Molecular cloning and characterization of alternatively spliced mRNA isoforms from psoriatic skin encoding a novel member of the S100 family

S100 Proteins in the Pathogenesis of Psoriasis and Atopic Dermatitis

The skin, the outermost layer of the human body, is exposed to various external stimuli that cause inflammatory skin reactions. These external stimulants trigger external epithelial cell damage and the release of intracellular substances. Following cellular damage or death, intracellular molecules are released that enhance tissue inflammation. As an important substance released from damaged cells, the S100 protein is a low-molecular-weight acidic protein with two calcium-binding sites and EF-hand motif domains. S100 proteins are widely present in systemic organs and interact with other proteins. Recent studies revealed the involvement of S100 in cutaneous inflammatory disorders, psoriasis, and atopic dermatitis. This review provides detailed information on the interactions among various S100 proteins in inflammatory diseases.

Pathogenic role of S100 proteins in psoriasis

Psoriasis is a chronic inflammatory skin disease. The histopathological features of psoriasis include excessive proliferation of keratinocytes and infiltration of immune cells. The S100 proteins are a group of EF-hand Ca2+-binding proteins, including S100A2, -A7, -A8/A9, -A12, -A15, which expression levels are markedly upregulated in psoriatic skin. These proteins exert numerous functions such as serving as intracellular Ca2+ sensors, transduction of Ca2+ signaling, response to extracellular stimuli, energy metabolism, and regulating cell proliferation and apoptosis. Evidence shows a crucial role of S100 proteins in the development and progress of inflammatory diseases, including psoriasis. S100 proteins can possibly be used as potential therapeutic target and diagnostic biomarkers. This review focuses on the pathogenic role of S100 proteins in psoriasis.

Pathogenesis, multi-omics research, and clinical treatment of psoriasis

Psoriasis is a common inflammatory skin disease involving interactions between keratinocytes and immune cells that significantly affects the quality of life. It is characterized by hyperproliferation and abnormal differentiation of keratinocytes and excessive infiltration of immune cells in the dermis and epidermis. The immune mechanism underlying this disease has been elucidated in the past few years. Research shows that psoriasis is regulated by the complex interactions among immune cells, such as keratinocytes, dendritic cells, T lymphocytes, neutrophils, macrophages, natural killer cells, mast cells, and other immune cells. An increasing number of signaling pathways have been found to be involved in the pathogenesis of psoriasis, which has prompted the search for new treatment targets. In the past decades, studies on the pathogenesis of psoriasis have focused on the development of targeted and highly effective therapies. In this review, we have discussed the relationship between various types of immune cells and psoriasis and summarized the major signaling pathways involved in the pathogenesis of psoriasis, including the PI3K/AKT/mTOR, JAK-STAT, JNK, and WNT pathways. In addition, we have discussed the results of the latest omics research on psoriasis and the epigenetics of the disease, which provide insights regarding its pathogenesis and therapeutic prospects; we have also summarized its treatment strategies and observations of clinical trials. In this paper, the various aspects of psoriasis are described in detail, and the limitations of the current treatment methods are emphasized. It is necessary to improve and innovate treatment methods from the molecular level of pathogenesis, and further provide new ideas for the treatment and research of psoriasis.

S100 Proteins as Novel Therapeutic Targets in Psoriasis and Other Autoimmune Diseases

Psoriasis is one of the most common inflammatory skin diseases affecting about 1-3% of the population. One of the characteristic abnormalities in psoriasis is the excessive production of antimicrobial peptides and proteins, which play an essential role in the pathogenesis of the disease. Antimicrobial peptides and proteins can be expressed differently in normal and diseased skin, reflecting their usefulness as diagnostic biomarkers. Moreover, due to their very important functions in innate immunity, members of host defense peptides and proteins are currently considered to be promising new therapeutic targets for many inflammatory diseases. Koebnerisin (S100A15) belongs to an S100 family of antimicrobial proteins, which constitute the multigenetic group of calcium-binding proteins involved in ion-dependent cellular functions and regulation of immune mechanisms. S100A15 was first discovered to be overexpressed in 'koebnerized' psoriatic skin, indicating its involvement in the disease phenotype and the same promising potential as a new therapeutic target. This review describes the involvement of antimicrobial peptides and proteins in inflammatory diseases' development and therapy. The discussion focuses on S100 proteins, especially koebnerisin, which may be involved in the underlying mechanism of the Köebner phenomenon in psoriasis, as well as other immune-mediated inflammatory diseases described in the last decade.

Transcriptional Basis of Psoriasis from Large Scale Gene Expression Studies: The Importance of Moving towards a Precision Medicine Approach

Transcriptome profiling techniques, such as microarrays and RNA sequencing (RNA-seq), are valuable tools for deciphering the regulatory network underlying psoriasis and have revealed large number of differentially expressed genes in lesional and non-lesional skin. Such approaches provide a more precise measurement of transcript levels and their isoforms than any other methods. Large cohort transcriptomic analyses have greatly improved our understanding of the physiological and molecular mechanisms underlying disease pathogenesis and progression. Here, we mostly review the findings of some important large scale psoriatic transcriptomic studies, and the benefits of such studies in elucidating potential therapeutic targets and biomarkers for psoriasis treatment. We also emphasised the importance of looking into the alternatively spliced RNA isoforms/transcripts in psoriasis, rather than focussing only on the gene-level annotation. The neutrophil and blood transcriptome signature in psoriasis is also briefly reviewed, as it provides the immune status information of patients and is a less invasive platform. The application of precision medicine in current management of psoriasis, by combining transcriptomic data, improves the clinical response outcome in individual patients. Drugs tailored to individual patient's genetic profile will greatly improve patient outcome and cost savings for the healthcare system.

Transcriptomic Profiling of Peripheral Edge of Lesions to Elucidate the Pathogenesis of Psoriasis Vulgaris

Elucidating transcriptome in the peripheral edge of the lesional (PE) skin could provide a better understanding of the molecules or signalings that intensify inflammation in the PE skin. Full-thickness biopsies of PE skin and uninvolved (UN) skin were obtained from psoriasis patients for RNA-seq. Several potential differentially expressed genes (DEGs) in the PE skin compared to those in the UN skin were identified. These DEGs enhanced functions such as angiogenesis, growth of epithelial tissue, chemotaxis and homing of cells, growth of connective tissues, and degranulation of myeloid cells beneath the PE skin. Moreover, the canonical pathways of IL-17A, IL-6, and IL-22 signaling were enriched by the DEGs. Finally, we proposed that inflammation in the PE skin might be driven by the IL-36/TLR9 axis or IL-6/Th17 axis and potentiated by IL-36α, IL-36γ, IL-17C, IL-8, S100A7, S100A8, S100A9, S100A15, SERPINB4, and hBD-2. Along with IL-36α, IL-17C, and IκBζ, ROCK2 could be an equally important factor in the pathogenesis of psoriasis, which may involve self-sustaining circuits between innate and adaptive immune responses via regulation of IL-36α and IL-36γ expression. Our finding provides new insight into signaling pathways in PE skin, which could lead to the discovery of new psoriasis targets.

Target molecules for future hidradenitis suppurativa treatment

The registration of the tumour necrosis factor-α inhibitor adalimumab in 2015 was a major step forward in the treatment of hidradenitis suppurativa/acne inversa (HS). However, it soon became evident that the effectiveness of adalimumab in daily practice was highly variable. A significant unmet medical need of HS patients remained, and the search for novel therapeutic targets was intensified. During the 10th European Hidradenitis Suppurativa Foundation (EHSF) e.V. Conference, reknown international HS investigators virtually presented and discussed the published data on these potential target molecules for future HS treatment. This article addresses the most promising molecules currently under investigation from a pathophysiological and clinical point of view. With phase III trials ongoing, the anti- interleukin (IL)-17 biologics bimekizumab and secukinumab are in the most advanced stage of clinical development showing promising results. In addition, targeting IL-1α with bermekimab has shown encouraging results in two clinical trials. Directing treatment at neutrophil recruitment and activation by targeting IL-36 with spesolimab fits well in the pathogenic concept of HS and clinical phase II trial results are pending. In contrast to in situ evidence, Complement 5a (C5a) and C5a receptor blockade have only shown greater clinical benefit in patients with severe HS. Inhibition of Janus kinase (JAK) 1 signalling in HS showed clinical efficacy only in the highest dosage, highlighting that careful surveillance of the balance between safety and efficacy of JAK inhibition is warranted. Overall, clinical efficacies of all novel treatments reported so far are modest. To guide drug development, more and better-defined translational data on the pathogenesis of this severe and enigmatic inflammatory skin disease are required.

Comprehensive analysis of the expression and prognosis for S100 in human ovarian cancer: A STROBE study

S100 family members are frequently deregulated in human malignancies, including ovarian cancer. However, the prognostic roles of each individual S100 family member in ovarian cancer (OC) patients remain elusive. In the present study, we assessed the prognostic roles and molecular function of 20 individual members of the S100 family in OC patients using GEPIA, Kaplan-Meier plotter, SurvExpress, GeneMANIA and Funrich database. Our results indicated that the mRNA expression levels of S100A1, S100A2, S100A4, S100A5, S100A11, S100A14, and S100A16 were significantly upregulated in patients with OC, and high mRNA expression of S100A1, S100A3, S100A5, S100A6, and S100A13 were significantly correlated with better overall survival, while increased S100A2, S100A7A, S100A10, and S100A11 mRNA expressions were associated with worse prognosis in OC patients. In stratified analysis, the trends of high expression of individual S100 members were nearly the same in different pathological grade, clinical stage, TP53 mutation status, and treatment. More importantly, S100 family signatures may be useful potential prognostic markers for OC. These findings suggest that S100 family plays a vital role in prognostic value and could potentially be an S100-targeted inhibitors for OC patients.

Transcriptomic responses of S100 family to bacterial and viral infection in zebrafish

The S100 family proteins are a group of small acidic polypeptides and have diverse functions in regulating many aspects of physiological processes. They are structurally conserved and possess two EF-hands which are central for calcium-mediated functions. In this study, 14 S100 cDNA sequences were determined in zebrafish and their genomic organizations confirmed. Re-analyzing the gene synteny of the S100 loci identified two major S100 loci in Chr16 and Chr19 which share remarkable conservation with the S100 locus in human Chr1, suggesting they may have evolved from a single locus during the teleost specific whole genome duplication event. It appears that the homologues of human S100G and S100P have been lost in zebrafish. Expression analysis reveals that S100W, ICN1 and ICN2 are markedly expressed in embryos. Further, the transcripts of S100 genes are relatively abundant in mucosal tissues such as gills and gut. Intraperitoneal injection of poly(I:C) resulted in up-regulation of most S100 genes in the gut and spleen, with highest induction of S100V2 and S100Z detected. In fish challenged with spring viremia of carp virus (SVCV), expression of most S100 family genes was increased in the spleen between day 1 and 7 post infection, with consistent induction seen for the S100A1, S100A10b, S100B, S100ICN1, S100T, S100U, S100V1 and S100Z. Interestingly, intraperitoneal injection of Edwardsiella tarda down-regulated S100 expression in the gut but resulted in induction in the spleen. The results demonstrate that the S100 family genes are differentially modulated by bacterial and viral pathogens in zebrafish.

The skin transcriptome in hidradenitis suppurativa uncovers an antimicrobial and sweat gland gene signature which has distinct overlap with wounded skin

Hidradenitis suppurativa (HS) is a debilitating chronic inflammatory skin disease resulting in non-healing wounds affecting body areas of high hair follicle and sweat gland density. The pathogenesis of HS is not well understood but appears to involve dysbiosis-driven aberrant activation of the innate immune system leading to excessive inflammation. Marked dysregulation of antimicrobial peptides and proteins (AMPs) in HS is observed, which may contribute to this sustained inflammation. Here, we analyzed HS skin transcriptomes from previously published studies and integrated these findings through a comparative analysis with a published wound healing data set and with immunofluorescence and qPCR analysis from new HS patient samples. Among the top differently expressed genes between lesional and non-lesional HS skin were members of the S100 family as well as dermcidin, the latter known as a sweat gland-associated AMP and one of the most downregulated genes in HS lesions. Interestingly, many genes associated with sweat gland function, such as secretoglobins and aquaporin 5, were decreased in HS lesional skin and we discovered that these genes demonstrated opposite expression profiles in healing skin. Conversely, HS lesional and wounded skin shared a common gene signature including genes encoding for S100 proteins, defensins, and genes encoding antiviral proteins. Overall, our results suggest that the pathogenesis of HS may be driven by changes in AMP expression and altered sweat gland function, and may share a similar pathology with chronic wounds.

Unique epithelial expression of S100A calcium binding protein A7A in the endometrium at conceptus implantation in pigs

Objective

S100A7A, a member of the S100 protein family, is involved in various biological processes, including innate immunity, antimicrobial function, and epithelial tumorigenesis. However, the expression and function of S100A7A in the endometrium during the estrous cycle and pregnancy are not well understood in pigs. Therefore, this study determined the expression and regulation of S100A7A at the maternal-conceptus interface in pigs.

Methods

We obtained endometrial tissues from pigs throughout the estrous cycle and pregnancy, conceptus tissues during early pregnancy, and chorioallantoic tissues during mid- to late pregnancy and analyzed the expression of S100A7A in these tissues. We also determined the effects of steroid hormones, estradiol-17β (E2) and progesterone, and interleukin-1β (IL1B) on S100A7A expression in endometrial tissues.

Results

We found that S100A7A was expressed in the endometrium during the estrous cycle and pregnancy in a pregnancy status- and stage-dependent manner and was localized to endometrial LE and superficial GE cells with strong intensity in LE cells on Day 12 of pregnancy. Early stage conceptuses and chorioallantoic tissues from Day 30 to term pregnancy also expressed S100A7A. The expression of S100A7A was increased by E2 and IL1B in endometrial tissues.

Conclusion

S100A7A was expressed at the maternal-conceptus interface at the initiation of implantation in response to conceptus-derived estrogen and IL1B and could be a unique endometrial epithelial marker for conceptus implantation in pigs. These findings provide an important insight into the understanding of conceptus-endometrial interactions for the successful establishment of pregnancy in pigs.

Preparation of the Oxidized and Reduced Forms of Psoriasin (S100A7)

Human S100A7 (psoriasin) is a metal-chelating host-defense protein expressed by epithelial cells. S100A7 possesses two Cys residues that generate two redox isoforms of the protein. In the oxidized form (S100A7_ox), Cys47 and Cys96 form an intramolecular disulfide bond, whereas these residues exist as free thiols in the reduced form (S100A7_red). In this chapter, we provide a step-by-step protocol for the purification of S100A7_ox and S100A7_red that affords each protein in high yield and purity. In this procedure, S100A7 is expressed in Escherichia coli BL21(DE3), and the homodimer is obtained following ammonium sulfate precipitation, folding, and column chromatography. Treatment of S100A7 with 1,4-dithiothreitol (DTT) affords S100A7_red. A Cu(II)-catalyzed oxidation reaction is employed to obtain S100A7_ox. A RP-HPLC method that allows for baseline separation of S100A7_ox and S100A7_red is provided, as well as a biochemical Zn(II)-binding assay that can be employed to evaluate the functional integrity of S100A7.

S100 Proteins in the Innate Immune Response to Pathogens

S100 proteins are distinct dimeric EF-hand Ca²⁺-binding proteins that can bind Zn²⁺, Mn²⁺, and other transition metals with high affinity at two sites in the dimer interface. Certain S100 proteins, including S100A7, S100A12, S100A8, and S100A9, play key roles in the innate immune response to pathogens. These proteins function via a "nutritional immunity" mechanism by depleting essential transition metals in the infection that are required for the invading organism to grow and thrive. They also act as damage-associated molecular pattern ligands, which activate pattern recognition receptors (e.g., Toll-like receptor 4, RAGE) that mediate inflammation. Here we present protocols for these S100 proteins for high-level production of recombinant protein, measurement of binding affinities using isothermal titration calorimetry, and an assay of antimicrobial activity.

Serum levels of psoriasin (S100A7) and koebnerisin (S100A15) as potential markers of atherosclerosis in patients with psoriasis

BACKGROUND

Psoriasin (S100A7) and koebnerisin (S100A15) are proinflammatory proteins upregulated in psoriasis, but their relation to atherosclerosis remains unclear.

AIM

To evaluate the role of serum psoriasin and koebnerisin as possible markers for subclinical atherosclerosis in patients with psoriasis.

METHODS

Serum levels of psoriasin and koebnerisin were measured by ELISA in 45 patients with psoriasis and in 45 healthy controls (HCs). Intima-media thickness (IMT) of the right and left common carotid arteries was measured to detect the presence of subclinical atherosclerosis. Clinical severity of psoriasis was estimated using the Psoriasis Area and Severity Index (PASI).

RESULTS

Compared with HCs, patients with psoriasis had significantly higher levels of psoriasin (26.61 ± 22.45 ng/mL vs. 6.31 ± 1.68 ng/mL, P < 0.001) and koebnerisin (21.2 ± 13.12 ng/mL vs. 12.2 ± 4.67 ng/mL, P = 0.001), and significantly higher IMT values (1.07 ± 0.4 mm vs. 0.61 ± 0.1 mm, P < 0.001). A positive correlation was observed between IMT and PASI (r = 0.78, P < 0.001), serum psoriasin (r = 0.48, P > 0.01) and serum koebnerisin (r = 0.48, P < 0.01). Patients with psoriasis with subclinical atherosclerosis had higher serum levels of koebnerisin compared with patients without subclinical atherosclerosis (P = 0.04), which was not observed for psoriasin (P = 0.94).

CONCLUSION

Serum psoriasin and koebnerisin correlate with IMT, underlining their value as a potential link between psoriasis and atherosclerosis. In particular, koebnerisin seems to be a useful marker of subclinical atherosclerosis in patients with psoriasis.

S100 Proteins As an Important Regulator of Macrophage Inflammation

The S100 proteins, a family of calcium-binding cytosolic proteins, have a broad range of intracellular and extracellular functions through regulating calcium balance, cell apoptosis, migration, proliferation, differentiation, energy metabolism, and inflammation. The intracellular functions of S100 proteins involve interaction with intracellular receptors, membrane protein recruitment/transportation, transcriptional regulation and integrating with enzymes or nucleic acids, and DNA repair. The S100 proteins could also be released from the cytoplasm, induced by tissue/cell damage and cellular stress. The extracellular S100 proteins, serving as a danger signal, are crucial in regulating immune homeostasis, post-traumatic injury, and inflammation. Extracellular S100 proteins are also considered biomarkers for some specific diseases. In this review, we will discuss the multi-functional roles of S100 proteins, especially their potential roles associated with cell migration, differentiation, tissue repair, and inflammation.

Th17 micro-milieu regulates NLRP1-dependent caspase-5 activity in skin autoinflammation

IL-1β is a potent player in cutaneous inflammation and central for the development of a Th17 micro-milieu in autoinflammatory diseases including psoriasis. Its production is controlled at the transcriptional level and by subsequent posttranslational processing via inflammatory caspases. In this study, we detected inflammatory caspase-5 active in epidermal keratinocytes and in psoriatic skin lesions. Further, interferon-γ and interleukin-17A synergistically induced caspase-5 expression in cultured keratinocytes, which was dependent on the antimicrobial peptide psoriasin (S100A7). However, diseases-relevant triggers for caspase-5 activity and IL-1β production remain unknown. Recently, extranuclear DNA has been identified as danger-signals abundant in the psoriatic epidermis. Here, we could demonstrate that cytosolic double-stranded (ds) DNA transfected into keratinocytes triggered the activation of caspase-5 and the release of IL-1β. Further, interleukin-17A promoted caspase-5 function via facilitation of the NLRP1-inflammasome. Anti-inflammatory vitamin D interfered with the IL-1β release and suppressed caspase-5 in keratinocytes and in psoriatic skin lesions. Our data link the disease-intrinsic danger signals psoriasin (S100A7) and dsDNA for NLPR1-dependent caspase-5 activity in psoriasis providing potential therapeutic targets in Th17-mediated skin autoinflammation.

S100 Proteins As an Important Regulator of Macrophage Inflammation

The S100 proteins, a family of calcium-binding cytosolic proteins, have a broad range of intracellular and extracellular functions through regulating calcium balance, cell apoptosis, migration, proliferation, differentiation, energy metabolism, and inflammation. The intracellular functions of S100 proteins involve interaction with intracellular receptors, membrane protein recruitment/transportation, transcriptional regulation and integrating with enzymes or nucleic acids, and DNA repair. The S100 proteins could also be released from the cytoplasm, induced by tissue/cell damage and cellular stress. The extracellular S100 proteins, serving as a danger signal, are crucial in regulating immune homeostasis, post-traumatic injury, and inflammation. Extracellular S100 proteins are also considered biomarkers for some specific diseases. In this review, we will discuss the multi-functional roles of S100 proteins, especially their potential roles associated with cell migration, differentiation, tissue repair, and inflammation.

Psoriasis-Specific RNA Isoforms Identified by RNA-Seq Analysis of 173,446 Transcripts

BACKGROUND

Several studies have been published that investigated potential links between transcriptome changes and psoriasis using microarrays and RNA-seq technologies, but no previous study has analyzed expression profile of alternatively spliced transcripts in psoriasis.

OBJECTIVES

Identification of potential alternatively spliced RNA isoforms with disease-specific expression profile.

METHODS

Using our published RNA sequencing data from lesional psoriatic (LP), non-lesional psoriatic (NLP), and normal control skin (C), we analyzed the differential expression of RNA splicing variants. LP sample was compared with NLP, as was LP with C and NLP with C.

RESULTS

Transcript-based annotation analyzed 173,446 transcripts (RNA isoforms), and around 9,000 transcripts were identified as differentially expressed between study groups. Several previously undescribed RNA variants were found. For instance, transcript ETV3_3 (ENST00000326786) was significantly downregulated in LP and NLP skin. ETV3 is a transcriptional repressor that contributes to the downstream anti-inflammatory effects of IL-10. We also identified diseases-specific transcripts (S100A7A, IL36RN_4, and IL36G_3) of genes already recognized to be involved in inflammation and immune response.

CONCLUSION

Psoriasis is characterized by significant differences in the expression of RNA alternative isoforms. Description of these new isoforms improves our knowledge about this complex disease.

S100A12 Is Part of the Antimicrobial Network against Mycobacterium leprae in Human Macrophages

Triggering antimicrobial mechanisms in macrophages infected with intracellular pathogens, such as mycobacteria, is critical to host defense against the infection. To uncover the unique and shared antimicrobial networks induced by the innate and adaptive immune systems, gene expression profiles generated by RNA sequencing (RNAseq) from human monocyte-derived macrophages (MDMs) activated with TLR2/1 ligand (TLR2/1L) or IFN-γ were analyzed. Weighed gene correlation network analysis identified modules of genes strongly correlated with TLR2/1L or IFN-γ that were linked by the “defense response” gene ontology term. The common TLR2/1L and IFN-γ inducible human macrophage host defense network contained 16 antimicrobial response genes, including S100A12, which was one of the most highly induced genes by TLR2/1L. There is limited information on the role of S100A12 in infectious disease, leading us to test the hypothesis that S100A12 contributes to host defense against mycobacterial infection in humans. We show that S100A12 is sufficient to directly kill Mycobacterium tuberculosis and Mycobacterium leprae. We also demonstrate that S100A12 is required for TLR2/1L and IFN-γ induced antimicrobial activity against M. leprae in infected macrophages. At the site of disease in leprosy, we found that S100A12 was more strongly expressed in skin lesions from tuberculoid leprosy (T-lep), the self-limiting form of the disease, compared to lepromatous leprosy (L-lep), the progressive form of the disease. These data suggest that S100A12 is part of an innate and adaptive inducible antimicrobial network that contributes to host defense against mycobacteria in infected macrophages.

Macrophage antimicrobial activity induced by innate and adaptive immune stimuli is crucial for controlling infection against intracellular pathogens. In order to characterize host defense pathways, we activated human macrophages with innate and adaptive immune stimuli known to induce antimicrobial activity against mycobacteria, identifying a set of 16 antimicrobial response genes. One of these, S100A12, is present in humans, but not mice, has limited studies in infectious disease. By studying leprosy as a model, we found that expression of S100A12 was greater in skin lesions from patients with the self-limiting versus the progressive form of the disease. Furthermore, we show that S100A12 is sufficient to kill mycobacteria and is required for decreasing the relative viability of M. leprae in infected macrophages.

Leukocyte-derived koebnerisin (S100A15) and psoriasin (S100A7) are systemic mediators of inflammation in psoriasis

BACKGROUND

Psoriasis is a systemic immune-mediated chronic inflammatory disease. In the skin, the antimicrobial proteins koebnerisin (S100A15) and psoriasin (S100A7) are overexpressed in the epidermis of psoriatic lesions and mediate inflammation as chemoattractants for immune cells. Their role for systemic inflammation in circulating leukocytes is unknown.

OBJECTIVE

The aim of the study was to identify circulating leukocyte populations as a source of koebnerisin and psoriasin. Further, immune-stimulatory effects of these S100A proteins on circulating leukocytes were evaluated and their role as therapeutic response markers in patients with psoriasis was analyzed upon UVB treatment.

METHODS

The expression and production of koebnerisin and psoriasin by leukocytes were assessed by quantitative real-time PCR (qRT-PCR) and immunoblotting. The S100A protein mediated regulation of proinflammatory cytokines by peripheral blood mononuclear cells (PBMCs) was measured with qRT-PCR and cytometric bead assay.

RESULTS

We identified circulating leukocytes as novel sources of koebnerisin (S100A15) and psoriasin (S100A7). Circulating leukocytes (PBMCs) of patients with psoriasis produced increased levels of koebnerisin and psoriasin compared to healthy individuals. Both S100A proteins further acted as 'alarmins' on PBMC to induce proinflammatory cytokines implicated in the pathogenesis of psoriasis, such as IL-1β, TNF-α, IL-6 and IL-8. Koebnerisin levels were suppressed in PBMC of psoriatic patients when effectively treated with narrow-band UVB.

CONCLUSIONS

Data suggest that koebnerisin and psoriasin are systemic pro-inflammatory mediators and koebnerisin acts as a therapeutic response marker in psoriasis.

The antimicrobial peptides psoriasin (S100A7) and koebnerisin (S100A15) suppress extracellular matrix production and proliferation of human fibroblasts

BACKGROUND/AIMS

Keloids result from aberrations in the normal wound healing cascade and can lead to pruritus, contractures and pain. The underlying mechanisms of excessive scarring are not yet understood, and most therapeutic strategies remain unsatisfactory. Psoriasin (S100A7) and koebnerisin (S100A15) are released by keratinocytes during physiological wound healing. We found S100 production is markedly decreased in keloid scar tissue. The disturbed epidermal S100 expression might contribute to keloid formation; thus, we studied their effect on dermal fibroblasts and extracellular matrix (ECM) production.

METHODS

S100 peptides, ECM regulation and distribution were analysed in normal and keloid tissue by quantitative PCR (qPCR), immunoblotting and immunofluorescent staining. Isolated dermal fibroblasts were incubated with S100 proteins, and the regulation of ECM and transforming growth factor (TGF)-β was determined using qPCR. Fibroblast proliferation and viability were determined by the 5-bromo-2'-deoxyuridine assay and crystal violet assay.

RESULTS

Keloid tissue featured a pronounced expression of ECMs, such as collagen types 1 and 3, whereas the production of psoriasin and koebnerisin was markedly decreased in keloid-derived cells and keloid tissue. Both S100 proteins inhibited the expression of collagens, fibronectin-1, α-smooth-muscle actin and TGF-β by fibroblasts. Further, they also suppressed fibroblast proliferation.

CONCLUSION

Psoriasin and koebnerisin show antifibrotic effects and may lead to novel preventive and therapeutic strategies for fibroproliferative diseases.

The secreted protein S100A7 (psoriasin) is induced by telomere dysfunction in human keratinocytes independently of a DNA damage response and cell cycle regulators

Background

Replicative senescence is preceded by loss of repeat sequences of DNA from the telomeres that eventually leads to telomere dysfunction, the accumulation of irreparable DNA double strand breaks and a DNA damage response (DDR). However, we have previously reported that whilst telomere dysfunction in human keratinocytes is associated with a permanent cell cycle arrest, the DDR was very weak and transcriptional profiling also revealed several molecules normally associated with keratinocytes terminal differentiation, including S100A7 (psoriasin).

Results

We show here that S100A7 and the closely related S100A15 (koebnerisin) are not induced by repairable or irreparable DSBs, ruling out the hypotheses that these genes are induced either by the low DDR observed or by non-specific cell cycle arrest. We next tested whether S100A7 was induced by the cell cycle effectors ARF (p14^ARF), CDKN2A (p16^INK4A) and TP53 (p53) and found that, although all induced a similar level of acute and permanent cell cycle arrest to telomere dysfunction, none induced S100A7 (except p53 over-expression at high levels), showing that cell cycle arrest is not sufficient for its induction. The closely related transcript S100A15 was also upregulated by telomere dysfunction, to a similar extent by p16^INK4A and p53 and to a lesser extent by p14^ARF.

Conclusions

Our results show that mere cell cycle arrest, the upregulation of senescence-associated cell cycle effectors and DNA damage are not sufficient for the induction of the S100 transcripts; they further suggest that whilst the induction of S100A15 expression is linked to both telomere-dependent and -independent senescence, S100A7 expression is specifically associated with telomere-dependent senescence in normal keratinocytes. As both S100A7 and S100A15 are secreted proteins, they may find utility in the early detection of human keratinocyte telomere dysfunction and senescence.

The new insight into the role of antimicrobial proteins-alarmins in the immunopathogenesis of psoriasis

The pathognesis of psoriasis still remains not fully elucidated. Recent advances favor the idea that interactions between innate and adaptive immune response drive inflammatory process in this disease. Innate antimicrobial peptides and proteins (AMPs) are diverse group of small molecules that provide the first line of defense against invading pathogens. In recent years, the novel functions of AMPs have been identified. There are three subclasses among AMPs that have gained the special interest as a potentially important player in the pathogenesis of psoriasis: cathelicidin, S100 proteins, and defensins. These AMPs have been shown to modulate and trigger host immune response in psoriasis acting as interplayer between innate and adaptive immune mechanisms. Overexpressed in psoriatic lesions, they prime immune cells for enhanced production of proinflammatory mediators and act as chemoattractant for leukocytes. Therefore, the novel term describing AMPs alarmins has been suggested. As multifunctional player in pathogenesis of psoriasis, AMPs may constitute potential target for therapeutic interventions. However, further investigations are required to establish the methods of downregulation of the aberrant proinflammatory functions of AMPs without increasing the risk of infections.

¹H, ¹³C and ¹⁵N resonance assignments of Ca²⁺-bound human S100A15

S100A15 (koebnerisin) is overexpressed in psoriatic skin and displays distinct localizations in skin and breast with divergent functions in inflammation. Here we report the backbone and side-chain resonance assignments for the Ca(2+)-bound human S100A15.

The emerging role of the receptor for advanced glycation end products on innate immunity

Cells from innate immune system are activated by the engagement of germ-line encoded pattern-recognition receptors (PRRs) in response to the microbial insult. These receptors are able to recognize either the presence of highly conserved microbial components called pathogen-associated molecular patterns or endogenous danger-associated molecular patterns. These danger signals are recognized by different types of (PRRs), including the receptor for advanced glycation end products. This new PRR share both ligands and intracellular signaling with Toll-like receptors and thus may cooperate with each other as essential partners to strength inflammatory response. This review summarizes recent advances in understanding the promiscuity of this receptor as well as its role in the context of innate immunity by triggering an inflammatory response when innate immune cells detect infection or tissue injury.

Molecular evolution of a novel marsupial S100 protein (S100A19) which is expressed at specific stages of mammary gland and gut development

S100 proteins are calcium-binding proteins involved in controlling diverse intracellular and extracellular processes such as cell growth, differentiation, and antimicrobial function. We recently identified a S100-like cDNA from the tammar wallaby (Macropus eugenii) stomach. Phylogentic analysis shows wallaby S100A19 forms a new clade with other marsupial and monotreme S100A19, while this group shows similarity to eutherian S100A7 and S100A15 genes. This is also supported by amino acid and domain comparisons. We show S100A19 is developmentally-regulated in the tammar wallaby gut by demonstrating the gene is expressed in the forestomach of young animals at a time when the diet consists of only milk, but is absent in older animals when the diet is supplemented with herbage. During this transition the forestomach phenotype changes from a gastric stomach into a fermentation sac and intestinal flora changes with diet. We also show that S100A19 is expressed in the mammary gland of the tammar wallaby only during specific stages of lactation; the gene is up-regulated during pregnancy and involution and not expressed during the milk production phase of lactation. Comparison of the tammar wallaby S100A19 protein sequence with S100 protein sequences from eutherian, monotreme and other marsupial species suggest the marsupial S100A19 has two functional EF hand domains, and an extended His tail. An evolutionary analysis of S100 family proteins was carried out to gain a better understanding of the relationship between the S100 family member functions. We propose that S100A19 gene/protein is the ancestor of the eutherian S100A7 gene/protein, which has subsequently modified its original function in eutherians. This modified function may have arisen due to differentiation of evolutionary pressures placed on gut and mammary gland developmental during mammal evolution. The highly regulated differential expression patterns of S100A19 in the tammar wallaby suggests that S100A19 may play a role in gut development, which differs between metatherians and eutherians, and/or include a potential antibacterial role in order to establish the correct flora and protect against spiral bacteria in the immature forestomach. In the mammary gland it may protect the tissue from infection at times of vulnerability during the lactation cycle.

Opposing functions of psoriasin (S100A7) and koebnerisin (S100A15) in epithelial carcinogenesis

The S100 protein family is involved in epithelial cell maturation and inflammation. Some S100 members are dysregulated during carcinogenesis and have been established as tumor markers. Psoriasin (S100A7) and koebnerisin (S100A15) are highly homologous proteins that have been first described in psoriasis, which is characterized by disturbed epidermal maturation and chronic inflammation. Despite their homology, both S100 proteins are distinct in expression and function through different receptors but synergize as chemoattractants and pro-inflammatory 'alarmins' to promote inflammation. Psoriasin and koebnerisin are further regulated with tumor progression in epithelial cancers. In tumor cells, high cytoplasmic expression of psoriasin and koebnerisin may prevent oncogenic activity, whereas their nuclear translocation and extracellular secretion are associated with tumor progression and poor prognosis. The present review outlines these opposing effects of psoriasin and koebnerisin in multifunctional pathways and mechanisms that are known to affect tumor cells ('seeds'), tumor environment ('soil') and tumor cell metastasis ('seeding') thereby influencing epithelial carcinogenesis.

Structural characterization of S100A15 reveals a novel zinc coordination site among S100 proteins and altered surface chemistry with functional implications for receptor binding

Background

S100 proteins are a family of small, EF-hand containing calcium-binding signaling proteins that are implicated in many cancers. While the majority of human S100 proteins share 25-65% sequence similarity, S100A7 and its recently identified paralog, S100A15, display 93% sequence identity. Intriguingly, however, S100A7 and S100A15 serve distinct roles in inflammatory skin disease; S100A7 signals through the receptor for advanced glycation products (RAGE) in a zinc-dependent manner, while S100A15 signals through a yet unidentified G-protein coupled receptor in a zinc-independent manner. Of the seven divergent residues that differentiate S100A7 and S100A15, four cluster in a zinc-binding region and the remaining three localize to a predicted receptor-binding surface.

Results

To investigate the structural and functional consequences of these divergent clusters, we report the X-ray crystal structures of S100A15 and S100A7D24G, a hybrid variant where the zinc ligand Asp24 of S100A7 has been substituted with the glycine of S100A15, to 1.7 Å and 1.6 Å resolution, respectively. Remarkably, despite replacement of the Asp ligand, zinc binding is retained at the S100A15 dimer interface with distorted tetrahedral geometry and a chloride ion serving as an exogenous fourth ligand. Zinc binding was confirmed using anomalous difference maps and solution binding studies that revealed similar affinities of zinc for S100A15 and S100A7. Additionally, the predicted receptor-binding surface on S100A7 is substantially more basic in S100A15 without incurring structural rearrangement.

Conclusions

Here we demonstrate that S100A15 retains the ability to coordinate zinc through incorporation of an exogenous ligand resulting in a unique zinc-binding site among S100 proteins. The altered surface chemistry between S100A7 and S100A15 that localizes to the predicted receptor binding site is likely responsible for the differential recognition of distinct protein targets. Collectively, these data provide novel insight into the structural and functional consequences of the divergent surfaces between S100A7 and S100A15 that may be exploited for targeted therapies.

Vitamin D analog calcipotriol suppresses the Th17 cytokine-induced proinflammatory S100 "alarmins" psoriasin (S100A7) and koebnerisin (S100A15) in psoriasis

The antimicrobial peptides (AMP) psoriasin (S100A7) and koebnerisin (S100A15) are differently induced in psoriatic skin. They act synergistically as chemoattractants and "alarmins" to amplify inflammation in psoriasis. Th17 cytokines are key players in psoriasis pathogenesis and vitamin D analogs feature anti-psoriatic effects; both of these activities could be mediated through epidermal AMP regulation. We show that supernatants of cultured psoriatic T cells induce and release psoriasin and koebnerisin from keratinocytes and the Th17 cytokines IL-17A, tumor necrosis factor-α, and IL-22 differently regulate psoriasin and koebnerisin reflecting their distinct expression pattern in normal and psoriatic skin. IL-17A is the principal inducer of both S100 and their expression is further amplified by cooperating Th17 cytokines in the micromilieu of psoriatic skin. Increased extracellular psoriasin and koebnerisin also synergize as "alarmins" to prime epidermal keratinocytes for production of immunotropic cytokines that further amplify the inflammatory response. Treatment of psoriatic plaques with the vitamin D analog calcipotriol interferes with the S100-mediated positive feedback loop by suppressing the increased production of psoriasin and koebnerisin in psoriatic skin and their Th17-mediated regulation in epidermal keratinocytes. Thus, targeting the S100-amplification loop could be a beneficial anti-inflammatory approach in psoriasis and other inflammatory skin diseases.

Novel S100A7 (psoriasin)/S100A15 (koebnerisin) subfamily: highly homologous but distinct in regulation and function

S100A7 (psoriasin) and S100A15 (koebnerisin) were first identified in inflamed psoriatic skin. They are of major interest because of their putative functional roles in innate immunity, epidermal cell maturation, and epithelial tumorigenesis. Human S100A7 and S100A15 have lately evolved by gene duplications within the epidermal differentiation complex (chromosome 1q21) during primate evolution forming a novel S100 subfamily. Therefore, S100A7 and S100A15 are almost identical in sequence (>90%) and are difficult to discriminate. Despite their high homology, S100A7 and S100A15 are distinct in tissue distribution, regulation, and function, and thus, exemplary for the diversity within the S100 family. Their different properties are compelling reasons to discriminate S100A7 (psoriasin) and S100A15 (koebnerisin) in epithelial homeostasis, inflammation, and cancer.

Gene from a psoriasis susceptibility locus primes the skin for inflammation

Psoriasis is a common complex genetic disease characterized by hyperplasia and inflammation in the skin; however, the relative contributions of epidermal cells and the immune system to disease pathogenesis remain unclear. Linkage studies have defined a psoriasis susceptibility locus (PSORS4) on 1q21, the epidermal differentiation complex, which includes genes for small S100 calcium-binding proteins. These proteins are involved in extracellular and intracellular signaling during epithelial host defense, linking innate and adaptive immunity. Inflammation-prone psoriatic skin constitutively expresses elevated concentrations of S100A7 (psoriasin) and S100A15 (koebnerisin) in the epidermis. Here, we report that genetically modified mice expressing elevated amounts of doxycycline-regulated mS100a7a15 in skin keratinocytes demonstrated an exaggerated inflammatory response when challenged by exogenous stimuli such as abrasion (Koebner phenomenon). This immune response was characterized by immune cell infiltration and elevated concentrations of T helper 1 (T(H)1) and T(H)17 proinflammatory cytokines, which have been linked to the pathogenesis of psoriasis and were further amplified upon challenge. Both inflammation priming and amplification required mS100a7a15 binding to the receptor of advanced glycation end products (RAGE). mS100a7a15 potentiated inflammation by acting directly as a chemoattractant for leukocytes, further increasing the number of inflammatory cells infiltrating the skin. This study provides a pathogenetic psoriasis model using a psoriasis candidate gene to link the epidermis and innate immune system in inflammation priming, highlighting the S100A7A15-RAGE axis as a potential therapeutic target.

Identification of differentially expressed genes in the uterine endometrium on day 12 of the estrous cycle and pregnancy in pigs

Maternal recognition of pregnancy in pigs occurs approximately on Day (D) 12 of pregnancy and is critical for embryo implantation. The presence of the conceptus in the uterine lumen during this period changes uterine endometrial function to prepare for attachment of the conceptus to the endometrial epithelial cells and maintain luteal function in the ovary. Although much is known about endometrial gene expression, the genes expressed in the uterine endometria and the cellular and molecular mechanisms of those gene products during the period of implantation and maternal recognition of pregnancy in pigs are still not completely defined. To better understand the interactions between the maternal uterus and conceptus during the implantation process, we searched genes differentially expressed in the endometria on D12 of pregnancy compared to those on D12 of the estrous cycle. A new reverse transcription-polymerase chain reaction (RT-PCR)-based method that involves annealing control primers (ACPs) was employed. Using 120 ACPs, we sequenced 12 differentially expressed genes (DEGs) and identified those genes using the Basic Local Alignment Search Tool (BLAST). Northern blot hybridization analysis confirmed the differential expression of those DEGs in the uterine endometrium. In situ hybridization analysis determined the cell-type specific expression of the DEGs in the uterine endometrium. Further analysis of the DEGs found in this study will provide insights into the cellular and molecular basis of maternal and fetal interactions during the period of maternal recognition of pregnancy in the pig. Mol. Reprod. Dev. 76: 75-84, 2009. (c) 2008 Wiley-Liss, Inc.

Highly homologous hS100A15 and hS100A7 proteins are distinctly expressed in normal breast tissue and breast cancer

Human S100A7 (psoriasin) is considered a marker for specific stages of breast cancer. hS100A15 is almost identical to hS100A7 and difficult to discriminate. We developed specific probes to distinguish hS100A7 and hS100A15, and demonstrate their differential distribution in normal breast tissue. Further, hS100A7 and S100A15 transcripts are elevated in ER/PR negative breast cancers, but hS100A15 protein is detected in all cancer specimens while hS100A7 protein is sporadically expressed. The differential regulation, expression and distribution of hS100A7 and hS100A15 and their reported distinct functions are compelling reasons to discriminate among these proteins in normal breast and breast cancers.

Chemotactic activity of S100A7 (Psoriasin) is mediated by the receptor for advanced glycation end products and potentiates inflammation with highly homologous but functionally distinct S100A15

Human S100A7 (psoriasin) is overexpressed in inflammatory diseases. The recently discovered, co-evolved hS100A15 is almost identical in sequence and up-regulated with hS100A7 during cutaneous inflammation. The functional role of these closely related proteins for inflammation remains undefined. By generating specific Abs, we demonstrate that hS100A7 and hS100A15 proteins are differentially expressed by specific cell types in the skin. Although highly homologous, both proteins are chemoattractants with distinct chemotactic activity for leukocyte subsets. We define RAGE (receptor for advanced glycation end products) as the hS100A7 receptor, whereas hS100A15 functions through a Gi protein-coupled receptor. hS100A7-RAGE binding, signaling, and chemotaxis are zinc-dependent in vitro, reflecting the previously reported zinc-mediated changes in the hS100A7 dimer structure. When combined, hS100A7 and hS100A15 potentiate inflammation in vivo. Thus, proinflammatory synergism in disease may be driven by the diverse biology of these almost identical proteins that have just recently evolved. The identified S100A7 interaction with RAGE may provide a novel therapeutic target for inflammation.

Comprehensive evaluation of genetic variation in S100A7 suggests an association with the occurrence of allergic rhinitis

Background

S100A7 is a calcium-binding protein with chemotactic and antimicrobial properties. S100A7 protein levels are decreased in nasal lavage fluid from individuals with ongoing allergic rhinitis, suggesting a role for S100A7 in allergic airway inflammation. The aims of this study were to describe genetic variation in S100A7 and search for associations between this variation and allergic rhinitis.

Methods

Peripheral blood was collected from 184 atopic patients with a history of pollen-induced allergic rhinitis and 378 non-atopic individuals, all of Swedish origin. DNA was extracted and the S100A7 gene was resequenced in a subset of 47 randomly selected atopic individuals. Nine polymorphisms were genotyped in 184 atopic and 378 non-atopic individuals and subsequently investigated for associations with allergic rhinitis as well as skin prick test results. Haplotypes were estimated and compared in the two groups.

Results

Thirteen polymorphisms were identified in S100A7, of which 7 were previously undescribed. rs3014837 (G/C), which gives rise to an Asp → Glu amino acid shift, had significantly increased minor allele frequency in atopic individuals. The major haplotype, containing the major allele at all sites, was more common in non-atopic individuals, while the haplotype containing the minor allele at rs3014837 was equally more common among the atopic individuals. Additionally, heterozygotes at this site had significantly higher scores in skin prick tests for 9 out of 11 tested allergens, compared to homozygotes.

Conclusion

This is the first study describing genetic variation, associated with allergy, in S100A7. The results indicate that rs3014837 is linked to allergic rhinitis in our Swedish population and render S100A7 a strong candidate for further investigations regarding its role in allergic inflammation.

Innate immunity and antimicrobial defense systems in psoriasis

Psoriasis is a chronic inflammatory disorder that is mediated by elements of the innate and adaptive immune systems. Its characteristic features in the skin consist of inflammatory changes in both dermis and epidermis, with abnormal keratinocyte differentiation and proliferation. Despite the elucidation of many aspects of psoriasis pathogenesis, some puzzling questions remain to be answered. A major question currently debated is whether psoriasis is a primary abnormality of the epidermal keratinocyte or a reflection of dysregulated bone marrow-derived immunocytes. In this review we will focus on understanding the role of the innate immune system in psoriasis and how this provides a rational solution to address the origin of this multifactorial disease. Innate immunity is nonspecific and genetically based. It protects the body against the constant risk of pathogens through the use of rapidly mobilized defenses that are able to recognize and kill a variety of threats (bacteria, fungi, viruses, etc). The key mechanisms of innate immune responses are the existence of receptors to recognize pathogens and the production of factors that kill pathogens, such as antimicrobial peptides and proteins. Any combination of excessive sensitivity of the innate detection system, or dysregulation of the response system, can manifest both an epidermal phenotype and an abnormal T-cell function. Thus, the multidimensional action of the innate immune system, its triggers, and its recently understood role in T-cell function argue for an important role for innate mechanisms of recognition and response in the pathogenesis of psoriasis.

Flagellin is the principal inducer of the antimicrobial peptide S100A7c (psoriasin) in human epidermal keratinocytes exposed to Escherichia coli

Epidermal keratinocytes (KCs) express antimicrobial peptides as a part of the innate immune response. It has recently been shown that the culture supernatant of Escherichia coli induces the expression of S100A7c (psoriasin) in KCs and that S100A7c efficiently kills E. coli. Here we have investigated which of the microbial components triggers the up-regulation of S100A7c expression. Exposure of human primary KCs to ligands of the human Toll-like receptors (TLRs) revealed that only the TLR5 ligand flagellin strongly induced the expression of S100A7c mRNA and protein, whereas all other TLR ligands had no significant effect. In contrast to the supernatant from flagellated wild-type (WT) E. coli, the supernatant of a flagellin-deficient E. coli strain (DeltaFliC) did not induce S100A7c expression. Small interfering RNA-mediated knockdown of TLR5 expression suppressed the ability of KCs to up-regulate S100A7c expression in response to both flagellin and WT E. coli supernatant. Taken together, our data demonstrate that bacterial flagellin is essential and sufficient for the induction of S100A7c expression in KCs by E. coli.

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.

Inactivation of MOXD2 and S100A15A by exon deletion during human evolution

We devised a bioinformatics method for systematic identification of putative human-specific exon-deletion mutations that occurred after the divergence of human and chimpanzee and experimentally verified 2 of the predicted mutations in MOXD2 and S100A15A genes. MOXD2 gene encodes a monooxygenase that is highly conserved in mammals and is mostly expressed in the olfactory epithelium in mouse. The presence of a deletion of the last 2 exons and a polymorphic nonsense mutation in exon 6 suggests that MOXD2 gene is inactive in humans. S100A15A is a member of the S100 family of calcium-binding proteins, the mouse ortholog of which is expressed during epidermal maturation. Human S100A15A gene is likely to be inactive because the start codon-bearing exon is deleted in human. We propose that modification or inactivation of MOXD2 and S100A15A genes have contributed to the loss of certain smell sense in humans and to the development of human skin.

S100A15, an antimicrobial protein of the skin: regulation by E. coli through Toll-like receptor 4

E. coli is a gram-negative bacterium rarely found on human skin. We investigated whether direct interaction of E. coli with keratinocytes might induce an innate immune response through recognition by pattern recognition receptors. The capacity of E. coli to activate innate immune responses and IL-8 induction was investigated. We found that E. coli significantly induced human S100A7 and S100A15 transcript abundance and IL-8 release in cultured primary human keratinocytes. S100A15 is a member of the S100 protein family with previously unknown function. E. coli induced effects could be inhibited by neutralizing Toll-like receptor 4 (TLR4) antibodies, suggesting that E. coli-induced IL-8 and S100A15 expression in human keratinocytes are TLR4 dependent. TLR4-/- mice lacked elevated mS100A15 expression after infection with E. coli in contrast to wild-type mice. In vitro, human S100A15 displayed antimicrobial activity against E. coli. Our findings suggest that E. coli modulates S100A15 and IL-8 expression of keratinocytes by recognition through TLR4.

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.

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.

Differential gene expression of S100 protein family in leukocytes from patients with Kawasaki disease

S100 family proteins are calcium-binding proteins, some of which have been shown to have intracellular and extracellular functions associated with inflammation. The serum concentration of S100A12 has been reported to increase in the acute phase of Kawasaki disease. The purpose of this study was to evaluate leukocyte gene expressions of S100 family proteins in the acute phase of Kawasaki disease. Ten paired blood samples were obtained from ten patients with Kawasaki disease in the acute phase and in the convalescent phase. We examined leukocyte expression levels of 18 S100 genes in the acute phase compared with those in the convalescent phase by using quantitative real-time polymerase chain reaction. Significantly elevated expression of seven S100 genes (S100A6, A8, A9, A11, A12, S100P, and S100Z) was observed in the acute phase.

CONCLUSION

Of the upregulated S100 genes, calgranulin members of S100 genes (S100A8, S100A9, and S100A12) were most highly expressed in the acute phase. Only one S100 gene, the S100A13 gene, exhibited a significantly decreased expression level in the acute phase.

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.

Phagocyte-specific calcium-binding S100 proteins as clinical laboratory markers of inflammation

The EF-hand homolog family of S100 proteins comprises the largest group of calcium-binding proteins. Within this S100 family, the phagocyte-specific calcium-binding proteins are pro-inflammatory molecules expressed and secreted by phagocytes, which play a pivotal role within the innate immune system. Although the exact biological functions of these proteins still remain to be defined in greater detail, there is evidence that they are involved in a pro-inflammatory axis associated with various inflammatory conditions. The three members of this group, S100A8, S100A9 and S100A12 are overexpressed at local sites of inflammation. High concentrations are found in synovial fluid, sputum, stool and blood plasma/serum during inflammation. Both the S100A8/S100A9 complex and S100A12 have been proven to be useful as diagnostic markers of inflammation especially in non-infectious inflammatory diseases such as arthritis, chronic inflammatory lung and bowel disease. They indicate phagocyte activation more sensitively than conventional parameters of inflammation. As a consequence, there is a strong correlation to the inflammation of various acute and chronic disorders, making these proteins sensitive parameters for the monitoring of disease activity and response to treatment in individual patients. The phagocyte-specific S100 proteins are able to indicate minimal residual inflammation, which is not detected by other diagnostic tests, and they may even be prospective markers for the outcome of patients. In this review, pro-inflammatory functions of S100 proteins and their usefulness as biomarkers of inflammation are presented.