Long-Range Enhancer Associated with Chromatin Looping Allows AP-1 Regulation of the Peptidylarginine Deiminase 3 Gene in Differentiated Keratinocyte

Transcription control at a distance is a critical mechanism, particularly for contiguous genes. The peptidylarginine deiminases (PADs) catalyse the conversion of protein-bound arginine into citrulline (deimination), a critical reaction in the pathophysiology of multiple sclerosis, Alzheimer's disease and rheumatoid arthritis, and in the metabolism of the major epidermal barrier protein filaggrin, a strong predisposing factor for atopic dermatitis. PADs are encoded by 5 clustered PADI genes (1p35-6). Unclear are the mechanisms controlling the expression of the gene PADI3 encoding the PAD3 isoform, a strong candidate for the deimination of filaggrin in the terminally differentiating epidermal keratinocyte. We describe the first PAD Intergenic Enhancer (PIE), an evolutionary conserved non coding segment located 86-kb from the PADI3 promoter. PIE is a strong enhancer of the PADI3 promoter in Ca2+-differentiated epidermal keratinocytes, and requires bound AP-1 factors, namely c-Jun and c-Fos. As compared to proliferative keratinocytes, calcium stimulation specifically associates with increased local DNase I hypersensitivity around PIE, and increased physical proximity of PIE and PADI3 as assessed by Chromosome Conformation Capture. The specific AP-1 inhibitor nordihydroguaiaretic acid suppresses the calcium-induced increase of PADI3 mRNA levels in keratinocytes. Our findings pave the way to the exploration of deimination control during tumorigenesis and wound healing, two conditions for which AP-1 factors are critical, and disclose that long-range transcription control has a role in the regulation of the gene PADI3. Since invalidation of distant regulators causes a variety of human diseases, PIE results to be a plausible candidate in association studies on deimination-related disorders or atopic disease

Deimination, Intermediate Filaments and Associated Proteins

International audienceDeimination (or citrullination) is a post-translational modification catalyzed by a calcium-dependent enzyme family of five peptidylarginine deiminases (PADs). Deimination is involved in physiological processes (cell differentiation, embryogenesis, innate and adaptive immunity, etc.) and in autoimmune diseases (rheumatoid arthritis, multiple sclerosis and lupus), cancers and neurodegenerative diseases. Intermediate filaments (IF) and associated proteins (IFAP) are major substrates of PADs. Here, we focus on the effects of deimination on the polymerization and solubility properties of IF proteins and on the proteolysis and cross-linking of IFAP, to finally expose some features of interest and some limitations of citrullinomes

Hydrophobic cluster analysis and secondary structure predictions revealed that major and minor structural subunits of K88-related adhesins of Escherichia coli share a common overall fold and differ structurally from other fimbrial subunits

AbstractThe structural relatedness of K88-related major and minor subunits was deduced from their sequences by hydrophobic cluster analysis (HCA) and secondary structure predictions produced by the profile neural network prediction program (PHD) on multiple sequence alignments. Although the weak residue identity between major and minor subunits is evidence of a high evolutionary distance, an overall structural similarity was observed. In addition, clear amphipathic conformations were conserved in predicted secondary structure. On the basis of this predicted structural similarity, a schematic 2D model of ClpG subunit was developed

La désimination ou citrullination

La désimination, aussi nommée citrullination, est une modification post-traductionnelle aux multiples facettes. Elle est impliquée dans de nombreux processus cellulaires physiologiques comme la régulation génique, le développement embryonnaire ou encore la différenciation terminale, mais aussi dans divers mécanismes physiopathologiques liés à des maladies humaines graves, comme la sclérose en plaques ou la polyarthrite rhumatoïde. La désimination, conversion enzymatique dépendante du calcium de peptidyl-arginines en peptidyl-citrullines, entraîne une perte de charge des protéines-substrats, ce qui a des conséquences majeures sur leur conformation, leur stabilité, leurs interactions et donc leurs fonctions. Chez l’homme, il existe cinq isotypes de peptidyl-arginine désiminases (1-4 et 6) présentant une expression tissulaire variable. Ces isotypes sont très homologues et étroitement régulés aux niveaux transcriptionnel et post-transcriptionnel, comme, probablement, par auto-désimination

Revisiting the Roles of Filaggrin in Atopic Dermatitis

The discovery in 2006 that loss-of-function mutations in the filaggrin gene (FLG) cause ichthyosis vulgaris and can predispose to atopic dermatitis (AD) galvanized the dermatology research community and shed new light on a skin protein that was first identified in 1981. However, although outstanding work has uncovered several key functions of filaggrin in epidermal homeostasis, a comprehensive understanding of how filaggrin deficiency contributes to AD is still incomplete, including details of the upstream factors that lead to the reduced amounts of filaggrin, regardless of genotype. In this review, we re-evaluate data focusing on the roles of filaggrin in the epidermis, as well as in AD. Filaggrin is important for alignment of keratin intermediate filaments, control of keratinocyte shape, and maintenance of epidermal texture via production of water-retaining molecules. Moreover, filaggrin deficiency leads to cellular abnormalities in keratinocytes and induces subtle epidermal barrier impairment that is sufficient enough to facilitate the ingress of certain exogenous molecules into the epidermis. However, although FLG null mutations regulate skin moisture in non-lesional AD skin, filaggrin deficiency per se does not lead to the neutralization of skin surface pH or to excessive transepidermal water loss in atopic skin. Separating facts from chaff regarding the functions of filaggrin in the epidermis is necessary for the design efficacious therapies to treat dry and atopic skin

cDNA cloning, gene organization and expression analysis of human peptidylarginine deiminase type I.

Peptidylarginine deiminases (PADs) catalyse a post-translational modification of proteins through the conversion of arginine residues into citrullines. The existence of four isoforms of PAD (types I, II, III and IV) encoded by four different genes, which are distinct in their substrate specificities and tissue-specific expression, was reported in rodents. In the present study, starting from epidermis polyadenylated RNA, we cloned by reverse transcriptase-PCR a full-length cDNA encoding human PAD type I. The cDNA was 2711 bp in length and encoded a 663-amino-acid sequence. The predicted protein shares 75% identity with the rat PAD type I sequence, but displays only 50-57% identity with the three other known human isoforms. We have described the organization of the human PAD type I gene on chromosome 1p36. A recombinant PAD type I was produced in Escherichia coli and shown to be enzymically active. Human PAD type I mRNAs were detected by reverse transcriptase-PCR not only in the epidermis, but also in various organs, including prostate, testis, placenta, spleen and thymus. In human epidermis extracts analysed by Western blotting, PAD type I was detected as a 70 kDa polypeptide, in agreement with its predicted molecular mass. As shown by immunohistochemistry, the enzyme was expressed in all the living layers of human epidermis, with the labelling being increased in the granular layer. This is the first description of the human PAD type I gene and the first demonstration of its expression in epidermis

Corrigendum to: Defects of corneocyte structural proteins and epidermal barrier in atopic dermatitis

International audienceThe main function of the epidermis is to establish a vital multifunctional barrier between the body and its external environment. A defective epidermal barrier is one of the key features of atopic dermatitis (AD), a chronic and relapsing inflammatory skin disorder that affects up to 20% of children and 2-3% of adults and often precedes the development of allergic rhinitis and asthma. This review summarizes recent discoveries on the origin of the skin barrier alterations in AD at the structural protein level, including hereditary and acquired components. The consequences of the epidermal barrier alteration on our current understanding of the pathogenesis of AD, and its possible implications on the treatment of patients, are discussed here