S100 Proteins in the Epidermis

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.

The effects of IL-20 subfamily cytokines on reconstituted human epidermis suggest potential roles in cutaneous innate defense and pathogenic adaptive immunity in psoriasis

IL-19, IL-20, IL-22, IL-24, and IL-26 are members of the IL-10 family of cytokines that have been shown to be up-regulated in psoriatic skin. Contrary to IL-10, these cytokines signal using receptor complex R1 subunits that are preferentially expressed on cells of epithelial origin; thus, we henceforth refer to them as the IL-20 subfamily cytokines. In this study, we show that primary human keratinocytes (KCs) express receptors for these cytokines and that IL-19, IL-20, IL-22, and IL-24 induce acanthosis in reconstituted human epidermis (RHE) in a dose-dependent manner. These cytokines also induce expression of the psoriasis-associated protein S100A7 and keratin 16 in RHE and cause persistent activation of Stat3 with nuclear localization. IL-22 had the most pronounced effects on KC proliferation and on the differentiation of KCs in RHE, inducing a decrease in the granular cell layer (hypogranulosis). Furthermore, gene expression analysis performed on cultured RHE treated with these cytokines showed that IL-19, IL-20, IL-22, and IL-24 regulate many of these same genes to variable degrees, inducing a gene expression profile consistent with inflammatory responses, wound healing re-epithelialization, and altered differentiation. Many of these genes have also been found to be up-regulated in psoriatic skin, including several chemokines, beta-defensins, S100 family proteins, and kallikreins. These results confirm that IL-20 subfamily cytokines are important regulators of epidermal KC biology with potentially pivotal roles in the immunopathology of psoriasis.

Crystal structure study on human S100A13 at 2.0 A resolution

The S100 protein family is the largest group of calcium-binding protein families, which consists of at least 25 members. S100A13, which is widely expressed in a variety of tissues, is a unique member of the S100 protein family. Previous reports showed that S100A13 might be involved in the stress-induced release of some signal peptide-less proteins (such as FGF-1 and IL-1alpha) and also associated with inflammatory functions. It was also reported that S100A13 is a new angiogenesis marker. Here we report the crystal structure of the Ca(2+)-bound form of S100A13 at 2.0 A resolution. S100A13 is a homodimer with four EF-hand motifs in an asymmetric unit, displaying a folding pattern similar to other S100 members. However, S100A13 has the unique structural feature with all alpha-helices being amphiphilic, which was not found in other members of S100s. We propose that this characteristic structure of S100A13 might be related to its ability to mediate the release of FGF-1 and IL-1alpha.

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.

Pathologies involving the S100 proteins and RAGE

The S100 proteins are exclusively expressed in vertebrates and are the largest subgroup within the superfamily of EF-hand Ca2(+)-binding proteins Generally, S100 proteins are organized as tight homodimers (some as heterodimers). Each subunit is composed of a C-terminal, 'canonical' EF-hand, common to all EF-hand proteins, and a N-terminal, 'pseudo' EF-hand, characteristic of S100 proteins. Upon Ca2(+)-binding, the C-terminal EF-hand undergoes a large conformational change resulting in the exposure of a hydrophobic surface responsible for target binding A unique feature of this protein family is that some members are secreted from cells upon stimulation, exerting cytokine- and chemokine-like extracellular activities via the Receptor for Advanced Glycation Endproducts, RAGE. Recently, larger assemblies of some S100 proteins (hexamers, tetramers, octamers) have been also observed and are suggested to be the active extracellular species required for receptor binding and activation through receptor multimerization Most S100 genes are located in a gene cluster on human chromosome 1q21, a region frequently rearranged in human cancer The functional diversification of S100 proteins is achieved by their specific cell- and tissue-expression patterns, structural variations, different metal ion binding properties (Ca2+, Zn2+ and Cu2+) as well as their ability to form homo-, hetero- and oligomeric assemblies Here, we review the most recent developments focussing on the biological functions of the S100 proteins and we discuss the presently available S100-specific mouse models and their possible use as human disease models In addition, the S100-RAGE interaction and the activation of various cellular pathways will be discussed. Finally, the close association of S100 proteins with cardiomyopathy, cancer, inflammation and brain diseases is summarized as well as their use in diagnosis and their potential as drug targets to improve therapies in the future.

Identification of poly(ADP-ribose)polymerase-1 and Ku70/Ku80 as transcriptional regulators of S100A9 gene expression

Background

S100 proteins, a multigenic family of non-ubiquitous cytoplasmic Ca²⁺-binding proteins, have been linked to human pathologies in recent years. Dysregulated expression of S100 proteins, including S100A9, has been reported in the epidermis as a response to stress and in association with neoplastic disorders. Recently, we characterized a regulatory element within the S100A9 promotor, referred to as MRE that drives the S100A9 gene expression in a cell type-specific, activation- and differentiation-dependent manner (Kerkhoff et al. (2002) J. Biol. Chem. 277, 41879–41887).

Results

In the present study, we investigated transcription factors that bind to MRE. Using the MRE motif for a pull-down assay, poly(ADP-ribose)polymerase-1 (PARP-1) and the heterodimeric complex Ku70/Ku80 were identified by mass spectrometry and confirmed by chromatin immunoprecipitation. Furthermore, TPA-induced S100A9 gene expression in HaCaT keratinocytes was blocked after the pharmacologic inhibition of PARP-1 with 1,5-isoquinolinediol (DiQ).

Conclusion

The candidates, poly(ADP-ribose)polymerase-1 (PARP-1) and the heterodimeric complex Ku70/Ku80, are known to participate in inflammatory disorders as well as tumorgenesis. The latter may indicate a possible link between S100 and inflammation-associated cancer.

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.

Psoriasin (S100A7) is significantly up-regulated in human epithelial skin tumours

PURPOSE

Psoriasin (S100A7) has originally been described to be expressed by psoriatic keratinocytes possibly as a result of altered differentiation and inflammation. As psoriasin was found to be overexpressed in human breast and bladder cancer suggesting a role in tumour progression, we investigated the expression of psoriasin in human epithelial skin tumours.

METHODS

Realtime reverse transcription-polymerase chain reaction experiments were performed to analyse the mRNA-expression levels of psoriasin together with involucrin as a marker for epithelial differentiation and interleukin-8 (IL-8) as a marker for inflammation in skin biopsy samples from patients with precancerous skin lesions (PSL, n = 6), squamous cell carcinoma (SCC, n = 11), basal cell carcinoma (BCC, n = 17), and healthy controls (n = 10).

RESULTS

Unexpectedly, mRNA expression levels for Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) revealed a variation of up to 600-fold in all cDNA-samples under investigation, indicating that GAPDH is not suitable as a housekeeping gene in human skin samples. Psoriasin mRNA expression was significantly up-regulated in samples of PSL, SCC and BCC. In situ hybridisation and immunohistochemical examinations identified psoriasin mRNA and protein expression in the differentiated layers of the epidermis. IL-8 mRNA expression was significantly up-regulated in SCC, however, there was no correlation between elevated levels of psoriasin and the expression of IL-8.

CONCLUSION

Similar to the findings in breast and bladder cancer, the up-regulation of psoriasin might play a role in the progression of skin cancer. The expression of psoriasin in human skin tumours seems to be independent from differentiation and inflammation.

Psoriasis: genetic associations and immune system changes

Psoriasis is a common inflammatory skin disease characterized by infiltration of inflammatory cells into the epidermis and altered keratinocyte differentiation. Psoriasis is currently thought of as a T-cell mediated 'Type-1' autoimmune disease. Gene expression changes in psoriasis lesions have been well documented, and strongly support an important role for tumor necrosis factor and interferon gamma signal pathways in its pathogenesis. The strongest genetic determinant of psoriasis identified to date lies within the class I region of the multiple histocompatibility locus antigen cluster, although its low penetrance implicates a requirement for other genetic risk factors. Multiple genome-wide linkage and an increasing number of association studies have been carried out, leading to multiple linkage peaks, and the identification of potential low risk variants. A number of these variants lie within genes encoding components of the immune system. However, the functional relationships between predisposing genetic variation is unclear, and presumably involves genetic susceptibility factors affecting both immune cell activation and keratinocyte differentiation. The interaction of environmental trigger factors with genetic effects is also not understood, but provide further evidence for the complex basis of this disease.

Effects of brief cutaneous JP-8 jet fuel exposures on time course of gene expression in the epidermis

The jet fuel jet propulsion fuel 8 (JP-8) has been shown to cause an inflammatory response in the skin, which is characterized histologically by erythema, edema, and hyperplasia. Studies in laboratory animal skin and cultured keratinocytes have identified a variety of changes in protein levels related to inflammation, oxidative damage, apoptosis, and cellular growth. Most of these studies have focused on prolonged exposures and subsequent effects. In an attempt to understand the earliest responses of the skin to JP-8, we have investigated changes in gene expression in the epidermis for up to 8 h after a 1-h cutaneous exposure in rats. After exposure, we separated the epidermis from the rest of the skin with a cryotome and isolated total mRNA. Gene expression was studied with microarray techniques, and changes from sham treatments were analyzed and characterized. We found consistent twofold increases in gene expression of 27 transcripts at 1, 4, and 8 h after the beginning of the 1-h exposure that were related primarily to structural proteins, cell signaling, inflammatory mediators, growth factors, and enzymes. Analysis of pathways changed showed that several signaling pathways were increased at 1 h and that the most significant changes at 8 h were in metabolic pathways, many of which were downregulated. These results confirm and expand many of the previous molecular studies with JP-8. Based on the 1-h changes in gene expression, we hypothesize that the trigger of the JP-8-induced, epidermal stress response is a physical disruption of osmotic, oxidative, and membrane stability which activates gene expression in the signaling pathways and results in the inflammatory, apoptotic, and growth responses that have been previously identified.

The Grainyhead-like epithelial transactivator Get-1/Grhl3 regulates epidermal terminal differentiation and interacts functionally with LMO4

Defective permeability barrier is an important feature of many skin diseases and causes mortality in premature infants. To investigate the control of barrier formation, we characterized the epidermally expressed Grainyhead-like epithelial transactivator (Get-1)/Grhl3, a conserved mammalian homologue of Grainyhead, which plays important roles in cuticle development in Drosophila. Get-1 interacts with the LIM-only protein LMO4, which is co-expressed in the developing mammalian epidermis. The epidermis of Get-1(-/-) mice showed a severe barrier function defect associated with impaired differentiation of the epidermis, including defects of the stratum corneum, extracellular lipid composition and cell adhesion in the granular layer. The Get-1 mutation affects multiple genes linked to terminal differentiation and barrier function, including most genes of the epidermal differentiation complex. Get-1 therefore directly or indirectly regulates a broad array of epidermal differentiation genes encoding structural proteins, lipid metabolizing enzymes and cell adhesion molecules. Although deletion of the LMO4 gene had no overt consequences for epidermal development, the epidermal terminal differentiation defect in mice deleted for both Get-1 and LMO4 is much more severe than in Get-1(-/-) mice with striking impairment of stratum corneum formation. These findings indicate that the Get-1 and LMO4 genes interact functionally to regulate epidermal terminal differentiation.

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.

Proteomic Analysis on the Alteration of Protein Expression in the Placental Villous Tissue of Early Pregnancy Loss

Early pregnancy loss is the most common complication of human reproduction. Given the complexities of early development, it is likely that many mechanisms are involved. Knowledge of differences in protein expression in parallel profiling is essential to understand the comprehensive pathophysiological mechanism underlying early pregnancy loss. To identify proteins with different expression profiles related to early pregnancy loss, we applied a proteomic approach and performed two-dimensional gel electrophoresis (2-DE) on six placental villous tissues from patients with early pregnancy loss and six from normal pregnant women, followed by comparison of the silver-stained 2-DE profiles. It was found that 13 proteins were downregulated and 5 proteins were upregulated significantly (P < 0.05) in early pregnancy loss as determined by spot volume. Among them, 10 downregulated and 2 upregulated spots were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Anomalies of these proteins, including three principal antioxidant enzymes (copper/zinc-superoxide dismutase, peroxiredoxin 3, and thioredoxin-like 1 protein), S100 calcium binding protein, galectin-1, chorionic somatomammotropin hormone 1, transthyretin, fas inhibitory molecule, eukaryotic translation elongation factor, RNA-binding protein, ubiquitin-conjugating enzyme E2N, and proteasome beta-subunit, indicate widespread failure in cell regulations and processes such as antioxidative defense, differentiation, cell proliferation, metabolism, apoptosis, transcription, and proteolysis in early pregnancy loss. This study has identified several proteins that are associated with placentation and early development, shedding a new insight into the proteins that may be potentially involved in the pathophysiological mechanisms underlying early pregnancy loss.

Expression profiling of radiation-induced genes in radiodermatitis of hairless mice

BACKGROUND

Radiation induces many cellular events leading to radiodermatitis.

OBJECTIVES

The aim of this study was to establish a radiodermatitis model using experimental animals, and to examine the expression profile of radiation-induced genes.

METHODS

Hairless mice were irradiated on the dorsal skin; then total RNAs were isolated and microarray hybridizations were performed.

RESULTS

Irradiation with a total of 40 Gy (10 Gy day-1 for four consecutive days) provokes radiodermatitis in the hairless mouse. After microarray analysis, 130 genes that showed upregulation by radiation were selected and organized into four different clusters, depending on the time-kinetic pattern. Classification of these genes into several functional categories revealed that various biological processes were globally affected by radiation. These include transcription regulation, signal transduction, cell communication, cell death regulation and metabolism.

CONCLUSIONS

These results demonstrate the complexity of the transcriptional profile of the radiation response, providing important clues on which to base further investigations of the molecular events underlying radiodermatitis.

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.

Cyclooxygenase-2 Is Involved in S100A2-Mediated Tumor Suppression in Squamous Cell Carcinoma

S100A2 is considered a putative tumor suppressor due to its loss or down-regulation in several cancer types. However, no mechanism has been described for the tumor suppressor role of S100A2. In this study, ectopic expression of S100A2 in the human malignant squamous cell carcinoma cell line KB resulted in a significant inhibition of proliferation, migration, and invasion. Moreover, S100A2 significantly reduced the number of colonies (>or=0.5 mm) formed in semisolid agar and decreased tumor growth and burden in nude mice. cDNA microarray analysis was used to compare mRNA expression profiles of vector- and S100A2-expressing isogenic cells. Among the genes deregulated by S100A2, the expression of cyclooxygenase-2 (COX-2) mRNA was significantly suppressed by S100A2 (2.4-fold). Western blot analysis confirmed that S100A2 reduced the expression of COX-2 protein in stably and transiently transfected KB and RPMI-2650 cells. COX-2 is frequently overexpressed in various types of cancer and plays an important role in tumor progression. Partial restoration of COX-2 expression attenuated the antitumor effect of S100A2 both in vitro and in vivo. Although the interplay between S100A2 and COX-2 remains to be clarified, these findings first showed a potent antitumor role of S100A2 in squamous cell carcinoma partly via reduced expression of COX-2.

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.

S100A8 and S100A9 in inflammation and cancer

Calprotectin (S100A8/A9), a heterodimer of the two calcium-binding proteins S100A8 and S100A9, was originally discovered as immunogenic protein expressed and secreted by neutrophils. Subsequently, it has emerged as important pro-inflammatory mediator in acute and chronic inflammation. More recently, increased S100A8 and S100A9 levels were also detected in various human cancers, presenting abundant expression in neoplastic tumor cells as well as infiltrating immune cells. Although, many possible functions have been proposed for S100A8/A9, its biological role still remains to be defined. Altogether, its expression and potential cytokine-like function in inflammation and in cancer suggests that S100A8/A9 may play a key role in inflammation-associated cancer.

Inflammatory manifestations of experimental lymphatic insufficiency

BACKGROUND

Sustained lymph stagnation engenders a pathological response that is complex and not well characterized. Tissue inflammation in lymphedema may reflect either an active or passive consequence of impaired immune traffic.

METHODS AND FINDINGS

We studied an experimental model of acute post-surgical lymphedema in the tails of female hairless, immunocompetent SKH-1 mice. We performed in vivo imaging of impaired immune traffic in experimental, murine acquired lymphatic insufficiency. We demonstrated impaired mobilization of immunocompetent cells from the lymphedematous region. These findings correlated with histopathological alterations and large-scale transcriptional profiling results. We found intense inflammatory changes in the dermis and the subdermis. The molecular pattern in the RNA extracted from the whole tissue was dominated by the upregulation of genes related to acute inflammation, immune response, complement activation, wound healing, fibrosis, and oxidative stress response.

CONCLUSIONS

We have characterized a mouse model of acute, acquired lymphedema using in vivo functional imaging and histopathological correlation. The model closely simulates the volume response, histopathology, and lymphoscintigraphic characteristics of human acquired lymphedema, and the response is accompanied by an increase in the number and size of microlymphatic structures in the lymphedematous cutaneous tissues. Molecular characterization through clustering of genes with known functions provides insights into processes and signaling pathways that compose the acute tissue response to lymph stagnation. Further study of genes identified through this effort will continue to elucidate the molecular mechanisms and lead to potential therapeutic strategies for lymphatic vascular insufficiency.

Molecular characterization of adenocarcinoma and squamous carcinoma of the uterine cervix using microarray analysis of gene expression

In an attempt to understand the molecular mechanisms for the different clinical features between adenocarcinoma/adenosquamous carcinoma (AC/ASC) and squamous carcinoma (SC) of the uterine cervix, we analyzed gene expression profiles of different histological subtypes of cervical cancer. Cancer specimens and the surrounding normal tissue counterparts were separately collected from cervical cancer patients undergoing type III radical hysterectomy. Paired total RNA (cancer and normal tissues) was isolated and analyzed with cDNA microarrays containing duplicate spots of 7 334 sequence-verified human cDNA clones. Selected differentially expressed genes specific for AC or SC were further verified using real-time quantitative polymerase chain reaction (RTQ-PCR) and immunohistochemistry. Genes, including CEACAM5, TACSTD1, S100P and MSLN were upregulated in AC. Contrarily, genes involved in epidermal differentiation complex such as S100A9 and ANXA8 were upregulated in SC. Cross-validation of the results using an independent but comparable group of patients with known long-term outcomes (n = 63, median follow-up 70.3 months; range, 4-208 months) showed that the correlation between the selected 6 differentially expressed genes and histology was highly significant. CEACAM5 (p < 0.0001) and TACSTD1 (p = 0.009) were significant prognostic factors by multivariate Cox proportional hazards regression analysis. The combination of cDNA microarray, RTQ-PCR and immunohistochemical results of this study showed that it is possible to define different gene profiles for AC and SC. Moreover, TACSTD1 expression may be a novel poor prognostic factor.

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.

Transcription promoter activity of the human S100A7 gene in oral squamous cell carcinoma cell lines

The S100A7 (psoriasin) gene has been shown to be markedly over-expressed in squamous cell carcinomas (SCCs) as well as in psoriasis. We herein examined the S100A7 gene promoter activity in human oral SCC cell lines to identify the putative SCC-specific regulatory regions for the S100A7 transcription. Functional deletion assays of 5'-flanking region demonstrated that the segments, (-1513 to -988), (-1954 to -1513) and (-3040 to -2578), play important roles in the transcription activity in the oral SCCs. The internal deletion of the short segments, (-1248 to -1110), (-1109 to -988) and (-1248 to -988), decreased this activity. These segments cloned upstream of the heterologous promoter increased the promoter activity in oral SCC cell line. Electrophoretic mobility shift assays, using the sequence segmental probes, (-1248 to -1110) and (-1109 to -988), showed different DNA-protein complex patterns depending on the types of used cell lines. One of the complexes was only observed in the oral SCCs. These data suggested that the segment from -1513 to -988 contains up-regulatory elements for the transcription activity of the S100A7 gene in oral SCCs.

Molecular pathology of breast apocrine carcinomas: A protein expression signature specific for benign apocrine metaplasia

Breast cancer is a heterogeneous disease that encompasses a wide range of histopathological types including: invasive ductal carcinoma, lobular carcinoma, medullary carcinoma, mucinous carcinoma, tubular carcinoma, and apocrine carcinoma among others. Pure apocrine carcinomas represent about 0.5% of all invasive breast cancers according to the Danish Breast Cancer Cooperative Group Registry, and despite the fact that they are morphologically distinct from other breast lesions, there are at present no standard molecular criteria available for their diagnosis. In addition, the relationship between benign apocrine changes and breast carcinoma is unclear and has been a matter of discussion for many years. Recent proteome expression profiling studies of breast apocrine macrocysts, normal breast tissue, and breast tumours have identified specific apocrine biomarkers [15-hydroxyprostaglandin dehydrogenase (15-PGDH) and hydroxymethylglutaryl coenzyme A reductase (HMG-CoA reductase)] present in early and advanced apocrine lesions. These biomarkers in combination with proteins found to be characteristically upregulated in pure apocrine carcinomas (psoriasin, S100A9, and p53) provide a protein expression signature distinctive for benign apocrine metaplasias and apocrine cystic lesions. These studies have also presented compelling evidence for a direct link, through the expression of the prostaglandin degrading enzyme 15-PGDH, between early apocrine lesions and pure apocrine carcinomas. Moreover, specific antibodies against the components of the expression signature have identified precursor lesions in the linear histological progression to apocrine carcinoma. Finally, the identification of proteins that characterize the early stages of mammary apocrine differentiation such as 15-PGDH, HMG-CoA reductase, and cyclooxygenase 2 (COX-2) has opened a window of opportunity for pharmacological intervention, not only in a therapeutic manner but also in a chemopreventive setting. Here we review published and recent results in the context of the current state of research on breast apocrine cancer.

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.

Surfactant Sodium Lauryl Sulfate Enhances Skin Vaccination

The skin is a highly accessible organ and thus provides an attractive immune environment for cost-effective, simple, and needle-free delivery of vaccines and immunomodulators. In this study, we pretreated mouse skin with an anionic surfactant, sodium lauryl sulfate (SLS), for a short period of time (10 min) followed by epicutaneous vaccination with hen egg lysozyme antigen. We demonstrated for the first time that pretreatment of skin with surfactant SLS significantly enhances the production of antibody to hen egg lysozyme. Short term pretreatment with SLS disorganized the stratum corneum, extracted partial lamellar lipids, induced the maturation of Langerhans cells, and did not result in epidermis thickening. To reveal the mechanism underlying these changes, particularly at the molecular level, we used a novel proteomic technique using ultrafiltration capillaries and mass spectrometry to identify in vivo proteins/peptides secreted in the SLS-pretreated skin. Two secretory proteins, named as calcium-binding protein S100A9 and thymosin beta4, were identified by this novel technique. These two proteins thus may provide new insight into the enhancing effect of surfactants on skin vaccination.

Regulatory role for Krüppel-like zinc-finger protein Gli-similar 1 (Glis1) in PMA-treated and psoriatic epidermis

In this study, we analyze the expression and potential function of the Krüppel-like zinc-finger protein Gli-similar protein 1 (Glis1) in normal and inflammatory skin and in the differentiation of epidermal keratinocytes. Glis1 mRNA is not expressed in normal human epidermis, but is significantly induced in psoriatic epidermis and in mouse skin upon treatment with the tumor promoter phorbol-12-myristate-13-acetate (PMA). The expression of Glis1 is restricted to the suprabasal layers. These observations suggest that Glis1 expression is associated with hyperplastic, inflammatory epidermis. Consistent with these findings, Glis1 mRNA is not expressed in undifferentiated or differentiated normal human epidermal keratinocytes (NHEK) in culture, but is dramatically induced after the addition of PMA or interferon gamma. A similar induction of Glis1 mRNA by PMA treatment was observed in the immortalized epidermal keratinocyte cell line NHEK-HPV, whereas PMA did not induce Glis1 in HaCaT cells or in several squamous cell carcinoma cell lines. To obtain insight into its function, Glis1 and a C-terminal deletion mutant Glis1DeltaC were expressed in NHEK-HPV cells and changes in epidermal differentiation and gene expression examined. Microarray analysis revealed that Glis1DeltaC promoted PMA-induced epidermal differentiation, as indicated by increased expression of many differentiation-specific genes. This, in association with its induction in psoriasis, suggests that transcriptional factor Glis1 is involved in the regulation of aberrant differentiation observed in psoriatic epidermis.

S100A2 gene is a direct transcriptional target of p53 homologues during keratinocyte differentiation

The p53 paralogues p73, p63 and their respective truncated isoforms have been shown to be critical regulators of developmental and differentiation processes. Indeed, both p73- and p63-deficient mice exhibit severe developmental defects. Here, we show that S100A2 gene, whose transcript and protein are induced during keratinocyte differentiation of HaCaT cells, is a direct transcriptional target of p73beta and DeltaNp63alpha and is required for proper keratinocyte differentiation. Transactivation assays reveal that p73beta and DeltaNp63alpha exert opposite transcriptional effects on S100A2 gene. While DeltaNp63alpha is found in vivo onto S100A2 regulatory regions predominantly in proliferating cells, p73beta is recruited in differentiating cells. Silencing of p73 impairs the induction of S100A2 during the differentiation of HaCaT cells. Moreover, silencing of p73 or S100A2 impairs the proper expression of keratinocyte differentiation markers. Of note, p53 family members do not trigger S100A2 gene expression in response to apoptotic doses of cisplatin and doxorubicin.

Microarray analysis of gene expression in cultured skin substitutes compared with native human skin

Cultured skin substitutes (CSS), prepared using keratinocytes, fibroblasts, and biopolymers, can facilitate closure of massive burn wounds by increasing the availability of autologous tissue for grafting. But because they contain only two cell types, skin substitutes cannot replace all of the functions of native human skin. To better understand the physiological and molecular differences between CSS and native skin, we undertook a comprehensive analysis of gene expression in native skin, cultured keratinocytes, cultured fibroblasts, and skin substitutes using Affymetrix gene chip microarrays. Hierarchical tree clustering identified six major clusters of coordinately regulated genes, using a list of 1030 genes that were the most differentially expressed between groups. These clusters correspond to biomarker pools representing expression signatures for native skin, fibroblasts, keratinocytes, and cultured skin. The expression analysis revealed that entire clusters of genes were either up- or downregulated upon combination of fibroblasts and keratinocytes in cultured skin grafts. Further, several categories of genes were overexpressed in CSS compared with native skin, including genes associated with hyperproliferative skin or activated keratinocytes. The observed pattern of expression indicates that CSS in vitro, which display a well-differentiated epidermal layer, exhibit a hyperproliferative phenotype similar to wounded native skin.

Defining the transcriptome of accelerated and replicatively senescent keratinocytes reveals links to differentiation, interferon signaling, and Notch related pathways

Epidermal keratinocytes (KCs) undergo highly orchestrated morphological and molecular changes during transition from proliferative compartment into growth arrested early and late differentiation layers, prior to dying in outermost cornified layers of normal skin. Creation of stratum corneum is vital to barrier function protecting against infection. Transcriptional events in KCs regulating complex processes of differentiation and host defense required to maintain constant epidermal thickness and resistance to infection in either young or aged skin are largely unknown. Furthermore, as terminal differentiation is characterized by irreversible loss of replicative potential culminating in dead layers at the skin surface, this process may be viewed as a form of senescence. However, a complete transcriptional profile of senescent (SN) human KCs has not been previously defined to permit delineation of molecular boundaries involving differentiation and senescence. To fill this void, we utilized global transcriptional analysis of KCs maintained in vitro as either cultures of proliferating (PR) cells, early and late confluent (LC) (accelerated senescence) cultures, or KCs undergoing replicative senescence. Global gene expression profiling revealed early confluent (EC) KCs were somewhat similar to PR KCs, while prominent differences were evident when compared to LC KCs; which were also distinct from replicatively SN KCs. While confluent KCs have in common several genes regulating differentiation with replicatively SN KCs, the latter cells expressed elevated levels of genes involved in interferon signaling and inflammatory pathways. These results provide new insights into cell autonomous transcriptional-based programs operative within KCs contributing to replicative senescence, with partial sharing of genes involved in differentiation. In addition, regulation of KC senescence may involve participation of interferon signaling pathways derived from the important role of KCs in protecting skin from infection. Integrating all of the transcriptional data revealed a key role for Notch receptor mediated signaling in the confluency induced differentiation phenotype using this model system.

Peptidoglycan recognition proteins Pglyrp3 and Pglyrp4 are encoded from the epidermal differentiation complex and are candidate genes for the Psors4 locus on chromosome 1q21

Psoriasis is a common inflammatory skin disease caused by genetic and environmental factors, including bacterial and viral infections. Since the skin is in constant contact with commensal and pathogenic microorganisms, we examined well-supported psoriasis genetic linkage intervals to identify genes encoding innate immune pattern recognition proteins that may play a role in pathogenesis. Two peptidoglycan recognition proteins, Pglyrp3 and Pglyrp4, are localized to the Psors4 locus on chromosome 1q21 in a gene cluster known as the epidermal differentiation complex (EDC). We show that these genes are expressed in the skin as well as in germinal centers in the tonsil. We tested 13 SNPs in or near these genes for association with psoriasis in two independent patient collections: a family-based patient set comprised of 375 individuals from 101 families, and a case-control patient collection of 282 patients with moderate to severe psoriasis and 192 healthy controls. In the family-based analysis, several SNPs in the Pglyrp3-Pglyrp4 locus show association with psoriasis (0.01 < P < 0.05). Multiple-SNP haplotypes incorporating Pglyrp3 and Pglyrp4 SNPs also show significant association in the transmission disequilibrium test (TDT; P < 0.01). In the case-control test, none of the SNPs that we tested show association with psoriasis when analyzed in single-SNP or haplotype-based tests. The discordance between the TDT and case-control results suggests that the two populations are significantly different in disease etiology, that the polymorphism responsible for the Psors4 linkage is elsewhere in the Pglyrp locus, or that the causative Psors4 polymorphism is in a location near but not in the Pglyrp locus. These data are consistent with previous reports of association of psoriasis with genes on 1q21, and suggest a role for Pglyrps in skin biology.

Vernix caseosa as a multi-component defence system based on polypeptides, lipids and their interactions

Vernix caseosa is a white cream-like substance that covers the skin of the foetus and the newborn baby. Recently, we discovered antimicrobial peptides/proteins such as LL-37 in vernix, suggesting host defence functions of vernix. In a proteomic approach, we have continued to characterize proteins in vernix and have identified 20 proteins, plus additional variant forms. The novel proteins identified, considered to be involved in host defence, are cystatin A, UGRP-1, and calgranulin A, B and C. These proteins add protective functions to vernix such as antifungal activity, opsonizing capacity, protease inhibition and parasite inactivation. The composition of the lipids in vernix has also been characterized and among these compounds the free fatty acids were found to exhibit antimicrobial activity. Interestingly, the vernix lipids enhance the antimicrobial activity of LL-37 in vitro, indicating interactions between lipids and antimicrobial peptides in vernix. In conclusion, vernix is a balanced cream of compounds involved in host defence, protecting the foetus and newborn against infection.

Getting under the skin: the immunogenetics of psoriasis

Psoriasis is a chronic inflammatory disorder of the skin that is mediated by T cells, dendritic cells and inflammatory cytokines. We now understand many of the cellular alterations that underlie this disease, and genomic approaches have recently been used to assess the alterations of gene expression in psoriatic skin lesions. Genetic susceptibility factors that contribute to predisposition to psoriasis are now also being identified. It is hoped that we will soon be able to correlate the cellular pathogenesis that occurs in psoriasis with these genetic factors. In this Review article, we describe what is known about genes that confer increased susceptibility to psoriasis, and we integrate this with what is known about the molecular and cellular mechanisms that occur in other inflammatory and autoimmune disorders.

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.

Late cornified envelope family in differentiating epithelia--response to calcium and ultraviolet irradiation

The late cornified envelope (LCE) gene cluster within the epidermal differentiation complex on human chromosome one (mouse chromosome three) contains multiple conserved genes encoding stratum-corneum proteins. Within the LCE cluster, genes form "groups" based on chromosomal position and protein homology. We link a recently accepted nomenclature for the LCE cluster (formerly XP5, small proline-rich-like, late-envelope protein genes) to gene structure, groupings, and chromosomal organization, and carry out a pan-cluster quantitative expression analysis in a variety of tissues and environmental conditions. This analysis shows that (i) the cluster organizes into two "skin" expressing groups and a third group with low-level, tissue-specific expression patterns in all barrier-forming epithelia tested, including internal epithelia; (ii) LCE genes respond "group-wise" to environmental stimuli such as calcium levels and ultraviolet (UV) light, highlighting the functional significance of groups; (iii) in response to UV stimulation there is massive upregulation of a single, normally quiescent, non-skin LCE gene; and (iv) heterogeneity occurs between individuals with one individual lacking expression of an LCE skin gene without overt skin disease, suggesting LCE genes affect subtle attributes of skin function. This quantitative and pan-cluster expression analysis suggests that LCE groups have distinct functions and that within groups regulatory diversification permits specific responsiveness to environmental challenge.

Epidermal stem cells: the cradle of epidermal determination, differentiation and wound healing

The field of epidermal stem cells has dramatically advanced in the last decade, leading to a better understanding of the molecular factors, signalling pathways and cellular events that identify and characterize stem cells, thus revealing their immense potential for therapeutic use. Furthermore, multipotent epidermal stem cells present the major advantage of easy accessibility with the discovery of their specific location within the bulge of the hair follicle. This review focuses on the most recent findings on epidermal stem cells, and their potential role in initial epidermal commitment, differentiation and wound healing processes in the skin.

Isolation and Characterization of Human Repetin, a Member of the Fused Gene Family of the Epidermal Differentiation Complex

The human repetin gene is a member of the "fused" gene family and localized in the epidermal differentiation complex on chromosome 1q21. The "fused" gene family comprises profilaggrin, trichohyalin, repetin, hornerin, the profilaggrin-related protein and a protein encoded by c1orf10. Functionally, these proteins are associated with keratin intermediate filaments and partially crosslinked to the cell envelope (CE). Here, we report the isolation and characterization of the human repetin gene and of its protein product. The repetin protein of 784 amino acids contains EF (a structure resembling the E helix-calcium-binding loop-F helix domain of parvalbumin) hands of the S100 type and internal tandem repeats typical for CE precursor proteins, a combination which is characteristic for "fused" proteins. Repetin expression is scattered in the normal epidermis but strong in the acrosyringium, the inner hair root sheat and in the filiform papilli of the tongue. Ultrastructurally, repetin is a component of cytoplasmic non-membrane "keratohyalin" F-granules in the stratum granulosum of normal epidermis, similar to profilaggrin. Finally, we show that EF hands are functional and reversibly bind Ca(2+). Our results indicate that repetin is indeed a member of the fused gene family similar to the prototypical members profilaggrin and trichohyalin.

Expression analysis of the mouse S100A7/psoriasin gene in skin inflammation and mammary tumorigenesis

Background

The human psoriasin (S100A7) gene has been implicated in inflammation and tumor progression. Implementation of a mouse model would facilitate further investigation of its function, however little is known of the murine psoriasin gene. In this study we have cloned the cDNA and characterized the expression of the potential murine ortholog of human S100A7/psoriasin in skin inflammation and mammary tumorigenesis.

Methods

On the basis of chromosomal location, phylogenetic analysis, amino acid sequence similarity, conservation of a putative Jab1-binding motif, and similarities of the patterns of mouse S100A7/psoriasin gene expression (measured by RT-PCR and in-situ hybridization) with those of human S100A7/psoriasin, we propose that mouse S100A7/psoriasin is the murine ortholog of human psoriasin/S100A7.

Results

Although mouse S100A7/psoriasin is poorly conserved relative to other S100 family members, its pattern of expression parallels that of the human psoriasin gene. In murine skin S100A7/psoriasin was significantly upregulated in relation to inflammation. In murine mammary gland expression is also upregulated in mammary tumors, where it is localized to areas of squamous differentiation. This mirrors the context of expression in human tumor types where both squamous and glandular differentiation occur, including cervical and lung carcinomas. Additionally, mouse S100A7/psoriasin possesses a putative Jab1 binding motif that mediates many downstream functions of the human S100A7 gene.

Conclusion

These observations and results support the hypothesis that the mouse S100A7 gene is structurally and functionally similar to human S100A7 and may offer a relevant model system for studying its normal biological function and putative role in tumor progression.

Aberrantly differentiated cells in benign pilomatrixoma reflect the normal hair follicle: immunohistochemical analysis of Ca2+-binding S100A2, S100A3 and S100A6 proteins

BACKGROUND

Pilomatrixoma is a common benign cutaneous tumour containing differentiated hair matrix cells. This tumour is mainly composed of basophilic, transitional, shadow and squamoid cells. Although some S100 proteins are expressed in a tissue-specific manner in the hair follicle (e.g. S100A2 in the outer root sheath, S100A3 in the cortex and cuticle, and S100A6 in the inner root sheath), little information is available concerning their distribution in the aberrantly differentiated tissues of pilomatrixoma.

OBJECTIVES

To characterize the disordered epithelial elements of pilomatrixoma by localizing S100A2, S100A3 and S100A6 proteins.

METHODS

Immunohistochemistry and dual-immunofluorescence microscopy were performed on 22 pilomatrixoma specimens using antibodies specific to the three proteins.

RESULTS

Tissue-specific distribution of the S100 proteins investigated was preserved in the morphologically disordered tumour tissues. Anti-S100A2 antibody stained squamoid cells and putative outer root sheath cells; basophilic and potential hair matrix cells were occasionally stained. S100A3 staining was found in transitional cells and putative cortical cells, and was strong in both dispersed cells and hair-like structures surrounding cells which were presumably cuticular cells. Anti-S100A6 antibody labelled some S100A3-negative transitional cell strands, potentially inner root sheath cells.

CONCLUSIONS

The epithelial elements of pilomatrixoma can be characterized using S100 proteins as biochemical markers. Our results show that pilomatrixomas retain a certain degree of differentiation indicative of distinct hair-forming cells.

Psoriatic scales: a promising source for the isolation of human skin-derived antimicrobial proteins

Patients with psoriasis, a chronic, hyperproliferative and noninfectious skin disease, suffer surprisingly fewer cutaneous infections than would be expected. This observation led us to the hypothesis that a local "chemical shield" in the form of antimicrobial proteins provides psoriatic skin with resistance against infection. We subsequently began a systematic analysis of in vitro antimicrobially active proteins in psoriatic-scale extracts. A biochemical approach with rigorous purification and characterization combined with antimicrobial testing identified a number of mostly new human antibiotic peptides and proteins. In this review, we will focus on the most prominent antimicrobial proteins in psoriatic-scale extracts, which we identified as the S100-protein psoriasin, human beta-defensin 2 (hBD-2), RNase 7, lysozyme, and human neutrophil defensin 1-3. Apart from these cutaneous, antimicrobial proteins, only a few others, including hBD-3, have been characterized. A great number of minor antimicrobial proteins await further structural characterization.

Gene expression profiling of ovine skin and wool follicle development using a combined ovine - bovine skin cDNA microarray

Low fibre diameter and high fleece weight are important determinants of the economic value of the Merino fleece. The combination of these traits is found in Merino sheep with high follicle densities resulting from a high secondary to primary follicle ratio. Morphological stages in the development of primary and secondary follicles of fetal sheep skin have been well described. We have used gene expression profiling of fetal skin to identify genes that may be important in controlling these follicle developmental processes. A combined ovine (2.3 K) and bovine (6.14 K) cDNA microarray of 2 fetal and 1 adult stage skin tissues was constructed to compare gene expression levels between fetal day 82, day 105, day 120 and adult sheep skin developmental stages. The transcript profile resulted in 238 differentially expressed array elements relative to the adult expression, which represented 132 unique genes. These clustered into 50 up- and 82 down-regulated genes and distinct gene ontologies including structural constituents, phosphate transport, signal transduction and organogenesis. Northern blot analysis of 2 selected genes, S100A7LI and TAGLN, validated the microarray results. This list of genes contains candidates of interest for further investigation into the molecular control of wool follicle development.

Antimicrobial psoriasin (S100A7) protects human skin from Escherichia coli infection

Human healthy skin is continuously exposed to bacteria, but is particularly resistant to the common gut bacterium Escherichia coli. We show here that keratinocytes secrete, as the main E. coli-killing compound, the S100 protein psoriasin in vitro and in vivo in a site-dependent way. In vivo treatment of human skin with antibodies to psoriasin inhibited its E. coli-killing properties. Psoriasin was induced in keratinocytes in vitro and in vivo by E. coli, indicating that its focal expression in skin may derive from local microbial induction. Zn(2+)-saturated psoriasin showed diminished antimicrobial activity, suggesting that Zn(2+) sequestration could be a possible antimicrobial mechanism. Thus, psoriasin may be key to the resistance of skin against E. coli.