Characterization of the Ca2+ -regulated ezrin-S100P interaction and its role in tumor cell migration

A predictive signature gene set for discriminating active from latent tuberculosis in Warao Amerindian children

BACKGROUND

Tuberculosis (TB) continues to cause a high toll of disease and death among children worldwide. The diagnosis of childhood TB is challenged by the paucibacillary nature of the disease and the difficulties in obtaining specimens. Whereas scientific and clinical research efforts to develop novel diagnostic tools have focused on TB in adults, childhood TB has been relatively neglected. Blood transcriptional profiling has improved our understanding of disease pathogenesis of adult TB and may offer future leads for diagnosis and treatment. No studies applying gene expression profiling of children with TB have been published so far.

RESULTS

We identified a 116-gene signature set that showed an average prediction error of 11% for TB vs. latent TB infection (LTBI) and for TB vs. LTBI vs. healthy controls (HC) in our dataset. A minimal gene set of only 9 genes showed the same prediction error of 11% for TB vs. LTBI in our dataset. Furthermore, this minimal set showed a significant discriminatory value for TB vs. LTBI for all previously published adult studies using whole blood gene expression, with average prediction errors between 17% and 23%. In order to identify a robust representative gene set that would perform well in populations of different genetic backgrounds, we selected ten genes that were highly discriminative between TB, LTBI and HC in all literature datasets as well as in our dataset. Functional annotation of these genes highlights a possible role for genes involved in calcium signaling and calcium metabolism as biomarkers for active TB. These ten genes were validated by quantitative real-time polymerase chain reaction in an additional cohort of 54 Warao Amerindian children with LTBI, HC and non-TB pneumonia. Decision tree analysis indicated that five of the ten genes were sufficient to classify 78% of the TB cases correctly with no LTBI subjects wrongly classified as TB (100% specificity).

CONCLUSIONS

Our data justify the further exploration of our signature set as biomarkers for potential childhood TB diagnosis. We show that, as the identification of different biomarkers in ethnically distinct cohorts is apparent, it is important to cross-validate newly identified markers in all available cohorts.

S100P is a metastasis-associated gene that facilitates transendothelial migration of pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is the 5th most common cause of cancer death in the UK and the 4th in the US. The vast majority of deaths following pancreatic cancer are due to metastatic spread, hence understanding the metastatic process is vital for identification of critically needed novel therapeutic targets. An enriched set of 33 genes differentially expressed in common between primary PDAC and liver metastases, when compared to normal tissues, was obtained through global gene expression profiling. This metastasis-associated gene set comprises transcripts from both cancer (S100P, S100A6, AGR2, etc.) and adjacent stroma (collagens type I, III, and V, etc.), thus reinforcing the concept of a continuous crosstalk between the two compartments in both primary tumours and their metastases. The expression of S100P, SFN, VCAN and collagens was further validated in additional primary PDACs and matched liver metastatic lesions, while the functional significance of one of the most highly expressed genes, S100P, was studied in more detail. We show that this protein increases the transendothelial migration of PDAC cancer cells in vitro, which was also confirmed in vivo experiments using a zebrafish embryo model. Thus S100P facilitates cancer cell intravasation/extravasation, critical steps in the hematogenous dissemination of pancreatic cancer cells.

Proteomic analysis of acquired tamoxifen resistance in MCF-7 cells reveals expression signatures associated with enhanced migration

Introduction

Acquired tamoxifen resistance involves complex signaling events that are not yet fully understood. Successful therapeutic intervention to delay the onset of hormone resistance depends critically on mechanistic elucidation of viable molecular targets associated with hormone resistance. This study was undertaken to investigate the global proteomic alterations in a tamoxifen resistant MCF-7 breast cancer cell line obtained by long term treatment of the wild type MCF-7 cell line with 4-hydroxytamoxifen (4-OH Tam).

Methods

We cultured MCF-7 cells with 4-OH Tam over a period of 12 months to obtain the resistant cell line. A gel-free, quantitative proteomic method was used to identify and quantify the proteome of the resistant cell line. Nano-flow high-performance liquid chromatography coupled to high resolution Fourier transform mass spectrometry was used to analyze fractionated peptide mixtures that were isobarically labeled from the resistant and control cell lysates. Real time quantitative PCR and Western blots were used to verify selected proteomic changes. Lentiviral vector transduction was used to generate MCF-7 cells stably expressing S100P. Online pathway analysis was performed to assess proteomic signatures in tamoxifen resistance. Survival analysis was done to evaluate clinical relevance of altered proteomic expressions.

Results

Quantitative proteomic analysis revealed a wide breadth of signaling events during transition to acquired tamoxifen resistance. A total of 629 proteins were found significantly changed with 364 up-regulated and 265 down-regulated. Collectively, these changes demonstrated the suppressed state of estrogen receptor (ER) and ER-regulated genes, activated survival signaling and increased migratory capacity of the resistant cell line. The protein S100P was found to play a critical role in conferring tamoxifen resistance and enhanced cell motility.

Conclusions

Our data demonstrate that the adaptive changes in the proteome of tamoxifen resistant breast cancer cells are characterized by down-regulated ER signaling, activation of alternative survival pathways, and enhanced cell motility through regulation of the actin cytoskeleton dynamics. Evidence also emerged that S100P mediates acquired tamoxifen resistance and migration capacity.

Association of increased S100B, S100A6 and S100P in serum levels with acute coronary syndrome and also with the severity of myocardial infarction in cardiac tissue of rat models with ischemia-reperfusion injury

OBJECTIVE

We aim to check if serum levels of receptor for advanced glycation endproduct (RAGE) ligands S100B, S100A6 and S100P were related to myocardial injury in acute coronary syndrome (ACS).

METHODS

Serum levels of S100B, S100A6, S100P, and soluble RAGE (sRAGE) were analyzed in 882 patients. Based upon clinical and laboratory findings, they were assigned into control (n=251), stable angina (n=211), and ACS (n=420). To verify clinical data of ACS, forty Sprague-Dawley rats were subjected to cardiac ischemia-reperfusion (I/R) injury by occluding proximal (large infarct size; n=20) or distal (small infarct size; n=20) left anterior descending coronary artery, and another 20 rats were in sham-operation group. The expressions of S100B, S100A6, S100P and RAGE in the myocardium were analyzed.

RESULTS

Serum levels of S100B, S100A6 and S100P were higher in ACS group than in stable angina and control groups, and sRAGE levels were higher in ACS patients versus controls (all p<0.01). S100B and S100P levels correlated significantly with CK-MB and troponin I levels in ACS group (all p<0.05). In multivariable regression analysis, S100B, S100A6, S100P and conventional risk factors were independently associated with ACS. In animal models, the expressions of S100B, S100A6 and S100P were closely related to infarct size (all p<0.05).

CONCLUSION

This study indicates that serum levels of S100B, S100A6 and S100P are associated with ACS, and serum levels and myocardial expression of these proteins are related to infarct size.

Proteomic identification of the differentially expressed proteins in human lung epithelial cells by airborne particulate matter

Exposure to airborne PM₁₀, particulate matter with a median aerodynamic diameter of less than 10 µm, is known to be associated with a number of adverse health effects. To gain a better understanding of the cytotoxic mechanism and to develop protein biomarker candidates for PM₁₀-induced toxicity, proteomic analyses were performed in human lung epithelial cells. Two-dimensional gel electrophoresis (2-DE) was followed by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) to analyze the proteins differentially expressed by exposure to PM₁₀. Analysis of 2-DE gels revealed more than 1270 protein spots in the cells, of which 36 showed changes of more than 2-fold on exposure to PM₁₀ (up-regulation, n = 6; down-regulation, n = 30). The glycolytic enzyme pyruvate kinase, which also plays a role in tumor metabolism, showed a marked increase in expression, whereas the cytoskeleton-related vinculin and anti-inflammatory annexin 1 showed marked decreases in expression.

S100P is a novel interaction partner and regulator of IQGAP1

Ca(2+)-binding proteins of the S100 family participate in intracellular Ca(2+) signaling by binding to and regulating specific cellular targets in their Ca(2+)-loaded conformation. Because the information on specific cellular targets of different S100 proteins is still limited, we developed an affinity approach that selects for protein targets only binding to the physiologically active dimer of an S100 protein. Using this approach, we here identify IQGAP1 as a novel and dimer-specific target of S100P, a member of the S100 family enriched in the cortical cytoskeleton. The interaction between S100P and IQGAP1 is strictly Ca(2+)-dependent and characterized by a dissociation constant of 0.2 μM. Binding occurs primarily through the IQ domain of IQGAP1 and the first EF hand loop of S100P, thus representing a novel structural principle of S100-target protein interactions. Upon cell stimulation, S100P and IQGAP1 co-localize at or in close proximity to the plasma membrane, and complex formation can be linked to altered signal transduction properties of IQGAP1. Specifically, the EGF-induced tyrosine phosphorylation of IQGAP1 that is thought to function in assembling signaling intermediates at IQGAP1 scaffolds in the subplasmalemmal region is markedly reduced in cells overexpressing S100P but not in cells expressing an S100P mutant deficient in IQGAP1 binding. Furthermore, B-Raf binding to IQGAP1 and MEK1/2 activation occurring downstream of IQGAP1 in EGF-triggered signaling cascades are compromised at elevated S100P levels. Thus, S100P is a novel Ca(2+)-dependent regulator of IQGAP1 that can down-regulate the function of IQGAP1 as a signaling intermediate by direct interaction.

S100P: a novel therapeutic target for cancer

S100P expression is described in many different cancers, and its expression is associated with drug resistance, metastasis, and poor clinical outcome. S100P is member of the S100 family of small calcium-binding proteins that have been reported to have either intracellular or extracellular functions, or both. Extracellular S100P can bind with the receptor for advanced glycation end products (RAGE) and activate cellular signaling. Through RAGE, S100P has been shown to mediate tumor growth, drug resistance, and metastasis. S100P is specifically expressed in cancer cells in the adult. Therefore, S100P is a useful marker for differentiating cancer cells from normal cells, and can aid in the diagnosis of cancer by cytological examination. The expression of S100P in cancer cells has been related to hypomethylation of the gene. Multiple studies have confirmed the beneficial effects of blocking S100P/RAGE in cancer cells, and different blockers are being developed including small molecules and antagonist peptides. This review summarizes the role and significance of S100P in different cancers.

Grading the commercial optical biosensor literature-Class of 2008: 'The Mighty Binders'

Optical biosensor technology continues to be the method of choice for label-free, real-time interaction analysis. But when it comes to improving the quality of the biosensor literature, education should be fundamental. Of the 1413 articles published in 2008, less than 30% would pass the requirements for high-school chemistry. To teach by example, we spotlight 10 papers that illustrate how to implement the technology properly. Then we grade every paper published in 2008 on a scale from A to F and outline what features make a biosensor article fabulous, middling or abysmal. To help improve the quality of published data, we focus on a few experimental, analysis and presentation mistakes that are alarmingly common. With the literature as a guide, we want to ensure that no user is left behind.

Binding of S100 proteins to RAGE: an update

The Receptor for Advanced Glycation Endproducts (RAGE) is a multi-ligand receptor of the immunoglobulin family. RAGE interacts with structurally different ligands probably through the oligomerization of the receptor on the cell surface. However, the exact mechanism is unknown. Among RAGE ligands are members of the S100 protein family. S100 proteins are small calcium binding proteins with high structural homology. Several members of the family have been shown to interact with RAGE in vitro or in cell-based assays. Interestingly, many RAGE ligands appear to interact with distinct domains of the extracellular portion of RAGE and to trigger various cellular effects. In this review, we summarize the modes of S100 protein-RAGE interaction with regard to their cellular functions.

Generation and characterization of a novel, permanently active S100P mutant

S100 proteins function as Ca2+ signal transducers by regulating cellular targets in their Ca2+ bound conformation. S100P is a member of the S100 protein family that can activate the membrane and F-actin binding protein ezrin in a Ca2+ dependent manner at least in vitro. Here we generated a novel tool to elucidate directly the S100P-ezrin interaction in vivo. This was achieved by constructing a S100P derivative that contained mutations in the two EF hand loops predicted to lock the protein in a permanently active state. The resulting S100P mutant, termed here S100P pa, could be purified as a soluble protein and showed biochemical properties displayed by wild-type S100P only in the presence of Ca2+. Importantly, S100P pa bound to the N-terminal domain of ezrin in the absence of Ca2+ showing an affinity only slightly reduced as compared to that of Ca2+-bound WT S100P. In line with this permanent complex formation, S100P pa colocalized with ezrin to plasma membrane protrusions of epithelial cells even in the absence of intracellular Ca2+ transients. Thus, S100P pa is a novel type of S100 protein mutant locked in a permanently active state that shows an unregulated complex formation with its cellular target ezrin.