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New mechanism of X-linked anhidrotic ectodermal dysplasia with immunodeficiency: impairment of ubiquitin binding despite normal folding of NEMO protein.

ABSTRACT: Nuclear factor-?B essential modulator (NEMO), the regulatory subunit of the I?B kinase complex, is a critical component of the NF-?B pathway. Hypomorphic mutations in the X-linked human NEMO gene cause various forms of anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID). All known X-linked EDA-ID-causing mutations impair NEMO protein expression, folding, or both. We describe here 2 EDA-ID-causing missense mutations that affect the same residue in the CC2-LZ domain (D311N and D311G) that do not impair NEMO production or folding. Structural studies based on pull-down experiments showed a defect in noncovalent interaction with K63-linked and linear polyubiquitin chains for these mutant proteins. Functional studies on the patients' cells showed an impairment of the classic NF-?B signaling pathways after activation of 2 NEMO ubiquitin-binding-dependent receptors, the TNF and IL-1? receptors, and in the CD40-dependent NF-?B pathway. We report the first human NEMO mutations responsible for X-linked EDA-ID found to affect the polyubiquitin binding of NEMO rather than its expression and folding. These experiments demonstrate that the binding of human NEMO to polyubiquitin is essential for NF-?B activation. They also demonstrate that the normal expression and folding of NEMO do not exclude a pathogenic role for NEMO mutations in patients with EDA-ID.

SUBMITTER: Hubeau M

PROVIDER: S-EPMC3251327 | biostudies-literature | 2011 Jul

REPOSITORIES: biostudies-literature

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New mechanism of X-linked anhidrotic ectodermal dysplasia with immunodeficiency: impairment of ubiquitin binding despite normal folding of NEMO protein.

Hubeau Marjorie M Ngadjeua Flora F Puel Anne A Israel Laura L Feinberg Jacqueline J Chrabieh Maya M Belani Kiran K Bodemer Christine C Fabre Isabelle I Plebani Alessandro A Boisson-Dupuis Stéphanie S Picard Capucine C Fischer Alain A Israel Alain A Abel Laurent L Veron Michel M Casanova Jean-Laurent JL Agou Fabrice F Bustamante Jacinta J

Blood 20110526 4

Nuclear factor-κB essential modulator (NEMO), the regulatory subunit of the IκB kinase complex, is a critical component of the NF-κB pathway. Hypomorphic mutations in the X-linked human NEMO gene cause various forms of anhidrotic ectodermal dysplasia with immunodeficiency (EDA-ID). All known X-linked EDA-ID-causing mutations impair NEMO protein expression, folding, or both. We describe here 2 EDA-ID-causing missense mutations that affect the same residue in the CC2-LZ domain (D311N and D311G) th ...[more]

PMID: 21622647

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Project description:BACKGROUND:Store-operated Ca2+ entry (SOCE) through Ca2+ release-activated Ca2+ channels is an essential signaling pathway in many cell types. Ca2+ release-activated Ca2+ channels are formed by ORAI1, ORAI2, and ORAI3 proteins and activated by stromal interaction molecule (STIM) 1 and STIM2. Mutations in the ORAI1 and STIM1 genes that abolish SOCE cause a combined immunodeficiency (CID) syndrome that is accompanied by autoimmunity and nonimmunologic symptoms. OBJECTIVE:We performed molecular and immunologic analysis of patients with CID, anhidrosis, and ectodermal dysplasia of unknown etiology. METHODS:We performed DNA sequencing of the ORAI1 gene, modeling of mutations on ORAI1 crystal structure, analysis of ORAI1 mRNA and protein expression, SOCE measurements, immunologic analysis of peripheral blood lymphocyte populations by using flow cytometry, and histologic and ultrastructural analysis of patient tissues. RESULTS:We identified 3 novel autosomal recessive mutations in ORAI1 in unrelated kindreds with CID, autoimmunity, ectodermal dysplasia with anhidrosis, and muscular dysplasia. The patients were homozygous for p.V181SfsX8, p.L194P, and p.G98R mutations in the ORAI1 gene that suppressed ORAI1 protein expression and SOCE in the patients' lymphocytes and fibroblasts. In addition to impaired T-cell cytokine production, ORAI1 mutations were associated with strongly reduced numbers of invariant natural killer T and regulatory T (Treg) cells and altered composition of γδ T-cell and natural killer cell subsets. CONCLUSION:ORAI1 null mutations are associated with reduced numbers of invariant natural killer T and Treg cells that likely contribute to the patients' immunodeficiency and autoimmunity. ORAI1-deficient patients have dental enamel defects and anhidrosis, representing a new form of anhidrotic ectodermal dysplasia with immunodeficiency that is distinct from previously reported patients with anhidrotic ectodermal dysplasia with immunodeficiency caused by mutations in the nuclear factor κB signaling pathway (IKBKG and NFKBIA).

Project description:BACKGROUND:Autosomal dominant anhidrotic ectodermal dysplasia with immune deficiency (AD EDA-ID) is caused by heterozygous point mutations at or close to serine 32 and serine 36 or N-terminal truncations in I?B? that impair its phosphorylation and degradation and thus activation of the canonical nuclear factor ? light chain enhancer of activated B cells (NF-?B) pathway. The outcome of hematopoietic stem cell transplantation is poor in patients with AD EDA-ID despite achievement of chimerism. Mice heterozygous for the serine 32I mutation in I?B? have impaired noncanonical NF-?B activity and defective lymphorganogenesis. OBJECTIVE:We sought to establish genotype-phenotype correlation in patients with AD EDA-ID. METHODS:A disease severity scoring system was devised. Stability of I?B? mutants was examined in transfected cells. Immunologic, biochemical, and gene expression analyses were performed to evaluate canonical and noncanonical NF-?B signaling in skin-derived fibroblasts. RESULTS:Disease severity was greater in patients with I?B? point mutations than in those with truncation mutations. I?B? point mutants were expressed at significantly higher levels in transfectants compared with truncation mutants. Canonical NF-?B-dependent IL-6 secretion and upregulation of the NF-?B subunit 2/p100 and RELB proto-oncogene, NF-?B subunit (RelB) components of the noncanonical NF-?B pathway were diminished significantly more in patients with point mutations compared with those with truncations. Noncanonical NF-?B-driven generation of the transcriptionally active p100 cleavage product p52 and upregulation of CCL20, intercellular adhesion molecule 1 (ICAM1), and vascular cell adhesion molecule 1 (VCAM1), which are important for lymphorganogenesis, were diminished significantly more in LPS plus ?-lymphotoxin ? receptor-stimulated fibroblasts from patients with point mutations compared with those with truncations. CONCLUSIONS:I?B? point mutants accumulate at higher levels compared with truncation mutants and are associated with more severe disease and greater impairment of canonical and noncanonical NF-?B activity in patients with AD EDA-ID.

Dataset Information

New mechanism of X-linked anhidrotic ectodermal dysplasia with immunodeficiency: impairment of ubiquitin binding despite normal folding of NEMO protein.

Publications

New mechanism of X-linked anhidrotic ectodermal dysplasia with immunodeficiency: impairment of ubiquitin binding despite normal folding of NEMO protein.

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