S100A6 (calcyclin) enhances the sensitivity to apoptosis via the upregulation of caspase-3 activity in Hep3B cells

Apoptotic Cell Death in Bicuspid-Aortic-Valve-Associated Aortopathy

The bicuspid aortic valve (BAV) is the most common cardiovascular congenital abnormality and is frequently associated with proximal aortopathy. We analyzed the tissues of patients with bicuspid and tricuspid aortic valve (TAV) regarding the protein expression of the receptor for advanced glycation products (RAGE) and its ligands, the advanced glycation end products (AGE), as well as the S100 calcium-binding protein A6 (S100A6). Since S100A6 overexpression attenuates cardiomyocyte apoptosis, we investigated the diverse pathways of apoptosis and autophagic cell death in the human ascending aortic specimen of 57 and 49 patients with BAV and TAV morphology, respectively, to identify differences and explanations for the higher risk of patients with BAV for severe cardiovascular diseases. We found significantly increased levels of RAGE, AGE and S100A6 in the aortic tissue of bicuspid patients which may promote apoptosis via the upregulation of caspase-3 activity. Although increased caspase-3 activity was not detected in BAV patients, increased protein expression of the 48 kDa fragment of vimentin was detected. mTOR as a downstream protein of Akt was significantly higher in patients with BAV, whereas Bcl-2 was increased in patients with TAV, assuming a better protection against apoptosis. The autophagy-related proteins p62 and ERK1/2 were increased in patients with BAV, assuming that cells in bicuspid tissue are more likely to undergo apoptotic cell death leading to changes in the wall and finally to aortopathies. We provide first-hand evidence of increased apoptotic cell death in the aortic tissue of BAV patients which may thus provide an explanation for the increased risk of structural aortic wall deficiency possibly underlying aortic aneurysm formation or acute dissection.

S100A6 Protein-Expression and Function in Norm and Pathology

S100A6, also known as calcyclin, is a calcium-binding protein belonging to the S100 protein family. It was first identified and purified more than 30 years ago. Initial structural studies, focused mostly on the mode and affinity of Ca²⁺ binding and resolution of the resultant conformational changes, were soon complemented by research on its expression, localization and identification of binding partners. With time, the use of biophysical methods helped to resolve the structure and versatility of S100A6 complexes with some of its ligands. Meanwhile, it became clear that S100A6 expression was altered in various pathological states and correlated with the stage/progression of many diseases, including cancers, indicative of its important, and possibly causative, role in some of these diseases. This, in turn, prompted researchers to look for the mechanism of S100A6 action and to identify the intermediary signaling pathways and effectors. After all these years, our knowledge on various aspects of S100A6 biology is robust but still incomplete. The list of S100A6 ligands is growing all the time, as is our understanding of the physiological importance of these interactions. The present review summarizes available data concerning S100A6 expression/localization, interaction with intracellular and extracellular targets, involvement in Ca²⁺-dependent cellular processes and association with various pathologies.

The Role of the S100 Protein Family in Glioma

The S100 protein family consists of 25 members and share a common structure defined in part by the Ca²⁺ binding EF-hand motif. Multiple members' dysregulated expression is associated with progression, diagnosis and prognosis in a broad range of diseases, especially in tumors. They could exert wide range of functions both in intracellular and extracellular, including cell proliferation, cell differentiation, cell motility, enzyme activities, immune responses, cytoskeleton dynamics, Ca²⁺ homeostasis and angiogenesis. Gliomas are the most prevalent primary tumors of the brain and spinal cord with multiple subtypes that are diagnosed and classified based on histopathology. Up to now the role of several S100 proteins in gliomas have been explored. S100A8, S100A9 and S100B were highly expression in serum and may present as a marker correlated with survival and prognosis of glioma patients. Individual member was confirmed as a new regulator of glioma stem cells (GSCs) and a mediator of mesenchymal transition in glioblastoma (GBM). Additionally, several members up- or downregulation have been reported to involve in the development of glioma by interacting with signaling pathways and target proteins. Here we detail S100 proteins that are associated with glioma, and discuss their potential effects on progression, diagnosis and prognosis.

Ca2+-dependent binding of S100A6 to cofilin-1 regulates actin filament polymerization-depolymerization dynamics

S100A6 is a Ca²⁺-binding protein belonging to the S100 family. Many reports indicate that S100A6 is involved in actin filament organization, however the mechanism of S100A6 action in this process is not fully understood. By screening S100A6 binding partners in NIH3T3 mouse fibroblasts, we have found that S100A6 binds cofilin-1, a protein required for the dynamics of actin polymerization and depolymerization. By applying various biochemical and cell biology assays, we have shown that S100A6 bound to cofilin-1 in a Ca²⁺-dependent manner and increased cofilin-1 affinity for F-actin. Microscopic analysis indicated that S100A6 significantly decreased severing of the actin filaments induced by cofilin-1. Moreover, in the presence of cofilin-1, S100A6 stabilized the filaments by inhibiting their depolymerization. When S100A6 was present at sub-stoichiometric concentrations in relation to actin, polymerization of G-actin accelerated by cofilin-1 was increased. At higher S100A6:actin ratios the polymerization rate was decreased. Altogether, these results show that S100A6 regulates actin filament dynamics by controlling activity of cofilin-1 and suggest that this regulation is Ca²⁺ -dependent.

S100 calcium binding protein A6 and associated long noncoding ribonucleic acids as biomarkers in the diagnosis and staging of primary biliary cholangitis

BACKGROUND

Primary biliary cholangitis (PBC) is a chronic and slowly progressing cholestatic disease, which causes damage to the small intrahepatic bile duct by immuno-regulation, and may lead to cholestasis, liver fibrosis, cirrhosis and, eventually, liver failure.

AIM

To explore the potential diagnosis and staging value of plasma S100 calcium binding protein A6 (S100A6) messenger ribonucleic acid (mRNA), LINC00312, LINC00472, and LINC01257 in primary biliary cholangitis.

METHODS

A total of 145 PBC patients and 110 healthy controls (HCs) were enrolled. Among them, 80 PBC patients and 60 HCs were used as the training set, and 65 PBC patients and 50 HCs were used as the validation set. The relative expression levels of plasma S100A6 mRNA, long noncoding ribonucleic acids LINC00312, LINC00472 and LINC01257 were analyzed using quantitative reverse transcription-polymerase chain reaction. The bile duct ligation (BDL) mouse model was used to simulate PBC. Then double immunofluorescence was conducted to verify the overexpression of S100A6 protein in intrahepatic bile duct cells of BDL mice. Human intrahepatic biliary epithelial cells were treated with glycochenodeoxycholate to simulate the cholestatic environment of intrahepatic biliary epithelial cells in PBC.

RESULTS

The expression of S100A6 protein in intrahepatic bile duct cells was up-regulated in the BDL mouse model compared with sham mice. The relative expression levels of plasma S100A6 mRNA, log10 LINC00472 and LINC01257 were up-regulated while LINC00312 was down-regulated in plasma of PBC patients compared with HCs (3.01 ± 1.04 vs 2.09 ± 0.87, P < 0.0001; 2.46 ± 1.03 vs 1.77 ± 0.84, P < 0.0001; 3.49 ± 1.64 vs 2.37 ± 0.96, P < 0.0001; 1.70 ± 0.33 vs 2.07 ± 0.53, P < 0.0001, respectively). The relative expression levels of S100A6 mRNA, LINC00472 and LINC01257 were up-regulated and LINC00312 was down-regulated in human intrahepatic biliary epithelial cells treated with glycochenodeoxycholate compared with control (2.97 ± 0.43 vs 1.09 ± 0.08, P = 0.0018; 2.70 ± 0.26 vs 1.10 ± 0.10, P = 0.0006; 2.23 ± 0.21 vs 1.10 ± 0.10, P = 0.0011; 1.20 ± 0.04 vs 3.03 ± 0.15, P < 0.0001, respectively). The mean expression of S100A6 in the advanced stage (III and IV) of PBC was up-regulated compared to that in HCs and the early stage (II) (3.38 ± 0.71 vs 2.09 ± 0.87, P < 0.0001; 3.38 ± 0.71 vs 2.57 ± 1.21, P = 0.0003, respectively); and in the early stage (II), it was higher than that in HCs (2.57 ± 1.21 vs 2.09 ± 0.87, P = 0.03). The mean expression of LINC00312 in the advanced stage was lower than that in the early stage and HCs (1.39 ± 0.29 vs 1.56 ± 0.33, P = 0.01; 1.39 ± 0.29 vs 2.07 ± 0.53, P < 0.0001, respectively); in addition, the mean expression of LINC00312 in the early stage was lower than that in HCs (1.56 ± 0.33 vs 2.07 ± 0.53, P < 0.0001). The mean expression of log10 LINC00472 in the advanced stage was higher than those in the early stage and HCs (2.99 ± 0.87 vs 1.81 ± 0.83, P < 0.0001; 2.99 ± 0.87 vs 1.77 ± 0.84, P < 0.0001, respectively). The mean expression of LINC01257 in both the early stage and advanced stage were up-regulated compared with HCs (3.88 ± 1.55 vs 2.37 ± 0.96, P < 0.0001; 3.57 ± 1.79 vs 2.37 ± 0.96, P < 0.0001, respectively). The areas under the curves (AUC) for S100A6, LINC00312, log10 LINC00472 and LINC01257 in PBC diagnosis were 0.759, 0.7292, 0.6942 and 0.7158, respectively. Furthermore, the AUC for these four genes in PBC staging were 0.666, 0.661, 0.839 and 0.5549, respectively. The expression levels of S100A6 mRNA, log10 LINC00472, and LINC01257 in plasma of PBC patients were decreased (2.35 ± 1.02 vs 3.06 ± 1.04, P = 0.0018; 1.99 ± 0.83 vs 2.33 ± 0.96, P = 0.036; 2.84 ± 0.92 vs 3.69 ± 1.54, P = 0.0006), and the expression level of LINC00312 was increased (1.95 ± 0.35 vs 1.73 ± 0.32, P = 0.0007) after treatment compared with before treatment using the paired t-test. Relative expression of S100A6 mRNA was positively correlated with log10 LINC00472 (r = 0.683, P < 0.0001); serum level of collagen type IV was positively correlated with the relative expression of log10 LINC00472 (r = 0.482, P < 0.0001); relative expression of S100A6 mRNA was positively correlated with the serum level of collagen type IV (r = 0.732, P < 0.0001). The AUC for the four biomarkers obtained in the validation set were close to the training set.

CONCLUSION

These four genes may potentially act as novel biomarkers for the diagnosis of PBC. Moreover, LINC00472 acts as a potential biomarker for staging in PBC.

Protective Effects of Cannabidiol on the Membrane Proteome of UVB-Irradiated Keratinocytes

Ultraviolet (UV) radiation contained in sunlight disturbs the redox state of skin cells, leading to changes in the structures and functions of macromolecules including components of biological membranes. Cannabidiol (CBD), which accumulates in biomembranes, may be a promising protective antioxidant compound. Accordingly, the aim of this study was to compare the effects of short-term (24 h) and long-term (48 h) CBD application on the proteomic profile of biological membranes in UVB-irradiated keratinocytes. The data obtained show that UVB radiation quantitatively and qualitatively modified cell membrane proteins, with a particular research focus on adducts of proteins with the lipid peroxidation products malondialdehyde (MDA) or 4-hydroxynonenal (4-HNE). CBD application reduced the UVB-enhanced level of these protein adducts. This was particularly notable amongst proteins related to cell proliferation and apoptosis. Moreover, CBD dramatically increased the UVB-induced expression of proteins involved in the regulation of protein translation and cell proliferation (S3a/L13a/L7a ribosomal proteins), the inflammatory response (S100/S100-A6 proteins), and maintenance of redox balance (peroxiredoxin-1, carbonyl reductase 1, and aldo-keto reductase family 1 members). In contrast, CBD effects on the level of 4-HNE-protein adducts involved in the antioxidant response and proteasomal degradation process indicate that CBD may protect keratinocytes in connection with protein catabolism processes or pro-apoptotic action.

Binding of S100A6 to actin and the actin-tropomyosin complex

S100A6 is a low molecular weight Ca²⁺-binding protein belonging to the S100 family. Many reports indicate that in the cell S100A6 has an influence on the organization of actin filaments, but so far no direct interaction between S100A6 and actin has been shown. In the present study we investigated binding of S100A6 to actin and the actin-tropomyosin complex. The analyses were performed on G- and F-actin and two tropomyosin isoforms-Tpm1.6 and Tpm1.8. Using purified proteins and a variety of biochemical approaches we have shown that, in a Ca²⁺-bound form, S100A6 directly interacts with G- and F-actin and with tropomyosin, preferentially with isoform Tpm1.8. S100A6 and tropomyosin bind to the same population of filaments and the presence of tropomyosin on the microfilament facilitates the binding of S100A6. By applying proximity ligation assay we have found that in NIH3T3 fibroblasts S100A6 forms complexes both with actin and with tropomyosin. These results indicate that S100A6, through direct interactions with actin and tropomyosin, might regulate the organization and functional properties of microfilaments.

Comparative evaluation of cannabinoid receptors, apelin and S100A6 protein in the heart of women of different age groups

Background

Recent studies have shown a significant role of the endocannabinoid system, apelin and S100A6 protein in the regulation of cardiovascular system functioning. The aim of the study was to compare and evaluate the distribution of cannabinoid receptors (CB1 and CB2), apelin and S100A6 protein in the heart of healthy women in different age groups.

Methods

The study was conducted on the hearts of 10 women (organ donors) without a history of cardiovascular disease, who were divided into two age groups: women older than 50 years and women under 50 years of age. Paraffin heart sections were processed by immunohistochemistry for detection of cannabinoids receptors (CB1 and CB2), apelin and S100A6 protein.

Results

CB1 and CB2 immunoreactivity in the cytoplasm of cardiomyocytes in the heart of women over 50 was weaker than in younger individuals. There was also strong immunoreactivity of CB1 in intercalated discs (ICDs) of the heart, only in women over 50. The presence of this receptor in this location was not found in women under 50. Apelin- and S100A6-immunoreactivity in the cardiomyocytes was stronger in older women compared to women under 50.The CB1, apelin and S100A6 immunostaining in the endothelium of myocardial vessels was weaker in women over 50 than in younger women, while intensity of CB2- immunoreaction in coronary endothelium was similar in both groups of women.

The results of the study indicate the important role of endocannabinoids, apelin, and S100A6 protein in cardiac muscle function.

Conclusion

This report might contribute to a better understanding of the role of endocannabinoid system, apelin and S100 proteins in heart function as well as shed new light on processes involved in age-related cardiomyopathy.

The Neurogenesis Actuator and NR2B/NMDA Receptor Antagonist Ro25-6981 Consistently Improves Spatial Memory Retraining Via Brain Region-Specific Gene Expression

NR2B-containing NMDA (NR2B/NMDA) receptors are important in controlling neurogenesis and are involved in generating spatial memory. Ro25-6981 is a selective antagonist at these receptors and actuates neurogenesis and spatial memory. Inter-structural neuroanatomical profiles of gene expression regulating adult neurogenesis and neuroapoptosis require examination in the context of memory retrieval and reversal learning. The aim was to investigate spatial memory retrieval and reversal learning in relation to gene expression-linked neurogenetic processes following blockade of NR2B/NMDA receptors by Ro25-6981. Rats were trained in Morris water maze (MWM) platform location for 5 days. Ro25-6981 was administered (protocol days 6–7) followed by retraining (days 15–18 or 29–32). Platform location was tested (on days 19 or 33) then post-mortem brain tissue sampling (on days 20 or 34). The expression of three genes known to regulate cell proliferation (S100a6), differentiation (Ascl1), and apoptosis (Casp-3) were concomitantly evaluated in the hippocampus, prefrontal cortex, and cerebellum in relation to the MWM performance protocol. Following initial training, Ro25-6981 enhanced visuospatial memory retrieval performance during further retraining (protocol days 29–32) but did not influence visuospatial reversal learning (day 33). Hippocampal Ascl1 and Casp-3 expressions were correspondingly increased and decreased while cerebellar S100a6 and Casp-3 activities were decreased and increased respectively 27 days after Ro25-6981 treatment. Chronological analysis indicated a possible involvement of new mature neurons in the reconfiguration of memory processes. This was attended by behavioral/gene correlations which revealed direct links between spatial memory retrieval enhancement and modified gene activity induced by NR2B/NMDA receptor blockade and upregulation.

Apigenin inhibits growth and induces apoptosis in human cholangiocarcinoma cells

A promising nutraceutical, apigenin, was recently revealed to exhibit biological activity in inhibiting several types of cancer. The effects of apigenin on the growth inhibition and apoptosis of the cholangiocarcinoma HuCCA-1 cell line were investigated. Protein alterations subsequent to apigenin treatment were studied using a proteomic approach. The values of 20, 50 and 90% inhibition of cell growth (IC₂₀, IC₅₀ and IC₉₀) were determined by MTT cell viability assay. Apoptotic cell death was detected using two different methods, a flow cytometric analysis (Muse Cell Analyzer) and DNA fragmentation assay. A number of conditions including attached and detached cells were selected to perform two-dimensional gel electrophoresis (2-DE) to study the alterations in the expression levels of treated and untreated proteins and identified by liquid chromatography (LC)/tandem mass spectrometry (MS/MS). The IC₂₀, IC₅₀ and IC₉₀ values of apigenin after 48 h treatment in HuCCA-1 cells were 25, 75 and 200 µM, respectively, indicating the cytotoxicity of this compound. Apigenin induced cell death in HuCCA-1 cells via apoptosis as detected by flow cytometric analysis and exhibited, as confirmed with DNA fragmentation, characteristics of apoptotic cells. A total of 67 proteins with altered expression were identified from the 2-DE analysis and LC/MS/MS. The cleavage of proteins involved in cytoskeletal, cytokeratin 8, 18 and 19, and high expression of S100-A6 and S100-A11 suggested that apoptosis was induced by apigenin via the caspase-dependent pathway. Notably, two proteins, heterogeneous nuclear ribonucleoprotein H and A2/B1, disappeared completely subsequent to treatment, suggesting the role of apigenin in inducing cell death. The present study indicated that apigenin demonstrates an induction of growth inhibition and apoptosis in cholangiocarcinoma cells and the apoptosis pathway was confirmed by proteomic analysis.

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.

Endothelin-Mediated Changes in Gene Expression in Isolated Purified Rat Retinal Ganglion Cells

PURPOSE

A growing body of evidence suggests that the vasoactive peptides endothelins (ETs) and their receptors (primarily the ETB receptor) are contributors to neurodegeneration in glaucoma. However, actions of ETs in retinal ganglion cells (RGCs) are not fully understood. The purpose of this study was to determine the effects of ETs on gene expression in primary RGCs.

METHODS

Primary RGCs isolated from rat pups were treated with 100 nM of ET-1, ET-2, or ET-3 for 24 hours. Total RNA was extracted followed by cDNA synthesis. Changes in gene expression in RGCs were detected using Affymetrix Rat Genome 230 2.0 microarray and categorized by DAVID analysis. Real-time PCR was used to validate gene expression, and immunocytochemistry and immunoblotting to confirm the protein expression of regulated genes.

RESULTS

There was more than 2-fold upregulation of 328, 378, or 372 genes, and downregulation of 48, 33, or 28 genes with ET-1, ET-2, or ET-3 treatment, respectively, compared to untreated controls. The Bcl-2 family, S100 family, matrix metalloproteinases, c-Jun, and ET receptors were the major genes or proteins that were regulated by endothelin treatment. Immunocytochemical staining revealed a significant increase in ETA receptor, ETB receptor, growth associated protein 43 (GAP-43), phosphorylated c-Jun, c-Jun, and Bax with ET-1 treatment. Protein levels of GAP-43 and c-Jun were confirmed by immunoblotting.

CONCLUSIONS

Expression of key proteins having regulatory roles in apoptosis, calcium homeostasis, cell signaling, and matrix remodeling were altered by treatment with endothelins. The elucidation of molecular mechanisms underlying endothelins' actions in RGCs will help understand endothelin-mediated neurodegenerative changes during ocular hypertension.

Influence of doxazosin on biosynthesis of S100A6 and atrial natriuretic factor peptides in the heart of spontaneously hypertensive rats

Hypertension frequently results in severe complications in cardiovascular system and histopathological changes in the heart. To better understand the cellular processes and signaling pathways responsible for the proper functioning of the heart, we decided to check whether doxazosin affects the density of structures containing S100A6 and atrial natriuretic factor in the heart of spontaneously hypertensive rats. The aim of this study is to find differences in the density of the structures containing S100A6 and atrial natriuretic factor in the heart of spontaneously hypertensive rats treated with doxazosin compared to untreated animals. Fragments of heart were collected from five spontaneously hypertensive rats and five spontaneously hypertensive rats receiving doxazosin for six weeks (dose 0.1 mg per 1 kg of body weight). On the paraffin sections S100A6 and atrial natriuretic factor peptides were localized in the heart using immunohistochemistry. Positive immunohistochemical reaction for S100A6 was observed in atrial and ventricular cardiomyocytes and in the coronary vasculature. In the heart of hypertensive rats treated with doxazosin the S100A6 immunoreactivity was significantly lower compared to untreated animals. Immunodetection of atrial natriuretic factor in the heart of rats confirmed presence of peptide in atrial myocardium. Delicate atrial natriuretic factor-immunoreactivity was observed also in few ventricular cardiomyocytes. The atrial natriuretic factor-immunosignal was significantly weaker in hearts of hypertensive rats receiving doxazosin compared to spontaneously hypertensive rats untreated. Since we found that doxazosin reduces the levels of S100A6 and atrial natriuretic factor peptides in the heart of spontaneously hypertensive rats, it can be assumed that cardiovascular disorders that occur in hypertension may be associated with disturbances of cellular processes and signaling pathways.

ADAR1 is required for differentiation and neural induction by regulating microRNA processing in a catalytically independent manner

Adenosine deaminases acting on RNA (ADARs) are involved in adenosine-to-inosine RNA editing and are implicated in development and diseases. Here we observed that ADAR1 deficiency in human embryonic stem cells (hESCs) significantly affected hESC differentiation and neural induction with widespread changes in mRNA and miRNA expression, including upregulation of self-renewal-related miRNAs, such as miR302s. Global editing analyses revealed that ADAR1 editing activity contributes little to the altered miRNA/mRNA expression in ADAR1-deficient hESCs upon neural induction. Genome-wide iCLIP studies identified that ADAR1 binds directly to pri-miRNAs to interfere with miRNA processing by acting as an RNA-binding protein. Importantly, aberrant expression of miRNAs and phenotypes observed in ADAR1-depleted hESCs upon neural differentiation could be reversed by an enzymatically inactive ADAR1 mutant, but not by the RNA-binding-null ADAR1 mutant. These findings reveal that ADAR1, but not its editing activity, is critical for hESC differentiation and neural induction by regulating miRNA biogenesis via direct RNA interaction.

Annexin A11 in disease

Ubiquitously expressed in many cell types, annexin A11 (Anxa11) is a member of the multigene family of Ca(2+)-regulated phospholipid-dependent and membrane-binding annexin proteins. Studies have shown that Anxa11 plays an important role in cell division, Ca(2+) signaling, vesicle trafficking and apoptosis. The deregulation and mutation of Anxa11 are involved in systemic autoimmune diseases, sarcoidosis and the development, chemoresistance and recurrence of cancers. Malfunction of Anxa11 may lead to or enhance the metastasis, invasion and drug resistance of cancers through the platelet-derived growth factor receptor (PDGFR) pathway and/or the mitogen-activated protein kinase (MAPK)/p53 pathway. In a variety of diseases, Anxa11 is most commonly reported to function through interactions with apoptosis-linked gene-2 protein (ALG-2) and/or calcyclin (S100A6). Although it has been little studied, Anxa11 is a promising biomarker for the diagnosis, treatment and prognosis of certain diseases. In this review, the associations of Anxa11 with Ca(2+)-regulated exocytosis, cytokinesis, sex differentiation, autoimmune diseases, thrombolysis and cancers are summarized and interpreted.

Distinct functional brain regional integration of Casp3, Ascl1 and S100a6 gene expression in spatial memory

Evaluating the brain structural expression of defined genes involved in basic biological processes of neurogenesis, apoptosis or neural plasticity may facilitate the understanding of genetic mechanisms underlying spatial memory. The aim of the present study was to compare Ascl1, Casp3 and S100a6 gene expression in the hippocampus, prefrontal cortex and cerebellum of adult rats in water maze spatial memory performance. After four days training, the mean platform time (<10s) was evidence of stable long-term spatial memory formation. Real time PCR analysis revealed a positive inter-structural correlation for S100a6/Casp gene expression between the prefrontal cortex and the cerebellum but a negative correlation for S100a6/Ascl1 transcribed genes between the prefrontal cortex and hippocampus during swimming in the active controls. However, during spatial memory performance there was only one inter-structural correlation between the prefrontal cortex and cerebellum with respect to Casp3 expression, though there were intra-structural correlations between Casp3/Ascl1 transcriptions within the prefrontal cortex and hippocampus as well as between Ascl1/S100a6 in the cerebellum. In active learners versus naive controls, the transcrption of all genes was augmented in the prefrontal cortex but Casp3 and Ascl1 were also elevated in hippocampus whilst only S100a6 increased in the cerebellum. The findings endorsed the role of the hippocampus in memory acquisition in addition to an integrative relationship with the prefrontal cortex and cerebellum. This structural and molecular configuration is important for creation of novel neural circuitry for consolidation and reconsolidation of memory trace with an involvement of coupled processes of neurogenesis, apoptosis or neural plasticity.

Mass spectrometry-based proteomics: the road to lung cancer biomarker discovery

Lung cancer is the leading cause of cancer death in men and women in Western nations, and is among the deadliest cancers with a 5-year survival rate of 15%. The high mortality caused by lung cancer is attributable to a late-stage diagnosis and the lack of effective treatments. So, it is crucial to identify new biomarkers that could function not only to detect lung cancer at an early stage but also to shed light on the molecular mechanisms that underlie cancer development and serve as the basis for the development of novel therapeutic strategies. Considering that DNA-based biomarkers for lung cancer showed inadequate sensitivity, specificity, and reproducibility, proteomics could represent a better tool for the identification of useful biomarkers and therapeutic targets for this cancer type. Among the proteomics technologies, the most powerful tool is mass spectrometry. In this review, we describe studies that use mass spectrometry-based proteomics technologies to analyze tumor proteins and peptides, which might represent new diagnostic, prognostic, and predictive markers for lung cancer. We focus in particular on those findings that hold promise to impact significantly on the clinical management of this disease.

Matrix-assisted laser desorption/ionization mass spectrometry reveals decreased calcylcin expression in small cell lung cancer

To date, most of the proteomic analyses on lung cancer tissue samples have been performed using surgical specimens, which are obtained after a diagnosis is made. To determine if a proteomic signature obtained from bronchoscopic biopsy samples could be found to assist with diagnosis, 50 lung cancer bronchoscopic biopsy samples and 13 adjacent normal lung tissue samples were analyzed using histology-directed, matrix-assisted laser desorption/ionization (MALDI) mass spectrometry (MS). Lung tissue samples were cryosectioned, and sinapinic acid was robotically deposited on areas of each tissue section enriched in epithelial cells, either tumor or normal. Mass spectra were acquired using a MALDI-time of flight instrument. Small cell lung cancers (SCLCs) demonstrated clearly different protein profiles from normal lung tissue and from non-small cell lung cancers (NSCLCs). Calcyclin (m/z= 10,094.7) was identified to be underexpressed in small cell lung cancers, as compared with non-small cell lung cancers and normal lung tissue. An immunohistochemistry study using 152 NSCLCs and 21 SCLCs confirmed significantly reduced calcyclin stain in SCLCs. Thus, protein profiles obtained from bronchoscopic biopsy samples via MALDI MS distinguish cancerous epithelium from normal lung tissue and between NSCLCs and SCLCs.

Resistance of MLL-AFF1-positive acute lymphoblastic leukemia to tumor necrosis factor-alpha is mediated by S100A6 upregulation

Mixed-lineage leukemia (MLL)-AFF1 (MLL-AF4)-positive acute lymphoblastic leukemia (ALL) is associated with poor prognosis, even after allogeneic hematopoietic stem cell transplantation (allo-HSCT). The resistance to graft-versus-leukemia (GVL) effects may be responsible for the poor effect of allo-HSCT on MLL-AFF1-positive ALL. Cytotoxic effector mechanisms mediated by tumor necrosis factor-alpha (TNF-α) was reported to contribute to the GVL effect. We showed that MLL-AFF1-positive ALL cell lines are resistant to TNF-α. To examine the mechanism of resistance to TNF-α of MLL-AFF1-positive leukemia, we focused on S100A6 as a possible factor. Upregulation of S100A6 expression and inhibition of the p53-caspase 8-caspase 3 pathway were observed only in MLL-AFF1-positive ALL cell lines in the presence of TNF-α. The effect of S100A6 on resistance to TNF-α by inhibition of the p53-caspase 8-caspase 3 pathway of MLL-AFF1-positive ALL cell lines were also confirmed by analysis using small interfering RNA against S100A6. This pathway was also confirmed in previously established MLL-AFF1 transgenic mice. These results suggest that MLL-AFF1-positive ALL escapes from TNF-α-mediated apoptosis by upregulation of S100A6 expression, followed by interfering with p53-caspase 8-caspase 3 pathway. These results suggest that S100A6 may be a promising therapeutic target for MLL-AFF1-positive ALL in combination with allo-HSCT.

Lung cancer proteomics: recent advances in biomarker discovery

Lung cancer is the most common cause of cancer death in both men and women in Western countries, with a 5-year survival rate of 15%, which is among the lowest of all cancers. The high mortality from lung cancer is due not only to the late stage diagnosis but also to the lack of effective treatments even for patients diagnosed with stage I lung cancer. Therefore, there is an urgent need to identify new markers for early diagnosis and prognosis that could serve to open novel therapeutic avenues. Proteomics can represent an important tool for the identification of biomarkers and therapeutic targets for lung cancer since DNA-based biomarkers did not prove to have adequate sensitivity, specificity, and reproducibility. In this paper we will describe studies focused on the identification of new diagnostic, prognostic, and predictive markers for lung cancer, using proteomics technologies.

Identification of tumoral glial precursor cells in neuroblastoma

Neuroblastic tumors (NBT) are composed by neuroblasts and Schwannian-like stroma. The origin of these two cell subtypes remains unclear. In this study, we describe, a neuroblastic-like subpopulation in neuroblastoma (NB) coexpressing GD2 and S100A6, neuroblastic and glial lineage markers respectively. The GD2(+)/S100A6(+) neuroblastic subpopulation was found to be enriched in low risk NB, distributed around the perivascular niche. Some stromal bundles showed GD2(+)/S100A6 costaining. Metastatic bone marrow specimens also showed GD2(+)/S100A6(+) cells. During in vitro retinoic acid induced differentiation of NB cell lines, rare GD2(+)/S100A6 neuroblatic cells appeared. We conclude that GD2(+)/S100A6(+) neuroblasts may represent a tumoral glial precursor subpopulation in NBT.

Proteomic evaluation and validation of cathepsin D regulated proteins in macrophages exposed to Streptococcus pneumoniae

Macrophages are central effectors of innate immune responses to bacteria. We have investigated how activation of the abundant macrophage lysosomal protease, cathepsin D, regulates the macrophage proteome during killing of Streptococcus pneumoniae. Using the cathepsin D inhibitor pepstatin A, we demonstrate that cathepsin D differentially regulates multiple targets out of 679 proteins identified and quantified by eight-plex isobaric tag for relative and absolute quantitation. Our statistical analysis identified 18 differentially expressed proteins that passed all paired t-tests (α = 0.05). This dataset was enriched for proteins regulating the mitochondrial pathway of apoptosis or inhibiting competing death programs. Five proteins were selected for further analysis. Western blotting, followed by pharmacological inhibition or genetic manipulation of cathepsin D, verified cathepsin D-dependent regulation of these proteins, after exposure to S. pneumoniae. Superoxide dismutase-2 up-regulation was temporally related to increased reactive oxygen species generation. Gelsolin, a known regulator of mitochondrial outer membrane permeabilization, was down-regulated in association with cytochrome c release from mitochondria. Eukaryotic elongation factor (eEF2), a regulator of protein translation, was also down-regulated by cathepsin D. Using absence of the negative regulator of eEF2, eEF2 kinase, we confirm that eEF2 function is required to maintain expression of the anti-apoptotic protein Mcl-1, delaying macrophage apoptosis and confirm using a murine model that maintaining eEF2 function is associated with impaired macrophage apoptosis-associated killing of Streptococcus pneumoniae. These findings demonstrate that cathepsin D regulates multiple proteins controlling the mitochondrial pathway of macrophage apoptosis or competing death processes, facilitating intracellular bacterial killing.

Proteomic study of thyroid tumors reveals frequent up-regulation of the Ca2+ -binding protein S100A6 in papillary thyroid carcinoma

BACKGROUND

The accurate diagnosis of thyroid tumors is challenging. Proteomics has emerged as a promising approach for the discovery of molecular diagnostic markers as a potential complement to routine diagnostics.

METHODS

Protein fractions from 29 frozen thyroid tumor tissue samples (10 papillary carcinomas, 9 follicular carcinomas, and 10 follicular adenomas) as well as from normal thyroid tissue were analyzed by surface enhanced laser desorption/ionization time-of-flight mass spectrometry followed by validation by Western blotting and immunohistochemistry.

RESULTS

A Ca2+ binding protein belonging to the S100 family, S100A6, was differentially expressed between papillary and follicular thyroid tumors. Moreover, two posttranslationally modified forms of S100A6 were observed and verified by liquid chromatography-coupled tandem mass spectrometry. Validation by Western blotting displayed a significantly higher expression of S100A6 in papillary thyroid carcinoma (PTC) in comparison with the other tumor groups or normal tissue (p < 0.05). Immunohistochemical analysis on 98 tumors showed that PTC cases had a significantly stronger cytosolic staining and a larger proportion of stained nuclei than follicular tumors. BRAF gene mutation was not significantly associated with S100A6 protein levels.

CONCLUSION

This study supports a role of S100A6 in thyroid tumorigenesis and as a potential aid in the discrimination between follicular thyroid tumors and PTC.

Identification of Siah-interacting protein as a potential regulator of apoptosis and curcumin resistance

The mechanism underlying curcumin (diferuloylmethane) resistance is still largely unknown. Here we employed proteomic approach to identify the Siah-interacting protein (SIP) as a candidate for detailed study, because the spot intensity of SIP on a two-dimensional gel displayed 70-90% reduction in curcumin-sensitive cells, but remained unchanged in curcumin-resistant sublines, after curcumin treatment. Both gain- and loss-of-function studies revealed that SIP promoted curcumin-induced apoptosis. Moreover, SIP underwent phosphorylation and nuclear translocation in curcumin-sensitive but not resistant cells, upon curcumin exposure. The nuclear translocation of SIP was remarkably impaired when a putative nuclear localization sequence (NLS, amino acid (aa) 143-159) was deleted or the serine 141 was mutated into alanine, whereas truncation of the N-terminal region (aa 1-43) obviously increased the nuclear import of SIP. In accordance with their nuclear localization, N-terminal truncation significantly enhanced the proapoptotic effect of SIP, whereas NLS deletion or Ser141Ala mutation attenuated the apoptosis-promoting activity of both wild-type- and N-terminal truncated-SIP. These data suggest that SIP plays a role in apoptosis and curcumin resistance, and the function of SIP may be regulated by different motifs, such as the NLS, N-terminal region and serine 141. Our findings provide new insights into the biological significance of SIP and the mechanisms of drug resistance.

S100A6 (calcyclin) deficiency induces senescence-like changes in cell cycle, morphology and functional characteristics of mouse NIH 3T3 fibroblasts

S100A6 (calcyclin) is a calcium binding protein with two EF-hand structures expressed mostly in fibroblasts and epithelial cells. We have established a NIH 3T3 fibroblast cell line stably transfected with siRNA against S100A6 to examine the effect of S100A6 deficiency on non-transformed cell physiology. We found that NIH 3T3 fibroblasts with decreased level of S100A6 manifested altered cell morphology and proliferated at a much slower pace than the control cells. Cell cycle analysis showed that a large population of these cells lost the ability to respond to serum and persisted in the G0/G1 phase. Furthermore, fibroblasts with diminished S100A6 level exhibited morphological changes and biochemical features of cellular senescence as revealed by beta-galactosidase and gelatinase assays. Also, S100A6 deficiency induced changes in the actin cytoskeleton and had a profound impact on cell adhesion and migration. Thus, we have shown that the S100A6 protein is involved in multiple aspects of fibroblast physiology and that its presence ensures normal fibroblast proliferation and function.

Patt1, a novel protein acetyltransferase that is highly expressed in liver and downregulated in hepatocellular carcinoma, enhances apoptosis of hepatoma cells

Protein acetylation is increasingly recognized as an important post-translational modification. Although a lot of protein acetyltransferases have been identified, a few putative acetyltransferases are yet to be studied. In this study, we identified a novel protein acetyltransferase, Patt1, which belongs to GNAT family. Patt1 exhibited histone acetyltransferase activity and auto-acetylation activity. Deletion and mutation analysis of the predicted acetyltransferase domain in Patt1 showed that the conserved Glu139 was an important residue for its protein acetyltransferase activity. Furthermore, we found that Patt1 was highly expressed in liver and significantly downregulated in hepatocellular carcinoma tissues. In addition, we showed that overexpression of Patt1 enhanced the apoptosis of hepatoma cells dependent on its acetyltransferase activity, whereas knockdown of Patt1 significantly protected Chang liver cells from apoptosis. These data suggest that Patt1 might be involved in the development of hepatocellular carcinoma, and could be served as a potential therapy target for hepatocellular carcinoma.

Renal gene and protein expression signatures for prediction of kidney disease progression

Although chronic kidney disease (CKD) is common, only a fraction of CKD patients progress to end-stage renal disease. Molecular predictors to stratify CKD populations according to their risk of progression remain undiscovered. Here we applied transcriptional profiling of kidneys from transforming growth factor-beta1 transgenic (Tg) mice, characterized by heterogeneity of kidney disease progression, to identify 43 genes that discriminate kidneys by severity of glomerular apoptosis before the onset of tubulointerstitial fibrosis in 2-week-old animals. Among the genes examined, 19 showed significant correlation between mRNA expression in uninephrectomized left kidneys at 2 weeks of age and renal disease severity in right kidneys of Tg mice at 4 weeks of age. Gene expression profiles of human orthologs of the 43 genes in kidney biopsies were highly significantly related (R(2) = 0.53; P < 0.001) to the estimated glomerular filtration rates in patients with CKD stages I to V, and discriminated groups of CKD stages I/II and III/IV/V with positive and negative predictive values of 0.8 and 0.83, respectively. Protein expression patterns for selected genes were successfully validated by immunohistochemistry in kidneys of Tg mice and kidney biopsies of patients with IgA nephropathy and CKD stages I to V, respectively. In conclusion, we developed novel mRNA and protein expression signatures that predict progressive renal fibrosis in mice and may be useful molecular predictors of CKD progression in humans.

Gene expression signature of cerebellar hypoplasia in a mouse model of Down syndrome during postnatal development

BACKGROUND

Down syndrome is a chromosomal disorder caused by the presence of three copies of chromosome 21. The mechanisms by which this aneuploidy produces the complex and variable phenotype observed in people with Down syndrome are still under discussion. Recent studies have demonstrated an increased transcript level of the three-copy genes with some dosage compensation or amplification for a subset of them. The impact of this gene dosage effect on the whole transcriptome is still debated and longitudinal studies assessing the variability among samples, tissues and developmental stages are needed.

RESULTS

We thus designed a large scale gene expression study in mice (the Ts1Cje Down syndrome mouse model) in which we could measure the effects of trisomy 21 on a large number of samples (74 in total) in a tissue that is affected in Down syndrome (the cerebellum) and where we could quantify the defect during postnatal development in order to correlate gene expression changes to the phenotype observed. Statistical analysis of microarray data revealed a major gene dosage effect: for the three-copy genes as well as for a 2 Mb segment from mouse chromosome 12 that we show for the first time as being deleted in the Ts1Cje mice. This gene dosage effect impacts moderately on the expression of euploid genes (2.4 to 7.5% differentially expressed). Only 13 genes were significantly dysregulated in Ts1Cje mice at all four postnatal development stages studied from birth to 10 days after birth, and among them are 6 three-copy genes. The decrease in granule cell proliferation demonstrated in newborn Ts1Cje cerebellum was correlated with a major gene dosage effect on the transcriptome in dissected cerebellar external granule cell layer.

CONCLUSION

High throughput gene expression analysis in the cerebellum of a large number of samples of Ts1Cje and euploid mice has revealed a prevailing gene dosage effect on triplicated genes. Moreover using an enriched cell population that is thought responsible for the cerebellar hypoplasia in Down syndrome, a global destabilization of gene expression was not detected. Altogether these results strongly suggest that the three-copy genes are directly responsible for the phenotype present in cerebellum. We provide here a short list of candidate genes.

Expression of S100A6 in cardiac myocytes limits apoptosis induced by tumor necrosis factor-alpha

S100A6 is induced in myocardium post-infarction in vivo and in response to growth factors and inflammatory cytokines in vitro. Forced expression of S100A6 in cardiomyocytes inhibits regulation of cardiac specific gene expression in response to trophic stimulation. To define regulation and function of S100A6, we characterized the human S100A6 promoter and mapped upstream regulatory elements in rat neonatal cardiac myocytes, fibroblasts, and vascular smooth muscle cells and defined a functional role for S100A6 in tumor necrosis factor-alpha-induced myocyte apoptosis. The functional S100A6 promoter was localized to region -167/+134 containing 167 upstream base pairs. The S100A6 promoter is regulated by positive (-361/-167 and -588/-361) and negative (-1371/-1194) elements. Tumor necrosis factor-alpha induced the maximal S100A6 promoter and transcription factor NF-kappaB (p65 subunit). Electrophoretic mobility shift showed that tumor necrosis factor-alpha induced p65 binding to a potential NF-kappaB-binding site at -460/-451. Chromatin immunoprecipitation analysis revealed p65 is recruited to the S100A6 promoter upon tumor necrosis factor-alpha stimulation. The NF-kappaB inhibitor caffeic acid phenethyl ester and mutation of the NF-kappaB-binding site inhibited S100A6 promoter activation by tumor necrosis factor-alpha. Tumor necrosis factor-alpha induced cardiac myocyte apoptosis. Specific inhibition of S100A6 using a small interfering RNA directed against S100A6 potentiated tumor necrosis factor-alpha-induced myocyte apoptosis, whereas overexpression of S100A6 by gene transfer prevented tumor necrosis factor-alpha-induced myocyte apoptosis by interfering with p53 phosphorylation. These results demonstrate that S100A6 is induced by tumor necrosis factor-alpha via an NF-kappaB-dependent mechanism, serving a role in homeostasis to limit tumor necrosis factor-alpha-induced apoptosis by regulating p53 phosphorylation.