[S100 calcium binding protein A16 promotes fat synthesis through endoplasmic reticulum stress in HepG2 cells]

The aim of this study was to investigate the role of S100 calcium binding protein A16 (S100A16) in lipid metabolism in hepatocytes and its possible biological mechanism. HepG2 cells (human hepatoma cell line) were cultured with fatty acid to establish fatty acid culture model. The control model was cultured without fatty acid. Each model was divided into three groups and transfected with S100a16 over-expression, shRNA and vector plasmids, respectively. The concentration of triglyceride (TG) in the cells was measured by kit, and the lipid droplets was observed by oil red O staining. Immunoprecipitation and mass spectrometry were used to find the interesting proteins interacting with S100A16, and the interaction was verified by immunoprecipitation. The further mechanism was studied by Western blot and qRT-PCR. The results showed that the intracellular lipid droplet and TG concentrations in the fatty acid culture model were significantly higher than those in the control model. The accumulation of intracellular fat in the S100a16 over-expression group was significantly higher than that in the vector plasmid transfection group. There was an interaction between heat shock protein A5 (HSPA5) and S100A16. Over-expression of S100A16 up-regulated protein expression levels of HSPA5, inositol-requiring enzyme 1α (IRE1α) and pIREα1, which belong to endoplasmic reticulum stress HSPA5/IRE1α-XBP1 pathway. Meanwhile, over-expression of S100A16 up-regulated the mRNA expression levels of adipose synthesis-related gene Srebp1c, Acc and Fas. In the S100a16 shRNA plasmid transfection group, the above-mentioned protein and mRNA levels were lower than those of vector plasmid transfection group. These results suggest that S100A16 may promote lipid synthesis in HepG2 cells through endoplasmic reticulum stress HSPA5/IRE1α-XBP1 pathway.

Loss of S100A1 expression leads to Ca2+ release potentiation in mutant mice with disrupted CaM and S100A1 binding to CaMBD2 of RyR1

Calmodulin (CaM) and S100A1 fine-tune skeletal muscle Ca2+ release via opposite modulation of the ryanodine receptor type 1 (RyR1). Binding to and modulation of RyR1 by CaM and S100A1 occurs predominantly at the region ranging from amino acid residue 3614-3640 of RyR1 (here referred to as CaMBD2). Using synthetic peptides, it has been shown that CaM binds to two additional regions within the RyR1, specifically residues 1975-1999 and 4295-4325 (CaMBD1 and CaMBD3, respectively). Because S100A1 typically binds to similar motifs as CaM, we hypothesized that S100A1 could also bind to CaMBD1 and CaMBD3. Our goals were: (1) to establish whether S100A1 binds to synthetic peptides containing CaMBD1 and CaMBD3 using isothermal calorimetry (ITC), and (2) to identify whether S100A1 and CaM modulate RyR1 Ca2+ release activation via sites other than CaMBD2 in RyR1 in its native cellular context. We developed the mouse model (RyR1D-S100A1KO), which expresses point mutation RyR1-L3625D (RyR1D) that disrupts the modulation of RyR1 by CaM and S100A1 at CaMBD2 and also lacks S100A1 (S100A1KO). ITC assays revealed that S100A1 binds with different affinities to CaMBD1 and CaMBD3. Using high-speed Ca2+ imaging and a model for Ca2+ binding and transport, we show that the RyR1D-S100A1KO muscle fibers exhibit a modest but significant increase in myoplasmic Ca2+ transients and enhanced Ca2+ release flux following field stimulation when compared to fibers from RyR1D mice, which were used as controls to eliminate any effect of binding at CaMBD2, but with preserved S100A1 expression. Our results suggest that S100A1, similar to CaM, binds to CaMBD1 and CaMBD3 within the RyR1, but that CaMBD2 appears to be the primary site of RyR1 regulation by CaM and S100A1.

The Calcium-Binding Protein S100A6 Accelerates Human Osteosarcoma Growth by Promoting Cell Proliferation and Inhibiting Osteogenic Differentiation

BACKGROUND/AIMS

Although osteosarcoma (OS) is the most common primary malignancy of bone, its molecular pathogenesis remains to be fully understood. We previously found the calcium-binding protein S100A6 was expressed in ∼80% of the analyzed OS primary and/or metastatic tumor samples. Here, we investigate the role of S100A6 in OS growth and progression.

METHODS

S100A6 expression was assessed by qPCR and Western blotting. Overexpression or knockdown of S100A6 was carried out to determine S100A6's effect on proliferation, cell cycle, apoptosis, tumor growth, and osteogenic differentiation.

RESULTS

S100A6 expression was readily detected in human OS cell lines. Exogenous S100A6 expression promoted cell proliferation in vitro and tumor growth in an orthotopic xenograft model of human OS. S100A6 overexpression reduced the numbers of OS cells in G1 phase and increased viable cells under serum starvation condition. Conversely, silencing S100A6 expression induced the production of cleaved caspase 3, and increased early stage apoptosis. S100A6 knockdown increased osteogenic differentiation activity of mesenchymal stem cells, while S100A6 overexpression inhibited osteogenic differentiation. BMP9-induced bone formation was augmented by S100A6 knockdown.

CONCLUSION

Our findings strongly suggest that S100A6 may promote OS cell proliferation and OS tumor growth at least in part by facilitating cell cycle progression, preventing apoptosis, and inhibiting osteogenic differentiation. Thus, it is conceivable that targeting S100A6 may be exploited as a novel anti-OS therapy.

[Role of S100A4 in the epithelial-mesenchymal transition of esophageal squamous cell carcinoma and its molecular mechanism]

OBJECTIVE

To explore the role of S100A4 in the epithelial-mesenchymal transition (EMT) in esophageal squamous cell carcinoma and its possible molecular mechanism.

METHODS

Three chemically synthesized S100A4 siRNA sequences were transiently transfected into esophageal carcinoma EC9706 cells. EC9706 cells transfected with negative siRNA, lipofectamine 2000, and vacant EC9706 cells were used as control. Fluorescence quantitative RT-PCR and Western blot were used to detect the inhibition rate of S100A4 siRNA. S100A4 siRNA2 with the best inhibition rate was chosen to transiently transfect into EC9706 cells under the same conditions. The EC9706 cells transfected with negative siRNA, lipofectamine 2000 and vacant EC9706 cells were also used as control. Fluorescence quantitative RT-PCR and Western blot were used to detect the mRNA and protein expressions of E-cadherin, vimentin and snail. The morphology of EC9706 cells was observed under an inverted microscope. Boyden chamber and scratch test were used to detect the invasion and migration ability of EC9706 cells, and CCK8 assay was used to detect the proliferation ability of EC9706 cells. EC9706 cells transfected with S100A4 siRNA2 were further transfected with snail eukaryotic expression vector. The EC9706 cells transfected with S100A4 siRNA, EC9706 cells transfected with snail eukaryotic expression vector and vacant EC9706 cells were used as control. The above indexes of all the groups were observed, too.

RESULTS

The S100A4 mRNA and protein expression levels of the S100A4 siRNA2 group were 0.417 ± 0.041 and 0.337 ± 0.039, the transmembrane cell number was 61.608 ± 8.937, the scratch healing distance was (0.216 ± 0.064) mm, the A value was 0.623 ± 0.084, the E-cadherin mRNA and protein levels were 0.619 ± 0.032 and 0.495 ± 0.034, the vimentin mRNA and protein levels were 0.514 ± 0.032 and 0.427 ± 0.028, the snail mRNA and protein levels were 0.573 ± 0.029 and 0.429 ± 0.041. These data were significantly different with the liposome group, the negative control group and the blank group (P < 0.05 for all). After the S100A4 siRNA2 treatment for 24 h, the appearance of EC9706 cells changed to epithelial cell morphology. The transmembrane cell number and the scratch healing distance of the S100A4 siRNA2+snail eukaryotic expression vector group were (69.382 ± 9.666) cells and (0.274 ± 0.029) mm, the A value was 0.823 ± 0.101, the snail mRNA and protein levels were 0.704 ± 0.037 and 0.625 ± 0.031, the vimentin mRNA and protein levels were 0.712 ± 0.046 and 0.609 ± 0.038, and these data were significantly higher than those of the Sl00A4 siRNA2 group (P < 0.05 for all). The E-cadherin mRNA and protein levels of the S100A4 siRNA2+eukaryotic expression vector group were 0.437 ± 0.038 and 0.381 ± 0.031, significantly lower than those of the S100A4 siRNA2 group (P < 0.05 for all). However, snail had no effect on the morphology of EC9706 cells.

CONCLUSIONS

S100A4 may be involved in the EMT process of esophageal squamous-cell carcinoma by regulating the expression of snail and then plays a role in the invasion and metastasis of esophageal carcinoma.

Proteomics analysis of melanoma metastases: association between S100A13 expression and chemotherapy resistance

BACKGROUND

Disseminated cutaneous malignant melanoma (CMM) is commonly unresponsive to standard chemotherapies, and there are as yet no predictive markers of therapy response.

METHODS

In the present study we collected fresh-frozen pretreatment lymph-node metastasis samples (n=14) from melanoma patients with differential response to dacarbazine (DTIC) or temozolomide (TMZ) chemotherapy, to identify proteins with an impact on treatment response. We performed quantitative protein profiling using tandem mass spectrometry and compared the proteome differences between responders (R) and non-responders (NR), matched for age, gender and histopathological type of CMM.

RESULTS

Biological pathway analyses showed several signalling pathways differing between R vs NR, including Rho signalling. Gene expression profiling data was available for a subset of the samples, and the results were compared with the proteomics data. Four proteins with differential expression between R and NR were selected for technical validation by immunoblotting (ISYNA1, F13A1, CSTB and S100A13), and CSTB and S100A13 were further validated on a larger sample set by immunohistochemistry (n=48). The calcium binding protein S100A13 was found to be significantly overexpressed in NR compared with R in all analyses performed.

CONCLUSIONS

Our results suggest that S100A13 is involved in CMM resistance to DTIC/TMZ.

Clinical significance of S100A2 expression in gastric cancer

Gastric carcinoma (GC) is one of the most common malignancies worldwide. To identify the candidate carcinoma-related biomarker in GC, comparative proteome technique was performed in resected GC tissues and matched adjacent non-cancerous gastric tissues (ANGT). As a result, S100A2 was successfully identified to be down-regulated significantly in GC compared with ANGT. Western blot analysis validated decreased expression of S100A2, and its expression level was related with the degree of tumor differentiation and status of lymph node metastasis in GC. Furthermore, immunohistochemistry analysis showed S100A2 down-expression was significantly associated with poor differentiation (P < 0.05), advanced depth of invasion (P < 0.05) and lymph node metastasis (P < 0.05) in GC. Kaplan-Meier curves showed that the relapse-free probability and the overall survival rate were significantly decreased with S100A2 expression decreasing (P < 0.05). Cox regression analysis indicated S100A2 down-expression was a negative independent prognostic biomarker for GC. A supplement of S100A2 protein by S100A2 expression vector significantly decreased the number of invaded cancer cells MGC-803. However, knockdown of S100A2 expression by siRNA interference compromised the invasion ability of MGC-803 cells. Moreover, S100A2 negatively regulated MEK/ERK signaling pathway, and activation of this signaling pathway by S100A2 down-regulation increased in vitro invasion of MGC-803 cells. In conclusion, this study demonstrated the clinical significance of S100A2 expression in GC, and loss of S100A2 expression contributes to GC development and progression. Therefore, the determination of S100A2 expression levels contributes to predict the outcome of GC patients.

A Calcium Binding Protein, S100A4, Mediates T Cell Dependent Cytotoxicity as a Transformation-Associated Antigen

The nature of the target molecule of TCR gamma delta T cell-mediated lysis remains to be determined. As we previously reported, #067 monoclonal antibody (mAb) recognizes one of the transformation-associated antigens, designated as #067 antigen. This antigen is expressed on the cell surface of rat fibrosarcoma W31 cells, which are established by transformation of fetal fibroblastic WFB cells with H-ras oncogene. It has been suggested that the #067 antigen is a target molecule for TCR gamma delta T cells since #067 mAb inhibited TCR gamma delta T cell-mediated lysis against #067 positive cells. In this study we attempted to identify the protein sequence of the #067 antigen. By using molecular cloning techniques, we demonstrated that a calcium binding protein, S100A4, was possibly one and the same molecule as the #067 antigen. It was shown that the expression of S100A4 was higher in W31 cells than in WFB cells at transcription and protein level. Flow cytometry and immunocytochemical studies showed that #067 antigen partially co-localized with S100A4 on the cell surface as well as the cytoplasm of W31 cells. Moreover, rabbit anti-S100A4 polyclonal antibodies (pAb) inhibited TCR gamma delta T cell-mediated lysis against #067 positive cells. Our results indicated that S100A4 may play a role as a possible target molecule for TCR gamma delta T cell-mediated lysis although how S100A4 is involved in TCR gamma delta T cell-mediated lysis remains to be determined.

Protein interactions between surface annexin A2 and S100A10 mediate adhesion of breast cancer cells to microvascular endothelial cells

Annexin A2 (AnxA2) and S100A10 are known to form a molecular complex. Using fluorescence-based binding assays, we show that both proteins are localised on the cell surface, in a molecular form that allows mutual interaction. We hypothesized that binding between these proteins could facilitate cell-cell interactions. For cells that express surface S100A10 and surface annexin A2, cell-cell interactions can be blocked by competing with the interaction between these proteins. Thus an annexin A2-S100A10 molecular bridge participates in cell-cell interactions, revealing a hitherto unexplored function of this protein interaction.

[Relationships between damage-associated molecular patterns and organ injury]

Recently studies have demonstrated that cell components called damage-associated molecular patterns (DAMPs) are secreted from cells in response to inflammation and organ injury. While DAMPs are maintained within the cell under normal conditions, they are secreted in response to systemic or chronic inflammation. DAMPs are recognized by pattern recognition receptors (PRRs) such as Toll-like receptor (TLR) and receptor for advanced glycation end products (RAGE). DAMPs also induce the phosphorylation of various intracellular proteins and activate NF-kappaB signaling. This induces an inflammatory response via cytokine production and activation of macrophages and dendritic cells. In essence, DAMPs alert the immune system to danger. Some DAMPs are considered therapeutic targets for acute systemic inflammation (e.g., sepsis). Indeed, anti-HMGB1 and anti-histone antibodies attenuated the inflammatory response and organ injury in a systemic inflammation model. Anti-RAGE antibodies were also shown to have beneficial effects in an animal inflammation model. These findings suggest that DAMPs may serve as novel therapeutic targets against severe systemic inflammation as well. We anticipate that in the near future, anti-DAMP therapy may become more widespread in the clinical setting.

Identification of prognostic factors in patients with metastatic gastrointestinal stromal tumors

PURPOSE

Gastrointestinal stromal tumors (GISTs) have a complex biology which is reflected by a marked clinical heterogeneity. Thus, there has been great interest in identifying prognostic factors influencing tumor recurrence and survival. The aim of this study was to identify potential clinical and immunohistochemical prognostic factors that may affect survival and treatment outcomes in patients with metastatic GISTs.

METHODS

Between 2000 and September 2011, a total of 41 patients with metastatic GISTs (29 males and 12 females; mean age: 57.4±11.8 years; range 29-74) were referred to the Department of Oncology, Uludag University Medical School. Survival analysis for a number of potential prognostic factors was made with the main outcome results of progression-free survival (PFS) and overall survival (OS7rpar;.

RESULTS

The most common sites of isolated metastases comprised the liver (n=18), followed by lymph nodes (n=5), the omentum (n=1), and the mesothelium (n=1). The remaining patients had metastases at multiple sites. Cox regression analysis identified ileal location as the only significant predictor of poor PFS both after first-line (p=0.023) and second-line therapy (p=0.016). Tumor location in the ileum (p=0.025) and S100 immunoreactivity (p=0.041) were both independent predictors of OS.

CONCLUSION

Tumor site and S100 positivity were the main significant independent predictors of clinical outcomes in patients with metastatic GISTs treated by standard of care.

S100A16 mediation of weight gain attenuation induced by dietary calcium

Dietary calcium influences the regulation of energy metabolism, and weight gain is attenuated by a high-calcium diet. S100A16 is a novel calcium-binding signaling protein of the EF-hand superfamily that promotes adipogenesis. This study aimed to investigate the effect of S100A16 on weight gain attenuation with a calcium-rich diet. An obese rat model was produced after feeding with a high-fat diet. Animals were randomly divided into 4 groups according to the diet provided over 8 weeks: normal diet group; high-fat, normal-calcium diet group; high-fat, high-calcium diet (HH) group; and high-fat, low-calcium diet group. Serum biochemistry was analyzed, and body weight and visceral fat pads were measured. Expression of S100A16 was assayed by Western blotting. Adipogenesis was detected by oil red O staining. Increases in body weight and visceral fat weight were attenuated in the HH group. High-calcium diets decreased the concentrations of serum total cholesterol and triglyceride. Expression of S100A16 decreased in the HH group. Using the 3T3-L1 preadipocyte model, it was observed that elevation of intracellular Ca(2+) via calcium ionophores led to the exclusion of S100A16 from the nucleus. Overexpression of S100A16 in 3T3-L1 preadipocytes enhanced adipogenesis, although a significant reduction in Akt phosphorylation was also detected. High-calcium diets were associated with a significant reduction in body weight gain. High-calcium diets may lead to nuclear exclusion of S100A16, which results in the inhibition of adipogenesis and enhanced insulin sensitivity.

S100 proteins in cartilage: role in arthritis

S100 proteins are low molecular weight calcium binding proteins expressed in vertebrates. The family constitutes 21 known members that are expressed in several tissues and cell types and play a major role in various cellular functions. Uniquely, members of the S100 family have both intracellular and extracellular functions. Several members of the S100 family (S100A1, S100A2, S100A4, S1008, S100A9, S100A11, and S100B) have been identified in human articular cartilage, and their expression is upregulated in diseased tissue. These S100 proteins elicit a catabolic signaling pathway via receptor for advanced glycation end products (RAGE) in cartilage and may promote progression of arthritis. This review summarizes our current understanding of the role of S100 proteins in cartilage biology and in the development of arthritis.

Respiratory disease and early serum S100A12 changes in very premature infants

AIM

The role of granulocyte-specific S100A12, a marker for inflammatory disorders, in newborn lung disease is unknown. We compared postnatal blood S100A12 concentrations against respiratory distress syndrome (RDS) and bronchopulmonary dysplasia (BPD).

METHODS

Blood samples from 92 newborns were collected on admission, 12 h, day 1, day 3-4 and day 7, and analysed for S100A12. IL-8 and IL-6 were assayed in 52 infants.

RESULTS

Infants with RDS were significantly more premature (median 27 vs. 34 weeks), more likely to receive antenatal corticosteroids (84% vs. 26%) and have lower neutrophil counts (median 2.4 vs. 3.8 × 10(9) /L) at admission. S100A12 levels peaked during the first day and were significantly lower in preterm infants with RDS compared to those without (median 250 vs. 616 ng/mL at 12 h, 281 vs. 828 ng/mL day 1, respectively). S100A12 levels were low among the 35 very preterm infants (24-29 week gestation) regardless of the presence of BPD (285 vs. 288 ng/mL on day 1). In comparison, IL-8 and IL-6 levels were not different between groups.

CONCLUSION

Plasma S100A12 is low in infants with RDS, possibly because of gestationally related differences in neutrophil response or to the effects of antenatal corticosteroids. It is therefore not a useful marker of BPD development.

Selective expression of S100A11 in lung cancer and its role in regulating proliferation of adenocarcinomas cells

S100A11, one secreted protein, is overexpressed in certain cancers. We investigated S100A11 expression in various subtypes of lung cancer and explored its role in cell proliferation. S100A11 mRNA level was examined in 45 pairs of frozen lung cancer tissues by reverse transcriptase PCR (RT-PCR). The specific expression and subcellular distribution of S100A11 were examined in 78 paraffin-embedded lung cancers, 2 benign lung diseases as well as 22 healthy lung tissues by immunohistochemistry. S100A11 protein level was further analyzed in the sera of 86 lung cancer patients and 50 healthy individuals by enzyme-linked immunosorbent assay. We found that both mRNA and protein levels of S100A11 were overexpressed in adenocarcinomas (ADC) and squamous cell carcinomas (SCC) compared with paired non-cancerous lung tissues, while S100A11 was detected downregulated in small cell lung cancers (SCLC). Further immunohistochemistry staining was positive for S100A11 only in non-small cell lung cancer (NSCLC) (ADC, SCC, large cell carcinomas, et al.), but not SCLC. Conclusively, we found S100A11 protein level increased in the sera of NSCLC patients. Furthermore, when S100A11 expression was knocked down in lung adenocarcinoma cells A549 and LTEP-a-2, the cell proliferation was significantly inhibited in vitro and in vivo.

The importance of Ca2+/Zn2+ signaling S100 proteins and RAGE in translational medicine

The Receptor for Advanced Glycation Endproducts (RAGE) is a multiligand receptor involved in a large number of human disorders. Identified first as the receptor for the Advanced Glycation Endproducts (AGEs), RAGE has emerged in recent years as a major receptor for many members of the S100 calcium and zinc binding protein family. The interaction with and the signaling triggered by several S100 proteins such as S100B and S100A12 have been studied in details and have shown concentration and cell type dependent signaling cascades. The S100 protein family consists of more than 20 members which present high amino-acid sequence and structural similarities. These small EF-hand calcium binding proteins interact with a large number of protein targets and are almost all been shown to be involved in cancer. In this review we discuss the recent knowledge about the role of S100 proteins and RAGE in human disorders.

The importance of Ca2+/Zn2+ signaling S100 proteins and RAGE in translational medicine

The Receptor for Advanced Glycation Endproducts (RAGE) is a multiligand receptor involved in a large number of human disorders. Identified first as the receptor for the Advanced Glycation Endproducts (AGEs), RAGE has emerged in recent years as a major receptor for many members of the S100 calcium and zinc binding protein family. The interaction with and the signaling triggered by several S100 proteins such as S100B and S100A12 have been studied in details and have shown concentration and cell type dependent signaling cascades. The S100 protein family consists of more than 20 members which present high amino-acid sequence and structural similarities. These small EF-hand calcium binding proteins interact with a large number of protein targets and are almost all been shown to be involved in cancer. In this review we discuss the recent knowledge about the role of S100 proteins and RAGE in human disorders.

Oral Uncaria rhynchophylla (UR) reduces kainic acid-induced epileptic seizures and neuronal death accompanied by attenuating glial cell proliferation and S100B proteins in rats

AIM OF THE STUDY

Epilepsy is a common clinical syndrome with recurrent neuronal discharges in cerebral cortex and hippocampus. Here we aim to determine the protective role of Uncaria rhynchophylla (UR), an herbal drug belong to Traditional Chinese Medicine (TCM), on epileptic rats.

MATERIALS AND METHODS

To address this issue, we tested the effect of UR on kainic acid (KA)-induced epileptic seizures and further investigate the underlying mechanisms.

RESULTS

Oral UR successfully decreased neuronal death and discharges in hippocampal CA1 pyramidal neurons. The population spikes (PSs) were decreased from 4.1 ± 0.4 mV to 2.1 ± 0.3 mV in KA-induced epileptic seizures and UR-treated groups, respectively. Oral UR protected animals from neuronal death induced by KA treatment (from 34 ± 4.6 to 191.7 ± 48.6 neurons/field) through attenuating glial cell proliferation and S100B protein expression but not GABAA and TRPV1 receptors.

CONCLUSIONS

The above results provide detail mechanisms underlying the neuroprotective action of UR on KA-induced epileptic seizure in hippocampal CA1 neurons.

Stable knockdown of S100A4 suppresses cell migration and metastasis of osteosarcoma

S100A4, a 10-12 kDa calcium-binding protein, plays functional roles in tumor progression and metastasis. The present study aimed to investigate the function of S100A4 in osteosarcoma (OS) metastasis, using a loss-of-function approach. Our previous expression profiling analysis revealed that S100a4 was preferentially expressed in the highly metastatic mouse OS cell line, LM8. Introducing a short hairpin ribonucleic acid (shRNA) targeting S100a4 using a newly established vector containing insulators and transposons, we established stable LM8 subclones with almost 100% silencing of endogenous S100a4 protein. These transfectants showed a significant suppression of cell migration in vitro as well as a marked reduction in their ability to colonize the lung and form pulmonary metastases in vivo following intravenous inoculation, whereas there was no significant change in cell proliferation or cell attachment to fibronectin, laminin, and type I collagen. Expression and phosphorylation of ezrin, an emerging OS metastasis-associated factor, and expression of MMPs, remained the same in S100a4-shRNA clones. In 61 human OS, immunohistochemical analysis showed that lesional cells in 85.2% samples expressed S100A4 protein, and the immunoreactivity was primarily cytoplasmic, but it also showed occasional nuclear localization. Chondroblastic and osteoblastic OS subtypes expressed more S100A4 than fibroblastic subtypes. The causative role of S100A4 in OS lung metastasis shown in the murine xenograft model, together with the high proportion of primary human OS expressing S100A4, suggest that S100A4 protein represents an important potential target for future OS therapy.

The trafficking of Na(V)1.8

The α-subunit of tetrodotoxin-resistant voltage-gated sodium channel Na(V)1.8 is selectively expressed in sensory neurons. It has been reported that Na(V)1.8 is involved in the transmission of nociceptive information from sensory neurons to the central nervous system in nociceptive [1] and neuropathic [24] pain conditions. Thus Na(V)1.8 has been a promising target to treat chronic pain. Here we discuss the recent advances in the study of trafficking mechanism of Na(V)1.8. These pieces of information are particularly important as such trafficking machinery could be new targets for painkillers.

Dopamine D2 receptor signaling modulates mutant ataxin-1 S776 phosphorylation and aggregation

Spinocerebellar ataxia 1 (SCA1) is a dominantly inherited neurodegenerative disease associated with progressive ataxia resulting from the loss of cerebellar Purkinje cells (PCs) and neurons in the brainstem. In PCs of SCA1 transgenic mice, the disease causing ataxin-1 protein mediates the formation of S100B containing cytoplasmic vacuoles and further self-aggregates to form intranuclear inclusions. The exact function of the ataxin-1 protein is not fully understood. However, the aggregation and neurotoxicity of the mutant ataxin-1 protein is dependent on the phosphorylation at serine 776 (S776). Although protein kinase A (PKA) has been implicated as the S776 kinase, the mechanism of PKA/ataxin-1 regulation in SCA1 is still not clear. We propose that a dopamine D(2) receptor (D2R)/S100B pathway may be involved in modulating PKA activity in PCs. Using a D2R/S100B HEK stable cell line transiently transfected with GFP-ataxin-1[82Q], we demonstrate that stimulation of the D2R/S100B pathway caused a reduction in mutant ataxin-1 S776 phosphorylation and ataxin-1 aggregation. Activation of PKA by forskolin resulted in an enhanced S776 phosphorylation and increased ataxin-1 nuclear aggregation, which was suppressed by treatment with D2R agonist bromocriptine and PKA inhibitor H89. Furthermore, treating SCA1 transgenic PC slice cultures with forskolin induced neurodegenerative morphological abnormalities in PC dendrites consistent with those observed in vivo. Taken together our data support a mechanism where PKA dependent mutant ataxin-1 phosphorylation and aggregation can be regulated by D2R/S100B signaling.

Metastasis-inducing S100A4 and RANTES cooperate in promoting tumor progression in mice

BACKGROUND

The tumor microenvironment has been described as a critical milieu determining tumor growth and metastases. A pivotal role of metastasis-inducing S100A4 in the development of tumor stroma has been proven in animal models and verified in human breast cancer biopsies. Expression and release of S100A4 has been shown in various types of stroma composing cells, including fibroblasts and immune cells. However, the events implicated in upstream and downstream pathways regulating the activity of the extracellular S100A4 protein in the tumor milieu remain unsolved.

METHODOLOGY/PRINCIPAL FINDINGS

We studied the interplay between the tumor cell-derived cytokine regulated-upon-activation, normal T-cell expressed and secreted (RANTES; CCL5) and S100A4 which were shown to be critical factors in tumor progression. We found that RANTES stimulates the externalization of S100A4 via microparticle shedding from the plasma membrane of tumor and stroma cells. Conversely, the released S100A4 protein induces the upregulation of fibronectin (FN) in fibroblasts and a number of cytokines, including RANTES in tumor cells as well as stimulates cell motility in a wound healing assay. Importantly, using wild type and S100A4-deficient mouse models, we demonstrated a substantial influence of tumor cell-derived RANTES on S100A4 release into blood circulation which ultimately increases the metastatic burden in mice.

CONCLUSIONS/SIGNIFICANCE

Altogether, the data presented strongly validate the pro-metastatic function of S100A4 in the tumor microenvironment and define how the tumor cell-derived cytokine RANTES acts as a critical regulator of S100A4-dependent tumor cell dissemination. Additionally, for the first time we demonstrated the mechanism of S100A4 release associated with plasma membrane microparticle shedding from various cells types.

S100 proteins regulate the interaction of Hsp90 with Cyclophilin 40 and FKBP52 through their tetratricopeptide repeats

S100 proteins are a subfamily of the EF-hand type calcium sensing proteins, the exact biological functions of which have not been clarified yet. In this work, we have identified Cyclophilin 40 (CyP40) and FKBP52 (called immunophilins) as novel targets of S100 proteins. These immunophilins contain a tetratricopeptide repeat (TPR) domain for Hsp90 binding. Using glutathione-S transferase pull-down assays and immunoprecipitation, we have demonstrated that S100A1 and S100A2 specifically interact with the TPR domains of FKBP52 and CyP40 in a Ca(2+)-dependent manner, and lead to inhibition of the CyP40-Hsp90 and FKBP52-Hsp90 interactions. These findings have suggested that the Ca(2+)/S100 proteins are TPR-targeting regulators of the immunophilins-Hsp90 complex formations.