Heat shock protein 90 associates with monarch-1 and regulates its ability to promote degradation of NF-kappaB-inducing kinase

Identification of a Novel NLRP12 Frameshift Mutation (Val730Glyfs∗41) by Whole-Exome Sequencing in Patients with Crohn’s Disease

NLRP12 encodes the nucleotide-binding leucine-rich repeat-containing receptor 12 protein and has been linked to familial cold autoinflammatory syndrome 2 (FCAS2). Previous studies have reported that NLRP12 protein can dampen inflammatory responses in DSS-induced mice colitis. To date, only four alterations in the NLRP12 gene have been associated with Crohn’s disease (CD). Here, we reported a novel heterozygous NLRP12 frameshift mutation (c.2188dupG, p.Val730Glyfs${}^{\ast }$41) identified by whole-exome sequencing in the proband with CD. The Sanger sequencing confirmed that his sister and father also carried this NLRP12 mutation, which cosegregated well with the CD phenotype. In silico analysis predicted this mutation to be disease-causing. Patients heterozygous for this mutation exhibited decreased NLRP12 protein levels in the peripheral blood and colon. Functional assays showed that mutant NLRP12 plasmid-transfected HEK293T cells exhibited significantly lower NLRP12 mRNA and protein levels than wild-type plasmid-transfected cells. The nonsense-mediated decay inhibitor NMDI14 significantly increased NLRP12 mRNA and protein levels in mutant plasmid-transfected cells. Overall, our results demonstrated that this heterozygous NLRP12 mutation (c.2188dupG) resulted in decreased NLRP12 expression, which might contribute to the mechanism underlying CD.

NLRP12 downregulates the Wnt/β-catenin pathway via interaction with STK38 to suppress colorectal cancer

Colorectal cancer (CRC) at advanced stages is rarely curable, underscoring the importance of exploring the mechanism of CRC progression and invasion. NOD-like receptor family member NLRP12 was shown to suppress colorectal tumorigenesis, but the precise mechanism was unknown. Here, we demonstrate that invasive adenocarcinoma development in Nlrp12-deficient mice is associated with elevated expression of genes involved in proliferation, matrix degradation, and epithelial-mesenchymal transition. Signaling pathway analysis revealed higher activation of the Wnt/β-catenin pathway, but not NF-κB and MAPK pathways, in the Nlrp12-deficient tumors. Using Nlrp12-conditional knockout mice, we revealed that NLRP12 downregulates β-catenin activation in intestinal epithelial cells, thereby suppressing colorectal tumorigenesis. Consistent with this, Nlrp12-deficient intestinal organoids and CRC cells showed increased proliferation, accompanied by higher activation of β-catenin in vitro. With proteomic studies, we identified STK38 as an interacting partner of NLRP12 involved in the inhibition of phosphorylation of GSK3β, leading to the degradation of β-catenin. Consistently, the expression of NLRP12 was significantly reduced, while p-GSK3β and β-catenin were upregulated in mouse and human colorectal tumor tissues. In summary, NLRP12 is a potent negative regulator of the Wnt/β-catenin pathway, and the NLRP12/STK38/GSK3β signaling axis could be a promising therapeutic target for CRC.

Negative regulatory NLRs mitigate inflammation via NF-κB pathway signaling in inflammatory bowel disease

A subset of Nucleotide-binding and leucine-rich repeat-containing receptors (NLRs) function to mitigate overzealous pro-inflammatory signaling produced by NF-κB activation. Under normal pathophysiologic conditions, proper signaling by these NLRs protect against potential autoimmune responses. These NLRs associate with several different proteins within both the canonical and noncanonical NF-κB signaling pathways to either prevent activation of the pathway or inhibit signal transduction. Inhibition of the NF-κB pathways ultimately dampens the production of pro-inflammatory cytokines and activation of other downstream pro-inflammatory signaling mechanisms. Dysregulation of these NLRs, including NLRC3, NLRX1, and NLRP12, have been reported in human inflammatory bowel disease (IBD) and colorectal cancer patients, suggesting the potential of these NLRs as biomarkers for disease detection. Mouse models deficient in these NLRs also have increased susceptibility to colitis and colitis-associated colorectal cancer. While current standard of care for IBD patients and FDA-approved therapeutics function to remedy symptoms associated with IBD and chronic inflammation, these negative regulatory NLRs have yet to be explored as potential drug targets. In this review, we describe a comprehensive overview of recent studies that have evaluated the role of NLRC3, NLRX1, and NLRP12 in IBD and colitis-associated colorectal cancer.

HSC70 as a sensor of low temperature: role in cold-triggered autoinflammatory disorders

Familial cold autoinflammatory syndrome (FCAS) is a subset of heritable autoinflammatory disorders wherein inflammatory symptoms aggravate upon exposure of the individual to subnormal temperature. In the past two decades, several mutations in various genes such as NLRP3, NLRP12, PLCG2 and NLRC4 have been identified that cause cold-triggered inflammation. However, our understanding of the mechanisms by which cells perceive subnormal temperature, and what keeps the inflammation under check until exposure to low temperature, is very limited. We hypothesise that recognition of FCAS-associated mutants as misfolded polypeptides by temperature-sensitive HSC70 (HSPA8) chaperone determines the FCAS phenotype. At 37 °C, HSC70 would interact with the mutant proteins, keeping them almost inactive, and loss of interaction at low temperature due to a conformational change in HSC70 would lead to their activation. The proposed mechanism of low temperature sensing in the context of FCAS may have wider implications for HSC70 as a cold temperature sensor in various pathological conditions where symptoms get aggravated upon exposure to low temperature.

Gene-Based Resistance to Erysiphe Species Causing Powdery Mildew Disease in Peas (Pisum sativum L.)

Globally powdery mildew (PM) is one of the major diseases of the pea caused by Erysiphe pisi. Besides, two other species viz. Erysiphe trifolii and Erysiphe baeumleri have also been identified to infect the pea plant. To date, three resistant genes, namely er1, er2 and Er3 located on linkage groups VI, III and IV respectively were identified. Studies have shown the er1 gene to be a Pisum sativum Mildew resistance Locus 'O' homologue and subsequent analysis has identified eleven alleles namely er1-1 to er1-11. Despite reports mentioning the breakdown of er1 gene-mediated PM resistance by E. pisi and E. trifolii, it is still the most widely deployed gene in PM resistance breeding programmes across the world. Several linked DNA markers have been reported in different mapping populations with varying linkage distances and effectiveness, which were used by breeders to develop PM-resistant pea cultivars through marker assisted selection. This review summarizes the genetics of PM resistance and its mechanism, allelic variations of the er gene, marker linkage and future strategies to exploit this information for targeted PM resistance breeding in Pisum.

Comparative transcriptome of compatible and incompatible interaction of Erysiphe pisi and garden pea reveals putative defense and pathogenicity factors

Comparative transcriptome analysis of Erysiphe pisi-infected pea (Pisum sativum) genotypes JI-2480 (resistant) and Arkel (susceptible) at 72 hours post-inoculation (hpi) was carried to detect molecular components involved in compatible and incompatible interactions. Differential gene expression was observed in Arkel and JI-2480 genotype at 72 hpi with E. pisi isolate (Ep01) using EdgeR software. Out of 32 217 transcripts, 2755 transcripts showed significantly altered gene expression in case of plants while 530 were related to E. pisi (P < 0.05). The higher transcript number of differentially expressed genes demonstrated peak activity of pathogenicity genes in plants at 72 hpi. Glycolysis was observed to be the major pathway for energy source during fungal growth. Differential gene expression of plant transcripts revealed significant expression of putative receptor and regulatory sequences involved in defense in the resistant, JI-2480 compared to susceptible, Arkel genotype. Expression of genes involved in defense and hormonal signaling, genes related to hypersensitive response, reactive oxygen species and phenylpropanoid pathway in JI-2480 indicated their crucial role in disease resistance against E. pisi. Down-regulation of transcription factors like-WRKY-28 and up-regulation of several putative pattern recognition receptors in JI-2480 compared to Arkel also suggested activation of host-mediated defense responses against E. pisi in pea.

Mining the Unmapped Reads in Bovine RNA-Seq Data Reveals the Prevalence of Bovine Herpes Virus-6 in European Dairy Cows and the Associated Changes in Their Phenotype and Leucocyte Transcriptome

Microbial RNA is detectable in host samples by aligning unmapped reads from RNA sequencing against taxon reference sequences, generating a score proportional to the microbial load. An RNA-Seq data analysis showed that 83.5% of leukocyte samples from six dairy herds in different EU countries contained bovine herpes virus-6 (BoHV-6). Phenotypic data on milk production, metabolic function, and disease collected during their first 50 days in milk (DIM) were compared between cows with low (1–200 and n = 114) or high (201–1175 and n = 24) BoHV-6 scores. There were no differences in milk production parameters, but high score cows had numerically fewer incidences of clinical mastitis (4.2% vs. 12.2%) and uterine disease (54.5% vs. 62.7%). Their metabolic status was worse, based on measurements of IGF-1 and various metabolites in blood and milk. A comparison of the global leukocyte transcriptome between high and low BoHV-6 score cows at around 14 DIM yielded 485 differentially expressed genes (DEGs). The top pathway from Gene Ontology (GO) enrichment analysis was the immune system process. Down-regulated genes in the high BoHV-6 cows included those encoding proteins involved in viral detection (DDX6 and DDX58), interferon response, and E3 ubiquitin ligase activity. This suggested that BoHV-6 may largely evade viral detection and that it does not cause clinical disease in dairy cows.

Exertional heat stroke leads to concurrent long-term epigenetic memory, immunosuppression and altered heat shock response in female mice

KEY POINTS

Exposure to exertional heat stroke (EHS) has been linked to increased long-term decrements of health. Epigenetic reprogramming is involved in the response to heat acclimation; however, whether the long-term effects of EHS are mediated by epigenetic reprogramming is unknown. In female mice, we observed DNA methylation reprogramming in bone marrow-derived (BMD) monocytes as early as 4 days of recovery from EHS and as late as 30 days compared with sham exercise controls. Whole blood, collected after 30 days of recovery from EHS, exhibited an immunosuppressive phenotype when challenged in vitro by lipopolysaccharide. After 30 days of recovery from EHS, BMD monocytes exhibited an altered in vitro heat shock response. The location of differentially methylated CpGs are predictive of both the immunosuppressive phenotype and altered heat shock responses.

ABSTRACT

Exposure to exertional heat stroke (EHS) has been linked to increased susceptibility to a second heat stroke, infection and cardiovascular disease. Whether these clinical outcomes are mediated by an epigenetic memory is unknown. Using a preclinical mouse model of EHS, we investigated whether EHS exposure produces a lasting epigenetic memory in monocytes and whether there are phenotypic alterations that may be consistent with these epigenetic changes. Female mice underwent forced wheel running at 37.5°C/40% relative humidity until symptom limitation, characterized by CNS dysfunction. Results were compared with matched exercise controls at 22.5°C. Monocytes were isolated from bone marrow after 4 or 30 days of recovery to extract DNA and analyse methylation. Broad-ranging alterations to the DNA methylome were observed at both time points. At 30 days, very specific alterations were observed to the promoter regions of genes involved with immune responsiveness. To test whether these changes might be related to phenotype, whole blood at 30 days was challenged with lipopolysaccharide (LPS) to measure cytokine secretion; monocytes were also challenged with heat shock to quantify mRNA expression. Whole blood collected from EHS mice showed markedly attenuated inflammatory responses to LPS challenge. Furthermore, monocyte mRNA from EHS mice showed significantly altered responses to heat shock challenge. These results demonstrate that EHS leads to a unique DNA methylation pattern in monocytes and altered immune and heat shock responsiveness after 30 days. These data support the hypothesis that EHS exposure can induce long-term physiological changes that may be linked to altered epigenetic profiles.

Nucleotide binding domain and leucine-rich repeat pyrin domain-containing protein 12: characterization of its binding to hematopoietic cell kinase

Protein-protein interactions are key to define the function of nucleotide binding domain (NBD) and leucine-rich repeat (LRR) family, pyrin domain (PYD)-containing protein 12 (NLRP12). cDNA encoding the human PYD + NBD of NLRP12 was used as bait in a yeast two-hybrid screen with a human leukocyte cDNA library as prey. Hematopoiesis cell kinase (HCK), a member of the c-SRC family of non-receptor tyrosine kinases, was among the top hits. The C-terminal 40 amino acids of HCK selectively bound to NLRP12's PYD + NBD, but not to that of NLRP3 and NLRP8. Amino acids F503, I506, Q507, L510, and D511 of HCK are critical for the binding of HCK's C-terminal 40 amino acids to NLRP12's PYD + NBD. Additionally, the C-terminal 30 amino acids of HCK are sufficient to bind to NLRP12's PYD + NBD, but not to its PYD alone nor to its NBD alone. In cell lines that express HCK endogenously, it was co- immunoprecipitated with stably expressed exogenous NLRP12. Also, NLRP12 co-immunoprecipitated and co-localized with HCK when both were overexpressed in 293T cells. In addition, in this overexpression system, steady-state NLRP12 protein expression levels significantly decreased when HCK was co-expressed. Bioinformatic analysis showed that HCK mRNA co-occurred with NLRP12 mRNA, but not with other NLRP mRNAs, in blood and marrow samples from acute myeloid leukemia (AML) patients. The mRNA of NLRP12 is also co-expressed with HCK in AML patient samples, and the levels of mRNA expression of each are correlated. Together these data suggest that NLRP12, through its binding to HCK, may have an effect on the pathogenesis of AML.

Canonical and noncanonical inflammasomes in intestinal epithelial cells

Inflammasomes are cytosolic, multimeric protein complexes capable of activating pro-inflammatory cytokines such as IL-1β and IL-18, which play a key role in host defence. Inflammasome components are highly expressed in the intestinal epithelium. In recent years, studies have begun to demonstrate that epithelial-intrinsic inflammasomes play a critical role in regulating epithelial homeostasis, both by defending the epithelium from pathogenic insult and through the regulation of the mucosal environment. However, the majority of research regarding inflammasome activation has focused on professional immune cells, such as macrophages. Here, we present an overview of the current understanding of inflammasome function in epithelial cells and at mucosal surfaces and, in particular, in the intestine.

NLRX1 Is a Multifaceted and Enigmatic Regulator of Immune System Function

Over the last decade, significant progress has been achieved in defining mechanisms underlying NLR regulation of immune system function. However, several NLR family members continue to defy our best attempts at characterization and routinely exhibit confounding data. This is particularly true for NLR family members that regulate signaling associated with the activation of other pattern recognition receptors. NLRX1 is a member of this NLR sub-group and acts as an enigmatic regulator of immune system function. NLRX1 has been shown to negatively regulate type-I interferon, attenuate pro-inflammatory NF-κB signaling, promote reactive oxygen species production, and modulate autophagy, cell death, and proliferation. However, the mechanism/s associated with NLRX1 modulation of these pathways is not fully understood and there are inconsistencies within the field. Likewise, it is highly likely that the full repertoire of biological functions impacted by NLRX1 are yet to be defined. Recent mouse studies have shown that NLRX1 significantly impacts a multitude of diseases, including cancer, virus infection, osteoarthritis, traumatic brain injury, and inflammatory bowel disease. Thus, it is essential that the underlying mechanism associated with NLRX1 function in each of these diseases be robustly defined. Here, we summarize the current progress in understanding mechanisms associated with NLRX1 function. We also offer insight into both unique and overlapping mechanisms regulated by NLRX1 that likely contribute to disease pathobiology. Ultimately, we believe that an improved understanding of NLRX1 will result in better defined mechanisms associated with immune system attenuation and the resolution of inflammation in a myriad of diseases.

Transcriptome analysis of normal-appearing white matter reveals cortisol- and disease-associated gene expression profiles in multiple sclerosis

Inter-individual differences in cortisol production by the hypothalamus–pituitary–adrenal (HPA) axis are thought to contribute to clinical and pathological heterogeneity of multiple sclerosis (MS). At the same time, accumulating evidence indicates that MS pathogenesis may originate in the normal-appearing white matter (NAWM). Therefore, we performed a genome-wide transcriptional analysis, by Agilent microarray, of post-mortem NAWM of 9 control subjects and 18 MS patients to investigate to what extent gene expression reflects disease heterogeneity and HPA-axis activity. Activity of the HPA axis was determined by cortisol levels in cerebrospinal fluid and by numbers of corticotropin-releasing neurons in the hypothalamus, while duration of MS and time to EDSS6 served as indicator of disease severity. Applying weighted gene co-expression network analysis led to the identification of a range of gene modules with highly similar co-expression patterns that strongly correlated with various indicators of HPA-axis activity and/or severity of MS. Interestingly, molecular profiles associated with relatively mild MS and high HPA-axis activity were characterized by increased expression of genes that actively regulate inflammation and by molecules involved in myelination, anti-oxidative mechanism, and neuroprotection. Additionally, group-wise comparisons of gene expression in white matter from control subjects and NAWM from (subpopulations of) MS patients uncovered disease-associated gene expression as well as strongly up- or downregulated genes in patients with relatively benign MS and/or high HPA-axis activity, with many differentially expressed genes being previously undescribed in the context of MS. Overall, the data suggest that HPA-axis activity strongly impacts on molecular mechanisms in NAWM of MS patients, but partly also independently of disease severity.

Proteasomal degradation of NOD2 by NLRP12 in monocytes promotes bacterial tolerance and colonization by enteropathogens

Mutations in the nucleotide-binding oligomerization domain protein 12 (NLRP12) cause recurrent episodes of serosal inflammation. Here we show that NLRP12 efficiently sequesters HSP90 and promotes K48-linked ubiquitination and degradation of NOD2 in response to bacterial muramyl dipeptide (MDP). This interaction is mediated by the linker-region proximal to the nucleotide-binding domain of NLRP12. Consequently, the disease-causing NLRP12 R284X mutation fails to repress MDP-induced NF-κB and subsequent activity of the JAK/STAT signaling pathway. While NLRP12 deficiency renders septic mice highly susceptible towards MDP, a sustained sensing of MDP through NOD2 is observed among monocytes lacking NLRP12. This loss of tolerance in monocytes results in greater colonization resistance towards Citrobacter rodentium. Our data show that this is a consequence of NOD2-dependent accumulation of inflammatory mononuclear cells that correlates with induction of interferon-stimulated genes. Our study unveils a relevant process of tolerance towards the gut microbiota that is exploited by an attaching/effacing enteric pathogen.

Mutations in nucleotide-binding oligomerization domain protein 12 (NLRP12) are known to effect inflammatory processes. Here the authors show that NLRP12-mediated proteasomal degradation of NOD2 in monocytes promotes bacterial tolerance and colonisation in a model of enteric infection.

The Inflammasome: Regulation of Nitric Oxide and Antimicrobial Host Defence

Nitric oxide (NO) is a gaseous signalling molecule that plays diverse physiological functions including antimicrobial host defence. During microbial infection, NO is synthesized by inducible NO synthase (iNOS), which is expressed by host immune cells through the recognition of microbial pattern molecules. Therefore, sensing pathogens or their pattern molecules by pattern recognition receptors (PRRs), which are located at the cell surface, endosomal and phagosomal compartment, or in the cytosol, is key in inducing iNOS and eliciting antimicrobial host defence. A group of cytosolic PRRs is involved in inducing NO and other antimicrobial molecules by forming a molecular complex called the inflammasome. Assembled inflammasomes activate inflammatory caspases, such as caspase-1 and caspase-11, which in turn process proinflammatory cytokines IL-1β and IL-18 into their mature forms and induce pyroptotic cell death. IL-1β and IL-18 play a central role in immunity against microbial infection through activation and recruitment of immune cells, induction of inflammatory molecules, and regulation of antimicrobial mediators including NO. Interestingly, NO can also regulate inflammasome activity in an autocrine and paracrine manner. Here, we discuss molecular mechanisms of inflammasome formation and the inflammasome-mediated regulation of host defence responses during microbial infections.

Inflammasome biology, molecular pathology and therapeutic implications

Inflammasomes are intracellular multiprotein signaling complexes, mainly present in myeloid cells. They commonly assemble around a cytoplasmic receptor of the nucleotide-binding leucine-rich repeat containing receptor (NLR) family, although other cytoplasmic receptors like pyrin have been shown to form inflammasomes. The nucleation of the multiprotein scaffolding platform occurs upon detection of a microbial, a danger or a homeostasis pattern by the receptor that will, most commonly, associate with the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD) through homotypic domain interactions resulting in recruitment of procaspase-1. This will lead to the autoproteolytic activation of caspase-1, which regulates the secretion of proinflammatory IL1β and IL18 cytokines and pyroptosis, a caspase-1-mediated form of cell death. Pyroptosis occurs through cleavage of Gasdermin D, a membrane pore forming protein. Recently, non-canonical inflammasomes have been described, which directly sense intracellular pathogens through caspase-4 and -5 in humans, leading to pyroptosis. Inflammasomes are important in host defense; however, a deregulated activity is associated with a number of inflammatory, immune and metabolic disorders. Furthermore, mutations in inflammasome receptor coding genes are causal for an increasing number of rare autoinflammatory diseases. Biotherapies targeting the products of inflammasome activation as well as molecules that directly or indirectly inhibit inflammasome nucleation and activation are promising therapeutic areas. This review discusses recent advances in inflammasome biology, the molecular pathology of several inflammasomes, and current therapeutic approaches in autoinflammatory diseases and in selected common multifactorial inflammasome-mediated disorders.

Modulating inflammation through the negative regulation of NF-κB signaling

Immune system activation is essential to thwart the invasion of pathogens and respond appropriately to tissue damage. However, uncontrolled inflammation can result in extensive collateral damage underlying a diverse range of auto-inflammatory, hyper-inflammatory, and neoplastic diseases. The NF-κB signaling pathway lies at the heart of the immune system and functions as a master regulator of gene transcription. Thus, this signaling cascade is heavily targeted by mechanisms designed to attenuate overzealous inflammation and promote resolution. Mechanisms associated with the negative regulation of NF-κB signaling are currently under intense investigation and have yet to be fully elucidated. Here, we provide an overview of mechanisms that negatively regulate NF-κB signaling through either attenuation of signal transduction, inhibition of posttranscriptional signaling, or interference with posttranslational modifications of key pathway components. While the regulators discussed for each group are far from comprehensive, they exemplify common mechanistic approaches that inhibit this critical biochemical signaling cascade. Despite their diversity, a commonality among these regulators is their selection of specific targets at key inflection points in the pathway, such as TNF-receptor-associated factor family members or essential kinases. A better understanding of these negative regulatory mechanisms will be essential to gain greater insight related to the maintenance of immune system homeostasis and inflammation resolution. These processes are vital elements of disease pathology and have important implications for targeted therapeutic strategies.

Innate Immune Cell Recovery Is Positively Regulated by NLRP12 during Emergency Hematopoiesis

With enhanced concerns of terrorist attacks, dual exposure to radiation and thermal combined injury (RCI) has become a real threat with devastating immunosuppression. NLRP12, a member of the NOD-like receptor family, is expressed in myeloid and bone marrow cells and was implicated as a checkpoint regulator of inflammatory cytokines, as well as an inflammasome activator. We show that NLRP12 has a profound impact on hematopoietic recovery during RCI by serving as a checkpoint of TNF signaling and preventing hematopoietic apoptosis. Using a mouse model of RCI, increased NLRP12 expression was detected in target tissues. Nlrp12^-/- mice exhibited significantly greater mortality, an inability to fight bacterial infection, heightened levels of proinflammatory cytokines, overt granulocyte/monocyte progenitor cell apoptosis, and failure to reconstitute peripheral myeloid populations. Anti-TNF Ab administration improved peripheral immune recovery. These data suggest that NLRP12 is essential for survival after RCI by regulating myelopoiesis and immune reconstitution.

Beyond the inflammasome: regulatory NOD-like receptor modulation of the host immune response following virus exposure

A complex interaction exists between elements of the host innate immune system and viral pathogens. It is essential that the host mount a robust immune response during viral infection and effectively resolve inflammation once the pathogen has been eliminated. Members of the nucleotide-binding domain leucine-rich repeat [NBD-LRR; known as NOD-like receptor (NLR)] family of cytosolic pattern-recognition receptors are essential components of these immunological processes and have diverse functions in the host antiviral immune response. NLRs can be subgrouped based on their general function. The inflammasome-forming subgroup of NLRs are the best-characterized family members, and several have been found to modulate the maturation of IL-1β and IL-18 following virus exposure. However, the members of the regulatory NLR subgroups are significantly less characterized. These NLRs uniquely function to modulate signalling pathways initiated by other families of pattern-recognition receptors, such as Toll-like receptors and/or Rig-I-like helicase receptors. Regulatory NLRs that augment pro-inflammatory pathways include nucleotide-binding oligomerization domain-containing protein 1 (NOD1) and NOD2, which have been shown to form a multiprotein complex termed the NODosome that significantly modulates IFN and NF-κB signalling following viral infection. Conversely, a second subgroup of regulatory NLRs functions to negatively regulate inflammation. These inhibitory NLRs include NLRX1, NLRP12 and NLRC3, which have been shown to interact with TRAF molecules and various kinases to modulate diverse cellular processes. Targeting NLR signalling following infection with a virus represents a novel and promising therapeutic strategy. However, significant effort is still required to translate the current understanding of NLR biology into effective therapies.

Broad targeting of resistance to apoptosis in cancer

Apoptosis or programmed cell death is natural way of removing aged cells from the body. Most of the anti-cancer therapies trigger apoptosis induction and related cell death networks to eliminate malignant cells. However, in cancer, de-regulated apoptotic signaling, particularly the activation of an anti-apoptotic systems, allows cancer cells to escape this program leading to uncontrolled proliferation resulting in tumor survival, therapeutic resistance and recurrence of cancer. This resistance is a complicated phenomenon that emanates from the interactions of various molecules and signaling pathways. In this comprehensive review we discuss the various factors contributing to apoptosis resistance in cancers. The key resistance targets that are discussed include (1) Bcl-2 and Mcl-1 proteins; (2) autophagy processes; (3) necrosis and necroptosis; (4) heat shock protein signaling; (5) the proteasome pathway; (6) epigenetic mechanisms; and (7) aberrant nuclear export signaling. The shortcomings of current therapeutic modalities are highlighted and a broad spectrum strategy using approaches including (a) gossypol; (b) epigallocatechin-3-gallate; (c) UMI-77 (d) triptolide and (e) selinexor that can be used to overcome cell death resistance is presented. This review provides a roadmap for the design of successful anti-cancer strategies that overcome resistance to apoptosis for better therapeutic outcome in patients with cancer.

Emerging significance of NLRs in inflammatory bowel disease

Pattern recognition receptors are essential mediators of host defense and inflammation in the gastrointestinal system. Recent data have revealed that toll-like receptors and nucleotide-binding domain and leucine-rich repeat-containing proteins (NLRs) function to maintain homeostasis between the host microbiome and mucosal immunity. The NLR proteins are a diverse class of cytoplasmic pattern recognition receptors. In humans, only about half of the identified NLRs have been adequately characterized. The majority of well-characterized NLRs participate in the formation of a multiprotein complex, termed the inflammasome, which is responsible for the maturation of interleukin-1β and interleukin-18. However, recent observations have also uncovered the presence of a novel subgroup of NLRs that function as positive or negative regulators of inflammation through modulating critical signaling pathways, including NF-κB. Dysregulation of specific NLRs from both proinflammatory and inhibitory subgroups have been associated with the development of inflammatory bowel disease (IBD) in genetically susceptible human populations. Our own preliminary retrospective data mining efforts have identified a diverse range of NLRs that are significantly altered at the messenger RNA level in colons from patients with IBD. Likewise, studies using genetically modified mouse strains have revealed that multiple NLR family members have the potential to dramatically modulate the immune response during IBD. Targeting NLR signaling represents a promising and novel therapeutic strategy. However, significant effort is necessary to translate the current understanding of NLR biology into effective therapies.

The multifaceted nature of NLRP12

NLRs are a class of cytoplasmic PRRs with various functions, ranging from pathogen/damage sensing to the modulation of inflammatory signaling and transcriptional control of MHC and related genes. In addition, some NLRs have been implicated in preimplantation and prenatal development. NLRP12 (also known as RNO, PYPAF7, and Monarch-1), a member of the family containing an N-terminal PYD, a NBD, and a C-terminal LRR region, is one of the first described NLR proteins whose role remains controversial. The interest toward NLRP12 has been boosted by its recent involvement in colon cancer, as well as in the protection against some severe infections, such as that induced by Yersinia pestis, the causative agent of plague. As NLRP12 is mainly expressed by the immune cells, and its expression is down-regulated in response to pathogen products and inflammatory cytokines, it has been predicted to play a role as a negative regulator of the inflammatory response. Herein, we present an overview of the NLR family and summarize recent insights on NLRP12 addressing its contribution to inflammatory signaling, host defense, and carcinogenesis.

NOD-Like Receptors: Master Regulators of Inflammation and Cancer

Cytosolic NOD-like receptors (NLRs) have been associated with human diseases including infections, cancer, and autoimmune and inflammatory disorders. These innate immune pattern recognition molecules are essential for controlling inflammatory mechanisms through induction of cytokines, chemokines, and anti-microbial genes. Upon activation, some NLRs form multi-protein complexes called inflammasomes, while others orchestrate caspase-independent nuclear factor kappa B (NF-κB) and mitogen activated protein kinase (MAPK) signaling. Moreover, NLRs and their downstream signaling components engage in an intricate crosstalk with cell death and autophagy pathways, both critical processes for cancer development. Recently, increasing evidence has extended the concept that chronic inflammation caused by abberant NLR signaling is a powerful driver of carcinogenesis, where it abets genetic mutations, tumor growth, and progression. In this review, we explore the rapidly expanding area of research regarding the expression and functions of NLRs in different types of cancers. Furthermore, we particularly focus on how maintaining tissue homeostasis and regulating tissue repair may provide a logical platform for understanding the liaisons between the NLR-driven inflammatory responses and cancer. Finally, we outline novel therapeutic approaches that target NLR signaling and speculate how these could be developed as potential pharmaceutical alternatives for cancer treatment.

Advances in Nod-like receptors (NLR) biology

The innate immune system is composed of a wide repertoire of conserved pattern recognition receptors (PRRs) able to trigger inflammation and host defense mechanisms in response to endogenous or exogenous pathogenic insults. Among these, nucleotide-binding and oligomerization domain (NOD)-like receptors (NLRs) are intracellular sentinels of cytosolic sanctity capable of orchestrating innate immunity and inflammatory responses following the perception of noxious signals within the cell. In this review, we elaborate on recent advances in the signaling mechanisms of NLRs, operating within inflammasomes or through alternative inflammatory pathways, and discuss the spectrum of their effector functions in innate immunity. We describe the progressive characterization of each NLR with associated controversies and cutting edge discoveries.

The dual role of nod-like receptors in mucosal innate immunity and chronic intestinal inflammation

Nucleotide-binding and oligomerization domain NOD-like receptors (NLRs) are highly conserved cytosolic pattern recognition receptors that play, in combination with toll-like receptors, a critical role in innate immunity and inflammation. These proteins are characterized by a central oligomerization domain termed nucleotide-binding domain, and a protein interaction domain containing leucine-rich repeats. Some NLRs, including NOD1 and NOD2, sense the cytosolic presence of conserved bacterial molecular signatures and drive the activation of mitogen-activated protein kinase and the transcription factor NF-κB. A different set of NLRs induces caspase-1 activation through the assembly of large protein complexes known as inflammasomes. Activation of NLR proteins results in secretion of pro-inflammatory cytokines and subsequent inflammatory responses. The critical role of NLRs in innate immunity is underscored by the fact that polymorphisms within their genes are implicated in the development of several immune-mediated diseases, including inflammatory bowel disease. Over the past few years, the role of NLRs in intestinal homeostasis has been highlighted, however the mechanism by which dysfunction in these proteins leads to aberrant inflammation is still the focus of much investigation. The purpose of this review is to systematically evaluate the function of NLRs in mucosal innate immunity and understand how genetic or functional alterations in these components can lead to the disruption of intestinal homeostasis, and the subsequent development of chronic inflammation.

Non-Inflammasome Forming NLRs in Inflammation and Tumorigenesis

Aberrant inflammation is an enabling characteristic of tumorigenesis. Thus, signaling cascades that alter inflammatory activation and resolution are of specific relevance to disease pathogenesis. Pattern recognition receptors (PRRs) are essential mediators of the host immune response and have emerged as critical elements affecting multiple facets of tumor pathobiology. The nucleotide-binding domain and leucine-rich repeat containing (NLR) proteins are intracellular PRRs that sense microbial and non-microbial products. Members of the NLR family can be divided into functional sub-groups based on their ability to either positively or negatively regulate the host immune response. Recent studies have identified a novel sub-group of non-inflammasome forming NLRs that negatively regulate diverse biological pathways associated with both inflammation and tumorigenesis. Understanding the mechanisms underlying the function of these unique NLRs will assist in the rationale design of future therapeutic strategies targeting a wide spectrum of inflammatory diseases and cancer. Here, we will discuss recent findings associated with this novel NLR sub-group and mechanisms by which these PRRs may function to alter cancer pathogenesis.

Enhanced cytotoxic effect of radiation and temozolomide in malignant glioma cells: targeting PI3K-AKT-mTOR signaling, HSP90 and histone deacetylases

Background

Despite aggressive treatment with radiation therapy and concurrent adjuvant temozolomide (TMZ), glioblastoma multiform (GBM) still has a dismal prognosis. We aimed to identify strategies to improve the therapeutic outcome of combined radiotherapy and TMZ in GBM by targeting pro-survival signaling from the epidermal growth factor receptor (EGFR).

Methods

Glioma cell lines U251, T98G were used. Colony formation, DNA damage repair, mode of cell death, invasion, migration and vasculogenic mimicry as well as protein expression were determined.

Results

U251 cells showing a low level of methyl guanine transferase (MGMT) were highly responsive to the radiosensitizing effect of TMZ compared to T98G cells having a high level of MGMT. Treatment with a dual inhibitor of Class I PI3K/mTOR, PI103; a HSP90 inhibitor, 17-DMAG; or a HDAC inhibitor, LBH589, further increased the cytotoxic effect of radiation therapy plus TMZ in U251 cells than in T98G cells. However, treatment with a mTOR inhibitor, rapamycin, did not discernibly potentiate the radiosensitizing effect of TMZ in either cell line. The mechanism of enhanced radiosensitizing effects of TMZ was multifactorial, involving impaired DNA damage repair, induction of autophagy or apoptosis, and reversion of EMT (epithelial-mesenchymal transition).

Conclusions

Our results suggest possible strategies for counteracting the pro-survival signaling from EGFR to improve the therapeutic outcome of combined radiotherapy and TMZ for high-grade gliomas.

An Update on PYRIN Domain-Containing Pattern Recognition Receptors: From Immunity to Pathology

Cytosolic pattern recognition receptors (PRRs) sense a wide range of endogenous danger-associated molecular patterns as well as exogenous pathogen-associated molecular patterns. In particular, Nod-like receptors containing a pyrin domain (PYD), called NLRPs, and AIM2-like receptors (ALRs) have been shown to play a critical role in host defense by facilitating clearance of pathogens and maintaining a healthy gut microflora. NLRPs and ALRs both encode a PYD, which is crucial for relaying signals that result in an efficient innate immune response through activation of several key innate immune signaling pathways. However, mutations in these PRRs have been linked to the development of auto-inflammatory and autoimmune diseases. In addition, they have been implicated in metabolic diseases. In this review, we summarize the function of PYD-containing NLRPs and ALRs and address their contribution to innate immunity, host defense, and immune-linked diseases.

Unsolved Mysteries in NLR Biology

NOD-like receptors (NLRs) are a class of cytoplasmic pattern-recognition receptors. Although most NLRs play some role in immunity, their functions range from regulating antigen presentation (NLRC5, CIITA) to pathogen/damage sensing (NLRP1, NLRP3, NLRC1/2, NLRC4) to suppression or modulation of inflammation (NLRC3, NLRP6, NLRP12, NLRX1). However, NLRP2, NLRP5, and NLRP7 are also involved in non-immune pathways such as embryonic development. In this review, we highlight some of the least well-understood aspects of NLRs, including the mechanisms by which they sense pathogens or damage. NLRP3 recognizes a diverse range of stimuli and numerous publications have presented potential unifying models for NLRP3 activation, but no single mechanism proposed thus far appears to account for all possible NLRP3 activators. Additionally, NLRC3, NLRP6, and NLRP12 inhibit NF-κB activation, but whether direct ligand sensing is a requirement for this function is not known. Herein, we review the various mechanisms of sensing and activation proposed for NLRP3 and other inflammasome activators. We also discuss the role of NLRC3, NLRP6, NLRP12, and NLRX1 as inhibitors and how they are activated and function in their roles to limit inflammation. Finally, we present an overview of the emerging roles that NLRP2, NLRP5, and NLRP7 play during embryonic development and postulate on the potential pathways involved.

Cellular stress response and innate immune signaling: integrating pathways in host defense and inflammation

Extensive research in the past decade has identified innate immune recognition receptors and intracellular signaling pathways that culminate in inflammatory responses. Besides its role in cytoprotection, the importance of cell stress in inflammation and host defense against pathogens is emerging. Recent studies have shown that proteins in cellular stress responses, including the heat shock response, ER stress response, and DNA damage response, interact with and regulate signaling intermediates involved in the activation of innate and adaptive immune responses. The effect of such regulation by cell stress proteins may dictate the inflammatory profile of the immune response during infection and disease. In this review, we describe the regulation of innate immune cell activation by cell stress pathways, present detailed descriptions of the types of stress response proteins and their crosstalk with immune signaling intermediates that are essential in host defense, and illustrate the relevance of these interactions in diseases characteristic of aberrant immune responses, such as chronic inflammatory diseases, autoimmune disorders, and cancer. Understanding the crosstalk between cellular stress proteins and immune signaling may have translational implications for designing more effective regimens to treat immune disorders.

Beyond pattern recognition: NOD-like receptors in dendritic cells

Innate instruction of adaptive immunity was proposed more than 20 years ago as a mechanism by which long-lived lymphocyte responses are targeted to appropriate antigens. At the time Charles Janeway proposed this theory, most of the innate immune receptors were unknown, and the pivotal role of the dendritic cell in instructing T cell priming was debated. There is now overwhelming evidence that the innate and adaptive branches of the immune system must interact to generate immunity. Much of this work has focused on families of innate immune receptors called pattern recognition receptors (PRRs) on dendritic cells, which translate these inflammatory triggers into productive T cell responses. Nevertheless, we are only beginning to understand how these defence molecules shape the generation of immunity. We review the varied roles of one class of PRRs, the NOD-like receptors (NLRs), in immune responses and propose a new model in which adaptive immunity requires coordinated PRR activation within the dendritic cell.

Proteomic and systems biology analysis of monocytes exposed to securinine, a GABA(A) receptor antagonist and immune adjuvant

Securinine, a GABA(A) receptor antagonist, has been reported to enhance monocyte cell killing of Coxiella burnetii without obvious adverse effects in vivo. We employed multiplex 2D gel electrophoresis using Zdyes, a new generation of covalently linked fluorescent differential protein detection dyes to analyze changes in the monocyte proteome in response to Securinine. Securinine antagonism of GABA(A) receptors triggers the activation of p38. We used the differential protein expression results to guide a search of the literature and network analysis software to construct a systems biology model of the effect of Securinine on monocytes. The model suggests that various metabolic modulators (fatty acid binding protein 5, inosine 5'-monophosphate dehydrogenase, and thioredoxin) are at least partially reshaping the metabolic landscape within the monocytes. The actin bundling protein L-plastin, and the Ca(2+) binding protein S100A4 also appear to have important roles in the immune response stimulated by Securinine. Fatty acid binding protein 5 (FABP5) may be involved in effecting lipid raft composition, inflammation, and hormonal regulation of monocytes, and the model suggests that FABP5 may be a central regulator of metabolism in activated monocytes. The model also suggests that the heat shock proteins have a significant impact on the monocyte immune response. The model provides a framework to guide future investigations into the mechanisms of Securinine action and with elaboration may help guide development of new types of immune adjuvants.

[Pattern recognition receptors]

Immunity is based on self/nonself discrimination. In vertebrates, two major systems, innate and adaptive immune systems, constitute host defense against invading microbes. Adaptive immunity is characterized by specific immune responses through B- or T-cell antigen receptors that are generated by somatic recombination, whereas nonspecific responses to microbes had been accentuated in innate immunity. However, the discovery of pattern recognition receptors (PRRs) that are encoded in the germ-line, including Toll-like receptors, RIG-I-like receptors, NOD-like receptors and AIM2-like receptors, advanced our understanding of a mechanism for innate immune recognition. These types of PRR recognize pathogen- or damage-associated molecular patterns (PAMPs or DAMPs) during infection or tissue damage, and commonly evoke the downstream gene induction programme, such as expression of type I interferons, inflammatory cytokines and chemokines. Dysregulation of PRR-triggered signal activation leads to pathologic inflammatory responses. In this regard, it has been shown that many of "autoinflammatory diseases", recently defined clinical entity, have putatively causative mutations in the genes that encode PRRs or their signaling mediators. In this review article, we describe recent overview of PRRs as innate sensors and update knowledge of "autoinflammatory diseases" particularly by focusing on their association with innate signaling.

The NOD-like receptor NLRP12 attenuates colon inflammation and tumorigenesis

NLRP12 is a member of the intracellular Nod-like receptor (NLR) family that has been suggested to downregulate the production of inflammatory cytokines, but its physiological role in regulating inflammation has not been characterized. We analyzed mice deficient in Nlrp12 to study its role in inflammatory diseases such as colitis and colorectal tumorigenesis. We show that Nlrp12-deficient mice are highly susceptible to colon inflammation and tumorigenesis, which is associated with increased production of inflammatory cytokines, chemokines, and tumorigenic factors. Enhanced colon inflammation and colorectal tumor development in Nlrp12-deficient mice are due to a failure to dampen NF-κB and ERK activation in macrophages. These results reveal a critical role for NLRP12 in maintaining intestinal homeostasis and providing protection against colorectal tumorigenesis.

The NLRP12 pyrin domain: structure, dynamics, and functional insights

The initial line of defense against infection is sustained by the innate immune system. Together, membrane-bound Toll-like receptors and cytosolic nucleotide-binding domain and leucine-rich repeat-containing receptors (NLR) play key roles in the innate immune response by detecting bacterial and viral invaders as well as endogenous stress signals. NLRs are multi-domain proteins with varying N-terminal effector domains that are responsible for regulating downstream signaling events. Here, we report the structure and dynamics of the N-terminal pyrin domain of NLRP12 (NLRP12 PYD) determined using NMR spectroscopy. NLRP12 is a non-inflammasome NLR that has been implicated in the regulation of Toll-like receptor-dependent nuclear factor-κB activation. NLRP12 PYD adopts a typical six-helical bundle death domain fold. By direct comparison with other PYD structures, we identified hydrophobic residues that are essential for the stable fold of the NLRP PYD family. In addition, we report the first in vitro confirmed non-homotypic PYD interaction between NLRP12 PYD and the pro-apoptotic protein Fas-associated factor 1 (FAF-1), which links the innate immune system to apoptotic signaling. Interestingly, all residues that participate in this protein:protein interaction are confined to the α2-α3 surface, a region of NLRP12 PYD that differs most between currently reported NLRP PYD structures. Finally, we experimentally highlight a significant role for tryptophan 45 in the interaction between NLRP12 PYD and the FAF-1 UBA domain.

Heat shock protein 90 regulates IκB kinase complex and NF-κB activation in angiotensin II-induced cardiac cell hypertrophy

Heat shock protein 90 (HSP90), one of the most abundant proteins in the cardiac cells is essential for cell survival. Previous studies have shown that angiotensin II induces cardiac cell hypertrophy. However, the role of HSP90 in the angiotensin II-induced cardiac hypertrophy is unclear. In this study, we showed that HSP90 regulated angiotensin II-induced hypertrophy via maintenance of the IκB kinase (IKK) complex stability in cardiac cells. An HSP90 inhibitor, geldanamycin (GA), significantly suppressed angiotensin II-induced [³H]leucine incorporation and atrial natriuretic factor expression in cardiac cells. GA also inhibited the NF-κB activation induced by angiotensin II. Importantly, treatment with GA caused a degradation of IKKα/β; on the other hand, a proteasome-specific inhibitor restored the level of IKKα/β. We also found that GA prevented HSP90-IKKs complex induced by angiotensin II in cardiac cells. The small interfering RNA (siRNA)-mediated knockdown of HSP90 expression significantly inhibited angiotensin II-induced cell hypertrophy and NF-κB activation. These results suggest that angiotensin II-induced cardiac hypertrophy requires HSP90 that regulates the stability and complex of IKK.

The kinase NIK as a therapeutic target in multiple myeloma

INTRODUCTION

Multiple myeloma (MM) is a neoplasm derived from B lymphocytes and often results in uncontrolled clonal expansion of antibody-secreting cells. While current treatments are able to prolong survival, MM remains incurable. Excessive NF-κB activity in MM contributes to tumor progression and survival.

AREAS COVERED

The contribution of NF-κB-inducing kinase (NIK) to alternative NF-κB signaling, where it is the key kinase, and classical NF-κB signaling. Modulation of NIK by natural and chemical factors and current and potential therapies for MM that target NIK.

EXPERT OPINION

Mutations affecting the activation of NIK have been identified in MM samples and cell lines, suggesting that NIK may be an important target for therapy of MM. NIK contributes to activation of both NF-κB pathways in MM, giving us the opportunity to limit two pathways contributing to oncogenic survival with a single therapeutic. Many of the mutations identified in MM cells result in the same outcome, hyperactive NIK, thus a single therapeutic may be effective in many patients even though they carry differing mutations. As NIK appears only to activate classical NF-κB when overexpressed, and in normal cells NIK levels are usually low, it is possible that therapeutics designed to limit the amount of NIK may not produce serious side effects in healthy cells.

Inflammasomes and their activation

The innate immune system relies on the recognition of pathogens by pattern recognition receptors as a first line of defense and to initiate the adaptive immune response. Substantial progress has been made in defining the role of Nod (nucleotide-binding oligimerization domain)-like receptors and AIM2 (absent in melanoma 2) as pattern recognition receptors that activate inflammasomes in macrophages. Inflammasomes are protein platforms essential for the activation of inflammatory caspases and subsequent maturation of their pro-inflammatory cytokine substrates and induction of pyroptosis. This paper summarizes recent developments regarding the function of Nod-like receptors in immunity and disease.

The inflammasome NLRs in immunity, inflammation, and associated diseases

Inflammasome activation leads to caspase-1 activation, which causes the maturation and secretion of pro-IL-1β and pro-IL-18 among other substrates. A subgroup of the NLR (nucleotide-binding domain, leucine-rich repeat containing) proteins are key mediators of the inflammasome. Studies of gene-deficient mice and cells have implicated NLR inflammasomes in a host of responses to a wide range of microbial pathogens, inflammatory diseases, cancer, and metabolic and autoimmune disorders. Determining exactly how the inflammasome is activated in these diseases and disease models remains a challenge. This review presents and integrates recent progress in the field.

Gene expression patterns of abalone, Haliotis tuberculata, during successive infections by the pathogen Vibrio harveyi

Since 1998, episodic mass mortality of the abalone Haliotistuberculata has been observed along the northern Brittany coast of France caused by a complex interaction among the host, pathogen and environmental factors. In the present study, abalone were submitted to two successive infections with the pathogen Vibrioharveyi under controlled conditions. During the first challenge, infection by V.harveyi resulted in 64% mortality of mature abalone. After a second infection of those surviving the first challenge, only 44% mortality was observed. Physiological variability in the host response appears to be a major determinant in susceptibility to V.harveyi. In order to isolate differentially expressed genes in H.tuberculata challenged with this bacterium, suppression subtractive hybridization (SSH) cDNA libraries were constructed from muscle of moribund abalone (susceptibles), surviving individuals (apparently resistant to the bacterium) and control (unexposed) animals. Of the 1152 clones sequenced, 218 different partial cDNA sequences were obtained and represented 69 known genes. Of these, 65 were identified for the first time in H.tuberculata. Using real-time PCR, a time-course study was conducted on 19 of the genes identified by SSH. A majority of differentially expressed transcripts were down-regulated in susceptible individuals as compared to their resistant counterparts. Bacterial challenge of abalone resulted in the up-regulation of three transcripts (encoding ferritin, heat shock protein HSP84 and fatty acid binding protein FABP) in those that survived exposure to V.harveyi. This study has identified potential candidates for further investigation into the functional basis of resistance and susceptibility to summer vibriosis outbreaks in abalone.

Proteomics: a strategy to understand the novel targets in protein misfolding and cancer therapy

Proteins carry out important functions as they fold themselves. Protein misfolding occurs during different biochemical processes and may lead to the development of diseases such as cancer, which is characterized by genetic instability. The cancer microenvironment exposes malignant cells to a variety of stressful conditions that may further promote protein misfolding. Tumor development and progression often arises from mutations that interfere with the appropriate function of tumor-suppressor proteins and oncogenes. These may be due to alteration of catalytic activity of the protein, loss of binding sites for effector proteins or alterations of the native folded protein conformation. Src family kinases, p53, mTOR and C-terminus of HSC70 interacting protein (CHIPs) are some examples associated with protein misfolding and tumorigenesis. Molecular chaperones, such as heat-shock protein (HSP)70 and HSP90, assist protein folding and recognize target misfolded proteins for degradation. It is likely that this misfolding in cancer is linked by common principles, and may, therefore, present an exciting possibility to identify common targets for therapeutic intervention. Here we aim to review a number of examples that show how alterations in the folding of tumor-suppressor proteins or oncogenes lead to tumorigenesis. The possibility of targeting the targets to repair or degrade protein misfolding in cancer therapy is discussed.

Genetics vs. entropy: longevity factors suppress the NF-kappaB-driven entropic aging process

Molecular studies in model organisms have identified potent longevity genes which can delay the aging process and extend the lifespan. Longevity factors promote stress resistance and cellular survival. It seems that the aging process itself is not genetically programmed but a random process involving the loss of molecular fidelity and subsequent accumulation of waste products. This age-related increase in cellular entropy is compatible with the disposable soma theory of aging. A large array of host defence systems has been linked to the NF-kappaB system which is an ancient signaling pathway specialized to host defence, e.g. functioning in immune system. Emerging evidence demonstrates that the NF-kappaB system is activated during aging. Oxidative stress and DNA damage increase with aging and elicit a sustained activation of the NF-kappaB system which has negative consequences, e.g. chronic inflammatory response, increase in apoptotic resistance, decline in autophagic cleansing, and tissue atrophy, i.e. processes that enhance the aging process. We will discuss the role of NF-kappaB system in the pro-aging signaling and will emphasize that several longevity factors seem to be inhibitors of NF-kappaB signaling and in that way they can suppress the NF-kappaB-driven entropic host defence catastrophe.

Alternate strategies of Hsp90 modulation for the treatment of cancer and other diseases

The 90 kDa heat shock protein (Hsp90) has become a validated target for the development of anti-cancer agents. Several Hsp90 inhibitors are currently under clinical trial investigation for the treatment of cancer. All of these agents inhibit Hsp90's protein folding activity by binding to the N-terminal ATP binding site of the Hsp90 molecular chaperone. Administration of these investigational drugs elicits induction of the heat shock response, or the overexpression of several Hsps, which exhibit antiapoptotic and pro-survival effects that may complicate the application of these inhibitors. To circumvent this issue, alternate mechanisms for Hsp90 inhibition that do not elicit the heat shock response have been identified and pursued. After providing background on the structure, function, and mechanism of the Hsp90 protein folding machinery, this review describes several mechanisms of Hsp90 modulation via small molecules that do not induce the heat shock response.

Increases in nuclear p65 activation in dystrophic skeletal muscle are secondary to increases in the cellular expression of p65 and are not solely produced by increases in IkappaB-alpha kinase activity

Dystrophin-deficient muscle exhibits substantial increases in nuclear NF-kappaB activation. To examine potential mechanisms for this enhanced activation, the present study employs conventional Western blot techniques to provide the first determination of the relative expression of NF-kappaB signaling molecules in adult nondystrophic and dystrophic (mdx) skeletal muscle. The results indicate that dystrophic muscle is characterized by increases in the whole cell expression of IkappaB-alpha, p65, p50, RelB, p100, p52, IKK, and TRAF-3. The proportion of phosphorylated IkappaB-alpha, p65, NIK, and IKKbeta, and the level of cytosolic IkappaB-alpha, were also increased in the mdx diaphragm. Proteasomal inhibition using MG-132 increased the proportion of phosphorylated IkappaB-alpha in nondystrophic diaphragm, but did not significantly increase this proportion in the mdx diaphragm. This result suggests that phosphorylated IkappaB-alpha accumulates in dystrophic cytosol because the rate of IkappaB-alpha degradation is lower than the effective rate of IkappaB-alpha synthesis and phosphorylation. Dystrophic increases in SUMO-1 (small ubiquitin modifier-1) protein and in Akt activation were also observed. The results indicate that increases in nuclear p65 activation in dystrophic muscle are not produced solely by increases in the activity of IkappaB-alpha kinase (IKK), but are due primarily to increases in the expression of p65 and other NF-kappaB signaling components.

Sensing pathogens and danger signals by the inflammasome

The NLR (nucleotide-binding domain leucine-rich repeat containing) family of intracellular sensors is a crucial component of the innate immune system. A number of NLR family members can form multiprotein complexes, called inflammasomes, and are capable of activating the cysteine protease caspase-1 in response to a wide range of stimuli including both microbial and self-molecules. Caspase-1 activation leads to processing and secretion of the proinflammatory cytokines interleukin-1beta (IL-1beta) and IL-18, which play crucial roles in host defense to infectious insults. Dysregulation of the inflammasome has also been linked to a number of autoinflammatory and autoimmune disorders. Recent advances in the inflammasome field will be discussed in this review.