NF-kappaB Essential Modulator Research Articles

IFI16 Positively Regulates RIG-I-Mediated Type I Interferon Production in a STING-Independent Manner.

Previous studies have shown that interferon gene-stimulating protein (STING) is essential for IFN-γ-inducible protein 16 (IFI16) as the DNA sensor and RNA sensor to induce transcription of type I interferon (IFN-I) and is essential for IFI16 to synergize with DNA sensor GMP-AMP (cGAMP) synthase (cGAS) in induction of IFN-I transcription. While other and our previous studies have shown that IFI16 enhanced retinoic acid-inducible gene I (RIG-I)-, which was an RNA sensor, and mitochondrial antiviral signaling (MAVS)-, which was the adaptor protein of RIG-I, induced production of IFN-I, so we wonder whether IFI16 regulates the signal pathway of RNA-RIG-I-MAVS-IFN-I in a STING-dependent manner. We used HEK 293T cells, which did not express endogenous STING and were unable to mount an innate immune response upon DNA transfection and found that IFI16 could enhance RIG-I- and MAVS-mediated induction of IFN-I in a STING-independent way. Furthermore, we found that upregulation of the expression of NF-kappa-B essential modulator (NEMO) by IFI16 was not the mechanism that IFI16 regulated the induction of IFN-I. In conclusion, we found that IFI16 regulated the signal pathway of RNA-RIG-I-MAVS-IFN-I in a STING-independent manner.

Epstein Barr Virus Positive Hodgkin's Lymphoma in a Patient with NEMO Deficiency

IntroductionHypomorphic mutations in the NF-kappaB essential modulator (NEMO) can manifest in diverse ways, but are best characterized by early susceptibility to viral, pyogenic and mycobacterial infections, ectodermal dysplasia and absent pneumococcal responses. We describe a case of EBV+ Hodgkin's lymphoma in a 9-year-old patient with NEMO on antimicrobial prophylaxis and immunoglobulin replacement therapy (IgRT). Case reportOur patient was diagnosed with NEMO deficiency at 2 years with initial presentation of recurrent pneumonia, recurrent skin abscesses and severe eczema herpeticum. His disease was moderately controlled with IgRT, and prophylaxis with trimethoprim/sulfamethoxazole, azithromycin and acylovir prophylaxis, with primary complications of continued recurrent pneumonia and finger clubbing. At 9 years of age however, he developed acute back pain and weakness, along with night sweats. MRI revealed thoracic spinal cord compression at T5 secondary to a possible neoplastic soft tissue mass. A laminectomy revealed Epstein Barr virus (EBV) positive Hodgkin lymphoma, stage 4 high risk due to PET positivity with uptake at large cervical chain nodal conglomerates bilaterally, mediastinal mass, thoracic paraspinal mass, periportal lymph nodes, splenic, and right medial femoral neck. He also had low level EBV viremia (EBV viral load 7,515 IU/mL). He was treated according to AHOD1331 with ABVE-PC (doxorubicin/bleomycin/vincristine/etoposide/prednisone), and also received rituximab and valganciclovir for treatment of EBV. He is now in remission after 4 months of treatment, and continues on IgRT, pneumocystis jiroveci pneumonia, mycobacterium avium complex, and herpes simplex virus prophylaxis. ConclusionPatients with certain inborn errors of immunity have a higher incidence of malignancy due to impaired immune function. Despite their viral susceptibility, EBV-induced lymphomas are not common in NEMO deficiency. NEMO patients may need further enhanced screening for development of malignancy, including regular surveillance for chronic, cancer-causing infections such as EBV and HPV.

Deletion of African Swine Fever Virus (ASFV) H240R Gene Attenuates the Virulence of ASFV by Enhancing NLRP3-Mediated Inflammatory Responses.

African swine fever (ASF) is a highly contagious infectious disease of domestic pigs and wild boars caused by African swine fever virus (ASFV), with a mortality rate of up to 100%. In order to replicate efficiently in macrophages and monocytes, ASFV has evolved multiple strategies to evade host antiviral responses. However, the underlying molecular mechanisms by which ASFV-encoded proteins execute immune evasion are not fully understood. In this study, we found that ASFV pH240R strongly inhibits transcription, maturation, and secretion of interleukin-1β (IL-1β). Importantly, pH240R not only targeted NF-κB signaling but also impaired NLRP3 inflammasome activation. In this mechanism, pH240R interacted with NF-kappa-B essential modulator (NEMO), a component of inhibitor of kappa B kinase (IKK) complex and subsequently reduced phosphorylation of IκBα and p65. In addition, pH240R bonded to NLRP3 to inhibit NLRP3 inflammasome activation, resulting in reduced IL-1β production. As expected, infection with H240R-deficient ASFV (ASFV-ΔH240R) induced more inflammatory cytokine expression both in vitro and in vivo than its parental ASFV HLJ/18 strain. Consistently, H240R deficiency reduced the viral pathogenicity in pigs compared with its parental strain. These findings reveal that the H240R gene is an essential virulence factor, and deletion of the H240R gene affects the pathogenicity of ASFV HLJ/18 by enhancing antiviral inflammatory responses, which provides insights for ASFV immune evasion mechanisms and development of attenuated live vaccines and drugs for prevention and control of ASF. IMPORTANCE African swine fever (ASF), caused by African swine fever virus (ASFV), is a highly contagious and acute hemorrhagic viral disease of domestic pigs, with a high mortality approaching 100%. ASFV has spread rapidly worldwide and caused huge economic losses and ecological consequences. However, the pathogenesis and immune evasion mechanisms of ASFV are not fully understood, which limits the development of safe and effective ASF attenuated live vaccines. Therefore, investigations are urgently needed to identify virulence factors that are responsible for escaping the host antiviral innate immune responses and provide a new target for development of ASFV live-attenuated vaccine. In this study, we determined that the H240R gene is an essential virulence factor, and its depletion affects the pathogenicity of ASFV by enhancing NLRP3-mediated inflammatory responses, which provides theoretical support for the development of an ASFV attenuated live vaccine.

Ethanol Exposure Induces Microglia Activation and Neuroinflammation through TLR4 Activation and SENP6 Modulation in the Adolescent Rat Hippocampus.

The ethanol-induced toll-like receptor 4 (TLR4) signal activation of microglia and neuroinflammation are observed in both adolescent and adult rat brains, but the regulatory mechanisms of some TLR4 signaling-related factors in this process are still unclear. SUMO-specific protease 6 (SENP6) inhibits neuroinflammation by dampening nuclear factor kappa-B (NF-κB) activation via the de-SUMOylation of NF kappa-B essential modulator (NEMO). This study investigates the effects of long-term ethanol consumption on neuroinflammation in the hippocampus of adolescent rats and the regulatory roles of TLR4 and SENP6. Twenty-one days of ethanol exposure in adolescent rats were used to develop an animal model. The number of microglia, microglial activation, and the expression of TLR4 in the hippocampus of adolescent rats were examined by immunoreactivity. The levels of TLR4, activation of NF-κB including IkB-α and p-NF-κB-p65, and SENP6 were measured by western blotting. Proinflammatory cytokines including TNF-α, IL-1β, and IL-6 were measured by enzyme-linked immunosorbent assay. The NF-κB activation and proinflammatory cytokines released in overexpressed SENP6 and siRNA targeting SENP6 microglial cells after treatment with ethanol were estimated in vitro. This study found that alcohol exposure increased the number of activated microglia and the levels of p-NF-κB-p65 and proinflammatory cytokines, while it decreased the SENP6 level in wild-type rats, but not in TLR4 knockout rats. The ethanol-induced increases of p-NF-κB-p65, TNF-α, and IL-1β were dampened by overxpression of SENP6 and enhanced in SENP6-siRNA microglia. Our data suggest that ethanol exposure during adolescence induces the microglia-mediated neuroinflammation via TLR4 activation, and SENP6 plays an essential role in dampening NF-κB activation and neuroinflammation.

Abstract 5235: Affecting activity of the linear ubiquitin chain assembly complex (LUBAC) with stapled alpha-helical peptides

Abstract The linear ubiquitin chain assembly complex (LUBAC) is the only E3 ubiquitin ligase known to generate linear polyubiquitin chains in vitro. LUBAC is composed of three proteins - HOIL-1L, HOIP and SHARPIN - of which the interaction between HOIL-1L and HOIP has been shown to be critical for LUBAC assembly and function. This interaction occurs between the ubiquitin-like (UBL) domain of HOIL-1L and the ubiquitin-associated (UBA) domain of HOIP. One known substrate of LUBAC is the regulatory subunit NEMO (NF kappa B essential modulator), part of the IKK complex, which results in activation of NF-κB. We hypothesize that disruption of the HOIL-1L-HOIP interaction would prevent LUBAC ubiquitylation activity and result in down-regulated activation of NF-κB. We have synthesized a family of small inhibitor peptides designed to mimic aspects of the bent alpha-helical interacting interface of HOIP-UBA. Here we demonstrate how single amino acid substitutions and hydrocarbon stapling can affect overall peptide shape and helicity, and correlate that structural information to peptide binding affinity, ability to affect LUBAC complex formation and resulting effect on LUBAC ubiquitylation activity in vitro. These findings continue to validate inhibition of LUBAC via interference with the HOIL-1L-HOIP interaction as a potential target to affect NF-κB signaling. Compounds which affect LUBAC activity have potential use in LUBAC-dependent NF-κB activation in the activated B cell-like (ABC) subtype of diffuse large B-cell lymphoma (DLBCL), the DLBCL subtype that is most resistant to current therapies. Citation Format: Amanda L. Whiting, Francisco Aguilar-Alonso, Joseph J. Mitala, Federico Bernal. Affecting activity of the linear ubiquitin chain assembly complex (LUBAC) with stapled alpha-helical peptides [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5235. doi:10.1158/1538-7445.AM2017-5235

New Insight Into the Pathogenesis of Cerebral Small-Vessel Diseases.

Cerebral small-vessel diseases (SVD) are a common cause of vascular dementia and disability in the elderly. Apart from risk containment, little can be done to prevent or to treat SVD. Although most cases occur sporadically, hereditary forms of the disease provide the chance to elucidate the molecular and cellular mechanisms leading to microvascular pathology. Along this line, authoritative reviews on SVD have been published.1–3 Here, we would like to extend current concepts of SVD by highlighting a molecular pathway that seems to be involved in several well-defined SVD, some of which are hereditary. As a new piece of evidence, we will focus on incontinentia pigmenti (IP), which has recently been shown to be associated with microvascular pathology of the brain and retina.4,5 As will be elaborated below, IP is a SVD that does not present in the elderly but rather during infancy. The young age of onset and the nonprogressive microvascular pathology lead to a clinical picture that differs from other SVD. We suggest the term developmental SVD for this form of presentation. IP is caused by mutations in the NEMO gene (NF-kappaB essential modulator), an essential modulator of the transcription factor nuclear factor (NF)-κB.6 NEMO maintains the viability of brain endothelial cells and stabilizes the blood–brain barrier (BBB).5 In NEMO -deficient animals, there is rarefaction of cerebral capillaries and hypoperfusion of the central nervous system (CNS). Disruption of the transforming growth factor (TGF)-β–activated kinase (TAK1) upstream of NEMO produces a similar pathology.5 Interestingly, TGF-β has also been involved in the pathogenesis of cerebral autosomal recessive arteriopathy with subcortical infarcts and leukoencephalopathy (CARASIL), cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), and the vascular changes of Alzheimer disease (AD),7–11 suggesting disturbed TGF-β signaling as a common …

Connecting Cell Death and Survival Pathways via the ASK1/IKKβ Interaction

Cells must constantly integrate pro‐death and pro‐survival signals, and respond accordingly. Dysregulation of this signal integration can lead to human disease, which highlights the importance of balancing life and death signaling inside the cell. Previously we reported the novel interaction between apoptosis signal regulating kinase 1 (ASK1) and the inhibitor of κB kinase β (IKKβ). As a key effector of cell stress signaling, ASK1 is tightly regulated. IKKβ is part of the IKK complex which transduces pro‐inflammatory signaling. The interaction between ASK1 and IKKβ creates a junction between cell death and survival pathways. Thus understanding how ASK1 interacts with IKKβ may offer strategies for therapeutic intervention. Truncation studies led to the identification of the binding interface at the carboxyl terminal regions of both ASK1 and IKKβ. This was also confirmed using competition assays showing that the C‐terminal fragment was capable of disrupting the association between the full‐length proteins. Functionally, the binding of IKKβ decreased ASK1‐mediated pro‐apoptotic signaling. The same C‐terminal of IKKβ is also responsible for mediating binding to NF‐kappa‐B essential modulator (NEMO). We found that the ASK1/IKKβ complex did not disrupt the NEMO/IKKβ interaction, raising the possibility that there are two distinct structural determinants governing separate protein‐protein interactions with a very narrow region of IKKβ. With the defined regions of the binding interface, small peptide antagonists will be utilized to validate the importance of the ASK1/IKK axis in the control of cell fate. This work was supported by the National Institutes of Health grant P01 CA116676.

Answer

Journal of Paediatrics and Child HealthVolume 50, Issue 11 p. 934-935 Letter to the EditorFree Access Answer First published: 06 November 2014 https://doi.org/10.1111/jpc.12562_2AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Incontinentia pigmenti is a rare, X-linked dominant disorder that presents at or soon after birth with characteristic cutaneous findings. The skin lesions usually present within the first 2 weeks of life and have four phases: vesicular, verrucous, hyperpigmented and atrophic. Overlap between them may occur. In the verrucous phase (seen in this case), the lesions tend to appear in the distal part of the limbs as the blisters began to heal. Non-cutaneous manifestations involve the teeth (hypodontia, anodontia and conical teeth), eye (strabismus, cataract and optic nerve atrophy) and the central nervous system (convulsions, spastic paralysis and motor retardation). The pathophysiology of the central nervous system problems is poorly understood but vascular, developmental, inflammatory, destructive and infectious processes have been proposed as possible mechanisms.1 Mutations in the NEMO gene (Xq28) that completely abolish expression of the NF-kappaB essential modulator are responsible for the disorder. A large deletion of NEMO exons 4 to 10 is found in approximately 80% of the patients.2 References 1Shuper A, Bryan RN, Singer HS. Destructive encephalopathy in incontinentia pigmenti: a primary disorder? Pediatr. Neurol. 1990; 6: 137– 140. CrossrefCASPubMedWeb of Science®Google Scholar 2Smahi A, Courtois G, Vabres P et al. Genomic rearrangement in NEMO impairs NF-kappaB activation and is a cause of incontinentia pigmenti. The International Incontinentia Pigmenti (IP) Consortium. Nature 2000; 405: 466– 472. CrossrefCASPubMedWeb of Science®Google Scholar Volume50, Issue11November 2014Pages 934-935 ReferencesRelatedInformation

A Case of Incontinentia Pigmenti with Multiple Brain Infarction

Incontinentia pigmenti (IP) is a rare X-linked dominant disease that is typically lethal to males and usually affect female patients. IP is a neurocutaneous disorder, involving the ectodermal tissues such as the skin, eyes, teeth, hair, and central nervous system. The pathogenesis of IP is linked to the gene mutation in the NFkappa B essential modulator (NEMO) on chromosome Xq28. We experienced one case of newborn with multiple vesiculobullous skin lesions over the entire body after birth. Skin biopsy and histologic studies revealed suspected IP stage I and the genetic analysis of the NEMO confirmed IP diagnosis. A brain MRI showed multiple cerebral infarctions and the infant has shown delayed development in follow-up clinic.

247 Serial Cytokine Expressions in Infants with Incontinentia Pigmenti

BackgroundNF-kB dysfunction resulting from NEMO (NF-kappaB essential modulator) mutation can lead to significant alterations in cytokine production. However, little is known about changes in the expression of downstream molecules in...

Serial cytokine expressions in infants with incontinentia pigmenti

NF-κB dysfunction resulting from NEMO (NF-kappaB essential modulator) mutation can lead to significant alterations in cytokine production. However, little is known about changes in the expression of downstream molecules in patients with incontinentia pigmenti (IP). We aim to investigate serial cytokine expressions during the first 2 years of life in young infants with IP, the period in which skin inflammation and morphological changes are most significant. Gene analysis and X-inactivation test were performed for the two neonates with IP. Peripheral mononuclear cells were obtained after birth and successively at 6-month interval up to the age of two years. Levels of TNF-α and IL-6 were analyzed with ELISA before and after stimulating with Toll-like receptor ligands. The result showed the male IP patient had normal NEMO allele. His cytokine level, although initially lower, had returned to a level comparable with those of controls at 12 months of age. The female infant had mutated NEMO gene. Her baseline TNF-α level was significantly higher than those of the control subjects at birth and remained high by 6 months of age. All cytokine responses had decreased significantly by 2 years of age, the time in which all vesicular skin lesions had resolved. Both infants had normal serum immunoglobulin level and remained infection free during the follow up period. To our knowledge, this is the first report that demonstrates serial changes of cytokine profiles in humans with IP. This study showed that in the presence of NEMO mutation, alteration of cytokine production was remarkable during the first year of life, which may account for the prominent inflammatory changes in skin morphology.

TAK1: Another mesh in the NF-κB – JNK controlled network causing hepatocellular carcinoma

The MAP3-kinase TGF-beta-activated kinase 1 (TAK1) critically modulates innate and adaptive immune responses and connects cytokine stimulation with activation of inflammatory signaling pathways. Here, we report that conditional ablation of TAK1 in liver parenchymal cells (hepatocytes and cholangiocytes) causes hepatocyte dysplasia and early-onset of hepatocarcinogenesis, coinciding with biliary ductopenia and cholestasis. TAK1-mediated cancer suppression is exerted through activating NF-kappaB in response to tumor necrosis factor (TNF) and through preventing Caspase-3-dependent hepatocyte and cholangiocyte apoptosis. Moreover, TAK1 suppresses a procarcinogenic and pronecrotic pathway, which depends on NF-kappaB-independent functions of the I kappaB-kinase (IKK)-subunit NF-kappaB essential modulator (NEMO). Therefore, TAK1 serves as a gatekeeper for a protumorigenic, NF-kappaB-independent function of NEMO in parenchymal liver cells.

Identification of a new NEMO/TRAF6 interface affected in incontinentia pigmenti pathology

NF-kappaB Essential MOdulator (NEMO) has been shown to play a critical role in NF-kappaB activation, as the regulatory subunit of IkappaB kinase. Upon cell stimulation, NEMO can be modified through phosphorylation, sumoylation or ubiquitination. In the latter case, not much is known regarding the exact function of this posttranslational modification. One of the E3 ligase responsible for K63-linked NEMO polyubiquitination is TRAF6, which participates in several signaling pathways controlling immunity, osteoclastogenesis, skin development and brain functions. We previously observed a potentially important interaction between NEMO and TRAF6. In this study, we defined in more detail the domains required for this interaction, uncovering a new binding site for TRAF6 located at the amino-terminus of NEMO and recognized by the coiled-coil domain of TRAF6. This site appears to work in concert with the previously identified NEMO ubiquitin-binding domain which binds polyubiquitinated chains, suggesting a dual mode of TRAF6 recognition. We also showed that E57K mutation of NEMO found in a mild form of the genetic disease incontinentia pigmenti, resulted in impaired TRAF6 binding and IL-1beta signaling. In contrast, activation of NF-kappaB by TNF-alpha was not affected. These data demonstrate that NEMO/TRAF6 interaction has physiological relevance and might represent a new target for therapeutic purposes.

Activation of Noncanonical NF-κB Signaling by the Oncoprotein Tio

NF-kappaB transcription factors are key regulators of cellular proliferation and frequently contribute to oncogenesis. The herpesviral oncoprotein Tio, which promotes growth transformation of human T cells in a recombinant herpesvirus saimiri background, potently induces canonical NF-kappaB signaling through membrane recruitment of the ubiquitin ligase tumor necrosis factor receptor-associated factor 6 (TRAF6). Here, we show that, in addition to Tio-TRAF6 interaction, the Tio-induced canonical NF-kappaB signal requires the presence of the regulatory subunit of the inhibitor of kappaB kinase (IKK) complex, NF-kappaB essential modulator (NEMO), and the activity of its key kinase, IKKbeta, to up-regulate expression of endogenous cellular inhibitor of apoptosis 2 (cIAP2) and interleukin 8 (IL-8) proteins. Dependent on TRAF6 and NEMO, Tio enhances the expression of the noncanonical NF-kappaB proteins, p100 and RelB. Independent of TRAF6 and NEMO, Tio mediates stabilization of the noncanonical kinase, NF-kappaB-inducing kinase (NIK). Concomitantly, Tio induces efficient processing of the p100 precursor molecule to its active form, p52, as well as DNA binding of nuclear p52 and RelB. In human T cells transformed by infection with a Tio-recombinant virus, sustained expression of p100, RelB, and cIAP2 depends on IKKbeta activity, yet processing to p52 remains largely unaffected by IKKbeta inhibition. However, long term inhibition of IKKbeta disrupts the continuous growth of the transformed cells and induces cell death. Hence, the Tio oncoprotein triggers noncanonical NF-kappaB signaling through NEMO-dependent up-regulation of p100 precursor and RelB, as well as through NEMO-independent generation of p52 effector.

TAK1 Suppresses a NEMO-Dependent but NF-κB-Independent Pathway to Liver Cancer

The MAP3-kinase TGF-beta-activated kinase 1 (TAK1) critically modulates innate and adaptive immune responses and connects cytokine stimulation with activation of inflammatory signaling pathways. Here, we report that conditional ablation of TAK1 in liver parenchymal cells (hepatocytes and cholangiocytes) causes hepatocyte dysplasia and early-onset hepatocarcinogenesis, coinciding with biliary ductopenia and cholestasis. TAK1-mediated cancer suppression is exerted through activating NF-kappaB in response to tumor necrosis factor (TNF) and through preventing Caspase-3-dependent hepatocyte and cholangiocyte apoptosis. Moreover, TAK1 suppresses a procarcinogenic and pronecrotic pathway, which depends on NF-kappaB-independent functions of the I kappaB-kinase (IKK)-subunit NF-kappaB essential modulator (NEMO). Therefore, TAK1 serves as a gatekeeper for a protumorigenic, NF-kappaB-independent function of NEMO in parenchymal liver cells.

Novel Insights into the Cellular Mechanisms of the Anti-inflammatory Effects of NF-κB Essential Modulator Binding Domain Peptides

The classical nuclear factor κB (NF-κB) signaling pathway is under the control of the IκB kinase (IKK) complex, which consists of IKK-1, IKK-2, and NF-κB essential modulator (NEMO). This complex is responsible for the regulation of cell proliferation, survival, and differentiation. Dysregulation of this pathway is associated with several human diseases, and as such, its inhibition offers an exciting opportunity for therapeutic intervention. NEMO binding domain (NBD) peptides inhibit the binding of recombinant NEMO to IKK-2 in vitro. However, direct evidence of disruption of this binding by NBD peptides in biological systems has not been provided. Using a cell system, we expanded on previous observations to show that NBD peptides inhibit inflammation-induced but not basal cytokine production. We report that these peptides cause the release of IKK-2 from an IKK complex and disrupt NEMO-IKK-2 interactions in cells. We demonstrate that by interfering with NEMO-IKK-2 interactions, NBD peptides inhibit IKK-2 phosphorylation, without affecting signaling intermediates upstream of the IKK complex of the NF-κB pathway. Furthermore, in a cell-free system of IKK complex activation by TRAF6 (TNF receptor-associated factor 6), we show that these peptides inhibit the ability of this complex to phosphorylate downstream substrates, such as p65 and inhibitor of κBα (IκBα). Thus, consistent with the notion that NEMO regulates IKK-2 catalytic activity by serving as a scaffold, appropriately positioning IKK-2 for activation by upstream kinase(s), our findings provide novel insights into the molecular mechanisms by which NBD peptides exert their anti-inflammatory effects in cells.

Protein–protein interactions involving IKKγ (NEMO) that promote the activation of NF‐κB

Inhibitor of kappaB kinase (IKK) gamma (IKKgamma), also referred to as nuclear factor kappaB (NF-kappaB) essential modulator (NEMO), is an important regulatory component of the IKK complex. The IKK complex is a signalosome that catalyzes the inducible phosphorylation of IkappaB proteins, which is a key step that leads to the activation of NF-kappaB. The exact functions of IKKgamma (NEMO) as part of the IKK complex have not yet been fully elucidated. This mini-review covers 16 proteins that have been reported to bind to IKKgamma and lead to the enhancement of the activities of the IKK complex, thus resulting in NF-kappaB activation. The major mechanisms by which these interactions are mediated involve the recognition of ubiquitinated upstream signaling components by IKKgamma or the modification of IKKgamma itself by ubiquitination. Additional mechanisms include the sumoylation or phosphorylation of IKKgamma and the modification of the tertiary or quaternary structure of IKKgamma.

Incontinetia pigmenti-related myopathy or unsolved “double trouble”?

Incontinentia pigmenti is an X-linked dominant or sporadic multisystemic disorder with involvement of skin, eyes and central nervous system which results from mutations in the gene for NF-kappaB essential modulator (NEMO). We report on a patient with genetically confirmed Bloch–Sulzberger syndrome, who presented with a progressive myopathy and cardiomyopathy. Genetic analyses revealed an intragenic deletion (Intron3 and Exon10) of the NEMO/IKKγ/IKKAP/IKBKG gene. Further complete sequencing of genes encoding for desmin, lamin A/C, emerin, and FHL1 showed no evidence of pathogenic mutations. A pathological expansion of CCTG repeats of the ZNF9 gene (PROMM) was ruled out by PCR amplification analysis. MLPA-analysis showed no evidence for duplications or deletions of the dystrophin gene. This report highlights the unusual combination of a genetically confirmed incontinentia pigmenti and a proximal myopathy and dilatative cardiomyopathy of unknown origin. We discuss that the striated muscle involvement (i) might be based on the observed intragenic deletion of the NEMO gene, or (ii) on an additional gene defect leading to an adult onset myopathy. Further studies on neuromuscular involvement in patients with incontinentia pigmenti are needed to clarify this issue.

Incontinentia pigmenti

Incontinentia pigmenti (IP) or Bloch-Sulzberger syndrome is a rare X-linked dominant genodermatosis related to the NF kappa B essential modulator (NEMO) gene with approximately 800 cases reported worldwide. It usually occurs in females characterized by cutaneous, skeletal, neurological, ocular and dental abnormalities as well as an increased risk of childhood malignancies. Herein, we report a case of IP in a 14-year-old girl emphasizing early diagnosis and adding to the current literature on the subject.

NEMO-binding Domains of Both IKKα and IKKβ Regulate IκB Kinase Complex Assembly and Classical NF-κB Activation

Proinflammatory NF-kappaB activation requires the IkappaB (inhibitor of NF-kappaB) kinase (IKK) complex that contains two catalytic subunits named IKKalpha and IKKbeta and a regulatory subunit named NF-kappaB essential modulator (NEMO). NEMO and IKKbeta are essential for tumor necrosis factor (TNF)-induced NF-kappaB activation, and we recently demonstrated that NEMO and IKKalpha are sufficient for interleukin (IL)-1-induced signaling. IKKalpha and IKKbeta both contain a functional NEMO-binding domain (NBD); however, the role of NEMO association with each kinase in NF-kappaB signaling and IKK complex formation remains unclear. To address this question, we stably reconstituted IKKalpha(-/-) and IKKbeta(-/-) murine embryonic fibroblasts (MEFs) with wild-type (WT) or NBD-deficient (DeltaNBD) versions of IKKalpha and IKKbeta, respectively. TNF-induced classical NF-kappaB activation in IKKbeta(-/-) MEFs was rescued by IKKbeta(WT) but not IKKbeta(DeltaNBD), whereas neither IKKbeta(WT) nor IKKbeta(DeltaNBD) affected IL-1-induced NF-kappaB signaling. As previously described, classical NF-kappaB transcriptional activity was absent in IKKalpha(-/-) cells. Reconstitution with either IKKalpha(WT) or IKKalpha(DeltaNBD) rescued both IL-1 and TNF-induced transcription, demonstrating that NEMO association is not required for IKKalpha-dependent regulation of NF-kappaB-dependent transcription. Stably expressed IKKalpha(WT) or IKKbeta(WT) associated with endogenous IKKs and NEMO in IKKalpha(-/-) or IKKbeta(-/-) MEFs, respectively, resulting in formation of the heterotrimeric IKKalpha-IKKbeta-NEMO complex. In contrast, although the IKKalpha(DeltaNBD) and IKKbeta(DeltaNBD) mutants associated with endogenous IKKs containing an NBD, these dimeric endogenous IKK-IKK(DeltaNBD) complexes did not associate with NEMO. These findings therefore demonstrate that formation of the heterotrimeric IKKalpha-IKKbeta-NEMO holocomplex absolutely requires two intact NEMO-binding domains.