Project description:Stringent regulation of TNF signaling prevents aberrant inflammation. TNF engages the canonical NF-kB pathway for activating the RelA:p50 heterodimer, which mediates specific expressions of pro-inflammatory and immune response genes. Importantly, the NF-kB system discriminates between time-varied TNF inputs. Negative feedback regulators of the canonical pathway, including IkBa, thought to ensure transient RelA:p50 responses to brief TNF stimulations. The noncanonical NF-kB pathway controls a separate RelB activity associated with immune differentiation. In a systems modeling approach, we uncovered an unexpected role of p100, a constituent of the noncanonical pathway, in TNF signaling. Brief TNF stimulation of p100-deficient cells produced an additional late NF-kB activity composed of the RelB:p50 heterodimer, which distorted the TNF-induced gene-expression program. Periodic TNF pulses augmented this RelB:p50 activity, which was reinforced by NF-kB-dependent RelB synthesis. In sum, the NF-kB system seems to engage distantly related molecular species for enforcing dynamical and gene controls of immune-activating TNF signaling.
Project description:Pro-inflammatory cytokines were shown to promote growth and survival of cancerous cells. TNF induced RelA:p50 NF-κB dimer via the canonical pathway is thought to link inflammation with cancer. Integrating biochemical and computational studies we identify that deficiency of non-canonical signal transducer p100 triggers a positive autoregulatory loop, which instead perpetuates an alternate RelB:p50 containing NF-κB activity upon TNF treatment. TNF stimulated RelB:p50 dimer is sufficient for mediating NF-κB target gene-expressions and suppressing apoptotic cellular death independent of principal NF-κB subunit RelA. We further demonstrate that activating mutations in non-canonical NF-κB module deplete multiple myeloma cells of p100, thereby, provoking autoregulatory RelB:p50 activation. Finally, autoregulatory control reinforces protracted pro-survival NF-κB response, albeit comprising of RelB:p50, upon TNF priming that protects myeloma cells with dysfunctional p100 from subsequent apoptotic insults. In sum, we present evidence for positive autoregulation mediated through the NF-κB system and its potential involvement in human neoplasm.
Project description:Developmental signals are known to modulate inflammation. How ever, the mechanistic insight that links developmental and inflammatory signaling remains elusive. In the current study, we identifya critical role of NF-kB system in mediating stimulus specific crosstalk that allows developmental LTbR signals to sustain inflammatory TLR4 induced RelA/NF-kB response and gene expression. LTbR activated non-canonical signaling targets canonical TLR4 induced, nfkb2 encoded p100 not only to deplete inhibitory IkBd/(p100)2, but also to supplement RelA:p52/NF-kB dimers. Robust crosstalk in the gut epithelial cells are important, as crosstalk-defective nfkb2-/- mice succumbed to gut infection by Citrobacter rodentium due to hypo-inflammatory responses. Finally, we present evidence for a crosstalk motif that integrates tissue microenvironment derived developmental cues to ameliorate the pathogen response. Total RNA from WT early passage MEFs stimulated with ligands LPS, LTbR and LPS+LTbR for 24hrs were analyzed for global gene expression levels
Project description:Developmental signals are known to modulate inflammation. How ever, the mechanistic insight that links developmental and inflammatory signaling remains elusive. In the current study, we identifya critical role of NF-kB system in mediating stimulus specific crosstalk that allows developmental LTbR signals to sustain inflammatory TLR4 induced RelA/NF-kB response and gene expression. LTbR activated non-canonical signaling targets canonical TLR4 induced, nfkb2 encoded p100 not only to deplete inhibitory IkBd/(p100)2, but also to supplement RelA:p52/NF-kB dimers. Robust crosstalk in the gut epithelial cells are important, as crosstalk-defective nfkb2-/- mice succumbed to gut infection by Citrobacter rodentium due to hypo-inflammatory responses. Finally, we present evidence for a crosstalk motif that integrates tissue microenvironment derived developmental cues to ameliorate the pathogen response.
Project description:The ubiquitination-dependent processing of NF-B2 (also known as p100) is a critical step in the activation of the noncanonical NF-B pathway. We investigated the molecular mechanisms regulating this process and showed that TRIM55 was the ubiquitin E3 ligase that mediated the ubiquitination of p100 and coordinated its processing. TRIM55 deficiency impaired noncanonical NF-B activation and B-cell function. Mice with a B cell-specific Trim55 deficiency exhibited reduced germinal center formation and antibody production. In addition, our data indicated a critical role of TRIM55 in the pathogenesis of lupus-like autoimmunological disorders, suggesting B-cell intrinsic functions of TRIM55 in humoral immune responses and autoimmunity. Mechanistically, the ubiquitination of p100 mediated by TRIM55 was crucial for p100 processing by VCP, an ATPase that mediates ubiquitin-dependent protein degradation by the proteasome. Furthermore, we found that TRIM55 facilitated the interaction between TRIM21 and VCP as well as TRIM21-mediated K63-ubiquitination of VCP, both of which were indispensable for the formation of the VCP-UFD1-NPL4 complex and p100 processing. Collectively, our results revealed a mechanism by which TRIM55 fine-tunes p100 processing and regulates B-cell-dependent immune responses in vivo, highlighting TRIM55 as a potential therapeutic target for lupus-like disease.
Project description:Background: Constitutive activation of the alternative NF-?B pathway leads to marginal zone B cell expansion and disorganized spleen microarchitecture. Furthermore, uncontrolled alternative NF-?B signaling results in the development and progression of cancer. We aimed here to learn about the mechanisms how does the constitutively active alternative NF-?B pathway exert its effects in these malignant processes. Methodology/Principal Findings: To explore the consequences of constitutive alternative NF-?B activation on genome-wide transcription, we compared gene expression profiles of wild-type and NF-kB2/p100-deficient (p100-/-) primary mouse embryonic fibroblasts (MEFs) and spleens. Microarray experiments revealed 73 differentially regulated genes in p100-/- vs. wild-type MEFs. Chromatin immunoprecipitation (ChIP) assays showed in p100-/- MEFs direct binding of RelB and p52 to the promoter of the enpp2 gene encoding Enpp2/Autotaxin, a protein with an important role in lymphocyte homing and cell migration. Gene ontology analysis revealed upregulation of genes with anti-apoptotic/proliferative activity (enpp2, serpina3g, traf1, rrad), chemotactic/locomotory activity (enpp2, ccl8), and lymphocyte homing activity (enpp2, cd34). Most importantly, biochemical analyses of MEFs and gene expression analyses of mice indicated a crosstalk between classical and alternative NF-?B pathways. Conclusions/Significance: The present results show that uncontrolled alternative NF-?B signaling is further enhanced by classical NF-?B activation, indicating that p100 deficiency alone is insufficient for full induction of a subset of genes by the alternative NF-?B pathway. cell type comparison (wt vs p100-/-) after genetic modification
Project description:Background: Constitutive activation of the alternative NF-κB pathway leads to marginal zone B cell expansion and disorganized spleen microarchitecture. Furthermore, uncontrolled alternative NF-κB signaling results in the development and progression of cancer. We aimed here to learn about the mechanisms how does the constitutively active alternative NF-κB pathway exert its effects in these malignant processes. Methodology/Principal Findings: To explore the consequences of constitutive alternative NF-κB activation on genome-wide transcription, we compared gene expression profiles of wild-type and NF-kB2/p100-deficient (p100-/-) primary mouse embryonic fibroblasts (MEFs) and spleens. Microarray experiments revealed 73 differentially regulated genes in p100-/- vs. wild-type MEFs. Chromatin immunoprecipitation (ChIP) assays showed in p100-/- MEFs direct binding of RelB and p52 to the promoter of the enpp2 gene encoding Enpp2/Autotaxin, a protein with an important role in lymphocyte homing and cell migration. Gene ontology analysis revealed upregulation of genes with anti-apoptotic/proliferative activity (enpp2, serpina3g, traf1, rrad), chemotactic/locomotory activity (enpp2, ccl8), and lymphocyte homing activity (enpp2, cd34). Most importantly, biochemical analyses of MEFs and gene expression analyses of mice indicated a crosstalk between classical and alternative NF-κB pathways. Conclusions/Significance: The present results show that uncontrolled alternative NF-κB signaling is further enhanced by classical NF-κB activation, indicating that p100 deficiency alone is insufficient for full induction of a subset of genes by the alternative NF-κB pathway.
Project description:TNF time course series of HelA tet off cells cultured in presence or absence of Dox; TNF is a pro-inflammatory cytokine that controls expression of inflammatory genetic networks. Although the Nuclear Factor-kB (NF-kB) pathway is crucial for mediating cellular TNF responses, the complete spectrum of NF-kB dependent genes is unknown. In this study, we used a tetracycline-regulated cell line expressing an NF-kB inhibitor to systematically identify NF-kB dependent genes. A microarray data set generated from a time course of TNF stimulation in the presence or absence of NF-kB signaling was analyzed. Methods: Cell culture, treatment and transfection-The human cervical epithelioid carcinoma cell line HeLa expressing tTA (HeLa Tet-Off) pBI-EGFP- IkBa Mut was constructed earlier (23). HeLa Tet-Off were grown in medium containing 90 % Dulbecco's Modified Eagle's Medium (DMEM), 10 % heat-inactivated fetal bovine serum (FBS), 4mM L-glutamine, 0.1 mM non-essential amino acids, 1 mM sodium pyruvate, 100 mg/ml G418, 100 units /ml penicillin G sodium, and 100 mg/ml streptomycin sulfate in a humidified atmosphere of 5 % CO2. For TNF stimulation, freshly isolated cells were split into two cultures, one group maintained in Dox, the other without for 7 d, a time at which IkBa Mut expression was maximal. Thereafter, recombinant human (rh) TNFa (25 ng/ml, final concentration) was added directly to the culture medium for indicated times prior to harvest. Oligonucleotide probe based microarray-Hu95Av2 GeneChip (Affymetrix Inc, Santa Clara, CA) containing 12,626 sequenced human genes were hybridized according to the manufacturer's recommendations and washed using both non-stringent (1 M NaCl, 25°C) and stringent (1 M NaCl, 50°C) conditions prior to staining with phycoerythrin streptavidin (10 mg/ml final). Arrays were scanned using a Gene Array Scanner (Hewlett Packard) and analyzed using the Gene Chip Analysis Suite 5 software (Affymetrix Inc). For each gene, 16-20 probe pairs are immobilized as ~25-mer oligonucleotides that hybridize throughout the mRNA; each probe pair is represented as a perfect match (PM) oligonucleotide and a mismatch (MM) oligonucleotide as hybridization control. The the Absolute Call [e.g., the gene is detected (present) or not (absent)] and the Signal Intensity (measure of mRNA abundance) is determined. Four independent experiments were performed identically including control (0 h), 1, 3 and 6 h TNF stimulation (25 ng/ml) in the presence or absence of Doxycyline (2 mg/ml) in growth medium. These are indicated as 180, 181, 220 and 266 series, and are considered replicates of each other.