S100 protein subcellular localization during epidermal differentiation and psoriasis

A role for T cell-derived interleukin 22 in psoriatic skin inflammation

Interleukin (IL)-22 is a T cell-derived cytokine that has been reported recently to induce cutaneous inflammation in an experimental murine model of psoriasis, and to induce in vitro an inflammatory-like phenotype. In the present study, we assessed the presence of IL-22 and the IL-22 receptor 1 (IL-22R1) in skin lesions, skin-derived T cells, as well as IL-22 levels in sera from patients with psoriasis. IL-22R1 and IL-10R2 transcripts are expressed at a similar level in psoriatic and healthy skin. In contrast, IL-22 mRNA expression was up-regulated in psoriatic skin lesions compared to normal skin, whereas IL-22 mRNA levels in peripheral blood mononuclear cells from psoriatic patients and normal subjects were similar. Circulating IL-22 levels were significantly higher in psoriatic patients than in normal subjects. T cells isolated from psoriatic skin produced higher levels of IL-22 in comparison to peripheral T cells isolated from the same patients. IL-10 was expressed at similar levels in skin biopsies and peripheral blood mononuclear cells of psoriatic patients and normal subjects. Finally, we show here that supernatants of lesional psoriatic skin-infiltrating T cells induce an inflammatory response by normal human epidermal keratinocytes, resembling that observed in psoriatic lesions. Taken together, the results reported in this study indicate that IL-22 is a cytokine produced by skin-infiltrating lymphocytes that is potentially involved in initiation and/or maintenance of the pathogenesis of psoriasis.

Epigenetic Control of the S100A6 (Calcyclin) Gene Expression

S100A6 (calcyclin) is a calcium-binding protein of cell-specific expression whose gene is clustered with other S100 genes within the epidermal differentiation complex, on human chromosome 1q21. Many S100 proteins, including S100A6, are expressed in human epidermis at various stages of differentiation and their expression is often deregulated in skin and epithelial cancers. To gain insight into the mechanism of regulation of S100A6 expression, we examined epigenetic marks, that is DNA methylation and histone modifications along the S100A6 gene. Sequencing of bisulfite-modified DNA within a 3,247 bp long genomic region encompassing the promoter/first exon CpG island, the coding sequence of the S100A6 gene and a downstream region showed that it is almost entirely methylation-free in S100A6 expressing human epidermoid carcinoma (Hep-2) cells and lymphocytes and methylated in S100A6-negative embryonic epithelial (HEK293) cells. Chromatin immunoprecipitation revealed profound differences in the level of histone H3 acetylation and methylation and in the in vivo binding of upstream regulatory factor (USF), to the S100A6 gene promoter in S100A6-negative and -positive cells. These data demonstrate that cell-specific S100A6 expression is under control of epigenetic mechanisms.

Human S100A15 splice variants are differentially expressed in inflammatory skin diseases and regulated through Th1 cytokines and calcium

The human calcium-binding protein (hS100A15) was first identified in inflamed hyperplastic psoriatic skin, where the S100A15 gene is transcribed into two mRNA splice variants, hS100A15-S and hS100A15-L. To compare the contribution of the human S100A15 (hS100A15) isoforms in skin inflammation and differentiation, we determined the expression, distribution and regulation of hS100A15-S and hS100A15-L in psoriasis and chronic atopic eczema compared with normal skin. We found that both hS100A15 transcripts were mainly distributed in the epidermis of normal and inflamed skin with hS100A15-L being the predominantly expressed mRNA isoform in both psoriasis and atopic eczema. In cultured keratinocytes, IL-1beta and Th1 cytokines significantly induced hS100A15-L compared with hS100A15-S. In contrast, Th2-derived cytokines had no influence on the expression of either hS100A15 splice variant. Differentiation of human keratinocytes induced by 1.2 mm calcium resulted in the upregulation of both hS100A15 mRNA isoforms. Our data show that both hS100A15 splice variants are differentially regulated and expressed with epidermal differentiation and skin inflammation. Overexpression of hS100A15 in chronic inflammatory skin diseases and regulation by inflammatory cytokines and calcium suggest that hS100A15 is involved in Th1-associated epithelial responses and epidermal maturation in normal and diseased human skin.

High-grade dysplasia in Barrett's esophagus is associated with increased expression of calgranulin A and B

OBJECTIVE

Patients with Barrett's esophagus (BE) are at risk of developing esophageal adenocarcinoma, which is usually preceded by dysplastic changes of the metaplastic mucosa. The aim of this study was to increase the understanding of the development of dysplastic lesions in BE through the identification of genes that are differentially transcribed in these tissue types.

MATERIAL AND METHODS

Paired biopsy samples from non-dysplastic BE, and high-grade dysplasia from a single patient were used for histological evaluation and gene expression profile analysis. In addition, relative mRNA levels of differentially expressed genes were tested to validate the association with the presence or absence of dysplasia by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) (58 biopsy samples containing squamous epithelium, non-dysplastic BE, high-grade dysplasia, or adenocarcinoma from 23 unrelated patients) and immunohistochemistry (9 sets of paired non-dysplastic/high-grade dysplasiac samples from 9 unrelated patients).

RESULTS

Microarray results from high-grade dysplasia showed 866 genes with a>2-fold difference in mRNA levels compared with non-dysplastic BE. Subsequent comparison of mRNA levels of the 22 genes with a>10-fold difference in 76 unrelated biopsies showed that only two of these genes, i.e. calgranulin A (S100A8; p=0.017) and calgranulin B (S100A9; p=0.022), were consistently up-regulated in high-grade dysplasia, as were protein levels for calgranulin A and B.

CONCLUSIONS

This is the first report of an association between the calprotectin complex, which is involved in chemotaxis of neutrophils, and the progression towards high-grade dysplasia in BE. It remains to be established whether differentially expressed proteins in biopsies form BE can be used to facilitate the diagnosis of advanced dysplasia in BE.

Proteomics unveil corticoid-induced S100A11 shuttling in keratinocyte differentiation

Unlike classical protein extraction techniques, proteomic mapping using a selective subcellular extraction kit revealed S100A11 as a new member of the S100 protein family modulated by glucocorticoids in keratinocytes. Glucocorticoids (GC)-induced S100A11 redistribution in the "organelles and membranes" compartment. Microscopic examination indicated that glucocorticoids specifically routed cytoplasmic S100A11 toward perinuclear compartment. Calcium, a key component of skin terminal differentiation, directed S100A11 to the plasma membrane as previously reported. When calcium was added to glucocorticoids, minor change was observed at the proteomic level while confocal microscopy revealed a rapid and dramatic translocation of S100A11 toward plasma membrane. This effect was accompanied by strong nuclear condensation, loss of mitochondrial potential and DNA content, and increased high molecular weight S100A11 immunoreactivity, suggesting corticoids accelerate calcium-induced terminal differentiation. Finally, our results suggest GC-induced S100A11 relocalization could be a key step in both keratinocyte homeostasis and glucocorticoids side effects in human epidermis.

On the role of the epidermal differentiation complex in ichthyosis vulgaris, atopic dermatitis and psoriasis

Undisturbed epidermal differentiation is crucial for an intact skin barrier function. The epidermal differentiation complex (EDC) is a cluster of genes on chromosome 1q21 encoding proteins that fulfil important functions in terminal differentiation in the human epidermis, including filaggrin, loricrin, S100 proteins and others. Recently, evidence emerged that variation within EDC genes plays an important role in the pathogenesis of three common skin disorders, ichthyosis vulgaris, atopic dermatitis (AD) and psoriasis. Two loss-of-function mutations in the filaggrin (FLG) gene, R501X and 2282del4, were identified as causative for ichthyosis vulgaris in 15 affected European families, and the mode of inheritance was found to be semidominant. As ichthyosis vulgaris and AD often occur concomitantly in affected individuals, these two mutations were subsequently investigated in AD patients and found to be strongly associated with the disease. Following this first report, seven replication studies have been performed that all confirm an association of these two mutations with AD (or AD subtypes) in several European cohorts. Additionally, two unique loss-of-function mutations in the FLG gene were identified in Japanese ichthyosis vulgaris families and found to be associated with AD in a Japanese cohort. Thus, the FLG mutations are among the most consistently replicated associations for AD. Additionally, linkage analysis has suggested that variation within the EDC might also predispose for psoriasis but the exact susceptibility variation(s) have not yet been elucidated. Taken together, these findings convincingly demonstrate the important role of barrier dysfunction in various common skin disorders.

Role of Scarf and Its Binding Target Proteins in Epidermal Calcium Homeostasis

The novel Ca2+-binding protein, Scarf (skin calmodulin-related factor) belongs to the calmodulin-like protein family and is expressed in the differentiated layers of the epidermis. To determine the roles of Scarf during stratification, we set out to identify the binding target proteins by affinity chromatography and subsequent analysis by mass spectrometry. Several binding factors, including 14-3-3s, annexins, calreticulin, ERp72 (endoplasmic reticulum protein 72), and nucleolin, were identified, and their interactions with Scarf were corroborated by co-immunoprecipitation and co-localization analyses. To further understand the functions of Scarf in epidermis in vivo, we altered the epidermal Ca2+ gradient by acute barrier disruption. The change in the expression levels of Scarf and its binding target proteins were determined by immunohistochemistry and Western blot analysis. The expression of Scarf, annexins, calreticulin, and ERp72 were up-regulated by Ca2+ gradient disruption, whereas the expression of 14-3-3s and nucleolin was reduced. Because annexins, calreticulin, and ERp72 have been implicated in Ca2+-induced cellular trafficking, including the secretion of lamellar bodies and Ca2+ homeostasis, we propose that the interaction of Scarf with these proteins might be crucial in the process of barrier restoration. On the other hand, down-regulation of 14-3-3s and nucleolin is potentially involved in the process of keratinocyte differentiation and growth inhibition. The calcium-dependent localization and up-regulation of Scarf and its binding target proteins were studied in mouse keratinocytes treated with ionomycin and during the wound-healing process. We found increased expression and nuclear presence of Scarf in the epidermis of the wound edge 4 and 7 days post-wounding, entailing the role of Scarf in barrier restoration. Our results suggest that Scarf plays a critical role as a Ca2+ sensor, potentially regulating the function of its binding target proteins in a Ca2+-dependent manner in the process of restoration of epidermal Ca2+ gradient as well as during epidermal barrier formation.

HaCaT keratinocytes overexpressing the S100 proteins S100A8 and S100A9 show increased NADPH oxidase and NF-kappaB activities

The calcium- and arachidonic acid (AA)-binding proteins S100A8 and S100A9 are involved in nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation in phagocytes. They are specifically expressed in myeloid cells, and are also found in epithelial cells in various (patho)physiological conditions. We have investigated the consequences of S100A8/A9 overexpression in epithelial cell lines on reactive oxygen species (ROS) generation and downstream signaling. Epithelial carcinoma HeLa cells, which exclusively express Nox2, showed dramatically increased activation of NADPH oxidase by phorbol 12-myristate 13-acetate after S100A8/A9 gene transfection. HaCaT keratinocytes overexpressing S100A8/A9 showed enhanced, transient ROS generation in response to the calcium ionophore A23187 compared to mock-transfected cells. Polymerase chain reaction analysis revealed mRNA transcripts for Nox1, Nox2, and Nox5 in HaCaT keratinocytes. Detailed transfection studies confirmed that NADPH oxidase activities in Nox1- and Nox5-transfected HeLa cells were enhanced after S100A8/A9 gene complementation. Furthermore, mutational analysis revealed that AA binding and Thr113 phosphorylation are important for S100A8/A9-enhanced activation of NADPH oxidase. Nuclear factor-kappaB (NF-kappaB) activation and interleukin-8 mRNA levels were increased in S100A8/A9-HaCaT keratinocytes, consistent with the view that NF-kappaB is a redox-sensitive transcription factor. Because they are expressed in epithelia under specific conditions, S100A8 and S100A9 might be involved in skin pathogenesis by modulating aspects of downstream signaling.

Oncostatin M Secreted by Skin Infiltrating T Lymphocytes Is a Potent Keratinocyte Activator Involved in Skin Inflammation

Cutaneous inflammatory diseases such as psoriasis vulgaris and atopic dermatitis are associated with altered keratinocyte function, as well as with a particular cytokine production profile of skin-infiltrating T lymphocytes. In this study we show that normal human epidermal keratinocytes express a functional type II oncostatin-M (OSM) receptor (OSMR) consisting of the gp130 and OSMRbeta components, but not the type I OSMR. The type II OSMR is expressed in skin lesions from both psoriatic patients and those with atopic dermatitis. Its ligand, OSM, induces via the recruitment of the STAT3 and MAP kinase pathways a gene expression profile in primary keratinocytes and in a reconstituted epidermis that is characteristic of proinflammatory and innate immune responses. Moreover, OSM is a potent stimulator of keratinocyte migration in vitro and increases the thickness of a reconstituted epidermis. OSM transcripts are enhanced in both psoriatic and atopic dermatitic skin as compared with healthy skin and mirror the enhanced production of OSM by T cells isolated from diseased lesions. Results from a microarray analysis comparing the gene-modulating effects of OSM with those of 33 different cytokines indicate that OSM is a potent keratinocyte activator similar to TNF-alpha, IL-1, IL-17, and IL-22 and that it acts in synergy with the latter cytokines in the induction of S100A7 and beta-defensin 2 expression, characteristic of psoriatic skin. Taken together, these results demonstrate that OSM and its receptor play an important role in cutaneous inflammatory responses in general and that the specific effects of OSM are associated with distinct inflammatory diseases depending on the cytokine environment.

A Novel Regulator of Telomerase

Recently we reported a differentiation-dependent inhibition of telomerase activity in human epidermis. Consistent with this observation we found that in keratinocyte cultures calcium-induced differentiation correlates with a decline in telomerase activity. To get further support for a role of calcium in the regulation of telomerase and to elucidate the underlying molecular mechanisms we investigated the effect of calcium on telomerase in the human epidermal keratinocyte line HaCaT. Treatment with thapsigargin, which increases intracellular calcium concentrations, inhibited telomerase activity without down-regulating the expression of hTERT (human telomerase reverse transcriptase). This observation together with the fact that increasing calcium reduced telomerase activity in cell-free extracts suggests that calcium directly interacts with the telomerase complex. This interaction could be mediated by the calcium-binding protein S100A8 as indicated by its ability to mimic the inhibitory effect of calcium. S100A8-induced reduction in telomerase activity was abrogated by S100A9. The ratio of both proteins remained constant in cells treated with thapsigargin, but their interactions were altered similarly in intact cells after thapsigargin treatment and in cell-free extracts in response to calcium. We hypothesize that calcium binds to S100A8/S100A9 complexes and alters their composition, thus enabling S100A8 to interact with the telomerase complex and inhibit its activity.

Genomic-scale analysis of psoriatic skin reveals differentially expressed insulin-like growth factor-binding protein-7 after phototherapy

BACKGROUND

Phototherapy is an effective therapy for psoriasis. The molecular mechanisms underlying its efficacy are not yet understood.

OBJECTIVES

To compare the expression profiles of psoriatic epidermis in patients before and after undergoing phototherapy with the purpose of expounding the molecular mechanisms underlying the efficacy of this therapeutic modality.

METHODS

Patients with psoriasis were investigated before and after full courses of phototherapy: three patients completed 3 weeks of heliotherapy at the Dead Sea; three patients received narrowband ultraviolet B (NB-UVB) for a total of 20-27 treatments. Epidermal samples were analysed using oligonucleotide microarrays. Our microarray results led us to explore further and to quantify a specific gene, insulin-like growth factor-binding protein-7 (IGFBP7), using real-time quantitative reverse transcriptase-polymerase chain reaction assays and immunohistochemical protein expression.

RESULTS

We identified 315 genes modulated by phototherapy: the expressions of 248 genes (142 up; 106 down) were changed by Dead Sea treatment, 116 (71 up; 45 down) by NB-UVB and 49 (37 up; 12 down) were modulated regardless of treatment. The differentially changed genes include S100 calcium-binding proteins, dendritic cell markers, tumour necrosis factor-alpha target genes, matrix metalloproteinases and NFkappaB target genes. We also found that IGFBP7 mRNA and protein were significantly underexpressed in psoriatic compared with normal epidermis, and that phototherapy significantly increased their expression.

CONCLUSIONS

IGFBP7 is underexpressed in psoriatic epidermis but is inducible by UVB.

Up-regulation of metastasis-promoting S100A4 (Mts-1) in rheumatoid arthritis: Putative involvement in the pathogenesis of rheumatoid arthritis

OBJECTIVE

To examine the involvement of the metastasis-inducing protein S100A4 (Mts-1) in the pathogenesis of rheumatoid arthritis (RA).

METHODS

Synovial tissue, synovial fluid, and plasma were obtained from RA and osteoarthritis (OA) patients who were undergoing joint surgery. Immunohistochemical and immunofluorescence analyses and enzyme-linked immunosorbent assays were used to determine the locations and concentrations of S100A4. The conformational structure of S100A4 in plasma and synovial fluid was determined after fractionation by size-exclusion chromatography, protein separation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western blot analysis. Expression of various S100 proteins in RA synovium was determined by immunofluorescence and double-staining using specific anti-S100 antibodies.

RESULTS

We found an up-regulation of S100A4 in cells infiltrating RA synovial tissue. Most cell types identified by cell-specific markers (fibroblasts, immune cells, and vascular cells) contributed to the production of S100A4 in RA synovial tissue. The pattern of S100A4 expression differed significantly from that of the proinflammatory proteins S100A9 and S100A12, which were restricted to phagocytes and granulocytes. The up-regulation of S100A4 in RA synovial tissue was consistent with the high concentrations of the protein in RA versus OA plasma (mean 1,100 versus 211 ng/ml) and synovial fluid (mean 1,980 versus 247 ng/ml). Moreover, we found that S100A4 in RA plasma and synovial fluid was present in bioactive multimeric (M-S100A4) conformations, whereas in OA, the majority of extracellular S100A4 was detected as the less active dimeric form. Consistent with our observations in tumor models, extracellular S100A4 stabilized the p53 tumor suppressor in RA synovial fibroblast-like cells and affected the regulation of p53 target genes, including Bcl-2, p21(WAF), and Hdm-2, as well as matrix metalloproteinases.

CONCLUSION

Overexpression of S100A4 in RA synovial tissue and its release as M-S100A4 can influence p53 function and modulate the expression of several genes that are potentially implicated in the disease process. Thus, S100A4 might play an important role in the pathogenesis of RA and might represent a new target for the treatment of RA.

S100A7 (Psoriasin)--mechanism of antibacterial action in wounds

S100A7, also called psoriasin, is a member of the S100 multigene family that is encoded in the epidermal differentiation complex on chromosome 1q21. S100A7 is highly expressed in epidermal hyperproliferative disease; however, its function is not well understood. These studies show high levels of monomer and covalently crosslinked high molecular weight S100A7 in human wound exudate and granulation tissue. Immunohistological studies suggest that this S100A7 is produced by keratinocytes surrounding the wound and is released into the wound exudate. S100A7 is also detected in keratinocyte-conditioned cell culture medium. Studies using recombinant S100A7 indicate that it adheres to and reduces E. coli survival. Mutation of the conserved carboxyl-terminal EF-hand calcium-binding motif or heat denaturation slightly reduces S100A7 antibacterial activity; however, the antibacterial activity is destroyed by protease treatment. Mutation of the zinc-binding motif, located at the C-terminus, reduces antibacterial activity; however, this reduction can be reversed by simultaneous removal of the amino terminus. This indicates the surprising finding that the central region of S100A7, including only amino acids 35-80, is sufficient for full antibacterial activity. These studies also indicate that reduced S100A7 association with bacteria is associated with reduced antibacterial activity.

Elevated serum levels of calcium-binding S100 proteins A8 and A9 reflect disease activity and abnormal differentiation of keratinocytes in psoriasis

BACKGROUND

The expression of calcium-binding S100 molecules organized within the epidermal differentiation complex on chromosome 1q21 is disturbed in hyperproliferative skin diseases such as psoriasis.

OBJECTIVES

We studied whether serum levels of S100 proteins A8 (S100A8) and A9 (S100A9) are elevated in psoriasis, correlated their amounts with disease activity and identified potential cellular sources.

METHODS

Serum obtained from psoriasis patients or from healthy individuals was studied for S100A8 and S100A9 levels by enzyme-linked immunosorbent assay. Data were correlated to disease activity as reflected by the Psoriasis Area and Severity Index (PASI). Cellular sources of S100A8 and S100A9 were identified by in situ hybridization and immunohistochemistry of lesional psoriatic and nonlesional, nonpsoriatic skin.

RESULTS

A significant increase of S100A8/S100A9 serum levels was found in patients with psoriasis compared with healthy controls. Grading the patients into two groups of severity, individuals with a PASI of <15 showed serum levels of 705+/-120 ng mL-1 (mean+/-SEM, n=18), those with a PASI of >or=15 showed levels of 1315+/-150 ng mL-1 (n=32) while controls presented with 365+/-50 ng mL-1. Performing in situ hybridization of lesional psoriatic skin we detected a dramatic induction of both S100A8 and S100A9 mRNA and protein primarily in the suprabasal layers of the epidermis while expression was negligible in nonlesional, nonpsoriatic interfollicular epidermis.

CONCLUSIONS

Our data demonstrate that hyperproliferation and abnormal differentiation of psoriatic skin is associated with a massive upregulation and secretion of S100A8 and S100A9, suggesting not only a prominent role of these molecules during intracellular calcium-dependent signalling but also implying distinct extracellular functions.

A characteristic subset of psoriasis-associated genes is induced by oncostatin-M in reconstituted epidermis

The pathological manifestations of psoriasis are orchestrated by many secreted proteins, but only a handful, tumor necrosis factor-alpha, IFN-gamma and IL-1, have been studied in great detail. Oncostatin-M (OsM) has also been found in psoriatic skin and we hypothesized that it makes a unique and characteristic contribution to the psoriatic processes. To define in-depth the molecular effects of OsM in epidermis, we used high-density DNA microarrays for transcriptional profiling of OsM-treated human skin equivalents. We identified 374 unambiguously OsM-regulated genes, out of 22,000 probed. OsM suppressed the expression of the "classical" epidermal differentiation markers, but strongly and specifically induced the S100A proteins. Cytoskeletal and complement proteins, proteases, and their inhibitors were also induced by OsM. Interestingly, a large set of genes was induced by OsM at early time points but suppressed later; these genes are known regulatory targets of IFN and thus provide a nexus between the OsM and IFN pathways. OsM induces IL-4 and suppresses the T-helper 1-type and IL-1-responsive signals, potentially attenuating the psoriatic pathology. The data suggest that OsM plays a unique role in psoriasis, different from all other, more thoroughly studied cytokines.

S100A7 (Psoriasin): a story of mice and men

S100 proteins are calcium-regulated proteins that regulate fundamental biological processes. S100A7 (psoriasin), functions as a transglutaminase substrate/cornified envelope precursor, signal transduction protein, chemokine, and antibacterial protein in normal epidermis. S100A7 is markedly increased in epidermal hyperproliferative disorders. The murine homolog of S100A7 and S10015 has been identified, providing a valuable tool for studying the regulation and function of this protein in epidermis.

Transcriptional profiling of epidermal differentiation

In epidermal differentiation basal keratinocytes detach from the basement membrane, stop proliferating, and express a new set of structural proteins and enzymes, which results in an impermeable protein/lipid barrier that protects us. To define the transcriptional changes essential for this process, we purified large quantities of basal and suprabasal cells from human epidermis, using the expression of beta4 integrin as the discriminating factor. The expected expression differences in cytoskeletal, cell cycle, and adhesion genes confirmed the effective separation of the cell populations. Using DNA microarray chips, we comprehensively identify the differences in genes expressed in basal and differentiating layers of the epidermis, including the ECM components produced by the basal cells, the proteases in both the basal and suprabasal cells, and the lipid and steroid metabolism enzymes in suprabasal cells responsible for the permeability barrier. We identified the signaling pathways specific for the two populations and found two previously unknown paracrine and one juxtacrine signaling pathway operating between the basal and suprabasal cells. Furthermore, using specific expression signatures, we identified a new set of late differentiation markers and mapped their chromosomal loci, as well as a new set of melanocyte-specific markers. The data represent a quantum jump in understanding the mechanisms of epidermal differentiation.

Epidermal barrier formation and recovery in skin disorders

Skin is at the interface between the complex physiology of the body and the external, often hostile, environment, and the semipermeable epidermal barrier prevents both the escape of moisture and the entry of infectious or toxic substances. Newborns with rare congenital barrier defects underscore the skin's essential role in a terrestrial environment and demonstrate the compensatory responses evoked ex utero to reestablish a barrier. Common inflammatory skin disorders such as atopic dermatitis and psoriasis exhibit decreased barrier function, and recent studies suggest that the complex response of epidermal cells to barrier disruption may aggravate, maintain, or even initiate such conditions. Either aiding barrier reestablishment or dampening the epidermal stress response may improve the treatment of these disorders. This Review discusses the molecular regulation of the epidermal barrier as well as causes and potential treatments for defects of barrier formation and proposes that medical management of barrier disruption may positively affect the course of common skin disorders.

The UVB-induced gene expression profile of human epidermis in vivo is different from that of cultured keratinocytes

In order to obtain a comprehensive picture of the molecular events regulating cutaneous photodamage of intact human epidermis, suction blister roofs obtained after a single dose of in vivo ultraviolet (UV)B exposure were used for microarray profiling. We found a changed expression of 619 genes. Half of the UVB-regulated genes had returned to pre-exposure baseline levels at 72 h, underscoring the transient character of the molecular cutaneous UVB response. Of special interest was our finding that several of the central p53 target genes remained unaffected following UVB exposure in spite of p53 protein accumulation. We next compared the in vivo expression profiles of epidermal sheets to that of cultured human epidermal keratinocytes exposed to UVB in vitro. We found 1931 genes that differed in their expression profiles between the two groups. The expression profile in intact epidemis was geared mainly towards DNA repair, whereas cultured keratinocytes responded predominantly by activating genes associated with cell-cycle arrest and apoptosis. These differences in expression profiles might reflect differences between mature differentiating keratinocytes in the suprabasal epidermal layers versus exponentially proliferating keratinocytes in cell culture. Our findings show that extreme care should be taken when extrapolating from findings based on keratinocyte cultures to changes in intact epidermis.

Purification, crystallization and preliminary X-ray diffraction of human S100A15

Human S100A15 is a novel member of the S100 family of EF-hand calcium-binding proteins and was recently identified in psoriasis, where it is significantly upregulated in lesional skin. The protein is implicated as an effector in calcium-mediated signal transduction pathways. Although its biological function is unclear, the association of the 11.2 kDa S100A15 with psoriasis suggests that it contributes to the pathogenesis of the disease and could provide a molecular target for therapy. To provide insight into the function of S100A15, the protein was crystallized to visualize its structure and to further the understanding of how the many similar calcium-binding mediator proteins in the cell distinguish their cognate target molecules. The S100A15 protein has been cloned, expressed and purified to homogeneity and produced two crystal forms. Crystals of form I are triclinic, with unit-cell parameters a = 33.5, b = 44.3, c = 44.8 angstroms, alpha = 71.2, beta = 68.1, gamma = 67.8 degrees and an estimated two molecules in the asymmetric unit, and diffract to 1.7 angstroms resolution. Crystals of form II are monoclinic, with unit-cell parameters a = 82.1, b = 33.6, c = 52.2 angstroms, beta = 128.2 degrees and an estimated one molecule in the asymmetric unit, and diffract to 2.0 angstroms resolution. This structural analysis of the human S100A15 will further aid in the phylogenic comparison between the other members of the S100 protein family, especially the highly homologous paralog S100A7.

The mouse S100A15 ortholog parallels genomic organization, structure, gene expression, and protein-processing pattern of the human S100A7/A15 subfamily during epidermal maturation

The calcium-binding proteins of the human S100A7/A15 (hS100A7/A15) subfamily are differentially expressed in normal and pathological epidermis. The hS100A7 (psoriasin) and S100A15 reside in a chromosomal cluster of highly similar paralogs. To exploit the power of mouse models for determining functions of gene products, the corresponding S100A7/A15 ortholog was cloned and examined in murine skin. The single mouse S100A15 (mS100A15) gene encodes a protein of 104 amino acids with a predicted molecular weight of 12,870 Da and two EF-hand calcium binding sites. Using gene-specific primers and specific antibodies, expression of mS100A15 in both skin and isolated keratinocytes is confined to differentiating granular and cornified epidermal cells. Immunoblotting of epidermal extracts revealed a series of high molecular weight bands that are also recognized by an antibody for transglutaminase-mediated protein crosslinks. mS100A15 expression is upregulated in cultured keratinocytes induced to differentiate by calcium or phorbol esters. Maximal induction occurs concordantly with expression of late differentiation markers. Induction is enhanced in keratinocytes overexpressing protein kinase Calpha and is dependent on activator protein-1 transcription factors. The regulation, expression pattern and crosslinking of mS100A15 are consistent with the characteristics of the human orthologs, providing a valid surrogate model to study changes in these proteins associated with cutaneous pathologies.

Genetic polymorphism and protein conformational plasticity in the calmodulin superfamily: two ways to promote multifunctionality

Calcium signaling pathways control a variety of cellular events such as gene transcription, protein phosphorylation, nucleotide metabolism, and ion transport. These pathways often involve a large number of calcium-binding proteins collectively known as the calmodulin or EF-hand protein superfamily. Many EF-hand proteins undergo a large conformational change upon binding to Ca(2+) and target proteins. All members of the superfamily share marked sequence homology and similar structural features required to sense Ca(2+). Despite such structural similarities, the functional diversity of EF-hand calcium-binding proteins is extraordinary. Calmodulin itself can bind >300 different proteins, and the many members of the neuronal calcium sensor and S100 protein families collectively recognize a largely different set of target proteins. Recent biochemical and structural studies of many different EF-hand proteins highlight remarkable similarities and variations in conformational responses to the common ligand Ca(2+) and their respective cellular targets. In this review, we examine the essence of molecular recognition activities and the mechanisms by which calmodulin superfamily proteins control a wide variety of Ca(2+) signaling processes.

Calcium Homeostasis in Human Placenta: Role of Calcium‐Handling Proteins

The human placenta is a transitory organ, representing during pregnancy the unique connection between the mother and her fetus. The syncytiotrophoblast represents the specialized unit in the placenta that is directly involved in fetal nutrition, mainly involving essential nutrients, such as lipids, amino acids, and calcium. This ion is of particular interest since it is actively transported by the placenta throughout pregnancy and is associated with many roles during intrauterine life. At term, the human fetus has accumulated about 25-30 g of calcium. This transfer allows adequate fetal growth and development, since calcium is vital for fetal skeleton mineralization and many cellular functions, such as signal transduction, neurotransmitter release, and cellular growth. Thus, there are many proteins involved in calcium homeostasis in the human placenta.

Calcium-binding proteins S100A8 and S100A9 as novel diagnostic markers in human prostate cancer

PURPOSE

S100 proteins comprise a family of calcium-modulated proteins that have recently been associated with epithelial tumors. We examined the expression of two members of this family, S100A8 and S100A9, together with the S100 receptor RAGE (receptor for advanced glycation end products) in human prostate adenocarcinomas and in prostatic intraepithelial neoplasia.

EXPERIMENTAL DESIGN

Tissue specimens of 75 patients with organ-confined prostate cancer of different grades were analyzed by immunohistochemistry for expression of S100A8, S100A9, and RAGE. In addition, in situ hybridization of S100A8 and S100A9 was done for 20 cases. An ELISA was applied to determine serum concentrations of S100A9 in cancer patients compared with healthy controls or to patients with benign prostatic hyperplasia (BPH).

RESULTS

S100A8, S100A9, and RAGE were up-regulated in prostatic intraepithelial neoplasia and preferentially in high-grade adenocarcinomas, whereas benign tissue was negative or showed weak expression of the proteins. There was a high degree of overlap of S100A8 and S100A9 expression patterns and of S100A8 or S100A9 and RAGE, respectively. Frequently, a gradient within the tumor tissue with an increased expression toward the invaded stroma of the prostate was observed. S100A9 serum levels were significantly elevated in cancer patients compared with BPH patients or healthy individuals.

CONCLUSION

Our data suggest that enhanced expression of S100A8, S100A9, and RAGE is an early event in prostate tumorigenesis and may contribute to development and progression or extension of prostate carcinomas. Furthermore, S100A9 in serum may serve as useful marker to discriminate between prostate cancer and BPH.

Psoriasis-like skin disease and arthritis caused by inducible epidermal deletion of Jun proteins

Psoriasis is a frequent, inflammatory disease of skin and joints with considerable morbidity. Here we report that in psoriatic lesions, epidermal keratinocytes have decreased expression of JunB, a gene localized in the psoriasis susceptibility region PSORS6. Likewise, inducible epidermal deletion of JunB and its functional companion c-Jun in adult mice leads (within two weeks) to a phenotype resembling the histological and molecular hallmarks of psoriasis, including arthritic lesions. In contrast to the skin phenotype, the development of arthritic lesions requires T and B cells and signalling through tumour necrosis factor receptor 1 (TNFR1). Prior to the disease onset, two chemotactic proteins (S100A8 and S100A9) previously mapped to the psoriasis susceptibility region PSORS4, are strongly induced in mutant keratinocytes in vivo and in vitro. We propose that the abrogation of JunB/activator protein 1 (AP-1) in keratinocytes triggers chemokine/cytokine expression, which recruits neutrophils and macrophages to the epidermis thereby contributing to the phenotypic changes observed in psoriasis. Thus, these data support the hypothesis that epidermal alterations are sufficient to initiate both skin lesions and arthritis in psoriasis.

Transcript and proteome analysis reveals reduced expression of calgranulins in head and neck squamous cell carcinoma

The calcium-binding proteins of the S100 and the annexin protein families have been implicated in a variety of important physiological functions including membrane remodeling, calcium-related intracellular signaling, cytoskeleton dynamics, tissue homeostasis, and formation of the cornified envelope in differentiating keratinocytes. Deregulated expression of members of these families has been reported in different types of neoplasia and other diseases, but the results were not consistent. Here we have applied a combination of cDNA microarrays, quantitative reverse transcriptase-PCR (qRT-PCR) and surface enhanced laser desorption ionisation-time of flight mass spectrometry (SELDI-TOF MS) to study differential expression of these genes in head and neck squamous cell carcinoma (HNSCC). The calgranulins A and B and annexins 1 and 2 were found to be down-regulated in HNSCC, compared with normal mucosa, at both the mRNA and protein level. Upon validation of the differential gene expression by tissue microarray immunohistochemistry, we detected novel expression patterns of calgranulins A and B both in normal mucosa as well as in HNSCC. In contrast to squamous cancer of skin and other cancers in which the calgranulins were found to be up-regulated, most HNSCC showed reduced and widely deranged staining patterns including heterogeneous nuclear, cytoplasmic and membranous staining, and even enhanced staining in the tumor stroma. These observations suggest that the normal function of the calgranulins A and B in mucosa might be different from that in skin.

The S100A7-c-Jun Activation Domain Binding Protein 1 Pathway Enhances Prosurvival Pathways in Breast Cancer

S100A7 is among the most highly expressed genes in preinvasive breast cancer, is a marker of poor survival when expressed in invasive disease, and promotes breast tumor progression in experimental models. To explore the mechanism of action, we examined the role of S100A7 in cell survival and found that overexpression of S100A7 in MDA-MB-231 cell lines promotes survival under conditions of anchorage-independent growth. This effect is paralleled by increased activity of nuclear factor-κB (3-fold) and phospho-Akt (4-fold), which are known to mediate prosurvival pathways. S100A7 and phospho-Akt are also correlated in breast tumors examined by immunohistochemistry (n = 142; P &lt; 0.0001; r = 0.34). To explore the underlying mechanism, we examined the role of a putative c-Jun activation domain-binding protein 1 (Jab1)–binding domain within S100A7 using a panel of MDA-MB-231 breast cell lines stably transfected with either S100A7 or S100A7 mutated at the Jab1 domain. Structural analysis by three-dimensional protein modeling, immunoprecipitation, and yeast two-hybrid assay and functional analysis using transfected reporter gene and Western blot assays revealed that the in vitro effects of S100A7 on phospho-Akt and the nuclear factor-κB pathway are dependent on the Jab1-binding site and the interaction with Jab1. Enhanced epidermal growth factor receptor signaling was also found to correlate with the increased phospho-Akt. Furthermore, the Jab1-binding domain is also necessary for the enhanced tumorigenicity conferred by S100A7 expression in murine xenograft tumors in vivo. We conclude that the S100A7-Jab1 pathway acts to enhance survival under conditions of cellular stress, such as anoikis, which may promote progression of breast cancer.

Epidermal differentiation: the role of proteases and their inhibitors

Dermatological diseases range from minor cosmetic problems to life-threatening conditions, as seen in some severe disorders of keratinization and cornification. These disorders are commonly due to abnormal epidermal differentiation processes, which result in disturbed barrier function of human skin. Elucidation of the cellular differentiation programs that regulate the formation and homeostasis of the epidermis is therefore of great importance for the understanding and therapy of these disorders. Much of the barrier function of human epidermis against the environment is provided by the cornified cell envelope (CE), which is assembled by transglutaminase (TGase)-mediated cross-linking of several structural proteins and lipids during the terminal stages of normal keratinocyte differentiation. The major constituents of the stratum corneum and the current knowledge on the formation of the stratum corneum will be briefly reviewed here. The discovery of mutations that underlie several human diseases caused by genetic defects in the protein or lipid components of the CE, and recent analyses of mouse mutants with defects in the structural components of the CE, catalyzing enzymes, and lipid processing, have highlighted their essential function in establishing the epidermal barrier. In addition, recent findings have provided evidence that a disturbed protease-antiprotease balance could cause faulty differentiation processes in the epidermis and hair follicle. The importance of regulated proteolysis in epithelia is well demonstrated by the recent identification of the SPINK5 serine proteinase inhibitor as the defective gene in Netherton syndrome, cathepsin C mutations in Papillon-Lefevre syndrome, cathepsin L deficiency infurless mice, targeted ablation of the serine protease Matriptase/MTSP1, targeted ablation of the aspartate protease cathepsin D, and the phenotype of targeted epidermal overexpression of stratum corneum chymotryptic enzyme in mice. Notably, our recent findings on the role of cystatin M/E and legumain as a functional dyad in skin and hair follicle cornification, a paradigm example of the regulatory functions exerted by epidermal proteases, will be discussed.

The cornified envelope: a model of cell death in the skin

The epidermis functions as a barrier against the environment by means of several layers of terminally differentiated, dead keratinocytes - the cornified layer, which forms the endpoint of epidermal differentiation and death. The cornified envelope replaces the plasma membrane of differentiating keratinocytes and consists of keratins that are enclosed within an insoluble amalgam of proteins, which are crosslinked by transglutaminases and surrounded by a lipid envelope. New insights into the molecular mechanisms and the physiological endpoints of cornification are increasing our understanding of the pathological defects of this unique form of programmed cell death, which is associated with barrier malfunctions and ichthyosis.

IL-22 inhibits epidermal differentiation and induces proinflammatory gene expression and migration of human keratinocytes

IL-22 belongs to a family of cytokines structurally related to IL-10, including IL-19, IL-20, IL-24, and IL-26. In contrast to IL-10, IL-22 has proinflammatory activities. IL-22 signals through a class II cytokine receptor composed of an IL-22-binding chain, IL-22RA1, and the IL-10RB subunit, which is shared with the IL-10R. In the present study, we show that short-term cultured human epidermal keratinocytes express a functional IL-22R but no IL-10R. Accordingly, IL-22 but not IL-10 induces STAT3 activation in keratinocytes. Using a cDNA array screening approach, real-time RT-PCR, and Western blot analysis, we demonstrate that IL-22 up-regulates, in a dose-dependent manner, the expression of S100A7, S100A8, S100A9, a group of proinflammatory molecules belonging to the S100 family of calcium-binding proteins, as well as the matrix metalloproteinase 3, the platelet-derived growth factor A, and the CXCL5 chemokine. In addition, IL-22 induces keratinocyte migration in an in vitro injury model and down-regulates the expression of at least seven genes associated with keratinocyte differentiation. Finally, we show that IL-22 strongly induces hyperplasia of reconstituted human epidermis. Taken together, these results suggest that IL-22 plays an important role in skin inflammatory processes and wound healing.

Expression patterns of S100A7 (psoriasin) and S100A9 (calgranulin-B) in keratinocyte differentiation

S100 proteins are involved in many biological processes. S100A7 and S100A9 have been shown to be markedly upregulated both in ductal carcinoma in situ of the breast and in psoriasis. We have examined the relationship between keratinocyte differentiation and the expression of the two proteins. Using Western blot analysis and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), both S100A7 and S100A9 were shown to be induced in normal primary keratinocytes (HEKn), when differentiation was promoted by high extracellular calcium, loss of contact with extracellular matrix and confluent conditions, as previously reported for S100A7 in mammary epithelial cells. Differentiation was confirmed by using RT-PCR for the differentiation marker keratin-1. Using immunohistochemistry with monoclonal antibodies, we compared the expression of the two proteins in a spectrum of conditions of dysregulated keratinocyte differentiation. We found a strikingly similar distribution of the proteins. Their expression correlated with the degree of keratinocyte differentiation. They were both absent in undifferentiated basalioma and strongly expressed in carcinoma in situ, as well as in keratoacanthoma and differentiated squamous cell carcinoma. In normal epithelium, they were expressed in the superficial, differentiated region of the epithelium rather than in the basal region. These findings support the hypothesis that these two S100 proteins are involved in keratinocyte differentiation.

SAGE profiling of UV-induced mouse skin squamous cell carcinomas, comparison with acute UV irradiation effects

Ultraviolet (UV) irradiation is the primary environmental insult responsible for the development of most common skin cancers. To better understand the multiple molecular events that contribute to the development of UV-induced skin cancer, in a first study, serial analysis of gene expression (SAGE) was used to compare the global gene expression profiles of normal SKH-1 mice epidermis with that of UV-induced squamous cell carcinomas (SCCs) from SKH-1 mice. More than 200 genes were found to be differentially expressed in SCCs compared to normal skin (P < 0.0005 level of significance). As expected, genes related to epidermal proliferation and differentiation were deregulated in SCCs relative to normal skin. However, various novel genes, not previously associated with skin carcinogenesis, were also identified as deregulated in SCCs. Northern blot analyses on various selected genes validated the SAGE findings: caspase-14 (reduced 8.5-fold in SCCs); cathepsins D and S (reduced 3-fold and increased 11.3-fold, respectively, in SCCs); decorin, glutathione S-transferase omega-1, hypoxia-inducible factor 1 alpha, insulin-like growth factor binding protein-7, and matrix metalloproteinase-13 (increased 18-, 12-, 12-, 18.3-, and 11-folds, respectively, in SCCs). Chemokine (C-C motif), ligand 27 (CCL27), which was found downregulated 12.7-fold in SCCs by SAGE, was also observed to be strongly downregulated 6-24 h after a single and multiple UV treatments. In a second independent study we compared the expression profile of UV-irradiated versus sham-treated SKH-1 epidermis. Interestingly, numerous genes determined to be deregulated 8 h after a single UV dose were also deregulated in SCCs. For instance, genes whose expression was upregulated both after acute UV-treated skin and SCCs included keratins 6 and 16, small proline-rich proteins, and S100 calcium binding protein A9. Studies like those described here do not only provide insights into genes and pathways involved in skin carcinogenesis but also allow us to identify early UV irradiation deregulated surrogate biomarkers of potential use in chemoprevention studies.

Protein Kinase Cα-Mediated Chemotaxis of Neutrophils Requires NF-κB Activity but Is Independent of TNFα Signaling in Mouse Skin In Vivo

Protein kinase C (PKC) isoforms are major regulators of cutaneous homeostasis and mediate inflammation in response to 12-O-tetradecanoylphorbol-13-acetate (TPA). We have previously reported that transgenic mice overexpressing PKCalpha in the skin exhibit severe intraepidermal neutrophilic inflammation and keratinocyte apoptosis when treated topically with TPA. Activation of PKCalpha increases the production of TNFalpha and the transcription of chemotactic factors (MIP-2, KC, S100A8/A9), vascular endothelial growth factor, and GM-CSF in K5-PKCalpha keratinocytes. In response to PKCalpha activation, NF-kappaB translocates to the nucleus and this is associated with IkappaB phosphorylation and degradation. Preventing IkappaB degradation reduces both the expression of inflammation-associated genes and chemoattractant release. To determine whether TNFalpha mediated NF-kappaB translocation and subsequent expression of proinflammatory factors, K5-PKCalpha mice were treated systemically with a dimeric soluble form of p75 TNFR (etanercept) or crossed with mice deficient for both TNFR isoforms, and keratinocytes were cultured in the presence of TNFalpha-neutralizing Abs. The in vivo treatment and TNFR deficiency did not prevent inflammation, and the in vitro treatment did not prevent NF-kappaB nuclear translocation after TPA. Together these results implicate PKCalpha as a regulator of a subset of cutaneous cytokines and chemokines responsible for intraepidermal inflammation independent of TNFalpha. PKCalpha inhibition may have therapeutic benefit in some human inflammatory skin disorders.

S100 proteins in mouse and man: from evolution to function and pathology (including an update of the nomenclature)

The S100 protein family is the largest subgroup within the superfamily of proteins carrying the Ca2+-binding EF-hand motif. Despite their small molecular size and their conserved functional domain of two distinct EF-hands, S100 proteins developed a plethora of tissue-specific intra- and extracellular functions. Accordingly, various diseases such as cardiomyopathies, neurodegenerative and inflammatory disorders, and cancer are associated with altered S100 protein levels. Here, we review the different S100 protein functions and related diseases from an evolutionary point of view. We analyzed the structural variations, which are the basis of functional diversification, as well as the genomic organization of the S100 family in human and compared it with the S100 repertoires in mouse and rat. S100 genes and proteins are highly conserved between the different mammalian species. Moreover, we identified evolutionary related subgroups of S100 proteins within the three species, which share functional similarity and form subclusters on the genomic level. The available S100-specific mouse models are summarized and the consequences of our results are discussed with regard to the use of genetically engineered mice as human disease models. An update of the S100 nomenclature is included, because some of the recently identified S100 genes and pseudogenes had to be renamed.

Dysregulated expression of S100A11 (calgizzarin) in prostate cancer and precursor lesions

S100A11 is a calcium-binding protein implicated in a variety of biologic functions such as proliferation and differentiation as well as in cancer. To further understand its role in prostate cancer, we performed immunohistochemistry on a series of benign, premalignant, malignant and metastatic prostate cancer tissues in addition to prostate cancer derived cell lines. In benign prostatic hyperplasia (n=30) and benign tissue adjacent to adenocarcinoma (n=54), S100A11 expression was significantly higher in basal cells compared with in luminal cells (P <0.001). A complete absence of staining was seen in 4/14 (29%) lesions of prostatic intraepithelial neoplasia. The majority of tumors, 39/54 (72%), showed significant overexpression of S100A11 compared with the luminal cells of adjacent benign epithelium (P <0.001), whereas 14/54 (26%) of cases showed an absence of staining. All 4 cases of metastatic cancer showed intense to moderate expression. There was a significant association between S100A11 expression and high pathologic stage (pT3b) versus lower stages (pT2a-3a; P=0.027), but not with tumor Gleason score or prostate-specific antigen levels. LNCaP, PC3, and Du145 cancer cell lines showed intense to moderate S100A11 expression by immunochemistry, which was confirmed by Western blotting and reverse-transcription polymerase chain reaction. A survey of 14 other types of normal tissues arranged on a tissue microarray showed that S100A11 is widely expressed amongst epithelia. Our finding of frequent dysregulated expression of S100A11 in cancer and precursor lesions, together with an association with high histological stage, suggests that S100A11 may be involved in prostate cancer development and progression.

Gene expression profiling of porokeratosis demonstrates similarities with psoriasis

BACKGROUND

Porokeratosis (PK) is a clinically heterogeneous entity associated with sharply demarcated, annular, or serpiginous lesions with a hyperkeratotic ridge. This disorder is associated with aberrant keratinocyte differentiation that histologically manifests as a stack of parakeratin termed the cornoid lamella; this structure represents the peripheral hyperkeratotic ridge of clinical lesions. Histologically, the keratinocytes forming the cornoid lamella demonstrate an altered differentiation program. However, the molecular basis of PK remains incompletely understood.

METHODS

As a first step in characterizing PK at the molecular level, gene expression profiling was performed on a cornoid lamella isolated from a large, Mibelli-type porokeratotic lesion. As a control, gene expression profiling of peripheral uninvolved epidermis was also performed. The gene expression profile of cornoid lamellar keratinocytes was compared with similar profiles obtained from a psoriatic plaque and cutaneous squamous cell carcinoma.

RESULTS

Our study demonstrates a striking similarity between the gene expression profiles of PK and psoriasis. In addition, novel markers of the porokeratotic keratinocytes were identified, including keratin 16, S-100 A8 and A9, and connexin 26.

CONCLUSIONS

This study supports the hypothesis that PK is a disorder of hyperproliferative keratinocytes exhibiting similarity at the molecular level to psoriasis. Consequently, some therapeutic modalities efficacious for psoriasis may be of benefit in PK.

Changes in expression level of genes as a function of time of day in the liver of rats

Daily, rhythmic variation in various biochemical, physiological, and behavioral events is a fundamental property of biological organization. Here, we report analysis of relative levels of gene expression in the liver of 16 Fischer 344 rats as a function of time of day. Expression levels were determined for 3906 genes using high-density oligonucleotide microarrays. Of the 3906 genes, 1171 (30%) were clearly expressed while 2735 (70%) were not expressed or the expression was too low to distinguish from background levels. The maximum estimated changes observed for most genes (1029, 88%) were less than 1.5-fold. Analysis of variance and the Kruskal-Wallis tests were used to identify 67 genes whose expression was significantly altered as a function of time of day. These significantly altered genes were classified according to their functions and fall into key cellular pathways including drug metabolism, ion transport, signal transduction, DNA binding and regulation of transcription, and immune response.

Probing the S100 protein family through genomic and functional analysis

The EF-hand superfamily of calcium binding proteins includes the S100, calcium binding protein, and troponin subfamilies. This study represents a genome, structure, and expression analysis of the S100 protein family, in mouse, human, and rat. We confirm the high level of conservation between mammalian sequences but show that four members, including S100A12, are present only in the human genome. We describe three new members of the S100 family in the three species and their locations within the S100 genomic clusters and propose a revised nomenclature and phylogenetic relationship between members of the EF-hand superfamily. Two of the three new genes were induced in bone-marrow-derived macrophages activated with bacterial lipopolysaccharide, suggesting a role in inflammation. Normal human and murine tissue distribution profiles indicate that some members of the family are expressed in a specific manner, whereas others are more ubiquitous. Structure-function analysis of the chemotactic properties of murine S100A8 and human S100A12, particularly within the active hinge domain, suggests that the human protein is the functional homolog of the murine protein. Strong similarities between the promoter regions of human S100A12 and murine S100A8 support this possibility. This study provides insights into the possible processes of evolution of the EF-hand protein superfamily. Evolution of the S100 proteins appears to have occurred in a modular fashion, also seen in other protein families such as the C2H2-type zinc-finger family.

S100 Proteins in the Epidermis

The S100 proteins comprise a family of 21 low molecular weight (9-13 kDa) proteins that are characterized by the presence of two calcium-binding EF-hand motifs. Fourteen S100 protein genes are located within the epidermal differentiation complex on human chromosome 1q21 and 13 S100 proteins (S100A2, S100A3, S100A4, S100A6, S100A7, S100A8, S100A9, S100A10, S100A11, S100A12, S100A15, S100B, and S100P) are expressed in normal and/or diseased epidermis. S100 proteins exist in cells as anti-parallel hetero- and homodimers and upon calcium binding interact with target proteins to regulate cell function. S100 proteins are of interest as mediators of calcium-associated signal transduction and undergo changes in subcellular distribution in response to extracellular stimuli. They also function as chemotactic agents and may play a role in the pathogenesis of epidermal disease, as selected S100 proteins are markedly overexpressed in psoriasis, wound healing, skin cancer, inflammation, cellular stress, and other epidermal states.

Transgenic mouse models support HCR as an effector gene in the PSORS1 locus

Genetic susceptibility for psoriasis is regulated to the greatest extent by the PSORS1 locus. Three psoriasis-associated susceptibility alleles have been identified within it, namely, HLACw6, HCR*WWCC and CDSN*5, but strong linkage disequilibrium between them has made it difficult to distinguish their individual genetic effects, and animal models to study their effects are not known. To study the function of HCR, we engineered transgenic mice with either a non-risk allele of HCR or the HCR*WWCC risk allele under the control of the cytokeratin-14 promoter. These choices were motivated by the apparently dominant effect of PSORS1 on psoriasis susceptibility and the physiological expression of HCR in basal keratinocytes. Transgenic mice appeared phenotypically normal and histologically their skin was indistinguishable from wild-type mice. Expression studies using Affymetrix arrays suggested that the HCR risk allele has specific functional consequences relevant to the pathogenesis of psoriasis. Comparison of gene expression changes between non-risk and risk allele mice revealed similarities to previous observations in human psoriatic skin, including upregulation of cytokeratins 6, 16 and 17 in risk allele mice. We also observed changes in the expression of genes associated with terminal differentiation and formation of the cornified cell envelope. Our results support the concept that HCR may constitute an essential gene in the PSORS1 locus. These observations are also compatible with a model that a susceptibility gene for psoriasis induces changes that are contributory but not sufficient by itself to produce the clinical phenotype.

S100A7 and the progression of breast cancer

The S100 gene family comprises more than 20 members whose protein sequences encompass at least one EF-hand Ca²⁺ binding motif. The expression of individual family members is not ubiquitous for all tissues and there appears to be an element of tissue-specific expression. Molecular analysis of breast tumors has revealed that several S100s, including S100A2, S100A4 and S100A7, exhibit altered expression levels during breast tumorigenesis and/or progression. Subsequent studies have started to describe a functional role for these S100 proteins as well as their mechanism of action and the biochemical pathways they modify. The present review outlines what is known about S100A7 in breast cancer and summarizes the need to better understand the importance of this protein in breast cancer.

Microtubule-Dependent Redistribution of a Cytoplasmic Cornified Envelope Precursor

Several cytoplasmic cornified envelope precursors have been described. Nevertheless, the mechanism whereby these proteins are positioned at the site of crosslink formation is not known. In this study, we examine the intracellular distribution of the cornified envelope precursor S100A11 (S100C) and the effects of the physiologic differentiating agent calcium on this distribution. S100A11 is localized in the cytoplasm of resting cultured human keratinocytes. Treatment with calcium causes S100A11 to relocate to the cell periphery. Immunoprecipitation studies reveal that S100A11 associates with microtubules, and inhibitor studies indicate that functional micro-tubules are required for S100A11 peripheral redistribution. Parallel studies indicate that S100A11 is not present in the Golgi or endoplasmic reticulum (ER), suggesting that S100A11 is not moved to the cell periphery via the classical Golgi/ER export pathway. Further evidence that the Golgi/ER is not involved is provided by the observation that the Golgi/ER disruptor brefeldin A does not alter movement. These results suggest that redistribution along microtubules is a mechanism whereby S100A11 is positioned at the cell periphery in preparation for transglutaminase-dependent crosslinking. Staining of epidermal tissue sections from uninvolved and psoriatic epidermis reveals strong staining at the cell periphery in the majority of suprabasal cells, confirming a peripheral distribution of S100A11 in vivo.

Modulation of Gene Expression Induced in Human Epidermis by Environmental Stress In Vivo

Environmental insults on the skin induce biologic responses through the modulation of expression of genes implicated in different cell functions. The aim of this study was to investigate the modulation of gene expression profile in human epidermis in vivo following different stresses. We determined the modulations of gene expression using cDNA macroarray in the epidermis of 28 healthy volunteers, following mild and physiologic insults, including: (1), tape stripping; (2) application of 10% sodium dodecyl sulfate; (3) daily application of vaseline; and (4), exposure to one minimal erythema dose of solar-simulated radiation. The analysis was performed 19 h after treatment. The reverse transcription-polymerase chain reaction method was used to confirm our results. We showed that: (1) the intensity of gene modulation was variable among the volunteers following the same skin stress; (2) the nature and intensity of skin treatment modified the pattern of gene expression; and (3) some genes were modulated only by specific stress, some others are modulated irrespective of the stress. GADD45, Bax, SAS, and granulocyte chemotactic protein-2 were overexpressed exclusively following solar-simulated radiation, whereas tape stripping led to the modulation of genes implicated in different pathways (inflammation, cell proliferation, cell differentiation, detoxification, etc.). Concerning common gene modulation, MRP8 and MRP14 were highly upregulated in human skin epidermis after solar-simulated radiation, vaseline application or tape stripping, and to a lower extent after sodium dodecyl sulfate. Such upregulation of the MRP 8/14 genes was confirmed at the protein level in an ex-vivo skin culture model following tape stripping and solar-simulated radiation. Together, these results suggest that MRP8 and MRP14 may be general, yet highly sensitive, markers for a great variety of skin stresses and that they are implicated in several epidermal repair pathways.

The novel murine Ca2+-binding protein, Scarf, is differentially expressed during epidermal differentiation

Calcium (Ca2+) signaling-dependent systems, such as the epidermal differentiation process, must effectively respond to variations in Ca2+ concentration. Members of the Ca2+-binding proteins play a central function in the transduction of Ca2+ signals, exerting their roles through a Ca2+-dependent interaction with their target proteins, spatially and temporally. By performing a suppression subtractive hybridization screen we identified a novel mouse gene, Scarf (skin calmodulin-related factor), which has homology to calmodulin (CaM)-like Ca2+-binding protein genes and is exclusively expressed in differentiating keratinocytes in the epidermis. The Scarf open reading frame encodes a 148-amino acid protein that contains four conserved EF-hand motifs (predicted to be Ca2+-binding domains) and has homology to mouse CaM, human CaM-like protein, hClp, and human CaM-like skin protein, hClsp. The functionality of Scarf EF-hand domains was assayed with a radioactive Ca2+-binding method. By Southern blot and computational genome sequence analysis, a highly related gene, Scarf2, was found 15 kb downstream of Scarf on mouse chromosome 13. The functional Scarf Ca2+-binding domains suggest a role in the regulation of epidermal differentiation through the control of Ca2+-mediated signaling.