Joining S100 proteins and migration: for better or for worse, in sickness and in health

Myosin Motors: Novel Regulators and Therapeutic Targets in Colorectal Cancer

Simple Summary

Colorectal cancer (CRC) is a deadly disease that may go undiagnosed until it presents at an advanced metastatic stage for which few interventions are available. The development and metastatic spread of CRC is driven by remodeling of the actin cytoskeleton in cancer cells. Myosins represent a large family of actin motor proteins that play key roles in regulating actin cytoskeleton architecture and dynamics. Different myosins can move and cross-link actin filaments, attach them to the membrane organelles and translocate vesicles along the actin filaments. These diverse activities determine the key roles of myosins in regulating cell proliferation, differentiation and motility. Either mutations or the altered expression of different myosins have been well-documented in CRC; however, the roles of these actin motors in colon cancer development remain poorly understood. The present review aims at summarizing the evidence that implicate myosin motors in regulating CRC growth and metastasis and discusses the mechanisms underlying the oncogenic and tumor-suppressing activities of myosins.

Abstract

Colorectal cancer (CRC) remains the third most common cause of cancer and the second most common cause of cancer deaths worldwide. Clinicians are largely faced with advanced and metastatic disease for which few interventions are available. One poorly understood aspect of CRC involves altered organization of the actin cytoskeleton, especially at the metastatic stage of the disease. Myosin motors are crucial regulators of actin cytoskeletal architecture and remodeling. They act as mechanosensors of the tumor environments and control key cellular processes linked to oncogenesis, including cell division, extracellular matrix adhesion and tissue invasion. Different myosins play either oncogenic or tumor suppressor roles in breast, lung and prostate cancer; however, little is known about their functions in CRC. This review focuses on the functional roles of myosins in colon cancer development. We discuss the most studied class of myosins, class II (conventional) myosins, as well as several classes (I, V, VI, X and XVIII) of unconventional myosins that have been linked to CRC development. Altered expression and mutations of these motors in clinical tumor samples and their roles in CRC growth and metastasis are described. We also evaluate the potential of using small molecular modulators of myosin activity to develop novel anticancer therapies.

An Integrated Bioinformatic Analysis of the S100 Gene Family for the Prognosis of Colorectal Cancer

Background

S100 family genes exclusively encode at least 20 calcium-binding proteins, which possess a wide spectrum of intracellular and extracellular functions in vertebrates. Multiple lines of evidences suggest that dysregulated S100 proteins are associated with human malignancies including colorectal cancer (CRC). However, the diverse expression patterns and prognostic roles of distinct S100 genes in CRC have not been fully elucidated.

Methods

In the current study, we analyzed the mRNA expression levels of S100 family genes and proteins and their associations with the survival of CRC patients using the Oncomine analysis and GEPIA databases. Expressions and mutations of S100 family genes were analyzed using the cBioPortal, and protein-protein interaction (PPI) networks of S100 proteins and their mutation-related coexpressed genes were analyzed using STRING and Cytoscape.

Results

We observed that the mRNA expression levels of S100A2, S100A3, S100A9, S100A11, and S100P were higher and the level of S100B was lower in CRC tissues than those in normal colon mucosa. A high S100A10 levels was associated with advanced-stage CRC. Results from GEPIA database showed that highly expressed S100A1 was correlated with worse overall survival (OS) and disease-free survival (DFS) and that overexpressions of S100A2 and S100A11 were associated with poor DFS of CRC, indicating that S100A1, S100A2, and S100A11 are potential prognostic markers. Unexpectedly, most of S100 family genes showed no significant prognostic values in CRC.

Conclusions

Our findings, though still need to be ascertained, offer novel insights into the prognostic implications of the S100 family in CRC and will inspire more clinical trials to explore potential S100-targeted inhibitors for the treatment of CRC.

S100A8 and S100A9 promote endothelial cell activation through the RAGE‑mediated mammalian target of rapamycin complex 2 pathway

S100 calcium binding protein A8 (S100A8) and A9 (S100A9) belong to the S100 family of calcium-binding proteins and have important roles in inflammation. They increase endothelial cell proliferation, thereby affecting inflammation, angiogenesis and tumorigenesis. However, the mechanism of action of S100A8/9 in endothelial cells needs further study. Therefore, the present study sought to investigate the effects of S100A8/9 on the proliferation and angiogenesis of human umbilical vein endothelial cells (HUVECs) and their mechanism of action. The viability of HUVECs was determined through a Cell Counting Kit-8 assay. The effect of S100A8/9 on the proliferation of HUVECs was detected by flow cytometry. Migration was evaluated by a Transwell migration assay. Apoptosis was evaluated by Annexin V-FITC and PI staining via flow cytometry. Western blot analysis and reverse transcription-quantitative polymerase chain reaction assays were performed to evaluate the activation of the phosphatidylinositol 3-phosphate kinase (PI3K)/Akt/mTOR pathway and mTOR complex 2 (mTORC2). We previously confirmed that S100A8/9 were consistently overexpressed at 1 and 7 days post-surgery in a rabbit vein graft model, which is the period when apoptosis changes to proliferation in neointimal hyperplasia. In the present study, proliferation, viability and migration were increased after treating HUVECs with S100A8/9. S100A8/9 stimulated the PI3K/Akt/mTOR pathway and mTORC2, which was significantly suppressed by a receptor for advanced glycation end products (RAGE)-blocking antibody. Furthermore, depleting expression of RAGE or mTORC2 protein components (rapamycin-insensitive companion of mTOR) by small interfering RNA was found to reduce the cell viability, migration and angiogenesis of S100A8/9-treated HUVECs. The development of neointimal hyperplasia is a complex process initiated by damage to endothelial cells. In conclusion, S100A8/9 has an important role in intimal hyperplasia by promoting cell growth and angiogenesis via RAGE signaling and activation of mTORC2.

Overexpression of S100A4 protects retinal ganglion cells against retinal ischemia-reperfusion injury in mice

BACKGROUND

Glaucoma is characterized by the neurodegeneration of retinal ganglion cells (RGCs) and the optic nerve. Numerous studies have reported that S100A4 participates in the metastasis of tumor cells and nerve protection. This study was intended to explore the role of S100A4 on RGCs under retinal ischemia-reperfusion (I/R) injury in mice.

METHODS

C57BL/6J mice were used to induce retinal I/R injury. The intravitreal administration of rAAV-EF1α-s100a4-EGFP-WPRE (rAAV-S100A4) or rAAV-EF1α-EGFP-WPRE-Pa was performed 4 weeks before I/R injury. Expression of S100A4 was detected by quantitative real-time PCR, immunofluorescence staining of retinal sections and western blot. Surviving RGCs were quantified using immunofluorescence staining. Staining of TUNEL was utilized to evaluate the apoptosis of retinal cells. Electroretinogram (ERG) was used to analyze retinal function. Expression of Akt, phospho-Akt, Bcl-2, and Bax were determined using western blotting to investigate the potential mechanisms of S100A4.

RESULTS

Retinal S100A4 level had no statistical difference 7 days after I/R injury. The rAAV-S100A4 was clearly demonstrated by the green fluorescence protein in many layers of the retina after intravitreal injection and up-regulated the expression of S100A4. I/R injury resulted in an increase of the apoptosis of retinal cells and the reduction of surviving RGCs, however, overexpressed S100A4 inhibited the apoptosis of cells and a decrease of RGCs. ERG analysis showed a drop on amplitude of a-wave and b-wave was impeded to some extent by overexpressing of S100A4. Up-regulation of S100A4 raised the expression of phospho-Akt and reduced Bax expression. Nevertheless, there were no significant changes in the levels of Bcl-2 and total Akt.

CONCLUSION

Our results indicate the neuroprotective effects of overexpressed S100A4 on RGCs by activating the Akt pathway and then inhibiting the apoptosis of cells after I/R injury. The use of S100A4 protein may be a novel therapeutic strategy for glaucoma.

RAGE and its ligands: from pathogenesis to therapeutics

Receptor for advanced glycation end products (RAGE) is an immunoglobulin-like receptor present on cell surface. RAGE binds to an array of structurally diverse ligands, acts as a pattern recognition receptor (PRR) and is expressed on cells of different origin performing different functions. RAGE ligation leads to the initiation of a cascade of signaling events and is implicated in diseases, such as inflammation, cancer, diabetes, vascular dysfunctions, retinopathy, and neurodegenerative diseases. Because of the significant involvement of RAGE in the progression of numerous diseases, RAGE signaling has been targeted through use of inhibitors and anti-RAGE antibodies as a treatment strategy and therapy. Here in this review, we have summarized the physical and physiological aspects of RAGE biology in mammalian system and the importance of targeting this molecule in the treatment of various RAGE mediated pathologies. Highlights Receptor for advanced glycation end products (RAGE) is a member of immunoglobulin superfamily of receptors and involved in many pathophysiological conditions. RAGE ligation with its ligands leads to initiation of distinct signaling cascades and activation of numerous transcription factors. Targeting RAGE signaling through inhibitors and anti-RAGE antibodies can be promising treatment strategy.

S100A4 is activated by RhoA and catalyses the polymerization of non-muscle myosin, adhesion complex assembly and contraction in airway smooth muscle

KEY POINTS

S100A4 is expressed in many tissues, including smooth muscle (SM), but its physiologic function is unknown. S100A4 regulates the motility of metastatic cancer cells by binding to non-muscle (NM) myosin II. Contractile stimulation causes the polymerization of NM myosin in airway SM, which is necessary for tension development. NM myosin regulates the assembly of adhesion junction signalling complexes (adhesomes) that catalyse actin polymerization. In airway SM, ACh (acetylcholine) stimulated the binding of S100A4 to the NM myosin heavy chain, which was catalysed by RhoA GTPase via the RhoA-binding protein, rhotekin. The binding of S100A4 to NM myosin was required for NM myosin polymerization, adhesome assembly and actin polymerization. S100A4 plays a critical function in the regulation of airway SM contraction by catalysing NM myosin filament assembly. The interaction of S100A4 with NM myosin may also play an important role in the physiologic function of other tissues.

ABSTRACT

S100A4 binds to the heavy chain of non-muscle (NM) myosin II and can regulate the motility of crawling cells. S100A4 is widely expressed in many tissues including smooth muscle (SM), although its role in the regulation of their physiologic function is not known. We hypothesized that S100A4 contributes to the regulation of contraction in airway SM by regulating a pool of NM myosin II at the cell cortex. NM myosin II undergoes polymerization in airway SM and regulates contraction by catalysing the assembly of integrin-associated adhesome complexes that activate pathways that catalyse actin polymerization. ACh stimulated the interaction of S100A4 with NM myosin II in airway SM at the cell cortex and catalysed NM myosin filament assembly. RhoA GTPase regulated the activation of S100A4 via rhotekin, which facilitated the formation of a complex between RhoA, S100A4 and NM myosin II. The depletion of S100A4, RhoA or rhotekin from airway SM tissues using short hairpin RNA or small interfering RNA prevented NM myosin II polymerization as well as the recruitment of vinculin and paxillin to adhesome signalling complexes in response to ACh, and inhibited actin polymerization and tension development. S100A4 depletion did not affect ACh-stimulated SM myosin regulatory light chain phosphorylation. The results show that S100A4 plays a critical role in tension development in airway SM tissue by catalysing NM myosin filament assembly, and that the interaction of S100A4 with NM myosin in response to contractile stimulation is activated by RhoA GTPase. These results may be broadly relevant to the physiologic function of S100A4 in other cell and tissue types.

Knockdown of ferritin heavy chain (FTH) inhibits the migration of prostate cancer through reducing S100A4, S100A2, and S100P expression

BACKGROUND

Ferritin plays a key role in the development of prostate cancer (PCa). Our earlier studies showed that the knockdown of ferritin heavy chain (FTH) suppressed the migration and invasion of the prostate cancer cell line (PC3). However, the mechanisms behind FTH in the cell migration regulation of PCa have not been thoroughly investigated.

METHODS

Isobaric tags for relative and absolute quantitation (iTRAQ) proteomics was used to analyze the protein expression in PC3 cells with FTH knockdown by small interfering RNAs and negative control cells. We subsequently ranked the differentially expressed proteins according to the change in expression. We further performed Gene Ontology (GO) analysis for the changing-expression protein. Finally, Western blot analysis was performed to determine the expression of the target protein.

RESULTS

Compared with the negative group, 420 proteins were downregulated, including proteins S100A4, S100P, and S100A2, while the expression of 442 protein was elevated in FTH-silencing PC3 cells (P<0.05, fold change >1.2). The mass spectrometry results showing decreased expression of protein S100A4, S100P, and S100A2 in the cells were further validated by Western blot (P<0.05). Levels of protein S100A4, S100A2, and S100P were reduced in FTH-silencing PC3 cells (P<0.05, fold change >1.6).

CONCLUSIONS

The downregulation of FTH expression reduced the level of protein S100A4, S100A2, and S100P, which all play a key role in the migration and invasion of tumor cells. Therefore, it is reasonable to assume that there are correlations between the expression of the S100A4, S100A2, and S100P genes with FTH. Based on this research, FTH may be a new biomarker for the diagnosis of PCa.

Exploring the wound healing, anti-inflammatory, anti-pathogenic and proteomic effects of lactic acid bacteria on keratinocytes

The topical application of lactic acid bacteria (LAB) is recognized as a useful approach to improve skin health. This work aims to characterize by a multidisciplinary approach, the wound healing, anti-inflammatory, anti-pathogens and proteomic effects of six LAB lysates, belonging to the genus Lactobacillus. Our results demonstrated that the lysates of tested LAB stimulated the proliferation of keratinocytes, and that L. plantarum SGL 07 and L. salivarius SGL 19 accelerated the re-epithelization by inducing keratinocyte migration. The bacterial lysates also reduced the secretion of specific pro-inflammatory mediators from keratinocytes. Furthermore, viable L. salivarius SGL 19 and L. fermentum SGL 10 had anti-pathogenic effects against S. aureus and S. pyogenes, while L. brevis SGL 12 and L. paracasei SGL 04 inhibited S. aureus and S. pyogenes, respectively. The tested lactobacilli lysates also induced specific proteome modulation of the exposed keratinocytes, involving dysregulation of proteins (such as interleukin enhancer-binding factor 2 and ATP-dependent RNA helicase) and pathways (such as cytokine, NF-kB, Hedgehog, and RUNX signaling) associated with their specific wound healing and anti-inflammatory effects. This study indicates the different potential of selected lactobacilli, suggesting that they may be successfully used in the future together with conventional therapies to bring relief from skin disorders.

S100A4 is secreted by airway smooth muscle tissues and activates inflammatory signaling pathways via receptors for advanced glycation end products

S100A4 is a low-molecular-mass (12 kDa) EF-hand Ca²⁺-binding S100 protein that is expressed in a broad range of normal tissue and cell types. S100A4 can be secreted from some cells to act in an autocrine or paracrine fashion on target cells and tissues. S100A4 has been reported in the extracellular fluids of subjects with several inflammatory diseases, including asthma. Airway smooth muscle plays a critical role in airway inflammation by synthesizing and secreting inflammatory cytokines. We hypothesized that S100A4 may play an immunomodulatory role in airway smooth muscle. Trachealis smooth muscle tissues were stimulated with recombinant His-S100A4, and the effects on inflammatory responses were evaluated. S100A4 induced the activation of Akt and NF-κB and stimulated eotaxin secretion. It also increased the expression of RAGE and endogenous S100A4 in airway tissues. Stimulation of airway smooth muscle tissues with IL-13 or TNF-α induced the secretion of S100A4 from the tissues and promoted the expression of endogenous receptors for advanced glycation end products (RAGE) and S100A4. The role of RAGE in mediating the responses to S100A4A was evaluated by expressing a mutant nonfunctional RAGE (RAGEΔcyto) in tracheal muscle tissues and by treating tissues with a RAGE inhibitor. S100A4 did not activate NF-κB or Akt in tissues that were expressing RAGEΔcyto or treated with a RAGE inhibitor, indicating that S100A4 mediates its effects by acting on RAGE. Our results demonstrate that inflammatory mediators stimulate the synthesis and secretion of S100A4 in airway smooth muscle tissues and that extracellular S100A4 acts via RAGE to mediate airway smooth muscle inflammation.

Downregulation of S100 calcium binding protein A12 inhibits the growth of glioma cells

Background

S100 calcium binding protein A12 (S100A12) is a member of the S100 protein family and is widely expressed in neutrophil and low expressed in lymphocytes and monocyte. However, the role of S100A12 in glioma has not yet been identified.

Methods

In the present study, we carried out immunohistochemical investigation of S100A12 in 81 glioma tissues to determine the expression of S100A12 in glioma cells, and evaluate the clinical significance of S100A12 in glioma patients. Futher we knockdown the S100A12 by shRNA, and evaluated cell proliferation, cell migration and cell apoptosis by MTT, colony formation assay, transwell assay,flow cytometry assa and western blot.

Results

We found that S100A12 was upregulated in tissues of glioma patients and the expression was correlated to WHO stage and tumor size. Further, we found that knockdown S100A12 inhibits the proliferation, migration and invasion of glioma cells through regulating cell apoptosis and EMT.

Conclusion

S100A12 plays a vital role in glioma progression, and may be an important regulatory molecule for biological behaviors of glioma cell lines.

Direct interaction of metastasis-inducing S100P protein with tubulin causes enhanced cell migration without changes in cell adhesion

Overexpression of S100P promotes breast cancer metastasis in animals and elevated levels in primary breast cancers are associated with poor patient outcomes. S100P can differentially interact with nonmuscle myosin (NM) isoforms (IIA > IIC > IIB) leading to the redistribution of actomyosin filaments to enhance cell migration. Using COS-7 cells which do not naturally express NMIIA, S100P is now shown to interact directly with α,β-tubulin in vitro and in vivo with an equilibrium Kd of 2-3 × 10-7 M. The overexpressed S100P is located mainly in nuclei and microtubule organising centres (MTOC) and it significantly reduces their number, slows down tubulin polymerisation and enhances cell migration in S100P-induced COS-7 or HeLa cells. It fails, however, to significantly reduce cell adhesion, in contrast with NMIIA-containing S100P-inducible HeLa cells. When taxol is used to stabilise MTs or colchicine to dissociate MTs, S100P's stimulation of migration is abolished. Affinity-chromatography of tryptic digests of α and β-tubulin on S100P-bound beads identifies multiple S100P-binding sites consistent with S100P binding to all four half molecules in gel-overlay assays. When screened by NMR and ITC for interacting with S100P, four chemically synthesised peptides show interactions with low micromolar dissociation constants. The two highest affinity peptides significantly inhibit binding of S100P to α,β-tubulin and, when tagged for cellular entry, also inhibit S100P-induced reduction in tubulin polymerisation and S100P-enhancement of COS-7 or HeLa cell migration. A third peptide incapable of interacting with S100P also fails in this respect. Thus S100P can interact directly with two different cytoskeletal filaments to independently enhance cell migration, the most important step in the metastatic cascade.

Mouse S100G protein exhibits properties characteristic of a calcium sensor

Bovine S100 G (calbindin D_9k, small Ca²⁺-binding protein of the EF-hand superfamily) is considered as a calcium buffer protein; i.e., the binding of Ca²⁺ practically does not change its general conformation. A set of experimental approaches has been used to study structural properties of apo- and Ca²⁺-loaded forms of mouse S100 G (81.4% identity in amino acid sequence with bovine S100 G). This analysis revealed that, in contrast to bovine S100 G, the removal of calcium ions increases α-helices content of mouse S100 G protein and enhances its accessibility to digestion by α-chymotrypsin. Furthermore, mouse apo-S100 G is characterized by a decreased surface hydrophobicity and reduced tendency for oligomerization. Such behavior is typical of calcium sensor proteins. Apo-state of mouse S100 G still has rather compact structure, which can be cooperatively unfolded by temperature and GdnHCl. Computational analysis of amino acid sequences of S100 G proteins shows that these proteins could be in a disordered state upon a removal of the bound calcium ions. The experimental data show that, although mouse apo-S100 G is flexible compared to the Ca²⁺-loaded state, the apo-form is not completely disordered and preserves some cooperatively meting structure. The origin of the unexpectedly high stability of mouse S100 G can be rationalized by an exceptionally strong association of its N- and C-terminal parts containing the EF-hands I and II, respectively.

Role of S100 proteins in health and disease

The S100 family of proteins contains 25 known members that share a high degree of sequence and structural similarity. However, only a limited number of family members have been characterized in depth, and the roles of other members are likely undervalued. Their importance should not be underestimated however, as S100 family members function to regulate a diverse array of cellular processes including proliferation, differentiation, inflammation, migration and/or invasion, apoptosis, Ca²⁺ homeostasis, and energy metabolism. Here we detail S100 target protein interactions that underpin the mechanistic basis to their function, and discuss potential intervention strategies targeting S100 proteins in both preclinical and clinical situations.

S100A12 is a promising biomarker in papillary thyroid cancer

S100A12 belongs to the S100 family and acts as a vital regulator in different types of tumors. However, the function of S100A12 in thyroid carcinoma has not yet been investigated. In this study, we analyzed the expression of S100A12 in human papillary thyroid cancer (PTC) samples and two PTC cell lines. In addition, we explored the effects of S100A12 on PTC cell progression in vitro and in vivo. Our results showed that S100A12 was significantly upregulated in PTC specimens. Moreover, silencing S100A12 markedly inhibited PTC cell proliferation, migration, invasion and cell cycle progression. In addition, knockdown of S100A12 significantly reduced the expression of CyclinD1, CDK4 and p-ERK in PTC cells. An in vivo study also showed that silencing S100A12 dramatically suppressed tumor cell growth and decreased Ki67 expression in a xenograft mouse model. This study provides novel evidence that S100A12 serves as an oncogene in PTC. Knockdown of S100A12 suppressed PTC cell proliferation, migration, and invasion and induced G0/G1 phase arrest via the inhibition of the ERK signaling pathway. Therefore, S100A12 may be a potent therapeutic target for PTC.

Differential association between S100A4 levels and insulin resistance in prepubertal children and adult subjects with clinically severe obesity

OBJECTIVES

S100A4 has been recently identified as an adipokine associated with insulin resistance (IR) in adult subjects with obesity. However, no data about its levels in children with obesity and only a few approaches regarding its potential mechanism of action have been reported. To obtain a deeper understanding of the role of S100A4 in obesity, (a) S100A4 levels were measured in prepubertal children and adult subjects with and without obesity and studied the relationship with IR and (b) the effects of S100A4 in cultured human adipocytes and vascular smooth muscle cells (VSMCs) were determined.

METHODS

Sixty-five children (50 with obesity, age 9.0 ±1.1 years and 15 normal weight, age 8.4 ±0.8 years) and fifty-nine adults (43 with severe obesity, age 46 ±11 years and 16 normal weight, age 45 ±9 years) were included. Blood from children and adults and adipose tissue samples from adults were obtained and analysed. Human adipocytes and VSMC were incubated with S100A4 to evaluate their response to this adipokine.

RESULTS

Circulating S100A4 levels were increased in both children (P = .002) and adults (P < .001) with obesity compared with their normal-weight controls. In subjects with obesity, S100A4 levels were associated with homeostatic model assessment-insulin resistance (HOMA-IR) in adults (βstd = .42, P = .008) but not in children (βstd = .12, P = .356). Human adipocytes were not sensitive to S100A4, while incubation with this adipokine significantly reduced inflammatory markers in VSMC.

CONCLUSIONS

Our human data demonstrate that higher S100A4 levels are a marker of IR in adults with obesity but not in prepubertal children. Furthermore, the in vitro results suggest that S100A4 might exert an anti-inflammatory effect. Further studies will be necessary to determine whether S100A4 can be a therapeutic target for obesity.

Alterations in innate immunity and epithelial cell differentiation are the molecular pillars of hidradenitis suppurativa

BACKGROUND

The large unmet need of hidradenitis suppurativa/acne inversa (HS) therapy requires the elucidation of disease-driving mechanisms and tissue targeting.

OBJECTIVE

Robust characterization of the underlying HS mechanisms and detection of the involved skin compartments.

METHODS

Hidradenitis suppurativa/acne inversa molecular taxonomy and key signalling pathways were studied by whole transcriptome profiling. Dysregulated genes were detected by comparing lesional and non-lesional skin obtained from female HS patients and matched healthy controls using the Agilent array platform. The differential gene expression was confirmed by quantitative real-time PCR and targeted protein characterization via immunohistochemistry in another set of female patients. HS-involved skin compartments were also recognized by immunohistochemistry.

RESULTS

Alterations to key regulatory pathways involving glucocorticoid receptor, atherosclerosis, HIF1α and IL17A signalling as well as inhibition of matrix metalloproteases were detected. From a functional standpoint, cellular assembly, maintenance and movement, haematological system development and function, immune cell trafficking and antimicrobial response were key processes probably being affected in HS. Sixteen genes were found to characterize HS from a molecular standpoint (DEFB4, MMP1, GJB2, PI3, KRT16, MMP9, SERPINB4, SERPINB3, SPRR3, S100A8, S100A9, S100A12, S100A7A (15), KRT6A, TCN1, TMPRSS11D). Among the proteins strongly expressed in HS, calgranulin-A, calgranulin-B and serpin-B4 were detected in the hair root sheath, koebnerisin and connexin-32 in stratum granulosum, transcobalamin-1 in stratum spinosum/hair root sheath, small prolin-rich protein-3 in apocrine sweat gland ducts/sebaceous glands-ducts and matrix metallopeptidase-9 in resident monocytes.

CONCLUSION

Our findings highlight a panel of immune-related drivers in HS, which influence innate immunity and cell differentiation in follicular and epidermal keratinocytes as well as skin glands.

Deletion of FHL2 in fibroblasts attenuates fibroblasts activation and kidney fibrosis via restraining TGF-β1-induced Wnt/β-catenin signaling

Four-and-a-half LIM domains protein 2 (FHL2) has been proposed involving in β-catenin activity. We previously reported that FHL2 mediates TGF-β1-induced tubular epithelial-to-mesenchymal transition through activating Wnt/β-catenin signaling. However, the potential role and mechanism for FHL2 in TGF-β1-induced fibroblast activation and kidney fibrosis remains unknown. Here, we initially observed higher levels of FHL2 expression in fibrotic kidneys from both patients and mice, especially in α-smooth muscle actin (α-SMA)-positive cells in the interstitium. In cultured interstitial fibroblasts, FHL2 expression was induced by TGF-β1. Knockdown of FHL2 remarkably suppressed TGF-β1-induced α-SMA, type I collagen, and fibronectin expression, while overexpression of FHL2 was sufficient to activate fibroblasts. In mice, fibroblast-specific deletion of FHL2 diminished renal induction of α-SMA, type I collagen, and fibronectin and interstitial extracellular matrix deposition at 2 weeks after ureteral obstruction. We next investigated Wnt/β-catenin activity and found that β-catenin was activated in most FHL2-positive cells in renal interstitium from mice with obstructive nephropathy. In vitro, TGF-β1 induced a physical interaction between FHL2 and β-catenin, especially in the nucleus. Downregulation of FHL2 inhibited TGF-β1-induced active β-catenin upregulation, β-catenin nuclear translocation, and β-catenin-mediated transcription, whereas overexpression of FHL2 was able to activate Wnt/β-catenin signaling. FHL2 overexpression-induced β-catenin-mediated gene transcription could be hindered by ICG-001, but FHL2 overexpression-induced upregulation of active β-catenin could not be. Collectively, this study reveals that the signal regulatory effect of FHL2 on β-catenin plays an important role in TGF-β1-induced fibroblast activation and kidney fibrosis.

S100 proteins in obesity: liaisons dangereuses

Obesity is an endemic pathophysiological condition and a comorbidity associated with hypercholesterolemia, hypertension, cardiovascular disease, type 2 diabetes mellitus, and cancer. The adipose tissue of obese subjects shows hypertrophic adipocytes, adipocyte hyperplasia, and chronic low-grade inflammation. S100 proteins are Ca2+-binding proteins exclusively expressed in vertebrates in a cell-specific manner. They have been implicated in the regulation of a variety of functions acting as intracellular Ca2+ sensors transducing the Ca2+ signal and extracellular factors affecting cellular activity via ligation of a battery of membrane receptors. Certain S100 proteins, namely S100A4, the S100A8/S100A9 heterodimer and S100B, have been implicated in the pathophysiology of obesity-promoting macrophage-based inflammation via toll-like receptor 4 and/or receptor for advanced glycation end-products ligation. Also, serum levels of S100A4, S100A8/S100A9, S100A12, and S100B correlate with insulin resistance/type 2 diabetes, metabolic risk score, and fat cell size. Yet, secreted S100B appears to exert neurotrophic effects on sympathetic fibers in brown adipose tissue contributing to the larger sympathetic innervation of this latter relative to white adipose tissue. In the present review we first briefly introduce S100 proteins and then critically examine their role(s) in adipose tissue and obesity.

Gpr126/Adgrg6 contributes to the terminal Schwann cell response at the neuromuscular junction following peripheral nerve injury

Gpr126/Adgrg6 is an adhesion G protein-coupled receptor essential for Schwann cell (SC) myelination with important contributions to repair after nerve crush injury. Despite critical functions in myelinating SCs, the role of Gpr126 within nonmyelinating terminal Schwann cells (tSCs) at the neuromuscular junction (NMJ), is not known. tSCs have important functions in synaptic maintenance and reinnervation, and after injury tSCs extend cytoplasmic processes to guide regenerating axons to the denervated NMJ. In this study, we show that Gpr126 is expressed in tSCs, and that absence of Gpr126 in SCs (SC-specific Gpr126 knockout, cGpr126) results in a NMJ maintenance defect in the hindlimbs of aged mice, but not in young adult mice. After nerve transection and repair, cGpr126 mice display delayed NMJ reinnervation, altered tSC morphology with decreased S100β expression, and reduced tSC cytoplasmic process extensions. The immune response promoting reinnervation at the NMJ following nerve injury is also altered with decreased macrophage infiltration, Tnfα, and anomalous cytokine expression compared to NMJs of control mice. In addition, Vegfa expression is decreased in muscle, suggesting that cGpr126 non-cell autonomously modulates angiogenesis after nerve injury. In sum, cGpr126 mice demonstrated delayed NMJ reinnervation and decreased muscle mass following nerve transection and repair compared to control littermates. The integral function of Gpr126 in tSCs at the NMJ provides the framework for new therapeutic targets for neuromuscular disease.

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.

An Update to Calcium Binding Proteins

Ca²⁺ binding proteins (CBP) are of key importance for calcium to play its role as a pivotal second messenger. CBP bind Ca²⁺ in specific domains, contributing to the regulation of its concentration at the cytosol and intracellular stores. They also participate in numerous cellular functions by acting as Ca²⁺ transporters across cell membranes or as Ca²⁺-modulated sensors, i.e. decoding Ca²⁺ signals. Since CBP are integral to normal physiological processes, possible roles for them in a variety of diseases has attracted growing interest in recent years. In addition, research on CBP has been reinforced with advances in the structural characterization of new CBP family members. In this chapter we have updated a previous review on CBP, covering in more depth potential participation in physiopathological processes and candidacy for pharmacological targets in many diseases. We review intracellular CBP that contain the structural EF-hand domain: parvalbumin, calmodulin, S100 proteins, calcineurin and neuronal Ca²⁺ sensor proteins (NCS). We also address intracellular CBP lacking the EF-hand domain: annexins, CBP within intracellular Ca²⁺ stores (paying special attention to calreticulin and calsequestrin), proteins that contain a C2 domain (such as protein kinase C (PKC) or synaptotagmin) and other proteins of interest, such as regucalcin or proprotein convertase subtisilin kexins (PCSK). Finally, we summarise the latest findings on extracellular CBP, classified according to their Ca²⁺ binding structures: (i) EF-hand domains; (ii) EGF-like domains; (iii) ɣ-carboxyl glutamic acid (GLA)-rich domains; (iv) cadherin domains; (v) Ca²⁺-dependent (C)-type lectin-like domains; (vi) Ca²⁺-binding pockets of family C G-protein-coupled receptors.

S100a4-Cre-mediated deletion of Patched1 causes hypogonadotropic hypogonadism: role of pituitary hematopoietic cells in endocrine regulation

Hormones produced by the anterior pituitary gland regulate an array of important physiological functions, but pituitary hormone disorders are not fully understood. Herein we report that genetically-engineered mice with deletion of the hedgehog signaling receptor Patched1 by S100a4 promoter-driven Cre recombinase (S100a4-Cre;Ptch1fl/fl mutants) exhibit adult-onset hypogonadotropic hypogonadism and multiple pituitary hormone disorders. During the transition from puberty to adult, S100a4-Cre;Ptch1fl/fl mice of both sexes develop hypogonadism coupled with reduced gonadotropin levels. Their pituitary glands also display severe structural and functional abnormalities, as revealed by transmission electron microscopy and expression of key genes regulating pituitary endocrine functions. S100a4-Cre activity in the anterior pituitary gland is restricted to CD45+ cells of hematopoietic origin, including folliculo-stellate cells and other immune cell types, causing sex-specific changes in the expression of genes regulating the local microenvironment of the anterior pituitary. These findings provide in vivo evidence for the importance of pituitary hematopoietic cells in regulating fertility and endocrine function, in particular during sexual maturation and likely through sexually dimorphic mechanisms. These findings support a previously unrecognized role of hematopoietic cells in causing hypogonadotropic hypogonadism and provide inroads into the molecular and cellular basis for pituitary hormone disorders in humans.

Ca2+-Binding Proteins of the EF-Hand Superfamily: Diagnostic and Prognostic Biomarkers and Novel Therapeutic Targets

A multitude of Ca²⁺-sensor proteins containing the specific Ca²⁺-binding motif (helix-loop-helix, called EF-hand) are of major clinical relevance in a many human diseases. Measurements of troponin, the first intracellular Ca-sensor protein to be discovered, is nowadays the "gold standard" in the diagnosis of patients with acute coronary syndrome (ACS). Mutations have been identified in calmodulin and linked to inherited ventricular tachycardia and in patients affected by severe cardiac arrhythmias. Parvalbumin, when introduced into the diseased heart by gene therapy to increase contraction and relaxation speed, is considered to be a novel therapeutic strategy to combat heart failure. S100 proteins, the largest subgroup with the EF-hand protein family, are closely associated with cardiovascular diseases, various types of cancer, inflammation, and autoimmune pathologies. The intention of this review is to summarize the clinical importance of this protein family and their use as biomarkers and potential drug targets, which could help to improve the diagnosis of human diseases and identification of more selective therapeutic interventions.

Fibrillin microfibrils and proteases, key integrators of fibrotic pathways

Supramolecular networks composed of multi-domain ECM proteins represent intricate cellular microenvironments which are required to balance tissue homeostasis and direct remodeling. Structural deficiency in ECM proteins results in imbalances in ECM-cell communication resulting often times in fibrotic reactions. To understand how individual components of the ECM integrate communication with the cell surface by presenting growth factors or providing fine-tuned biomechanical properties is mandatory for gaining a better understanding of disease mechanisms in the quest for new therapeutic approaches. Here we provide an overview about what we can learn from inherited connective tissue disorders caused primarily by mutations in fibrillin-1 and binding partners as well as by altered ECM processing leading to defined structural changes and similar functional knock-in mouse models. We will utilize this knowledge to propose new molecular hypotheses which should be tested in future studies.

ZEB1 and IL-6/11-STAT3 signalling cooperate to define invasive potential of pancreatic cancer cells via differential regulation of the expression of S100 proteins

Background

S100 proteins have been implicated in various aspects of cancer, including epithelial-mesenchymal transitions (EMT), invasion and metastasis, and also in inflammatory disorders. Here we examined the impact of individual members of this family on the invasion of pancreatic ductal adenocarcinoma (PDAC) cells, and their regulation by EMT and inflammation.

Methods

Invasion of PDAC cells was analysed in zebrafish embryo xenografts and in transwell invasion assays. Expression and regulation of S100 proteins was studied in vitro by immunoblotting, quantitative PCR and immunofluorescence, and in pancreatic lesions by immunohistochemistry.

Results

Whereas the expression of most S100 proteins is characteristic for epithelial PDAC cell lines, S100A4 and S100A6 are strongly expressed in mesenchymal cells and upregulated by ZEB1. S100A4/A6 and epithelial protein S100A14 respectively promote and represses cell invasion. IL-6/11-STAT3 pathway stimulates expression of most S100 proteins. ZEB1 synergises with IL-6/11-STAT3 to upregulate S100A4/A6, but nullifies the effect of inflammation on S100A14 expression.

Conclusion

EMT/ZEB1 and IL-6/11-STAT3 signalling act independently and congregate to establish the expression pattern of S100 proteins, which drives invasion. Although ZEB1 regulates expression of S100 family members, these effects are masked by IL-6/11-STAT3 signalling, and S100 proteins cannot be considered as bona fide EMT markers in PDAC.

MRP14 enhances the ability of macrophage to recruit T cells and promotes obesity-induced insulin resistance

Objective:

Myeloid-related protein-14 (MRP14) and its binding partner MRP8 play an essential role in innate immune function and have been implicated in a variety of inflammatory diseases. However, the role of MRP14 in obesity-induced inflammation and insulin resistance is not well defined. This study investigated the role of MRP14 in macrophage-mediated adipose tissue inflammation and obesity-induced insulin resistance.

Subjects and Results:

Wild-type (WT) and Mrp14^−/− mice were fed a high-fat diet or normal chow for 12 weeks. Tissue-resident macrophages in both adipose tissue and liver from obese WT mice expressed higher levels of MRP14 in the visceral adipose fat and liver compared to the lean mice. Mrp14^−/− mice demonstrated a significantly improved post-prandial insulin sensitivity, as measured by intraperitoneal glucose tolerance test and insulin tolerance testing. Macrophages secreted MRP14 in response to inflammatory stimuli such as LPS. Extracellular MRP8/14 induced the production of CCL5 and CXCL9. Deficiency of MRP14 did not affect macrophage proliferation, mitochondrial respiration, and glycolytic function, but Mrp14^−/− macrophages showed a reduced ability to attract T cells. Depletion of the extracellular MRP14 reduced the T cell attracting ability of WT macrophages to a level similar to Mrp14^−/− macrophages.

Conclusion:

Our data indicates that MRP14 deficiency decreases obesity-induced insulin resistance and MRP8/14 regulates T cell recruitment through the induction of T cell chemoattractant production from macrophages.

Towards a circulating marker of hepato-visceral fat excess: S100A4 in adolescent girls with polycystic ovary syndrome - Evidence from randomized clinical trials

S100A4 is a marker of subcutaneous adipose tissue dysfunction. Polycystic ovary syndrome (PCOS) is often driven by hepato-visceral adiposity. PCOS phenotypes are normalized more by reduction of central fat with spironolactone/pioglitazone/metformin (SPIOMET) than by oral contraceptive (OC) treatment. We studied whether circulating S100A4 concentrations are high in adolescents with PCOS and, if so, whether they normalize more with OC or SPIOMET. Assessments included circulating S100A4, endocrine markers, body composition, abdominal fat partitioning in controls (n = 12) and girls with PCOS (n = 51; age 15.8 y; body mass index [BMI] 24.5 kg/m² ), and 1-year changes in girls with PCOS randomized for OC (n = 27) or SPIOMET (n = 24) treatment. Mean S100A4 concentrations were 71% higher (P < 0.001) in girls with PCOS than in controls and associated with hepato-visceral adiposity (r = 0.47; P = 0.001); S100A4 concentrations decreased more (P < 0.01) with SPIOMET, those decreases associating to hepato-visceral fat loss (r = 0.50; P < 0.0001). S100A4 may become a circulating marker of hepato-visceral fat excess in adolescents with PCOS.

On the origin of proteins in human drusen: The meet, greet and stick hypothesis

Retinal drusen formation is not only a clinical hallmark for the development of age-related macular degeneration (AMD) but also for other disorders, such as Alzheimer's disease and renal diseases. The initiation and growth of drusen is poorly understood. Attention has focused on lipids and minerals, but relatively little is known about the origin of drusen-associated proteins and how they are retained in the space between the basal lamina of the retinal pigment epithelium and the inner collagenous layer space (sub-RPE-BL space). While some authors suggested that drusen proteins are mainly derived from cellular debris from processed photoreceptor outer segments and the RPE, others suggest a choroidal cell or blood origin. Here, we reviewed and supplemented the existing literature on the molecular composition of the retina/choroid complex, to gain a more complete understanding of the sources of proteins in drusen. These "drusenomics" studies showed that a considerable proportion of currently identified drusen proteins is uniquely originating from the blood. A smaller, but still large fraction of drusen proteins comes from both blood and/or RPE. Only a small proportion of drusen proteins is uniquely derived from the photoreceptors or choroid. We next evaluated how drusen components may "meet, greet and stick" to each other and/or to structures like hydroxyapatite spherules to form macroscopic deposits in the sub-RPE-BL space. Finally, we discuss implications of our findings with respect to the previously proposed homology between drusenogenesis in AMD and plaque formation in atherosclerosis.

S100A8 and S100A9 proteins form part of a paracrine feedback loop between pancreatic cancer cells and monocytes

Background

The secretion of soluble factors enables communication between tumour cells and the surrounding microenvironment and plays an important role in oncogenesis. Pancreatic ductal adenocarcinoma (PDAC) is characterised by a highly reactive microenvironment, harbouring a variety of cell types, including S100A8/S100A9-expressing monocytes. S100A8/S100A9 proteins regulate the behaviour of cancer cells by inducing pre-metastatic cascades associated with cancer spread. The aim of this study was to examine how S100A8/A9 proteins mediate tumour-stroma crosstalk in PDAC.

Methods

Cytokine profiling of pancreatic cancer cell-derived conditioned media was performed using Bio-Plex Pro 27 Plex Human Cytokine assays. Protein expression and activation of downstream signalling effectors and NF-κB were assessed by western blotting analysis and reporter assays respectively.

Results

Stimulation of cultured pancreatic cancer cells with S100A8 and S100A9 increased the secretion of the pro-inflammatory cytokines IL-8, TNF-α, and FGF. S100A8, but not S100A9 induced PDGF secretion. Conversely, pancreatic cancer cell-derived conditioned media and the individual cytokines, TNF-α and TGF-β induced the expression of S100A8 and S100A9 proteins in the HL-60 monocytic cell line and primary human monocytes, while FGF and IL-8 induced the expression of S100A9 only. S100A8 and S100A9 activated MAPK and NF-κB signalling in pancreatic cancer. This was partially mediated via activation of the receptor of advanced glycosylation end-product (RAGE).

Conclusion

S100A8 and S100A9 proteins induce specific cytokine secretion from PDAC cells, which in turn enhances the expression of S100A8/A9. This paracrine crosstalk could have implications for PDAC invasiveness and metastatic potential.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5161-4) contains supplementary material, which is available to authorized users.

Alarmin S100A11 initiates a chemokine response to the human pathogen Toxoplasma gondii

Toxoplasma gondii is a common protozoan parasite that infects up to one-third of the world’s population. Notably, very little is known about innate immune-sensing mechanisms for this obligate intracellular parasite by human cells. Here, by applying an unbiased biochemical screening approach, we have identified that human monocytes recognized the presence of T. gondii infection via detection of the alarmin S100A11 protein, which is released from parasite-infected cells via caspase-1-dependent mechanisms. S100A11 induced a potent chemokine response to T. gondii via engagement of its receptor RAGE and regulated monocyte recruitment in vivo by inducing expression of the chemokine CCL2. Our experiments have revealed a sensing system for T. gondii by human cells that is based on detection infection-mediated release of alarmin S100A11 and RAGE-dependent induction of CCL2, a crucial chemokine required for host resistance to the parasite.

CPT1A-mediated succinylation of S100A10 increases human gastric cancer invasion

Gastric cancer (GC) is a malignancy of the lining of the stomach and is prone to distant metastasis, which involves a variety of complex molecules. The S100 proteins are a family of calcium-binding cytosolic proteins that possess a wide range of intracellular and extracellular functions and play pivotal roles in the invasion and migration of tumour cells. Among these, S100A10 is known to be overexpressed in GC. Lysine succinylation, a recently identified form of protein post-translational modification, is an important regulator of cellular processes. Here, we demonstrated that S100A10 was succinylated at lysine residue 47 (K47), and levels of succinylated S100A10 were increased in human GC. Moreover, K47 succinylation of S100A10 was stabilized by suppression of ubiquitylation and subsequent proteasomal degradation. Furthermore, carnitine palmitoyltransferase 1A (CPT1A) was found to function as a lysine succinyltransferase that interacts with S100A10. Succinylation of S100A10 is regulated by CPT1A, while desuccinylation is regulated by SIRT5. Overexpression of a succinylation mimetic mutant, K47E S100A10, increased cell invasion and migration. Taken together, this study reveals a novel mechanism of S100A10 accumulation mediated by succinylation in GC, which promotes GC progression and is regulated by the succinyltransferase CPT1A and SIRT5-mediated desuccinylation.

S100 Proteins in Acute Myeloid Leukemia

The S100 protein family contains 20 functionally expressed members, which are commonly dysregulated in cancer. Their wide range of functions includes cell proliferation, cell differentiation, regulation of transcription factors, inflammation, chemotaxis, and angiogenesis. S100 proteins have in several types of cancer proven to be biomarkers for disease progression and prognosis. Acute myeloid leukemia (AML) is a highly heterogeneous and aggressive disease in which immature myeloblasts replace normal hematopoietic cells in the bone marrow. This review focuses on the S100 protein family members, which commonly are dysregulated in AML, and on the consequences of their dysregulation in the disorder. Like in other cancers, it appears as if S100 proteins are potential biomarkers for leukemogenesis. Furthermore, several S100 members seem to be involved in maintaining the leukemic phenotype. For these reasons, specific S100 proteins might serve as prognostic biomarkers, especially in the patient subset with intermediate/undetermined risk, and as potential targets for patient-adjusted therapy. Because the question of the most suitable candidate S100 biomarkers in AML still is under discussion, because particular AML subgroups lead to specific S100 signatures, and because downstream effects and the significance of co-expression of potential S100 binding partners in AML are not fully elucidated yet, we conclude that a panel of S100 proteins will probably be best suited for prognostic purposes.

High expression of S100A12 on intratumoral stroma cells indicates poor prognosis following surgical resection of hepatocellular carcinoma

The S100 protein family is widely involved in the pathological process of various types of cancer. However, the prognostic value of the S100 protein family member S100A12 in hepatocellular carcinoma (HCC) remains unknown. A total of 139 patients undergoing curative surgical resection for HCC from December 2005 to June 2006 were investigated. Immunohistochemistry of S100A12 tissue was performed and expression was classified according to the total positive staining area. Co-expression of S100A12 with cluster of differentiation (CD)11B, CD15 and CD68 was evaluated using immunofluorescence. Associations between S100A12 expression and preoperative clinicopathological parameters were assessed using a χ² test or independent sample Student's t-test. Kaplan-Meier estimator survival analysis and multivariate Cox's proportional hazard regression model were used to evaluate the prognostic value of S100A12 expression. The expression of S100A12 was restricted exclusively to stroma cells, primarily to myeloid-derived immune cells, CD15-positive neutrophils and CD68-positive macrophages in particular. A total positive staining area of 1,600 µm² was selected as the threshold between high and low S100A12 expression. There was a statistically significant association between intratumoral S100A12 expression and tumor differentiation (P=0.010). High expression of S100A12 on intratumoral stroma cells was an independent prognostic factor for the overall (P=0.002) and disease-free survival (P=0.007) rates of HCC following curative surgical resection. No significant association was identified between peritumoral S100A12 expression and HCC prognosis. The results of the present study demonstrated that high expression of S100A12 on intratumoral stroma cells is associated with poor HCC prognosis following curative resection, which may serve as a potential target for an adjuvant therapy.

S100P enhances the motility and invasion of human trophoblast cell lines

S100P has been shown to be a marker for carcinogenesis where its expression in solid tumours correlates with metastasis and a poor patient prognosis. This protein's role in any physiological process is, however, unknown. Here we first show that S100P is expressed both in trophoblasts in vivo as well as in some corresponding cell lines in culture. We demonstrate that S100P is predominantly expressed during the early stage of placental formation with its highest expression levels occurring during the first trimester of gestation, particularly in the invading columns and anchoring villi. Using gain or loss of function studies through overexpression or knockdown of S100P expression respectively, our work shows that S100P stimulates both cell motility and cellular invasion in different trophoblastic and first trimester EVT cell lines. Interestingly, cell invasion was seen to be more dramatically affected than cell migration. Our results suggest that S100P may be acting as an important regulator of trophoblast invasion during placentation. This finding sheds new light on a hitherto uncharacterized molecular mechanism which may, in turn, lead to the identification of novel targets that may explain why significant numbers of confirmed human pregnancies suffer complications through poor placental implantation.

Differential proteomics of lesional vs. non-lesional biopsies revealed non-immune mechanisms of alopecia areata

Alopecia areata (AA) is one of the common hair disorders for which treatment is frequently ineffective and associated with relapsing episodes. Better understanding of disease mechanisms and novel therapeutic targets are thus required. From 10 AA patients, quantitative proteomics using LTQ-Orbitrap-XL mass spectrometer revealed 104 down-regulated, 4 absent, 3 up-regulated and 11 newly present proteins in lesional vs. non-lesional biopsies. Among these, the decreased levels of α-tubulin, vimentin, heat shock protein 70 (HSP70), HSP90, annexin A2 and α-enolase were successfully confirmed by Western blotting. Protein-protein interactions network analysis using STRING tool revealed that the most frequent biological processes/networks of the down-regulated proteins included tissue development, cell differentiation, response to wounding and catabolic process, whereas those for the up-regulated proteins included biological process, metabolic process, cellular transport, cellular component organization and response to stimulus. Interestingly, only 5 increased/newly present proteins were associated with the regulation of immune system, which may not be the predominant pathway in AA pathogenic mechanisms as previously assumed. In summary, we report herein the first proteome dataset of AA demonstrating a number of novel pathways, which can be linked to the disease mechanisms and may lead to discovery of new therapeutic targets for AA.

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.

Endogenous DAMPs, Category I: Constitutively Expressed, Native Molecules (Cat. I DAMPs)

This chapter provides the reader with a collection of endogenous DAMPs in terms of constitutively expressed native molecules. The first class of this category refers to DAMPs, which are passively released from necrotic cells, and includes the most prominent subclasses of high mobility group box I and heat shock proteins. Further subclasses of DAMPs that are passively released from necrotic cells include S100 proteins, nucleic acids, histones, pro-forms of interleukin-1-family members, mitochondria-derived N-formylated peptides, F-actin, and heme. A particular subclass of these passively released DAMPs are molecules, which indirectly activate the inflammasome, including adenosine-5′-triphosphate, monosodium urate crystals, cholesterol crystals, some lipolytic species, and beta-amyloid. All these passively released DAMPs are characterized by their capability to promote necroinflammatory responses. The second class of this Category I refers to molecules, which are exposed on the surface of stressed cells. They include the subclass of phagocytosis-facilitating molecules such as calreticulin, as well as the subclass of MHC-I-related molecules such as MHC-I-related molecule A and B. These DAMPs are capable of inducing the activation of innate lymphoid cells and unconventional T cells. One of these DAMPs, the major histocompatibility complex I-related molecule A, is shown to act as a bona fide transplantation antigen. In sum, the endogenous constitutively expressed native molecules represent an impressive category of DAMPs with extraordinary properties, which play a critical role in the pathogenesis of many human diseases.

S100A6 - focus on recent developments

The Ca2+-binding protein, S100A6, belongs to the S100 family. Binding of Ca2+ induces a conformational change, which causes an increase in the overall S100A6 hydrophobicity and allows it to interact with many targets. S100A6 is expressed in different normal tissues and in many tumors. Up to now it has been shown that S100A6 is involved in cell proliferation, cytoskeletal dynamics and tumorigenesis, and that it might have some extracellular functions. In this review, we summarize novel discoveries concerning S100A6 targets, its involvement in cellular signaling pathways, and presence in stem/progenitor cells, extracellular matrix and body fluids of diseased patients.

S100A8/A9 increases the mobilization of pro-inflammatory Ly6Chigh monocytes to the synovium during experimental osteoarthritis

BACKGROUND

Monocytes are dominant cells present within the inflamed synovium during osteoarthritis (OA). In mice, two functionally distinct monocyte subsets are described: pro-inflammatory Ly6C^high and patrolling Ly6C^low monocytes. Alarmins S100A8/A9 locally released by the synovium during inflammatory OA for prolonged periods may be dominant proteins involved in stimulating recruitment of Ly6C^high monocytes from the circulation to the joint. Our objective was to investigate the role of S100A8/A9 in the mobilization of Ly6C^high and Ly6C^low monocytic populations to the inflamed joint in collagenase-induced OA (CiOA).

METHOD

S100A8 was injected intra-articularly to investigate monocyte influx. CiOA was induced by injection of collagenase into knee joints of wild-type C57BL/6 (WT), and S100a9^-/- mice. Mice were sacrificed together with age-matched saline-injected control mice (n = 6/group), and expression of monocyte markers, pro-inflammatory cytokines, and chemokines was determined in the synovium using ELISA and RT-qPCR. Cells were isolated from the bone marrow (BM), spleen, blood, and synovium and monocytes were identified using FACS.

RESULTS

S100A8/A9 was highly expressed during CiOA. Intra-articular injection of S100A8 leads to elevated expression of monocyte markers and the monocyte-attracting chemokines CCL2 and CX3CL1 in the synovium. At day 7 (d7) after CiOA induction in WT mice, numbers of Ly6C^high, but not Ly6C^low monocytes, were strongly increased (7.6-fold) in the synovium compared to saline-injected controls. This coincided with strong upregulation of CCL2, which preferentially attracts Ly6C^high monocytes. In contrast, S100a9^-/- mice showed a significant increase in Ly6C^low monocytes (twofold) within the synovium at CiOA d7, whereas the number of Ly6C^high monocytes remained unaffected. In agreement with this finding, the Ly6C^low mobilization marker CX3CL1 was significantly higher within the synovium of S100a9^-/- mice. Next, we studied the effect of S100A8/A9 on release of Ly6C^high monocytes from the BM into the circulation. A 14% decrease in myeloid cells was found in WT BM at CiOA d7. No decrease in myeloid cells in S100a9^-/- BM was found, suggesting that S100A8/A9 promotes the release of myeloid populations from the BM.

CONCLUSION

Induction of OA locally leads to strongly elevated S100A8/A9 expression and an elevated influx of Ly6C^high monocytes from the BM to the synovium.

Activation of tissue plasminogen activator by metastasis-inducing S100P protein

S100P protein in human breast cancer cells is associated with reduced patient survival and, in a model system of metastasis, it confers a metastatic phenotype upon benign mammary tumour cells. S100P protein possesses a C-terminal lysine residue. Using a multiwell in vitro assay, S100P is now shown for the first time to exhibit a strong, C-terminal lysine-dependent activation of tissue plasminogen activator (tPA), but not of urokinase-catalysed plasminogen activation. The presence of 10 μM calcium ions stimulates tPA activation of plasminogen 2-fold in an S100P-dependent manner. S100P physically interacts with both plasminogen and tPA in vitro, but not with urokinase. Cells constitutively expressing S100P exhibit detectable S100P protein on the cell surface, and S100P-containing cells show enhanced activation of plasminogen compared with S100P-negative control cells. S100P shows C-terminal lysine-dependent enhancement of cell invasion. An S100P antibody, when added to the culture medium, reduced the rate of invasion of wild-type S100P-expressing cells, but not of cells expressing mutant S100P proteins lacking the C-terminal lysine, suggesting that S100P functions outside the cell. The protease inhibitors, aprotinin or α-2-antiplasmin, reduced the invasion of S100P-expressing cells, but not of S100P-negative control cells, nor cells expressing S100P protein lacking the C-terminal lysine. It is proposed that activation of tPA via the C-terminal lysine of S100P contributes to the enhancement of cell invasion by S100P and thus potentially to its metastasis-promoting activity.

Deficiency in Calcium-Binding Protein S100A4 Impairs the Adjuvant Action of Cholera Toxin

The calcium-binding protein S100A4 has been described to promote pathological inflammation in experimental autoimmune and inflammatory disorders and in allergy and to contribute to antigen presentation and antibody response after parenteral immunization with an alum-adjuvanted antigen. In this study, we extend these findings by demonstrating that mice lacking S100A4 have a defective humoral and cellular immune response to mucosal (sublingual) immunization with a model protein antigen [ovalbumin (OVA)] given together with the strong mucosal adjuvant cholera toxin (CT), and that this impairment is due to defective adjuvant-stimulated antigen presentation by antigen-presenting cells. In comparison to wild-type (WT) mice, mice genetically lacking S100A4 had reduced humoral and cellular immune responses after immunization with OVA plus CT, including a complete lack of detectable germinal center reaction. Further, when stimulated in vitro with OVA plus CT, S100A4^−/− dendritic cells (DCs) showed impaired responses in several CT-stimulated immune regulatory molecules including the co-stimulatory molecule CD86, inflammasome-associated caspase-1 and IL-1β. Coculture of OVA-specific OT-II T cells with S100A4^−/− DCs that had been pulse incubated with OVA plus CT resulted in impaired OT-II T cell proliferation and reduced production of Th1, Th2, and Th17 cytokines compared to similar cocultures with WT DCs. In accordance with these findings, transfection of WT DCs with S100A4-targeting small interfering RNA (siRNA) but not mock-siRNA resulted in significant reductions in the expression of caspase-1 and IL-1β as well as CD86 in response to CT. Importantly, also engraftment of WT DCs into S100A4^−/− mice effectively restored the immune response to immunization in the recipients. In conclusion, our results demonstrate that deficiency in S100A4 has a strong impact on the development of both humoral and cellular immunity after mucosal immunization using CT as adjuvant.

Calcium-Mediated Control of S100 Proteins: Allosteric Communication via an Agitator/Signal Blocking Mechanism

Allosteric proteins possess dynamically coupled residues for the propagation of input signals to distant target binding sites. The input signals usually correspond to "effector is present" or "effector is not present". Many aspects of allosteric regulation remain incompletely understood. This work focused on S100A11, a dimeric EF-hand protein with two hydrophobic target binding sites. An annexin peptide (Ax) served as the target. Target binding is allosterically controlled by Ca²⁺ over a distance of ∼26 Å. Ca²⁺ promotes formation of a [Ca₄ S100 Ax₂] complex, where the Ax peptides are accommodated between helices III/IV and III'/IV'. Without Ca²⁺ these binding sites are closed, precluding interactions with Ax. The allosteric mechanism was probed by microsecond MD simulations in explicit water, complemented by hydrogen exchange mass spectrometry (HDX/MS). Consistent with experimental data, MD runs in the absence of Ca²⁺ and Ax culminated in target binding site closure. In simulations on [Ca₄ S100] the target binding sites remained open. These results capture the essence of allosteric control, revealing how Ca²⁺ prevents binding site closure. Both HDX/MS and MD data showed that the metalation sites become more dynamic after Ca²⁺ loss. However, these enhanced dynamics do not represent the primary trigger of the allosteric cascade. Instead, a labile salt bridge acts as an incessantly active "agitator" that destabilizes the packing of adjacent residues, causing a domino chain of events that culminates in target binding site closure. This agitator represents the starting point of the allosteric signal propagation pathway. Ca²⁺ binding rigidifies elements along this pathway, thereby blocking signal transmission. This blocking mechanism does not conform to the commonly held view that allosteric communication pathways generally originate at the sites where effectors interact with the protein.

S100A6 protein: functional roles

S100A6 protein belongs to the A group of the S100 protein family of Ca2+-binding proteins. It is expressed in a limited number of cell types in adult normal tissues and in several tumor cell types. As an intracellular protein, S100A6 has been implicated in the regulation of several cellular functions, such as proliferation, apoptosis, the cytoskeleton dynamics, and the cellular response to different stress factors. S100A6 can be secreted/released by certain cell types which points to extracellular effects of the protein. RAGE (receptor for advanced glycation endproducts) and integrin β1 transduce some extracellular S100A6's effects. Dosage of serum S100A6 might aid in diagnosis in oncology.

Boundary cap neural crest stem cell transplants contribute Mts1/S100A4-expressing cells in the glial scar

AIM

During development, boundary cap neural crest stem cells (bNCSCs) assist sensory axon growth into the spinal cord. Here we repositioned them to test if they assist regeneration of sensory axons in adult mice after dorsal root avulsion injury.

MATERIALS & METHODS

Avulsed mice received bNCSC or human neural progenitor (hNP) cell transplants and their contributions to glial scar formation and sensory axon regeneration were analyzed with immunohistochemistry and transganglionic tracing.

RESULTS

hNPs and bNCSCs form similar gaps in the glial scar, but unlike hNPs, bNCSCs contribute Mts1/S100A4 (calcium-binding protein) expression to the scar and do not assist sensory axon regeneration.

CONCLUSION

bNCSC transplants contribute nonpermissive Mts1/S100A4-expressing cells to the glial scar after dorsal root avulsion.

S100-alarmins: potential therapeutic targets for arthritis

INTRODUCTION

In arthritis, inflammatory processes are triggered by numerous factors that are released from joint tissues, promoting joint destruction and pathological progression. During inflammation, a novel family of pro-inflammatory molecules called alarmins is released, amplifying inflammation and joint damage. Areas covered: With regard to the role of the alarmins S100A8 and S100A9 in the pathogenesis of arthritis, recent advances and the future prospects in terms of therapeutic implications are considered. Expert opinion: There is still an urgent need for novel treatment strategies addressing the local mechanisms of joint inflammation and tissue destruction, offering promising therapeutic alternatives. S100A8 and S100A9, which are the most up-regulated alarmins during arthritis, are endogenous triggers of inflammation, defining these proteins as promising targets for local suppression of arthritis. In murine models, the blockade of S100A8/S100A9 ameliorates inflammatory processes, including arthritis, and there are several lines of evidence that S100-alarmins may already be targeted in therapeutic approaches in man.

Molecular mechanisms of tumour invasion: regulation by calcium signals

Intracellular calcium (Ca²⁺ ) signals are key regulators of multiple cellular functions, both healthy and physiopathological. It is therefore unsurprising that several cancers present a strong Ca²⁺ homeostasis deregulation. Among the various hallmarks of cancer disease, a particular role is played by metastasis, which has a critical impact on cancer patients' outcome. Importantly, Ca²⁺ signalling has been reported to control multiple aspects of the adaptive metastatic cancer cell behaviour, including epithelial-mesenchymal transition, cell migration, local invasion and induction of angiogenesis (see Abstract Figure). In this context Ca²⁺ signalling is considered to be a substantial intracellular tool that regulates the dynamicity and complexity of the metastatic cascade. In the present study we review the spatial and temporal organization of Ca²⁺ fluxes, as well as the molecular mechanisms involved in metastasis, analysing the key steps which regulate initial tumour spread.

Knockdown of BC200 RNA expression reduces cell migration and invasion by destabilizing mRNA for calcium-binding protein S100A11

Although BC200 RNA is best known as a neuron-specific non-coding RNA, it is overexpressed in various cancer cells. BC200 RNA was recently shown to contribute to metastasis in several cancer cell lines, but the underlying mechanism was not understood in detail. To examine this mechanism, we knocked down BC200 RNA in cancer cells, which overexpress the RNA, and examined cell motility, profiling of ribosome footprints, and the correlation between cell motility changes and genes exhibiting altered ribosome profiles. We found that BC200 RNA knockdown reduced cell migration and invasion, suggesting that BC200 RNA promotes cell motility. Our ribosome profiling analysis identified 29 genes whose ribosomal occupations were altered more than 2-fold by BC200 RNA knockdown. Many (> 30%) of them were directly or indirectly related to cancer progression. Among them, we focused on S100A11 (which showed a reduced ribosome footprint) because its expression was previously shown to increase cellular motility. S100A11 was decreased at both the mRNA and protein levels following knockdown of BC200 RNA. An actinomycin-chase experiment showed that BC200 RNA knockdown significantly decreased the stability of the S100A11 mRNA without changing its transcription rate, suggesting that the downregulation of S100A11 was mainly caused by destabilization of its mRNA. Finally, we showed that the BC200 RNA-knockdown-induced decrease in cell motility was mainly mediated by S100A11. Together, our results show that BC200 RNA promotes cell motility by stabilizing S100A11 transcripts.