Caspase-containing complexes in the regulation of cell death and inflammation

G Protein-Coupled Estrogen Receptor-Mediated Anti-Inflammatory and Mucosal Healing Activity of a Trimethylpyridinol Analogue in Inflammatory Bowel Disease

Inflammatory bowel disease (IBD) is characterized by abnormal immune responses, including elevated proinflammatory cytokines, such as tumor necrosis factor-α (TNFα) and interleukin-6 (IL-6) in the gastrointestinal (GI) tract. This study presents the synthesis and anti-inflammatory evaluation of 2,4,5-trimethylpyridin-3-ol analogues, which exhibit dual inhibition of TNFα- and IL-6-induced inflammation. Analysis using in silico methods, including 3D shape-based target identification, modeling, and docking, identified G protein-coupled estrogen receptor 1 (GPER) as the molecular target for the most effective analogue, 6-26, which exhibits remarkable efficacy in ameliorating inflammation and restoring colonic mucosal integrity. This was further validated by surface plasmon resonance (SPR) assay results, which showed direct binding to GPER, and by the results showing that GPER knockdown abolished the inhibitory effects of 6-26 on TNFα and IL-6 actions. Notably, 6-26 displayed no cytotoxicity, unlike G1 and G15, a well-known GPER agonist and an antagonist, respectively, which induced necroptosis independently of GPER. These findings suggest that the GPER-selective compound 6-26 holds promise as a therapeutic candidate for IBD.

Interleukin-1β converting enzyme (ICE): A comprehensive review on discovery and development of caspase-1 inhibitors

Caspase-1 is a critical mediator of the inflammatory process by activating various pro-inflammatory cytokines such as pro-IL-1β, IL-18 and IL-33. Uncontrolled activation of caspase-1 leads to various cytokines-mediated diseases. Thus, inhibition of Caspase-1 is considered therapeutically beneficial to halt the progression of such diseases. Currently, rilonacept, canakinumab and anakinra are in use for caspase-1-mediated autoinflammatory diseases. However, the poor pharmacokinetic profile of these peptides limits their use as therapeutic agents. Therefore, several peptidomimetic inhibitors have been developed, but only a few compounds (VX-740, VX-765) have advanced to clinical trials; because of their toxic profile. Several small molecule inhibitors have also been progressing based on the three-dimensional structure of caspase-1. However there is no successful candidate available clinically. In this perspective, we highlight the mechanism of caspase-1 activation, its therapeutic potential as a disease target and potential therapeutic strategies targeting caspase-1 with their limitations.

A Review on Inflammasomes and Immune Checkpoints in Pre-Eclampsia Complicated with Tuberculosis and Human Immune Deficiency Virus

The current review evaluates how inflammasomes and immune checkpoints are regulated in pre-eclampsia (PE) associated with tuberculosis (TB) and Human Immune Deficiency Virus (HIV). Studies indicate that inflammasomes such as (NRLP3, NEK7, and AIM2) and immune checkpoints such as (CLT4, PD-1, TIM3, and LAG-3) are dysregulated in TB- and HIV-infected individuals, and also in pre-eclamptic pregnancies, which explains why pregnant women who are either infected with TB or HIV have an increased risk of developing PE. Evidence suggests that inhibition of inflammasomes and immune checkpoints may assist in the development of novel anti-inflammatory drugs for the prevention and management of PE in patients with or without TB and HIV infection.

Preeclampsia and COVID-19: the Role of Inflammasome Activation

PURPOSE OF REVIEW

It is well established that controlled immune activation and balance is critical for women's reproductive health and successful pregnancy outcomes. Research in recent decades in both clinical and animal studies has demonstrated that aberrant immune activation and inflammation play a role in the development and progression of women's reproductive health and pregnancy-related disorders. Inflammasomes are multi-protein cytoplasmic complexes that mediate immune activation. In this review, we summarize current knowledge on the role of inflammasome activation in pregnancy-related disorders.

RECENT FINDINGS

Increased activation of inflammasome is associated with multiple women's health reproductive disorders and pregnancy-associated disorders, including preeclampsia (PreE). Inflammasome activation is also associated with the novel coronavirus disease 2019 (COVID-19) disease caused by the SARS-Cov-2 virus. We and others have observed a positive association between increased PreE incidences with the onset of the COVID-19 pandemic. Here, we present our recent data indicating increased inflammasome activation, represented by caspase-1 activity, in women with COVID-19 and PreE compared to normotensive pregnant women COVID-19. The role of inflammation in pregnancy-related disorders is an area of intense research interest. With the onset of the COVID-19 pandemic and the associated increase in PreE observed clinically, there is a greater need to identify mechanisms of pathophysiology and targets to treat this maternal disorder. Inflammasome activation is associated with PreE and COVID-19 infection and may hold therapeutic potential to improve outcomes associated with PreE and curb the morbidity attributed to PreE.

AREL1 E3 ubiquitin ligase inhibits TNF-induced necroptosis via the ubiquitination of MTX2

Previously, we reported on a novel anti-apoptotic E3 ubiquitin ligase, apoptosis-resistant E3 ubiquitin protein ligase 1 (AREL1), that ubiquitinates inhibitors of apoptosis proteins antagonists. The present study demonstrated that AREL1 ubiquitinated Metaxin 2 (MTX2), which was involved in TNF-induced necroptosis. MTX2 has been identified as a protein that belongs to the Metaxin family. It interacts with another Metaxin protein, Metaxin 1 (MTX1), which is localized in the outer membrane of mitochondria, and is involved in TNF-induced necroptosis. This study found that AREL1 interacted with MTX2, but not MTX1, while the amino-terminal domain of MTX2 interacted with MTX1, AREL1 interacted with the carboxyl-terminal domain of MTX2. Furthermore, AREL1 expression led to a decrease in the protein expression of MTX2, but not MTX1. However, a mutant form of AREL1, AREL1C790A, which is deficient for E3 activity, did not cause MTX2 degradation. Moreover, the protein levels of MTX2 were increased by AREL1 knockdown. Therefore, these results implied that AREL1 ubiquitinates and promotes the degradation of MTX2. The expression of MTX2, together with MTX1, enhanced TNF-induced necroptosis. However, AREL1 inhibited necroptosis even in cells expressing Metaxin proteins. Therefore, these results suggested that the inhibition of AREL1-dependent ubiquitination of MTX2 could be beneficial to sensitize tumor cells to TNF-induced necroptosis.

Interleukin-37: The Effect of Anti-Inflammatory Response in Human Coronary Artery Endothelial Cells

Interleukin-37 (IL-37) is unique in the IL-1 family since it broadly suppresses innate immunity and elevates in humans with inflammatory and autoimmune diseases. IL-37 shows definite groups and transcripts for human IL37 gene, but it is still not completely understood the effect and mechanisms of inflammatory response in endothelial cells. It is well accepted that endothelial dysfunction caused by inflammation is a key initiating event in atherosclerotic plaque formation, which leads to the occurrence and development of the cardiovascular adverse events in clinical since the inflammatory responses of endothelial cells could induce and enhance the deposition of extensive lipid and the formation of atherosclerotic plaque in the intima. Thus, it is essential to investigate the role and potential mechanisms in endothelial inflammatory response to prevent the formation and development of many cardiovascular diseases including atherosclerosis. So far, the recent studies have revealed that IL-37 is able to inhibit inflammatory response by suppressing the TLR2-NF-κB-ICAM-1 pathway intracellularly in human coronary artery endothelial cells (HCAECs). Further, the role of IL-37 may be related to the IL-18 pathway extracellularly and involved in the adhesion and transmigration of neutrophils in HCAECs.

Holding All the CARDs: How MALT1 Controls CARMA/CARD-Dependent Signaling

The scaffold proteins CARMA1-3 (encoded by the genes CARD11, -14 and -10) and CARD9 play major roles in signaling downstream of receptors with immunoreceptor tyrosine activation motifs (ITAMs), G-protein coupled receptors (GPCR) and receptor tyrosine kinases (RTK). These receptors trigger the formation of oligomeric CARMA/CARD-BCL10-MALT1 (CBM) complexes via kinases of the PKC family. The CBM in turn regulates gene expression by the activation of NF-κB and AP-1 transcription factors and controls transcript stability. The paracaspase MALT1 is the only CBM component having an enzymatic (proteolytic) activity and has therefore recently gained attention as a potential drug target. Here we review recent advances in the understanding of the molecular function of the protease MALT1 and summarize how MALT1 scaffold and protease function contribute to the transmission of CBM signals. Finally, we will highlight how dysregulation of MALT1 function can cause pathologies such as immunodeficiency, autoimmunity, psoriasis, and cancer.

Calmodulin antagonist enhances DR5-mediated apoptotic signaling in TRA-8 resistant triple negative breast cancer cells

Patients with triple negative breast cancer (TNBC) have no successful "targeted" treatment modality, which represents a priority for novel therapy strategies. Upregulated death receptor 5 (DR5) expression levels in breast cancer cells compared to normal cells enable TRA-8, a DR5 specific agonistic antibody, to specifically target malignant cells for apoptosis without inducing normal hepatocyte apoptosis. Drug resistance is a common obstacle in TRAIL-based therapy for TNBC. Calmodulin (CaM) is overexpressed in breast cancer. In this study, we characterized the novel function of CaM antagonist in enhancing TRA-8 induced cytotoxicity in TRA-8 resistant TNBC cells and its underlying molecular mechanisms. Results demonstrated that CaM antagonist(s) enhanced TRA-8 induced cytotoxicity in a concentration and time-dependent manner for TRA-8 resistant TNBC cells. CaM directly bound to DR5 in a Ca²⁺ dependent manner, and CaM siRNA promoted DR5 recruitment of FADD and caspase-8 for DISC formation and TRA-8 activated caspase cleavage for apoptosis in TRA-8 resistant TNBC cells. CaM antagonist, trifluoperazine, enhanced TRA-8 activated DR5 oligomerization, DR5-mediated DISC formation, and TRA-8 activated caspase cleavage for apoptosis, and decreased anti-apoptotic pERK, pAKT, XIAP, and cIAP-1 expression in TRA-8 resistant TNBC cells. These results suggest that CaM could be a key regulator to mediate DR5-mediated apoptotic signaling, and suggests a potential strategy for using CaM antagonists to overcome drug resistance of TRAIL-based therapy for TRA-8 resistant TNBC.

Calmodulin Binding to Death Receptor 5-mediated Death-Inducing Signaling Complex in Breast Cancer Cells

Activation of death receptor-5 (DR5) leads to the formation of death-inducing signaling complex (DISC) for apoptotic signaling. TRA-8, a DR5 specific agonistic antibody, has demonstrated significant cytotoxic activity in vitro and in vivo without inducing hepatotoxicity. Calmodulin (CaM) that is overexpressed in breast cancer plays a critical role in regulating DR5-mediated apoptosis. However, the mechanism of CaM in regulating DR5-mediated apoptotic signaling remains unknown. In this study, we characterized CaM binding to DR5-mediated DISC for apoptosis in TRA-8 sensitive breast cancer cell lines using co-immunoprecipitation, fluorescence microscopic imaging, caspase signaling analysis, and cell viability assay. Results show that upon DR5 activation, CaM was recruited into DR5-mediated DISC in a calcium dependent manner. CaM antagonist, trifluoperazine (TFP), inhibited CaM recruitment into the DISC and attenuated DISC formation. DR5 oligomerization is critical for DISC formation for apoptosis. TFP decreased TRA-8 activated DR5 oligomerization, which was consistent with TFP's effect on DR5-mediated DISC formation. TFP and Ca²⁺ chelator, EGTA, impeded TRA-8-activated caspase-dependent apoptotic signaling, and TFP decreased TRA-8-induced cell cytotoxicity. These results demonstrated CaM binding to DR5-mediated DISC in a calcium dependent manner and may identify CaM as a key regulator of DR5-mediated DISC formation for apoptosis in breast cancer. J. Cell. Biochem. 118: 2285-2294, 2017. © 2017 Wiley Periodicals, Inc.

Effects of seawater acidification on gene expression: resolving broader-scale trends in sea urchins

Sea urchins are ecologically and economically important calcifying organisms threatened by acidification of the global ocean caused by anthropogenic CO2 emissions. Propelled by the sequencing of the purple sea urchin (Strongylocentrotus purpuratus) genome, profiling changes in gene expression during exposure to high pCO2 seawater has emerged as a powerful and increasingly common method to infer the response of urchins to ocean change. However, analyses of gene expression are sensitive to experimental methodology, and comparisons between studies of genes regulated by ocean acidification are most often made in the context of major caveats. Here we perform meta-analyses as a means of minimizing experimental discrepancies and resolving broader-scale trends regarding the effects of ocean acidification on gene expression in urchins. Analyses across eight studies and four urchin species largely support prevailing hypotheses about the impact of ocean acidification on marine calcifiers. The predominant expression pattern involved the down-regulation of genes within energy-producing pathways, a clear indication of metabolic depression. Genes with functions in ion transport were significantly over-represented and are most plausibly contributing to intracellular pH regulation. Expression profiles provided extensive evidence for an impact on biomineralization, epitomized by the down-regulation of seven spicule matrix proteins. In contrast, expression profiles provided limited evidence for CO2-mediated developmental delay or induction of a cellular stress response. Congruence between studies of gene expression and the ocean acidification literature in general validates the accuracy of gene expression in predicting the consequences of ocean change and justifies its continued use in future studies.

Non-apoptotic function of caspases in a cellular model of hydrogen peroxide-associated colitis

Oxidative stress, caused by reactive oxygen species (ROS), is a major contributor to inflammatory bowel disease (IBD)-associated neoplasia. We mimicked ROS exposure of the epithelium in IBD using non-tumour human colonic epithelial cells (HCEC) and hydrogen peroxide (H2 O2 ). A population of HCEC survived H2 O2 -induced oxidative stress via JNK-dependent cell cycle arrests. Caspases, p21(WAF1) and γ-H2AX were identified as JNK-regulated proteins. Up-regulation of caspases was linked to cell survival and not, as expected, to apoptosis. Inhibition using the pan-caspase inhibitor Z-VAD-FMK caused up-regulation of γ-H2AX, a DNA-damage sensor, indicating its negative regulation via caspases. Cell cycle analysis revealed an accumulation of HCEC in the G1 -phase as first response to oxidative stress and increased S-phase population and then apoptosis as second response following caspase inhibition. Thus, caspases execute a non-apoptotic function by promoting cells through G1 - and S-phase by overriding the G1 /S- and intra-S checkpoints despite DNA-damage. This led to the accumulation of cells in the G2 /M-phase and decreased apoptosis. Caspases mediate survival of oxidatively damaged HCEC via γ-H2AX suppression, although its direct proteolytic inactivation was excluded. Conversely, we found that oxidative stress led to caspase-dependent proteolytic degradation of the DNA-damage checkpoint protein ATM that is upstream of γ-H2AX. As a consequence, undetected DNA-damage and increased proliferation were found in repeatedly H2 O2 -exposed HCEC. Such features have been associated with neoplastic transformation and appear here to be mediated by a non-apoptotic function of caspases. Overexpression of upstream p-JNK in active ulcerative colitis also suggests a potential importance of this pathway in vivo.

Cationic lipids activate intracellular signaling pathways

Cationic liposomes are commonly used as a transfection reagent for DNA, RNA or proteins and as a co-adjuvant of antigens for vaccination trials. A high density of positive charges close to cell surface is likely to be recognized as a signal of danger by cells or contribute to trigger cascades that are classically activated by endogenous cationic compounds. The present review provides evidence that cationic liposomes activate several cellular pathways like pro-apoptotic and pro-inflammatory cascades. An improved knowledge of the relationship between the cationic lipid properties (nature of the lipid hydrophilic moieties, hydrocarbon tail, mode of organization) and the activation of these pathways opens the way to the use and design of cationic tailored for a specific application (e.g. for gene transport or as adjuvants).

The infectious bursal disease virus RNA-binding VP3 polypeptide inhibits PKR-mediated apoptosis

Infectious bursal disease virus (IBDV) is an avian pathogen responsible for an acute immunosuppressive disease that causes major losses to the poultry industry. Despite having a bipartite dsRNA genome, IBDV, as well as other members of the Birnaviridae family, possesses a single capsid layer formed by trimers of the VP2 capsid protein. The capsid encloses a ribonucleoprotein complex formed by the genome associated to the RNA-dependent RNA polymerase and the RNA-binding polypeptide VP3. A previous report evidenced that expression of the mature VP2 IBDV capsid polypeptide triggers a swift programmed cell death response in a wide variety of cell lines. The mechanism(s) underlying this effect remained unknown. Here, we show that VP2 expression in HeLa cells activates the double-stranded RNA (dsRNA)-dependent protein kinase (PKR), which in turn triggers the phosphorylation of the eukaryotic initiation factor 2α (eIF2α). This results in a strong blockade of protein synthesis and the activation of an apoptotic response which is efficiently blocked by coexpression of a dominant negative PKR polypeptide. Our results demonstrate that coexpression of the VP3 polypeptide precludes phosphorylation of both PKR and eIF2α and the onset of programmed cell death induced by VP2 expression. A mutation blocking the capacity of VP3 to bind dsRNA also abolishes its capacity to prevent PKR activation and apoptosis. Further experiments showed that VP3 functionally replaces the host-range vaccinia virus (VACV) E3 protein, thus allowing the E3 deficient VACV deletion mutant WRΔE3L to grow in non-permissive cell lines. According to results presented here, VP3 can be categorized along with other well characterized proteins such us VACV E3, avian reovirus sigmaA, and influenza virus NS1 as a virus-encoded dsRNA-binding polypeptide with antiapoptotic properties. Our results suggest that VP3 plays a central role in ensuring the viability of the IBDV replication cycle by preventing programmed cell death.

Apoptotic and non-apoptotic roles of caspases in neuronal physiology and pathophysiology

Caspases are cysteine proteases that mediate apoptosis, which is a form of regulated cell death that effectively and efficiently removes extra and unnecessary cells during development. In the mature nervous system, caspases are not only involved in mediating cell death but also regulatory events that are important for neural functions, such as axon pruning and synapse elimination, which are necessary to refine mature neuronal circuits. Furthermore, caspases can be reactivated to cause cell death as well as non-lethal changes in neurons during numerous pathological processes. Thus, although a global activation of caspases leads to apoptosis, restricted and localized activation may control normal physiology and pathophysiology in living neurons. This Review explores the multiple roles of caspase activity in neurons.

Expression of NF-κB-related proteins and their modulation during TNF-α-provoked apoptosis in prostate cancer cells

BACKGROUND

The involvement of TNF-α in cancer development is controversial, since this cytokine was reported to act either as tumor promoter or suppressor. TNF-α may activate signaling pathways critical for life/death decisions, such as mitogen-activated protein kinases (MAPKs) and the anti-apoptotic NF-κB pathway. In this work, we investigate the activation status of NF-κB-related proteins in human prostate cancerous versus normal epithelium, and the alterations in the NF-κB pathway in relation to cell death in TNF-α-treated LNCaP (androgen-independent cells) and PC3 (androgen-independent) prostate cancer cell lines.

METHODS

The expression of phospho-p38-MAPK, phospho-IKK-α/β and phospho-IκB-α, total IκB-α, and p65- and p50-NF-κB, were analyzed by immunohistochemistry in cancerous and normal prostate samples. The toxicity of TNF-α in LNCaP and PC3 cells, with or without kinase and NF-κB inhibitors, was assessed by changes on viability (MTT assay) and apoptosis (loss of DNA, annexin-V binding, and caspase cleavage/activation). Expression of NF-κB-related proteins in these cell lines was measured by Western blot.

RESULTS

Phospho-IκB-α, phospho-IKK-α/β and phospho-p38 levels, cytoplasmic p50 to IκB-α ratio, and nuclear p50 and p65, levels, were increased in cancerous epithelium, suggesting activation of the NF-κB pathway in prostatic malignance. TNF-α caused apoptosis with higher efficacy in LNCaP cells, and this response was potentiated by p38-MAPK inhibitor (LNCaP cells) and IKK-β inhibitor (both cell lines). However, the protective action of IKK-β was mediated by NF-κB only in LNCaP cells.

CONCLUSIONS

IKK-β mediates both NF-κB-dependent and -independent anti-apoptotic functions in prostate cancerous epithelium. IKK-β and p38-MAPK may represent useful therapeutic targets against prostate cancer.

Apoptosis in pre-Bilaterians: Hydra as a model

Hydra is a member of the ancient metazoan phylum Cnidaria and is an especially well investigated model organism for questions of the evolutionary origin of metazoan processes. Apoptosis in Hydra is important for the regulation of cellular homeostasis under different conditions of nutrient supply. The molecular mechanisms leading to apoptosis in Hydra are surprisingly extensive and comparable to those in mammals. Genome wide sequence analysis has revealed the presence of large caspase and Bcl-2 families, the apoptotic protease activating factor (APAF-1), inhibitors of apoptotic proteases (IAPs) and components of a putative death receptor pathway. Regulation of apoptosis in Hydra may involve BH-3 only proteins and survival pathways, possibly including insulin signalling.

The human cytomegalovirus UL36 gene controls caspase-dependent and -independent cell death programs activated by infection of monocytes differentiating to macrophages

The cellular protease caspase-8 activates extrinsic apoptosis and also functions to promote monocyte-to-macrophage differentiation. Differentiation-induced alterations to antiviral caspase-8-dependent cell death pathways are unclear. Here, we show THP-1 monocyte-to-macrophage differentiation alters the specific cell death pathways activated in response to human cytomegalovirus (HCMV) infection. Employing viruses with mutations in UL36, the gene that encodes the viral inhibitor of caspase-8 activation (vICA), our data indicate that both caspase-dependent and -independent death pathways are activated in response to infection. Activation of caspase-dependent and -independent cell death responses restricted growth of vICA-deficient viruses, and vICA/pUL36 inhibited either response. Thus, these studies also reveal that the UL36 gene controls a caspase-independent cell death pathway. The impact of caspases on control of antiviral responses differed at early and late stages of macrophage differentiation. Early in differentiation, vICA-deficient virus-induced cell death was dependent on caspases and inhibited by the pan-caspase inhibitor z-VAD(OMe)-fluoromethyl ketone. In contrast, virus-induced death at late times of differentiation was caspase independent. Additional unlabeled and fluorescent inhibitors indicated that caspase-8 promoted death from within infected cells at early but not late stages of differentiation. These data highlight the multifunctional role of vICA/pUL36 as HCMV encounters various antiviral responses during macrophage differentiation.

The Jekyll and Hyde functions of caspases

Apoptosis is an ancient form of regulated cell death that functions under pathological and nonpathological contexts in all metazoans. More than a decade of intense research has led to extensive characterization of the core molecular mechanisms for apoptotic cell death. This includes the identification of a family of cysteine proteases, caspases, which are critical for the execution of apoptosis. Whereas completion of the proteolytic caspase cascade leads to elimination of a cell by apoptosis, caspase activation, when finely tuned, directs alternative cellular functions independent of cell death. Exciting recent developments have focused on uncovering nonapoptotic roles of caspases ranging from immune regulation to spermatogenesis, in highly specialized cellular frameworks.

Human initiator caspases trigger apoptotic and autophagic phenotypes in Saccharomyces cerevisiae

Caspases are a family of proteases that participate in the progression and execution of the apoptotic program. However, regulation of the caspase activation and their substrates has not yet been fully elucidated. Here we explore the effect of the ectopic expression of the human initiator caspases-8 and -10 in Saccharomyces cerevisiae. Our results showed that the expression of human CASP10 and CASP8 triggers certain apoptotic markers such as a massive production of reactive oxygen species (ROS), chromatin condensation and phosphatidylserine externalization, finally leading to cell death. In response to hydroxyurea (HU), yeast cells expressing caspase-10 did not reduce the replication of DNA and escaped to the intra-S checkpoint of the cell cycle. In addition, caspase-10 expression induced yeast vacuolization and a vacuole-associated phenotype resembling autophagy. Other intracellular alterations such as disorganization of the actin cytoskeleton, cell wall damage, and aberrations within the endoplasmic reticulum lumen were also associated with caspase-10 expression. Furthermore, caspase-induced cell death was completely dependent on the proteolytic activation of the enzyme but, in contrast, was not dependent on either of the endogenous yeast apoptotic proteins Aif1 and Mca1 or the mitochondria.

The Fas-FADD death domain complex structure unravels signalling by receptor clustering

The Death Inducing Signaling Complex (DISC) formed by Fas receptor, FADD and caspase-8 is a pivotal trigger of apoptosis1-3. The Fas/FADD DISC represents a receptor platform, which once assembled initiates the induction of programmed cell death. A highly oligomeric network of homotypic protein interactions comprised of the death domains (DD) of Fas and FADD is at the center of DISC formation4, 5. Thus characterising the mechanistic basis for the Fas/FADD interaction is paramount for understanding DISC signaling but has remained enigmatic largely due to a lack of structural data. We have successfully formed and isolated the Fas/FADD DD complex and here we report the 2.7 Å crystal structure. The complex shows a tetrameric arrangement of four FADD DDs bound to four Fas DDs. We show that an opening of the Fas DD exposes the FADD binding site and simultaneously generates a Fas/Fas bridge. The result is a regulatory Fas/FADD complex bridge governed by weak protein:protein interactions revealing a model where the complex functions as a mechanistic switch. This switch prevents accidental DISC assembly, yet allows for highly processive DISC formation and clustering upon a sufficient stimulus. Thus besides depicting a previously unknown mode of death domain interactions, these results further uncover a mechanism for receptor signaling solely by oligomerization and clustering events.

Differential expression of Cathepsin S and X in the spinal cord of a rat neuropathic pain model

Background

Ample evidence suggests a substantial contribution of cellular and molecular changes in the spinal cord to the induction and persistence of chronic neuropathic pain conditions. While for a long time, proteases were mainly considered as protein degrading enzymes, they are now receiving growing interest as signalling molecules in the pain pathology. In the present study we focused on two cathepsins, CATS and CATX, and studied their spatiotemporal expression and activity during the development and progression of neuropathic pain in the CNS of the rat 5^th lumbar spinal nerve transection model (L5T).

Results

Immediately after the lesion, both cathepsins, CATS and CATX, were upregulated in the spinal cord. Moreover, we succeeded in measuring the activity of CATX, which was substantially increased after L5T. The differential expression of these proteins exhibited the same spatial distribution and temporal progression in the spinal cord, progressing up to the medulla oblongata in the late phase of chronic pain. The cellular distribution of CATS and CATX was, however, considerably different.

Conclusion

The cellular distribution and the spatio-temporal development of the altered expression of CATS and CATX suggest that these proteins are important players in the spinal mechanisms involved in chronic pain induction and maintenance.

Control of apoptosis by human cytomegalovirus

Caspase-dependent apoptosis has an important role in controlling viruses, and as a result, viruses often encode proteins that target this pathway. Caspase-dependent apoptosis can be activated from within the infected cell as an intrinsic response to replication-associated stresses or through death-inducing signals produced extrinsically by immune cells. Cytomegaloviruses (CMVs) encode a mitochondria-localized inhibitor of apoptosis, vMIA, and a viral inhibitor of caspase activation, vICA, the functional homologs of Bcl-2 related and c-FLIP proteins, respectively. Evidence from viral mutants deleting either vMIA or vICA suggests that each is necessary and sufficient to promote survival of infected cells undergoing caspase-dependent apoptosis. Additional proteins, including pUL38, IE1(491a), and IE2(579aa), can prevent apoptosis induced by various stimuli, while viruses with deletions of UL38, M45, or m41 undergo apoptosis. The viral RNA, beta2.7, binds mitochondrial respiratory complex I, maintains ATP production late in infection, and prevents death induced by a mitochondrial poison. Thus, CMV alters cell intrinsic defenses employing apoptosis, and multiple viral gene products together control death-inducing stimuli to promote survival.

Effects of lithium and deafferentation on expression of glycogen synthase kinase-3beta, NFkappaB, beta-catenin and pCreb in the chick cochlear nucleus

The avian brainstem serves as a useful model to answer the question of how afferent activity influences the viability of target neurons. Approximately 20-30% of neurons in the avian cochlear nucleus, nucleus magnocellularis (NM) die following deafferentation (i.e., deafness produced by cochlea removal). Interestingly, Bcl-2 mRNA (but not protein) is upregulated in 20-30% of NM neurons following deafferentation. We have recently shown that chronic treatments of lithium upregulates the neuroprotective protein Bcl-2 and increases neuronal survival following deafferentation. The pathways leading to the upregulation of Bcl-2 expression following these two manipulations are unknown. The present experiments examine changes in glycogen synthase kinase-3 beta (Gsk-3beta), and transcription factors nuclear factor kappaB (NFkappaB), beta-catenin, and pCreb following lithium administration and following deafferentation. These molecules are known to be influenced by lithium and to regulate Bcl-2 expression in other model systems. Lithium decreased immunolabeling for Gsk-3beta and increased expression for all three transcription factors. Deafferentation, however, did not alter Gsk-3beta or NFkappaB, resulted in lower beta-catenin expression, but did increase pCreb immunoreactivity. While it is possible that pCreb is a common link in the regulation of Bcl-2 following these two manipulations, the timing and distribution of pCreb labeling suggests that it is not the sole determinant of Bcl-2 upregulation following deafferentation. It is likely that the regulation of Bcl-2 gene expression by lithium and by deafferentation involves different molecular pathways.

Analysis of apoptosis regulatory genes expression in the bone marrow (BM) of adult de novo Myelodysplastic Syndromes (MDS)

The aim of the present study was to examine caspases, granzyme B and bcl-2 family mRNA expression and the degree of apoptosis in the bone marrow (BM) of 46 Myelodysplastic Syndromes (MDS) and to correlate our findings with clinical parameters. The degree of apoptosis was determined by Annexin V, whereas expression of genes was determined using a multiprobe RNase Protection System. A positive correlation was found between caspases 8, 5, 3, 2, 1 and the level of apoptosis. bfl1 and mcl1 levels were significantly higher in patients with BM blasts >5%. Cases with ratio of bid expression >1 compared to normal pool were associated with IPSS values < or =1.