASP9 and CASP10 targets and determined the machine parameters by 10-fold cross-validation. We evaluated the performance of our SVMQA method on various benchmarking datasets. Results show that SVMQA outperformed the existing best single-model QA methods both in ranking provided protein models and in selecting the best model from the pool. According to the CASP12 assessment, SVMQA was the best method in selecting good-quality models from decoys in terms of GDTloss. AVAILABILITY AND IMPLEMENTATION: SVMQA method can be freely downloaded from http://lee.kias.re.kr/SVMQA/SVMQA_eval.tar.gz. CONTACT: jlee@kias.re.kr. SUPPLEMENTARY INFORMATION: Supplementary data are available at Bioinformatics online.

MicroRNA-421 inhibits caspase-10 expression and promotes breast cancer progression.

Breast cancer is one of the most prevalent and fatal diseases around the world. The mechanism of tumorigenesis in breast cancer remains to be clarified. miR-421 plays an oncogenic role in many cancers. Although, the clinical significance of miR-421 in patients with breast cancer is still to be investigated. Caspase-10 is one of the initiator of apoptosis. But the relationship between miR-421 and caspase-10 has not been investigated. In the present study, we found that miR-421 was expressed much higher in breast cancer tissues compared to those in adjacent non-tumor tissues. Furthermore, miR-421 promotes cell proliferation and colony formation in vitro. miR-421 inhibits cell apoptosis probably through restraining caspase-10 expression. Thus, miR-421 might be a potential diagnostic maker and therapeutic target for breast cancer.

Interferon α Induces the Apoptosis of Cervical Cancer HeLa Cells by Activating both the Intrinsic Mitochondrial Pathway and Endoplasmic Reticulum Stress-Induced Pathway.

The interferon α (IFN-α) has been often used as a sensitizing agent for the treatment of various malignancies such as hepatocellular carcinoma, malignant melanoma, and renal cell cancer by promoting the apoptosis of thesetumor cell types. However, the effect of IFN-α on cervical cancer remains unknown. In this study, HeLa cells were used as a testing model for the treatment of IFN-α on cervical cancer. The results indicate that IFN-α markedly inhibits the proliferation and induces the apoptosis of HeLa cells. The activation of caspase 3, the up-regulation of both Bim and cleaved poly (ADP-ribose) polymerase (PARP) 1, the down-regulation of Bcl-xL, as well as the release of cytochrome c from mitochondria were significantly induced upon IFN-α treatment, indicating that the intrinsic apoptotic pathway could be activated by IFN-α treatment. In addition, caspase 4-which is involved in the endoplasmic reticulum (ER) stress-induced apoptosis-was activated in response to IFN-α treatment. Knocking down caspase 4 by small interfering RNA (siRNA) markedly reduced the IFN-α-mediated cell apoptosis. However, no significant changes in the expressions of caspases 8 and 10 were observed upon IFN-α treatment, indicating that the apoptosis caused by IFN-α might be independent of the extrinsic apoptotic pathway. These findings suggest that IFN-α may possess anti-cervical cancer capacity by activating cell apoptosis via the intrinsic mitochondrial pathway and caspase-4-related ER stress-induced pathway.

Impaired Endothelial Regeneration Through Human Parvovirus B19-Infected Circulating Angiogenic Cells in Patients With Cardiomyopathy.

Human parvovirus B19 (B19V) is a common pathogen in microvascular disease and cardiomyopathy, owing to infection of endothelial cells. B19V replication, however, is almost restricted to erythroid progenitor cells (ErPCs). Endothelial regeneration attributable to bone marrow-derived circulating angiogenic cells (CACs) is a prerequisite for organ function. Because of many similarities of ErPCs and CACs, we hypothesized that B19V is a perpetrator of impaired endogenous endothelial regeneration. B19V DNA and messenger RNA from endomyocardial biopsy specimens, bone marrow specimens, and circulating progenitor cells were quantified by polymerase chain reaction analysis. The highest B19V DNA concentrations were found in CD34(+)KDR(+) cells from 17 patients with chronic B19V-associated cardiomyopathy. B19V replication intermediates could be detected in nearly half of the patients. Furthermore, chronic B19V infection was associated with impaired endothelial regenerative capacity. B19V infection of CACs in vitro resulted in expression of transcripts encoding B19V proteins. The capsid protein VP1 was identified as a novel inducer of apoptosis, as were nonstructural proteins. Inhibition studies identified so-called death receptor signaling with activation of caspase-8 and caspase-10 to be responsible for apoptosis induction. B19V causally impaired endothelial regeneration with spreading of B19V in CACs in an animal model in vivo. We thus conclude that B19V infection and damage to CACs result in dysfunctional endogenous vascular repair, supporting the emergence of primary bone marrow disease with secondary end-organ damage.

Differential response of head and neck cancer cell lines to TRAIL or Smac mimetics is associated with the cellular levels and activity of caspase-8 and caspase-10.

BACKGROUND: Current treatment strategies for head and neck cancer are associated with significant morbidity and up to 50% of patients relapse, highlighting the need for more specific and effective therapeutics. Tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) and Smac mimetics (SMs) are promising anticancer agents, but their effect on head and neck squamous cell carcinoma (HNSCC) remains unknown. METHODS: We examined the response of a panel of nine HNSCC cell lines to TRAIL and SMs and investigated the mechanism of cell type-specific response by functional analysis. RESULTS: Head and neck cancer cell lines revealed a converse response pattern with three cell lines being highly sensitive to Smac-164 (SM) but resistant to TRAIL, whereas the other six were sensitive to TRAIL but resistant to SM. Distinct protein expression and activation patterns were found to be associated with susceptibility of HNSCC cell lines to TRAIL and SM. Tumour necrosis factor-related apoptosis-inducing ligand sensitivity was associated with high caspase-8 and Bid protein levels, and TRAIL-sensitive cell lines were killed via the type II extrinsic apoptotic pathway. Smac mimetic-sensitive cells expressed low levels of caspase-8 and Bid but had high TNF-α expression. Smac mimetic-induced cell death was associated with caspase-10 activation, suggesting that in the absence of caspase-8, caspase-10 mediates response to SM. Cotreatment with TNF-α sensitised the resistant cells to SM, demonstrating a decisive role for TNF-α-driven feedback loop in SM sensitivity. CONCLUSIONS: Tumour necrosis factor-related apoptosis-inducing ligand and SMs effectively kill HNSCC cell lines and therefore represent potential targeted therapeutics for head and neck cancer. Distinct molecular mechanisms determine the sensitivity to each agent, with levels of TNF-α, caspase-8, Bid and caspase-10 providing important predictive biomarkers of response to these agents.

SSThread: Template-free protein structure prediction by threading pairs of contacting secondary structures followed by assembly of overlapping pairs.

Acquiring the three-dimensional structure of a protein from its amino acid sequence alone, despite a great deal of work and significant progress on the subject, is still an unsolved problem. SSThread, a new template-free algorithm is described here that consists of making several predictions of contacting pairs of α-helices and ß-strands derived from a database of experimental structures using a knowledge-based potential, secondary structure prediction, and contact map prediction followed by assembly of overlapping pair predictions to create an ensemble of core structure predictions whose loops are then predicted. In a set of seven CASP10 targets SSThread outperformed the two leading methods for two targets each. The targets were all ß-strand containing structures and most of them have a high relative contact order which demonstrates the advantages of SSThread. The primary bottlenecks based on sets of 74 and 21 test cases are the pair prediction and loop prediction stages.

Increasing maternal body mass index is associated with systemic inflammation in the mother and the activation of distinct placental inflammatory pathways.

Obese pregnant women have increased levels of proinflammatory cytokines in maternal circulation and placental tissues. However, the pathways contributing to placental inflammation in obesity are largely unknown. We tested the hypothesis that maternal body mass index (BMI) was associated with elevated proinflammatory cytokines in maternal and fetal circulations and increased activation of placental inflammatory pathways. A total of 60 women of varying pre-/early pregnancy BMI, undergoing delivery by Cesarean section at term, were studied. Maternal and fetal (cord) plasma were collected for analysis of insulin, leptin, IL-1beta, IL-6, IL-8, monocyte chemoattractant protein (MCP) 1, and TNFalpha by multiplex ELISA. Activation of the inflammatory pathways in the placenta was investigated by measuring the phosphorylated and total protein expression of p38-mitogen-activated protein kinase (MAPK), c-Jun-N-terminal kinase (JNK)-MAPK, signal transducer-activated transcription factor (STAT) 3, caspase-1, IL-1beta, IkappaB-alpha protein, and p65 DNA-binding activity. To determine the link between activated placental inflammatory pathways and elevated maternal cytokines, cultured primary human trophoblast (PHT) cells were treated with physiological concentrations of insulin, MCP-1, and TNFalpha, and inflammatory signaling analyzed by Western blot. Maternal BMI was positively correlated with maternal insulin, leptin, MCP-1, and TNFalpha, whereas only fetal leptin was increased with BMI. Placental phosphorylation of p38-MAPK and STAT3, and the expression of IL-1beta protein, were increased with maternal BMI; phosphorylation of p38-MAPK was also correlated with birth weight. In contrast, placental NFkappaB, JNK and caspase-1 signaling, and fetal cytokine levels were unaffected by maternal BMI. In PHT cells, p38-MAPK was activated by MCP-1 and TNFalpha, whereas STAT3 phosphorylation was increased following TNFalpha treatment. Maternal BMI is associated with elevated maternal cytokines and activation of placental p38-MAPK and STAT3 inflammatory pathways, without changes in fetal systemic inflammatory profile. Activation of p38-MAPK by MCP-1 and TNFalpha, and STAT3 by TNFalpha, suggests a link between elevated proinflammatory cytokines in maternal plasma and activation of placental inflammatory pathways. We suggest that inflammatory processes associated with elevated maternal BMI may influence fetal growth by altering placental function.

Investigation of the caspase-dependent mitochondrial apoptotic pathway in mononuclear cells of patients with systemic Lupus erythematosus.

BACKGROUND: This study aimed to explore the role of apoptosis initiators, caspase-9, caspase-10, mitochondrial anti-viral signaling protein (MAVS), and interferon regulatory factor 7 (pIRF7), in patients with systemic lupus erythematosus (SLE). METHODS: Leukocyte apoptosis was determined by flow cytometry, including annexin V, APO2.7, and 7-amino-actinomycin D (7-AAD) on each subtype of leukocyte in 35 patients with SLE, 15 disease controls, and 17 volunteer normal controls. Levels of caspase-9, caspase-10, MAVS, and pIRF7 in mononuclear cells and the disease activity index (SLEDAI) in the SLE patients were determined. Correlation among intracellular adaptor proteins and caspase levels were calculated. RESULTS: The SLE patients had higher APO2.7 in total leukocyte, lymphocyte, and monocytes, and higher late apoptosis markers in total leukocytes and neutrophils than normal controls (all p < 0.05). Disease activity was positively associated with the APO2.7 of CD19+ cells in SLE, but negatively associated with MAVS and caspase-9 levels (all p < 0.05). Markers of viral infection and anti-virus transcription factors like MDA5, MAVS, and pIRF7 were significantly higher in SLE patients than in disease controls (p < 0.05). Caspase-9 and caspase-10 levels positively correlated with MAVS and pIRF7 in SLE patients (p < 0.05). CONCLUSIONS: The disease activity of SLE is positively associated with APO2.7 level of CD19+ cells but negatively associated with MAVS and caspase-9 levels, which all point to a mitochondrial pathway.

AK2 activates a novel apoptotic pathway through formation of a complex with FADD and caspase-10.

Mitochondrial proteins function as essential regulators in apoptosis. Here, we show that mitochondrial adenylate kinase 2 (AK2) mediates mitochondrial apoptosis through the formation of an AK2-FADD-caspase-10 (AFAC10) complex. Downregulation of AK2 attenuates etoposide- or staurosporine-induced apoptosis in human cells, but not that induced by tumour-necrosis-factor-related apoptosis-inducing ligand (TRAIL) or Fas ligand (FasL). During intrinsic apoptosis, AK2 translocates to the cytoplasm, whereas this event is diminished in Apaf-1 knockdown cells and prevented by Bcl-2 or Bcl-X(L). Addition of purified AK2 protein to cell extracts first induces activation of caspase-10 via FADD and subsequently caspase-3 activation, but does not affect caspase-8. AFAC10 complexes are detected in cells undergoing intrinsic cell death and AK2 promotes the association of caspase-10 with FADD. In contrast, AFAC10 complexes are not detected in several etoposide-resistant human tumour cell lines. Taken together, these results suggest that, acting in concert with FADD and caspase-10, AK2 mediates a novel intrinsic apoptotic pathway that may be involved in tumorigenesis.

CD95 triggers Orai1-mediated localized Ca2+ entry, regulates recruitment of protein kinase C (PKC) ß2, and prevents death-inducing signaling complex formation.

The death receptor CD95 plays a pivotal role in immune surveillance and immune tolerance. Binding of CD95L to CD95 leads to recruitment of the adaptor protein Fas-associated death domain protein (FADD), which in turn aggregates caspase-8 and caspase-10. Efficient formation of the CD95/FADD/caspase complex, known as the death-inducing signaling complex (DISC), culminates in the induction of apoptosis. We show that cells exposed to CD95L undergo a reorganization of the plasma membrane in which the Ca(2+) release-activated Ca(2+) channel Orai1 and the endoplasmic reticulum-resident activator stromal interaction molecule 1 colocalize with CD95 into a micrometer-sized cluster in which the channel elicits a polarized entry of calcium. Orai1 knockdown and expression of a dominant negative construct (Orai1E106A) reveal that on CD95 engagement, the Orai1-driven localized Ca(2+) influx is fundamental to recruiting the Ca(2+)-dependent protein kinase C (PKC) ß2 to the DISC. PKCß2 in turn transiently holds the complex in an inactive status, preventing caspase activation and transmission of the apoptotic signal. This study identifies a biological role of Ca(2+) and the Orai1 channel that drives a transient negative feedback loop, introducing a lag phase in the early steps of the CD95 signal. We suggest that these localized events provide a time of decision to prevent accidental cell death.

Study of the potential role of CASPASE-10 mutations in the development of autoimmune lymphoproliferative syndrome.

Autoimmune lymphoproliferative syndrome (ALPS) is a primary disorder of lymphocyte homeostasis, leading to chronic lymphoproliferation, autoimmune cytopenia, and increased risk of lymphoma. The genetic landscape of ALPS includes mutations in FAS, FASLG, and FADD, all associated with apoptosis deficiency, while the role of CASP10 defect in the disease remains debated. In this study, we aimed to assess the impact of CASP10 variants on ALPS pathogenesis. We benefit from thousands of genetic analysis datasets performed in our Institute's genetic platform to identify individuals carrying CASP10 variants previously suspected to be involved in ALPS outcome: p.C401LfsX15, p.V410I and p.Y446C, both at heterozygous and homozygous state. Clinical and laboratory features of the six included subjects were variable but not consistent with ALPS. Two individuals were healthy. Comprehensive analyses of CASP10 protein expression and FAS-mediated apoptosis were conducted and compared to healthy controls and ALPS patients with FAS mutations. Missense CASP10 variants (p.V410I and p.Y446C), which are common in the general population, did not disrupt CASP10 expression, nor FAS-mediated apoptosis. In contrast, homozygous p.C401LfsX15 CASP10 variant lead to a complete abolished CASP10 expression but had no impact on FAS-mediated apoptosis function. At heterozygous state, this p.C401LfsX15 variant lead to a reduced CASP10 protein levels but remained associated with a normal FAS-mediated apoptosis function. These findings demonstrate that CASPASE 10 is dispensable for FAS-mediated apoptosis. In consequences, CASP10 defect unlikely contribute to ALPS pathogenesis, since they did not result in an impairment of FAS-mediated apoptosis nor in clinical features of ALPS in human. Moreover, the absence of FAS expression up-regulation in subjects with CASP10 variants rule out any compensatory mechanisms possibly involved in the normal apoptosis function observed. In conclusion, this study challenges the notion that CASP10 variants contribute to the development of ALPS.

Cathepsin D primes caspase-8 activation by multiple intra-chain proteolysis.

During the resolution of inflammatory responses, neutrophils rapidly undergo apoptosis. A direct and fast activation of caspase-8 by cathepsin D was shown to be crucial in the initial steps of neutrophil apoptosis. Nevertheless, the activation mechanism of caspase-8 remains unclear. Here, by using site-specific mutants of caspase-8, we show that both cathepsin D-mediated proteolysis and homodimerization of caspase-8 are necessary to generate an active caspase-8. At acidic pH, cathepsin D specifically cleaved caspase-8 but not the initiator caspase-9 or -10 and significantly increased caspase-8 activity in dimerizing conditions. These events were completely abolished by pepstatin A, a pharmacological inhibitor of cathepsin D. The cathepsin D intra-chain proteolysis greatly stabilized the active site of caspase-8. Moreover, the main caspase-8 fragment generated by cathepsin D cleavage could be affinity-labeled with the active site probe biotin-VAD-fluoromethyl ketone, suggesting that this fragment is enzymatically active. Importantly, in an in vitro cell-free assay, the addition of recombinant human caspase-8 protein, pre-cleaved by cathepsin D, was followed by caspase-3 activation. Our data therefore indicate that cathepsin D is able to initiate the caspase cascade by direct activation of caspase-8. As cathepsin D is ubiquitously expressed, this may represent a general mechanism to induce apoptosis in a variety of immune and nonimmune cells.

TRAIL induces autophagic protein cleavage through caspase activation in melanoma cell lines under arginine deprivation.

Arginine deprivation is a promising strategy for treating ASS-negative malignant tumors including melanoma. However, autophagy can potentially counteract the effectiveness of this treatment by acting as a pro-survival pathway. By combining tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) with arginine deprivation using ADI-PEG20 (pegylated arginine deiminase), we achieved enhanced apoptosis and accelerated cell death in melanoma cell lines. This implies a switch from autophagy to apoptosis. In our current investigation, we found that TRAIL could induce the cleavage of two key autophagic proteins, Beclin-1 and Atg5, in the combination treatment. Using specific inhibitors for individual caspases, we found that caspase-8 inhibitor could completely abolish the cleavage. Furthermore, caspase-8 inhibitor was able to fully reverse the enhanced cytotoxicity induced by TRAIL. Inhibitors for caspase-3, 6, 9, and 10 were able to block the cleavage of these two autophagic proteins to some extent and correspondingly rescue cells from the cytotoxicity of the combination of TRAIL and arginine deprivation. In contrast, calpain inhibitor could not prevent the cleavage of either Beclin-1 or Atg5, and was unable to prevent cell death. Overall, our data indicate that the cleavage of Beclin-1 and Atg5 by TRAIL-initiated caspase activation is one of the mechanisms that lead to the enhancement of the cytotoxicity in the combination treatment.

Gelsolin Inhibits the Proliferation of Colon Cancer Cells by Enhancing the Expression of TNFR2/CASP10 as a Death Receptor Pathway.

BACKGROUND: Colon cancer has the second highest incidence rate of digestive system tumors. It relies on surgical treatment, radiotherapy and chemotherapy, and targeted drug therapy. OBJECTIVE: To study the mechanism of GSN in the proliferation of colon cancer cells. MATERIALS AND METHODS: The expression of gelsolin (GSN) was analyzed with the data of colon cancer patients in the TCGA database. SW620 cells were treated by GSN in vitro and the gene expression was detected by immunoblotting and quantitative PCR. RESULTS: The expression of GSN was found significantly low in colon cancer cells and correlated with the prognosis of patients. The SW620 cell line cultured in vitro was treated with exogenous GSN. SW620 can be significantly inhibited above the concentration of 250 µg/ml. The results of immunoblotting and quantitative PCR showed that exogenous GSN can effectively improve the transcription level of death receptor-related pathway genes such as TNFR2 and CASP10. CONCLUSION: This study found that GSN inhibited the proliferation of SW620 cells in vitro by upregulating the expression of death receptor pathway-related proteins.

Zonisamide improves Fas/FasL-mediated apoptosis and inflammation in a degenerative cervical myelopathy rat model.

Degenerative cervical myelopathy (DCM) is a severe condition of the spinal cord caused by chronic compression. However, no studies to date have examined the effects of zonisamide (ZNS) on DCM via the Fas/FasL-mediated pathway. The aim of this study was to investigate the effects of ZNS on a DCM rat model and to explore the potential mechanisms. First, 40 adult Sprague-Dawley rats were used to establish the DCM rat model and were individually divided into four groups: the Sham group, DCM model group (DCM), ZNS group (DCM model rats treated with ZNS, 30 mg/kg/day), and ZNS + CD95 group (DCM model rats treated with ZNS and CD95). Histopathology injury and cell apoptosis, Fas and Fas ligand (FasL) expression and Fas/FasL relative protein levels were detected by hematoxylin and eosin staining, TUNEL assay, and immunofluorescence and western blotting, respectively. The results of our study demonstrated that ZNS could promote motor recovery while reversing histopathological injury and cell apoptosis in DCM rats. Moreover, Iba-1, Fas and FasL expression in DCM rats was decreased, accompanied by a decrease in cleaved caspase-3/caspase-3, cleaved caspase-8/caspase-8, cleaved caspase-9/caspase-9, cleaved caspase-10/caspase-10 and B-cell lymphoma-2 (Bcl-2)/Bcl-2 associated X (Bax) levels. All these results revealed that ZNS attenuates DCM injury in a rat model via the regulation of Fas and FasL signaling. Our study indicated that ZNS had beneficial effects on DCM and thus provided a novel theoretical approach for subsequent academic and clinical research on DCM injury.