Beyond Pattern Recognition: TLR2 Promotes Chemotaxis, Cell Adhesion, and Migration in THP-1 Cells

The interaction between monocytes and endothelial cells in inflammation is central to chemoattraction, adhesion, and transendothelial migration. Key players, such as selectins and their ligands, integrins, and other adhesion molecules, and their functions in these processes are well studied. Toll-like receptor 2 (TLR2), expressed in monocytes, is critical for sensing invading pathogens and initiating a rapid and effective immune response. However, the extended role of TLR2 in monocyte adhesion and migration has only been partially elucidated. To address this question, we performed several functional cell-based assays using monocyte-like wild type (WT), TLR2 knock-out (KO), and TLR2 knock-in (KI) THP-1 cells. We found that TLR2 promotes the faster and stronger adhesion of monocytes to the endothelium and a more intense endothelial barrier disruption after endothelial activation. In addition, we performed quantitative mass spectrometry, STRING protein analysis, and RT-qPCR, which not only revealed the association of TLR2 with specific integrins but also uncovered novel proteins affected by TLR2. In conclusion, we show that unstimulated TLR2 influences cell adhesion, endothelial barrier disruption, migration, and actin polymerization.

Comparative and Temporal Characterization of LPS and Blue-Light-Induced TLR4 Signal Transduction and Gene Expression in Optogenetically Manipulated Endothelial Cells

In endothelial cells (ECs), stimulation of Toll-like receptor 4 (TLR4) by the endotoxin lipopolysaccharide (LPS) induces the release of diverse pro-inflammatory mediators, beneficial in controlling bacterial infections. However, their systemic secretion is a main driver of sepsis and chronic inflammatory diseases. Since distinct and rapid induction of TLR4 signaling is difficult to achieve with LPS due to the specific and non-specific affinity to other surface molecules and receptors, we engineered new light-oxygen-voltage-sensing (LOV)-domain-based optogenetic endothelial cell lines (opto-TLR4-LOV LECs and opto-TLR4-LOV HUVECs) that allow fast, precise temporal, and reversible activation of TLR4 signaling pathways. Using quantitative mass-spectrometry, RT-qPCR, and Western blot analysis, we show that pro-inflammatory proteins were not only expressed differently, but also had a different time course when the cells were stimulated with light or LPS. Additional functional assays demonstrated that light induction promoted chemotaxis of THP-1 cells, disruption of the EC monolayer and transmigration. In contrast, ECs incorporating a truncated version of the TLR4 extracellular domain (opto-TLR4 ΔECD2-LOV LECs) revealed high basal activity with fast depletion of the cell signaling system upon illumination. We conclude that the established optogenetic cell lines are well suited to induce rapid and precise photoactivation of TLR4, allowing receptor-specific studies.

Dichotomous Role of Tumor Necrosis Factor in Pulmonary Barrier Function and Alveolar Fluid Clearance

Alveolar-capillary leak is a hallmark of the acute respiratory distress syndrome (ARDS), a potentially lethal complication of severe sepsis, trauma and pneumonia, including COVID-19. Apart from barrier dysfunction, ARDS is characterized by hyper-inflammation and impaired alveolar fluid clearance (AFC), which foster the development of pulmonary permeability edema and hamper gas exchange. Tumor Necrosis Factor (TNF) is an evolutionarily conserved pleiotropic cytokine, involved in host immune defense against pathogens and cancer. TNF exists in both membrane-bound and soluble form and its mainly -but not exclusively- pro-inflammatory and cytolytic actions are mediated by partially overlapping TNFR1 and TNFR2 binding sites situated at the interface between neighboring subunits in the homo-trimer. Whereas TNFR1 signaling can mediate hyper-inflammation and impaired barrier function and AFC in the lungs, ligand stimulation of TNFR2 can protect from ventilation-induced lung injury. Spatially distinct from the TNFR binding sites, TNF harbors within its structure a lectin-like domain that rather protects lung function in ARDS. The lectin-like domain of TNF -mimicked by the 17 residue TIP peptide- represents a physiological mediator of alveolar-capillary barrier protection. and increases AFC in both hydrostatic and permeability pulmonary edema animal models. The TIP peptide directly activates the epithelial sodium channel (ENaC) -a key mediator of fluid and blood pressure control- upon binding to its α subunit, which is also a part of the non-selective cation channel (NSC). Activity of the lectin-like domain of TNF is preserved in complexes between TNF and its soluble TNFRs and can be physiologically relevant in pneumonia. Antibody- and soluble TNFR-based therapeutic strategies show considerable success in diseases such as rheumatoid arthritis, psoriasis and inflammatory bowel disease, but their chronic use can increase susceptibility to infection. Since the lectin-like domain of TNF does not interfere with TNF's anti-bacterial actions, while exerting protective actions in the alveolar-capillary compartments, it is currently evaluated in clinical trials in ARDS and COVID-19. A more comprehensive knowledge of the precise role of the TNFR binding sites versus the lectin-like domain of TNF in lung injury, tissue hypoxia, repair and remodeling may foster the development of novel therapeutics for ARDS.

Proteome analysis of NRF2 inhibition in melanoma reveals CD44 up-regulation and increased apoptosis resistance upon vemurafenib treatment

Malignant melanoma is the deadliest form of skin cancer and NRF2 has been proposed as a main regulator of tumor cell malignancy. Still the mechanisms how NRF2 is contributing to melanoma progression are incompletely understood. Here we analyzed the effects of either NRF2 induction or depletion, and we also quantified changes on the whole cell proteome level. Our results showed that inhibition of NRF2 leads to a loss of reactive oxygen species protection, but at the same time to an induction of an epithelial mesenchymal transition (EMT) phenotype and an up‐regulation of the stem cell marker CD44. Additionally, cells devoid of NRF2 showed increased cell viability after treatment with a MYC and a BRAF inhibitor. Importantly, survival upon vemurafenib treatment was dependent on CD44 expression. Finally, analysis of archival melanoma patient samples confirmed a vice versa relationship of NRF2 and CD44 expression. In summary, we recorded changes in the proteome after NRF2 modulation in melanoma cells. Surprisingly, we identified that NRF2 inhibition lead to induction of an EMT phenotype and an increase in survival of cells after apoptosis induction. Therefore, we propose that it is important for future therapies targeting NRF2 to consider blocking EMT promoting pathways in order to achieve efficient tumor therapy.

Light-Inducible Spatio-Temporal Control of TLR4 and NF-κB-Gluc Reporter in Human Pancreatic Cell Line

Augmented Toll-like receptor 4 (TLR4) expression was found in nearly 70% of patients with pancreatic adenocarcinoma, which is correlated with increased tumorigenesis and progression. In this study, we engineered a new light-oxygen-voltage-sensing (LOV) domain-based optogenetic cell line (opto-TLR4 PANC-1) that enables time-resolved activation of the NF-κB and extracellular-signal regulated kinases (ERK)1/2 signalling pathway upon blue light-sensitive homodimerisation of the TLR4-LOV fusion protein. Continuous stimulation with light indicated strong p65 and ERK1/2 phosphorylation even after 24 h, whereas brief light exposure peaked at 8 h and reached the ground level 24 h post-illumination. The cell line further allows a voltage-dependent TLR4 activation, which can be continuously monitored, turned on by light or off in the dark. Using this cell line, we performed different phenotypic cell-based assays with 2D and 3D cultures, with the aim of controlling cellular activity with spatial and temporal precision. Light exposure enhanced cell attachment, the formation and extension of invadopodia, and cell migration in 3D spheroid cultures, but no significant changes in proliferation or viability could be detected. We conclude that the opto-TLR4 PANC-1 cell line is an ideal tool for investigating the underlying molecular mechanisms of TLR4, thereby providing strategies for new therapeutic options.

Loss of SR-BI Down-Regulates MITF and Suppresses Extracellular Vesicle Release in Human Melanoma

Melanoma is a skin tumor with a high tendency for metastasis and thus is one of the deadliest cancers worldwide. Here, we investigated the expression of the scavenger receptor class B type 1 (SR-BI), a high-density lipoprotein (HDL) receptor, and tested for its role in melanoma pigmentation as well as extracellular vesicle release. We first analyzed the expression of SR-BI in patient samples and found a strong correlation with MITF expression as well as with the melanin synthesis pathway. Hence, we asked whether SR-BI could also play a role for the secretory pathway in metastatic melanoma cells. Interestingly, gain- and loss-of-function of SR-BI revealed regulation of the proto-oncogene MET. In line, SR-BI knockdown reduced expression of the small GTPase RABB22A, the ESCRT-II protein VPS25, and SNAP25, a member of the SNARE complex. Accordingly, reduced overall extracellular vesicle generation was detected upon loss of SR-BI. In summary, SR-BI expression in human melanoma enhances the formation and transport of extracellular vesicles, thereby contributing to the metastatic phenotype. Therapeutic targeting of SR-BI would not only interfere with cholesterol uptake, but also with the secretory pathway, therefore suppressing a key hallmark of the metastatic program.

Structural analysis and interaction studies of acyl-carrier protein (acpP) of Staphylococcus aureus, an extraordinarily thermally stable protein

Acyl-carrier-protein (acpP) is an essential protein in fatty acid biosynthesis of Staphylococcus aureus [Cronan, J.E. and Thomas, J. (2009). Complex enzymes in microbial natural product biosynthesis, part B: polyketides, aminocoumarins and carbohydrates.

METHOD

Enzymol. 459, 395-433; Halavaty, A.S., Kim, Y., Minasov, G., Shuvalova, L., Dubrovska, I., Winsor, J., Zhou, M., Onopriyenko, O., Skarina, T., Papazisi, L., et al. (2012). Structural characterization and comparison of three acyl-carrier-protein synthases from pathogenic bacteria. Acta Crystallogr. Sect. D Biol. Crystallogr. 68, 1359-1370]. The inactive apo-form is converted to the active holo-enzyme by acyl-carrier protein synthase (acpS) through addition of a 4'-phosphopantetheine group from coenzyme A to a conserved serine residue of acpP [Flugel, R.S., Hwangbo, Y., Lambalot, R.H., Cronan, J.E., and Walsh, C.T. (2000). Holo-(acyl-carrier protein) synthase and phosphopantetheinyl transfer in Escherichia coli. J. Biol. Chem. 275, 959-968; Lambalot, R.H. and Walsh, C.T. (1995). Cloning, overproduction, and characterization of the Escherichia coli holo-acyl-carrier protein synthase. J. Biol. Chem. 270, 24658-24661]. Once activated, acpP acts as an anchor for the growing fatty acid chain. Structural data from X-ray crystallographic analysis reveals that, despite its small size (8 kDa), acpP adopts a distinct, mostly α-helical structure when complexed with acpS [Halavaty, A.S., Kim, Y., Minasov, G., Shuvalova, L., Dubrovska, I., Winsor, J., Zhou, M., Onopriyenko, O., Skarina, T., Papazisi, L., et al. (2012). Structural characterization and comparison of three acyl-carrier-protein synthases from pathogenic bacteria. Acta Crystallogr. Sect. D Biol. Crystallogr. 68, 1359-1370; Byers, D.M. and Gong, H. (2007). Acyl carrier protein: structure-function relationships in a conserved multifunctional protein family. Biochem. Cell Biol. 85, 649-662]. We expressed and purified recombinant, active S. aureus acpP from Escherichia coli and mimicked the beginning of fatty acid biosynthesis by employing an [14C]-acp loading assay. Surprisingly, acpP remained functional even after heat treatment at 95°C for up to 10 min. NMR data from 2D-HSQC experiments as well as interaction studies with acpS confirmed that acpP is structured and active both before and after heat treatment, with no significant differences between the two. Thus, our data suggest that S. aureus acpP is a highly stable protein capable of maintaining its structure at high temperatures.

Assembly and use of high-density recombinant peptide chips for large-scale ligand screening is a practical alternative to synthetic peptide libraries

Background

Recombinant peptide chips could constitute a versatile complementation to state-of-the-art in situ (chemical on-chip) synthesis, particle-based printing, or pre-manufactured peptide spotting. Bottlenecks still impeding a routine implementation - from restricted peptide lengths, low diversity and low array densities to high costs - could so be overcome.

Methods

To assess overall performance, we assembled recombinant chips composed of 38,400 individual peptide spots on the area of a standard 96-well microtiter plate from comprehensive, highly diverse (>107 single clones) short random peptide libraries.

Results

Screening of altogether 476,160 clones against Streptavidin uncovered 2 discrete new binders: a characteristic HPQ-motif containing VSHPQAPF and a cyclic CSGSYGSC peptide. Interactions were technically confirmed by fluorescence polarization as well as biolayer-interferometry, and their potential suitability as novel detection tags evaluated by detection of a peptide-fused exemplary test protein.

Conclusion

From our data we conclude that the presented technical pipeline can reliably identify novel hits, useful as first-generation binders or templates for subsequent ligand design plus engineering.

A Screening Approach for Identifying Gliadin Neutralizing Antibodies on Epithelial Intestinal Caco-2 Cells

Celiac disease (CD) is a chronic inflammatory condition caused by the ingestion of gliadin-containing food in genetically susceptible individuals. Undigested peptides of gliadin exert various effects, including increased intestinal permeability and inflammation in the small intestine. Although many therapeutic approaches are in development, a gluten-free diet is the only effective treatment for CD. Affecting at least 1% of the population in industrialized countries, it is important to generate therapeutic options against CD. Here, we describe the establishment of a high-throughput screening (HTS) platform based on AlphaLISA and electrical cell–substrate impedance sensing (ECIS) technology for the identification of anti-inflammatory and barrier-protective compounds in human enterocytes after pepsin-trypsin-digested gliadin (PT-gliadin) treatment. Our results show that the combination of these HTS technologies enables fast, reliable, simple, and label-free screening of IgY antibodies against PT-gliadin. Using this platform, we have identified a new chicken anti-PT-gliadin IgY antibody as a potential anti-CD agent.

Design, Synthesis, and Cytotoxicity of 5-Fluoro-2-methyl-6-(4-aryl-piperazin-1-yl) Benzoxazoles

To design new compounds suitable as starting points for anticancer drug development, we have synthesized a novel series of benzoxazoles with pharmaceutically advantageous piperazine and fluorine moieties attached to them. The newly synthesized benzoxazoles and their corresponding precursors were evaluated for cytotoxicity on human A-549 lung carcinoma cells and non-cancer HepaRG hepatocyes. Some of these new benzoxazoles show potential anticancer activity, while two of the intermediates show lung cancer selective properties at low concentrations where healthy cells are unaffected, indicating a selectivity window for anticancer compounds.

The combinatorial approach of laser-captured microdissection and reverse transcription quantitative polymerase chain reaction accurately determines HER2 status in breast cancer

Background

HER2 expression in breast cancer correlates with increased metastatic potential, higher tumor recurrence rates and improved response to targeted therapies. Fluorescence in situ hybridization (FISH) and immunohistochemistry (IHC) are two methods commonly used for the analysis of HER2 in the clinic. However, lack of standardization, technical variability in laboratory protocols and subjective interpretation are major problems associated with these testing procedures.

Methods

Here we evaluated the applicability of reverse-transcription quantitative polymerase chain reaction (RT-qPCR) for HER2 testing in breast cancer. We tested thirty formaldehyde-fixed and paraffin-embedded tumor samples by RT-qPCR, FISH and IHC and analysed and compared the data from the three methods.

Results

We found that laser-captured microdissection is essential for the accurate determination of HER2 expression by RT-qPCR. When isolating RNA from total tumor tissue we obtained a significant number of false negative results. However, when using RNA from purified cancer cells the RT-qPCR data were fully consistent with FISH and IHC. In addition we provide evidence that ductal carcinomas might be further classified by the differential expression of HER3 and HER4.

Conclusions

Laser-captured microdissection in combination with RT-qPCR is a precise and cost-effective diagnostic approach for HER2 testing in cancer. The PCR assay is simple, accurate and robust and can easily be implemented and standardized in clinical laboratories.

Whole-transcriptome gene expression profiling in an epidermolysis bullosa simplex Dowling-Meara model keratinocyte cell line uncovered novel, potential therapeutic targets and affected pathways

Background

To be able to develop effective therapeutics for epidermolysis bullosa simplex (EBS), it is necessary to elucidate the molecular pathomechanisms that give rise to the disease’s characteristic severe skin-blistering phenotype.

Results

Starting with a whole-transcriptome microarray analysis of an EBS Dowling-Meara model cell line (KEB7), we identified 207 genes showing differential expression relative to control keratinocytes. A complementary qRT-PCR study of 156 candidates confirmed 76.58 % of the selected genes to be significantly up-regulated or down-regulated (p-value <0.05) within biological replicates. Our hit list contains previously identified genes involved in epithelial cell proliferation, cell-substrate adhesion, and responses to diverse biological stimuli. In addition, we identified novel candidate genes and potential affected pathways not previously considered as relevant to EBS pathology.

Conclusions

Our results broaden our understanding of the molecular processes dysregulated in EBS.

Electronic supplementary material

The online version of this article (doi:10.1186/s13104-015-1783-7) contains supplementary material, which is available to authorized users.

Alpha-catulin contributes to drug-resistance of melanoma by activating NF-κB and AP-1

Melanoma is the most dangerous type of skin cancer accounting for 48,000 deaths worldwide each year and an average survival rate of about 6-10 months with conventional treatment. Tumor metastasis and chemoresistance of melanoma cells are reported as the main reasons for the insufficiency of currently available treatments for late stage melanoma. The cytoskeletal linker protein α-catulin (CTNNAL1) has been shown to be important in inflammation, apoptosis and cytoskeletal reorganization. Recently, we found an elevated expression of α-catulin in melanoma cells. Ectopic expression of α-catulin promoted melanoma progression and occurred concomitantly with the downregulation of E-cadherin and the upregulation of mesenchymal genes such as N-cadherin, Snail/Slug and the matrix metalloproteinases 2 and 9. In the current study we showed that α-catulin knockdown reduced NF-κB and AP-1 activity in malignant melanoma cells. Further, downregulation of α-catulin diminished ERK phosphorylation in malignant melanoma cells and sensitized them to treatment with chemotherapeutic drugs. In particular, cisplatin treatment led to decreased ERK-, JNK- and c-Jun phosphorylation in α-catulin knockdown melanoma cells, which was accompanied by enhanced apoptosis compared to control cells. Altogether, these results suggest that targeted inhibition of α-catulin may be used as a viable therapeutic strategy to chemosensitize melanoma cells to cisplatin by down-regulation of NF-κB and MAPK pathways.

Antimicrobial and anti-inflammatory activities of endophytic fungi Talaromyces wortmannii extracts against acne-inducing bacteria

Acne vulgaris is the most common skin disease, causing significant psychosocial problems such as anxiety and depression similar to a chronic illness for those afflicted. Currently, obtainable agents for acne treatment have limited use. Thus, development of novel agents to treat this disease is a high medical need. The anaerobic bacterium Propionibacterium acnes has been implicated in the inflammatory phase of acne vulgaris by activating pro-inflammatory mediators such as the interleukin-8 (IL-8) via the NF-κB and MAPK pathways. Talaromyces wortmannii is an endophytic fungus, which is known to produce high bioactive natural compounds. We hypothesize that compound C but also the crude extract from T. wortmannii may possess both antibacterial activity especially against P. acnes and also anti-inflammatory properties by inhibiting TNF-α-induced ICAM-1 expression and P. acnes-induced IL-8 release. Treatment of keratinocytes (HaCaT) with P. acnes significantly increased NF-κB and activator protein-1 (AP-1) activation, as well as IL-8 release. Compound C inhibited P. acnes-mediated activation of NF-κB and AP-1 by inhibiting IκB degradation and the phosphorylation of ERK and JNK MAP kinases, and IL-8 release in a dose-dependent manner. Based on these results, compound C has effective antimicrobial activity against P. acnes and anti-inflammatory activity, and we suggest that this substance or the crude extract are alternative treatments for antibiotic/anti-inflammatory therapy for acne vulgaris.

Novel Aeruginosin-865 from Nostoc sp. as a potent anti-inflammatory agent

Aeruginosin-865 (Aer-865), isolated from terrestrial cyanobacterium Nostoc sp. Lukešová 30/93, is the first aeruginosin-type peptide containing both a fatty acid and a carbohydrate moiety, and is the first aeruginosin to be found in the genus Nostoc. Mass spectrometry, chemical and spectroscopic analysis as well as one- and two-dimensional NMR and chiral HPLC analysis of Marfey derivatives were applied to determine the peptidic sequence: D-Hpla, D-Leu, 5-OH-Choi, Agma, with hexanoic and mannopyranosyl uronic acid moieties linked to Choi. We used an AlphaLISA assay to measure the levels of proinflammatory mediators IL-8 and ICAM-1 in hTNF-α-stimulated HLMVECs. Aer-865 showed significant reduction of both: with EC50 values of (3.5±1.5) μg mL(-1) ((4.0±1.7) μM) and (50.0±13.4) μg mL(-1) ((57.8±15.5) μM), respectively. Confocal laser scanning microscopy revealed that the anti-inflammatory effect of Aer-865 was directly associated with inhibition of NF-κB translocation to the nucleus. Moreover, Aer-865 did not show any cytotoxic effect.

Real-time monitoring of relative peptide-protein interaction strengths in the yeast two-hybrid system

The yeast two-hybrid (Y2H) system is one of the most technically straightforward, effective, and widely used tools for the discovery of the binary peptide or protein interactions. However, its exceptional detection sensitivity poses a serious challenge for affinity ranking and hence prioritizing the resultant large number of putative interactors for follow-up analyses. To overcome this apparent bottleneck, we describe here a novel yeast growth curve-based interaction-monitoring approach that permits semiautomatic quantification, comparison, and statistically ascertained scoring of a large collection of Y2H interactions under real-time conditions. Initially, we conducted a proof-of-concept test of five literature-validated peptide-protein interactions with known affinities in the low μM range, and subsequently used the method to classify 88 novel vitamin D receptor-binding peptides derived from high-throughput screening of a highly diverse artificial peptide aptamer library. Based on our in-depth data evaluation, we conclude that real-time monitoring of clone growth as a measure of relative binding strength offers a facile, cost-effective, accurate, reproducible, and further adaptable complement to standard Y2H-derived clone management.

Deciphering the calcitriol-induced transcriptomic response in keratinocytes: presentation of novel target genes

Numerous studies to date have been aimed at unraveling the large suite of calcitriol (1α,25-dihydroxyvitamin D(3)) response genes in diverse tissues including skin, where this hormone is involved in regulating keratinocyte proliferation, differentiation, permeability barrier formation, innate immunity promotion, antimicrobial peptide production, and wound healing. However, the various approaches differ considerably in probed cell types, scale, throughput, and statistical reliability and do, of note, not reveal much overlap. To further expand our knowledge on presently elusive targets and characterize the extent of fragmentation of existing datasets, we have performed whole-transcriptome microarray examinations of calcitriol-treated human primary keratinocytes. Out of 28,869 genes investigated, we uncovered 86 differentially expressed (67 upregulated and 19 downregulated) candidates that were functionally clustered into five annotation categories: response to wounding, protease inhibition, secondary metabolite biosynthesis, cellular migration, and amine biosynthetic processes. A complementary RTq-PCR study of 78 nominees selected thereof demonstrated significant differential expression of 55 genes (48 upregulated and seven downregulated) within biological replicates. Our hit list contains nine previously authenticated targets (16.36%, proof of concept) and 46 novel genes (83.6%) that have not yet been explicitly described as being differentially regulated within human primary keratinocytes. Direct vitamin D receptor response element predictions within the regulatory promoter regions of 50 of the RTq-PCR-validated targets agreed with known biological functionality and corroborated our stringent data validation pipeline. Altogether, our results indicate the value of continuing these kinds of gene expression studies, which contribute to an enhanced comprehension of calcitriol-mediated processes that may be dysregulated in human skin pathophysiology.

Mesalamine modulates intercellular adhesion through inhibition of p-21 activated kinase-1

Mesalamine (5-ASA) is widely used for the treatment of ulcerative colitis, a remitting condition characterized by chronic inflammation of the colon. Knowledge about the molecular and cellular targets of 5-ASA is limited and a clear understanding of its activity in intestinal homeostasis and interference with neoplastic progression is lacking. We sought to identify molecular pathways interfered by 5-ASA, using CRC cell lines with different genetic background. Microarray was performed for gene expression profile of 5-ASA-treated and untreated cells (HCT116 and HT29). Filtering and analysis of data identified three oncogenic pathways interfered by 5-ASA: MAPK/ERK pathway, cell adhesion and β-catenin/Wnt signaling. PAK1 emerged as a consensus target of 5-ASA, orchestrating these pathways. We further investigated the effect of 5-ASA on cell adhesion. 5-ASA increased cell adhesion which was measured by cell adhesion assay and transcellular-resistance measurement. Moreover, 5-ASA treatment restored membranous expression of adhesion molecules E-cadherin and β-catenin. Role of PAK1 as a mediator of mesalamine activity was validated in vitro and in vivo. Inhibition of PAK1 by RNA interference also increased cell adhesion. PAK1 expression was elevated in APC^min polyps and 5-ASA treatment reduced its expression. Our data demonstrates novel pharmacological mechanism of mesalamine in modulation of cell adhesion and role of PAK1 in APC^min polyposis. We propose that inhibition of PAK1 expression by 5-ASA can impede with neoplastic progression in colorectal carcinogenesis. The mechanism of PAK1 inhibition and induction of membranous translocation of adhesion proteins by 5-ASA might be independent of its known anti-inflammatory action.

A Combined Impedance and AlphaLISA-Based Approach to Identify Anti-inflammatory and Barrier-Protective Compounds in Human Endothelium

Chronic inflammation is at least partially mediated by the chemokine-mediated attraction and by the adhesion molecule–directed binding of leukocytes to the activated endothelium. Therefore, it is therapeutically important to identify anti-inflammatory compounds able to control the interaction between leukocytes and the endothelial compartments of the micro- and macrocirculation. When testing novel drug candidates, it is, however, of the utmost importance to detect side effects, such as potential cytotoxic and barrier-disruptive activities. Indeed, minor changes in the endothelial monolayer integrity may increase the permeability of small blood vessels and capillaries, which, in extreme cases, can lead to edema development. Here, we describe the development of a high-throughput screening (HTS) platform, based on AlphaLISA technology, able to identify anti-inflammatory nontoxic natural or synthetic compounds capable of reducing tumor necrosis factor (TNF)–induced chemokine (interleukin [IL]–8) and adhesion molecule (ICAM-1) expression in human lung microvascular endothelial cells. Quantification of cell membrane–expressed ICAM-1 and of cell culture supernatant–associated levels of IL-8 was analyzed in HTS. In parallel, we monitored monolayer integrity and endothelial cell viability using the electrical cell substrate impedance sensing method. This platform allowed us to identify natural secondary metabolites from cyanobacteria, capable of reducing ICAM-1 and IL-8 levels in TNF-activated human microvascular endothelial cells in the absence of endothelial monolayer barrier disruption.

Pleiotropic neuroprotective and metabolic effects of Actovegin's mode of action

This article reviews the mechanisms of action of Actovegin in the context of its preclinical effects and new concepts in the pharmacological treatment of neurological disorders. Actovegin is an ultrafiltrate of calf blood, composed of more than 200 biological substances. The drug is used for a broad spectrum of diseases, including disturbances of peripheral and cerebral blood circulation, burns, impaired wound healing, radiation-induced damage and diabetic polyneuropathy. Actovegin is composed of small molecules present under normal physiological conditions, therefore pharmacokinetic and pharmacodynamic studies to determine its active substance are not feasible. Preclinical data have revealed that it improves metabolic balance by increasing glucose uptake and improving oxygen uptake under conditions of ischemia. Actovegin also resists the effects of gamma-irradiation and stimulates wound healing. More recent preclinical studies have suggested that anti-oxidative and anti-apoptotic mechanisms of action specifically underlie the neuroprotective properties of Actovegin. The drug has been found to exert these beneficial effects experimentally, in primary rat hippocampal neurons and in an STZ-rat model of diabetic polyneuropathy, while also providing evidence that it positively affects the functional recovery of neurons. Latest data suggest that Actovegin also has a positive influence on the NF-κB pathway, but many molecular and cellular pathways remain unexplored. In particular, Actovegin's influence on neuroplasticity, neurogenesis and neurotrophicity are questions that ideally should be answered by future research. Nevertheless, it is clear that the multifactorial and complex nature of Actovegin underlies its pleiotropic neuroprotective mechanisms of action and positive effect on clinical outcomes.

α-Catulin downregulates E-cadherin and promotes melanoma progression and invasion

Metastasis is associated with poor prognosis for melanoma responsible for about 90% of skin cancer-related mortality. To metastasize, melanoma cells must escape keratinocyte control, invade across the basement membrane and survive in the dermis by resisting apoptosis before they can intravasate into the circulation. α-Catulin (CTNNAL1) is a cytoplasmic molecule that integrates the crosstalk between nuclear factor-kappa B and Rho signaling pathways, binds to β-catenin and increases the level of both α-catenin and β-catenin and therefore has potential effects on inflammation, apoptosis and cytoskeletal reorganization. Here, we show that α-catulin is highly expressed in melanoma cells. Expression of α-catulin promoted melanoma progression and occurred concomitantly with the downregulation of E-cadherin and the upregulation of expression of mesenchymal genes such as N-cadherin, Snail/Slug and the matrix metalloproteinases 2 and 9. Knockdown of α-catulin promoted adhesion to and inhibited migration away from keratinocytes in an E-cadherin-dependent manner and decreased the transmigration through a keratinocyte monolayer, as well as in Transwell assays using collagens, laminin and fibronectin coating. Moreover, knockdown promoted homotypic spheroid formation and concomitantly increased E-cadherin expression along with downregulation of transcription factors implicated in its repression (Snail/Slug, Twist and ZEB). Consistent with the molecular changes, α-catulin provoked invasion of melanoma cells in a three-dimensional culture assay by the upregulation of matrix metalloproteinases 2 and 9 and the activation of ROCK/Rho. As such, α-catulin may represent a key driver of the metastatic process, implicating potential for therapeutic interference.

PIM-1 kinase interacts with the DNA binding domain of the vitamin D receptor: a further kinase implicated in 1,25-(OH)2D3 signaling

BACKGROUND

The vitamin D3 receptor (VDR) is responsible for mediating the pleiotropic and, in part, cell-type-specific effects of 1,25-dihydroxyvitamin D3 (calcitriol) on the cardiovascular and the muscle system, on the bone development and maintenance, mineral homeostasis, cell proliferation, cell differentiation, vitamin D metabolism, and immune response modulation.

RESULTS

Based on data obtained from genome-wide yeast two-hybrid screenings, domain mapping studies, intracellular co-localization approaches as well as reporter transcription assay measurements, we show here that the C-terminus of human PIM-1 kinase isoform2 (amino acid residues 135-313), a serine/threonine kinase of the calcium/calmodulin-regulated kinase family, directly interacts with VDR through the receptor's DNA-binding domain. We further demonstrate that PIM-1 modulates calcitriol signaling in HaCaT keratinocytes by enhancing both endogenous calcitriol response gene transcription (osteopontin) and an extrachromosomal DR3 reporter response.

CONCLUSION

These results, taken together with previous reports of involvement of kinase pathways in VDR transactivation, underscore the biological relevance of this novel protein-protein interaction.

From the ORFeome concept to highly comprehensive, full-genome screening libraries

Recombination-based cloning techniques have in recent times facilitated the establishment of genome-scale single-gene ORFeome repositories. Their further handling and downstream application in systematic fashion is, however, practically impeded because of logistical plus economic challenges. At this juncture, simultaneously transferring entire gene collections in compiled pool format could represent an advanced compromise between systematic ORFeome (an organism's entire set of protein-encoding open reading frames) projects and traditional random library approaches, but has not yet been considered in great detail. In our endeavor to merge the comprehensiveness of ORFeomes with a basically simple, streamlined, and easily executable single-tube design, we have here produced five different pooled screening-ready libraries for both Staphylococcus aureus and Homo sapiens. By evaluating the parallel transfer efficiencies of differentially sized genes from initial polymerase chain reaction (PCR) product amplification to entry and final destination library construction via quantitative real-time PCR, we found that the complexity of the gene population is fairly stably maintained once an entry resource has been successfully established, and that no apparent size-selection bias loss of large inserts takes place. Recombinational transfer processes are hence robust enough for straightforwardly achieving such pooled screening libraries.

TNF: a moonlighting protein at the interface between cancer and infection

The remarkable ability of TNF, especially in combination with Interferon-gamma or melphalan, to inhibit the growth of malignant tumor cells is so far unmatched. Unfortunately, its high systemic toxicity and hepatotoxicity prevent its systemic use in cancer patients. An elegant manner to circumvent this problem is the isolated limb and liver perfusion for the treatment of melanoma, soft tissue sarcoma and liver tumors, respectively, although the latter method can lead to a reversible hepatotoxicity. In order to allow also the treatment of other cancers with TNF, new strategies have to be developed that aim at sensitizing tumor cells to TNF and at reducing its systemic and liver toxicity, without losing its antitumor efficiency. Moreover, the lectin-like domain of TNF, which is spatially distinct from the receptor binding sites, could be useful in reducing cancer treatment-related pulmonary edema formation. This review will discuss some recent developments in these areas, which can lead to a renewed interest in TNF for the systemic treatment of cancer.

Endothelial cell-based methods for the detection of cyanobacterial anti-inflammatory and wound-healing promoting metabolites

Acute lung injury is accompanied by an increased endothelial chemokine production and adhesion molecule expression, which may result in an extensive neutrophil infiltration. Moreover, a destruction of the alveolar epithelium and capillary endothelium may result in permeability edema. As such, the search for novel anti-inflammatory substances, able to downregulate these parameters as well as the tissue damage holds therapeutic promise. We therefore describe here the use of human endothelial cell-based in vitro assays for the detection of anti-inflammatory and wound-healing metabolites from cyanobacteria.

Relative Quantitation of Protein–Protein Interaction Strength Within the Yeast Two-Hybrid System via Fluorescenceβ-Galactosidase Activity Detection in a High-Throughput and Low-Cost Manner

The yeast two-hybrid (Y2H) method is capable of delivering vast amounts of interacting positive yeast colonies from a single library screen, particularly if a multifunctional protein is used as bait. However, the selection of definitive colonies for further molecular analysis is limited by both technical practicality and high costs. Here we demonstrate a cost-effective and simple method for the rapid selection and ranking of those Y2H-positive interaction clones that are suitable for further analysis. We performed a Y2H screen for the identification of human transforming growth factor beta2- interacting proteins in a human skin keratinocyte library. The identified clones were ranked by the amount of beta-galactosidase enzyme produced, as well as by the interaction strength of the positive colonies. The combination of high-throughput microplate fluorescence readers and specific fluorescence assays can be utilized for relative quantitation of protein-protein interaction strength of Y2H-positive colonies in crude yeast-cell lysates. We demonstrate here that the high sensitivity of the fluorescence approach can bypass cumbersome conventional methods of cell lysis used in beta-galactosidase assays, and still deliver accurate values for analysis of protein interaction data. Finally, we also achieved a better understanding of general aspects of beta-galactosidase measurements in the Y2H system, such as protein normalization, the influence of yeast culture incubation time on optimal beta-galactosidase detection, and the linearity of beta-galactosidase detection in crude cell lysates.

Translational regulator RpL10p/Grc5p interacts physically and functionally with Sed1p, a dynamic component of the yeast cell surface

Biogenesis of an active ribosome complement and a dynamic cell surface complement are two major determinants of cellular growth. In yeast, the 60S ribosomal subunit protein RpL10p/Grc5p functions during successive stages in ribosome biogenesis, specifically rRNA processing, nucle(ol)ar preribosomal subunit assembly, nucleo-cytoplasmic transport and cytoplasmic maturation of ribosomes. Here, we report that a two-hybrid screen identified yeast genes SED1, ACS2 and PLB3 as encoding proteins physically interacting with both ribosomal RpL10p/Grc5p and its human homologue hRpL10p/QMp. SED1 encodes a differentially expressed cell wall protein which is proposed to be first transiently secreted to the plasma membrane as a GPI (glycosylated derivative of phosphoinositol)-anchored form and to be then transferred to the glucan layer of the cell wall. Ectopic expression of SED1 rescues both the aberrant growth phenotype and the translation defect of grc5-1(ts) temperature-sensitive cells. Furthermore, we report that Sed1p associates with translating ribosomes suggesting a novel, cytoplasmic role for Sed1p. ACS2 encodes one of the two yeast acetyl-CoA synthases and represents a key enzyme in one of several metabolic routes to produce acetyl-CoA, which in turn is indispensable for lipid biosynthesis. PLB3 encodes a phospholipase, which is active in the breakdown of membrane lipids. Our results support the view that Grc5p/RpL10p links ribosome function to membrane turnover and cell surface biogenesis.

GRC5 and NMD3 function in translational control of gene expression and interact genetically

The yeast gene, GRC5 (growth control), is a member of the highly conserved QM gene family, the human member of which has been associated with the suppression of Wilms' tumor. GRC5 encodes ribosomal protein L10, which is thought to play a regulatory role in the translational control of gene expression. A revertant screen identified four spontaneous revertants of the mutant grc5-1ts allele. Genetic and phenotypic analysis showed that these represent one gene, NMD3, and that the interaction of NMD3 and GRC5 is gene-specific. NMD3 was previously identified as a component of the nonsense-mediated mRNA decay pathway. The point mutations within NMD3 reported here may define a domain important for the functional interaction of Grc5p and Nmd3p.