SILAC-based quantitative proteomics and microscopy analysis of cancer cells treated with the N-glycolyl GM3-specific anti-tumor antibody 14F7

Cancer immunotherapy represents a promising approach to specifically target and treat cancer. The most common mechanisms by which monoclonal antibodies kill cells include antibody-dependent cell-mediated cytotoxicity, complement-dependent cytotoxicity and apoptosis, but also other mechanisms have been described. 14F7 is an antibody raised against the tumor-associated antigen NeuGc GM3, which was previously reported to kill cancer cells without inducing apoptotic pathways. The antibody was reported to induce giant membrane lesions in tumor cells, with apparent changes in the cytoskeleton. Here, we investigated the effect of humanized 14F7 on HeLa cells using stable isotope labeling with amino acids in cell culture (SILAC) in combination with LC-MS and live cell imaging. 14F7 did not kill the HeLa cells, however, it caused altered protein expression (MS data are available via ProteomeXchange with identifier PXD024320). Several cytoskeletal and nucleic-acid binding proteins were found to be strongly down-regulated in response to antibody treatment, suggesting how 14F7 may induce membrane lesions in cells that contain higher amounts of NeuGc GM3. The altered expression profile identified in this study thus contributes to an improved understanding of the unusual killing mechanism of 14F7.

Factor VII activating protease (FSAP) inhibits the outcome of ischemic stroke in mouse models

The outcome of ischemic stroke can be improved by further refinements of thrombolysis and reperfusion strategies. Factor VII activating protease (FSAP) is a circulating serine protease that could be important in this context. Its levels are raised in patients as well as mice after stroke and a single nucleotide polymorphism (SNP) in the coding sequence, which results in an inactive enzyme, is linked to an increased risk of stroke. In vitro, FSAP cleaves fibrinogen to promote fibrinolysis, activates protease-activated receptors, and decreases the cellular cytotoxicity of histones. Based on these facts, we hypothesized that FSAP can be used as a treatment for ischemic stroke. A combination of tissue plasminogen activator (tPA), a thrombolytic drug, and recombinant serine protease domain of FSAP (FSAP-SPD) improved regional cerebral perfusion and neurological outcome and reduced infarct size in a mouse model of thromboembolic stroke. FSAP-SPD also improved stroke outcomes and diminished the negative consequences of co-treatment with tPA in the transient middle cerebral artery occlusion model of stroke without altering cerebral perfusion. The inactive MI-isoform of FSAP had no impact in either model. FSAP enhanced the lysis of blood clots in vitro, but in the tail transection model of hemostasis, FSAP-SPD treatment provoked a faster clotting time indicating that it also has pro-coagulant actions. Thus, apart from enhancing thrombolysis, FSAP has multiple effects on stroke progression and represents a promising novel therapeutic strategy in the treatment of ischemic stroke.

Crystal structure of MOA in complex with a peptide fragment: A protease caught in flagranti

The Marasmius oreades agglutinin (MOA) is the holotype of an emerging family of fungal chimerolectins and an active Ca2+/Mn2+-dependent protease, which exhibits a unique papain-like fold with special active site features. Here we investigated the functional significance of the structural elements differentiating MOA from other papain-like cysteine proteases. X-ray crystal structures of MOA co-crystallized with two synthetic substrates reveal cleaved peptides bound to the catalytic site, corresponding to the final products of the proteolytic reaction. Anomalous diffraction data on crystals grown in the presence of calcium and manganese, cadmium or zinc resolve the calcium/manganese preference of MOA and elucidate the inhibitory roles of zinc and cadmium towards papain-like cysteine proteases in general. The reported structures, together with activity data of MOA active site variants, point to a conservation of the general proteolysis mechanism established for papain. Ultimately, the findings suggest that papain and the papain-like domain of MOA are the product of convergent evolution.

Evidence of PKC Binding and Translocation to Explain the Anticancer Mechanism of Chlorogenic Acid in Breast Cancer Cells

Chlorogenic acid (CGA) exhibits potentials towards liver, breast and skin cancer. Cancer cells stimulated with CGA exhibits differential expression of transcriptional factors and regulatory molecules but the molecular target of the molecule is not known. Superposition of biophoric elements of CGA with Curcumin gives maximum common substructure score of 0.90. Molecular modeling studies further suggest that CGA fits into the C1b domain of PKC with extensive interaction with residues lining binding site. It binds PKC in a concentration dependent manner with dissociation constant KD, 28.84±3.95 μM. PKC-CGA complex is stable with minimal distortion to the 3-D structure and maintains the hydrogen bonding between ligand and receptor during simulation period. Cells stimulated with CGA causes 12.1 ± 0.56% PKC translocation from the cytosol to the plasma membrane. It disturbs the cell cycle and arrest the cancer cell at the G1 phase with a reduction in S-phase. Chlorogenic acid exhibits killing of cancer cells in a dose-dependent manner with an IC50 of 75.88 ± 4.54μg/ml and 52.5 ± 4.72μg/ml towards MDAMB-231 and MCF-7 cells respectively. It induces apoptosis in cancer cells as evident by AO/EtBr staining and degradation of genomic DNA to give a laddering pattern. Apoptosis in cancer cells involves mitochondrial pathway as supported by a reduction in mitochondrial potentials and release of cyt-C into the cytosol. Hence, the current study has established PKC as an important signaling molecule to the observed anti-cancer effects of CGA and provides the impetus to design better CGA analogs for improved anti-cancer potential against the malignant tumor.

Analysis of the substrate specificity of Factor VII activating protease (FSAP) and design of specific and sensitive peptide substrates

Factor VII (FVII) activating protease (FSAP) is a circulating serine protease that is likely to be involved in a number of disease conditions such as stroke, atherosclerosis, liver fibrosis, thrombosis and cancer. To date, no systematic information is available about the substrate specificity of FSAP. Applying phage display and positional scanning substrate combinatorial library (PS-SCL) approaches we have characterised the specificity of FSAP towards small peptides. Results were evaluated in the context of known protein substrates as well as molecular modelling of the peptides in the active site of FSAP. The representative FSAP-cleaved sequence obtained from the phage display method was Val-Leu-Lys-Arg-Ser (P4-P1'). The sequence X-Lys/Arg-Nle-Lys/Arg (P4-P1) was derived from the PS-SCL method. These results show a predilection for cleavage at a cluster of basic amino acids on the nonprime side. Quenched fluorescent substrate (Ala-Lys-Nle-Arg-AMC) (amino methyl coumarin) and (Ala-Leu-Lys-Arg-AMC) had a higher selectivity for FSAP compared to other proteases from the hemostasis system. These substrates could be used to measure FSAP activity in a complex biological system such as plasma. In histone-treated plasma there was a specific activation of pro-FSAP as validated by the use of an FSAP inhibitory antibody, corn trypsin inhibitor to inhibit Factor XIIa and hirudin to inhibit thrombin, which may account for some of the haemostasis-related effects of histones. These results will aid the development of further selective FSAP activity probes as well as specific inhibitors that will help to increase the understanding of the functions of FSAP in vivo.

Polyporus squamosus Lectin 1a (PSL1a) Exhibits Cytotoxicity in Mammalian Cells by Disruption of Focal Adhesions, Inhibition of Protein Synthesis and Induction of Apoptosis

PSL1a is a lectin from the mushroom Polyporus squamosus that binds to sialylated glycans and glycoconjugates with high specificity and selectivity. In addition to its N-terminal carbohydrate-binding domain, PSL1a possesses a Ca²⁺-dependent proteolytic activity in the C-terminal domain. In the present study, we demonstrate that PSL1a has cytotoxic effects on mammalian cancer cells, and we show that the cytotoxicity is dependent on the cysteine protease activity. PSL1a treatment leads to cell rounding and detachment from the substratum, concomitant with disruption of vinculin complexes in focal adhesions. We also demonstrate that PSL1a inhibits protein synthesis and induces apoptosis in HeLa cells, in a time- and concentration-dependent manner.

3-Amino-4-aminoximidofurazan derivatives: small molecules possessing antimicrobial and antibiofilm activity against Staphylococcus aureus and Pseudomonas aeruginosa

AIM

The therapeutic treatment of microbial infections involving biofilm becomes quite challenging because of its increasing antibiotic resistance capacities. Towards this direction, in the present study we have evaluated the antibiofilm property of synthesized 3-amino-4-aminoximidofurazan compounds having polyamine skeleton. These derivatives were synthesized by incorporating furazan and biguanide moieties.

METHODS AND RESULTS

Different 3-amino-4-aminoximidofurazan derivatives (PI1-4) were synthesized via protic acid catalysis and subsequently characterized by (1) H NMR and (13) C NMR spectra, recorded at 400 and 100 MHz respectively. We have tested the antimicrobial and antibiofilm activities of these synthetic derivatives (PI1-4) against both Staphylococcus aureus and Pseudomonas aeruginosa. The compounds so tested were also compared with standard antibiotics namely Tobramycin (Ps. aeruginosa) and Azithromycin (Staph. aureus) which were used as a positive control in all experimental sets. All these compounds (PI1-4) exhibited moderate to significant antimicrobial activities against both micro-organisms wherein compound PI3 showed maximum activity. Biofilm inhibition of both micro-organisms was then evaluated by crystal violet and safranin staining, estimation of biofilm total protein and microscopy methods using sub-MIC dose of these compounds. Results showed that all compounds executed anti biofilm activity against both Staph. aureus and Ps. aeruginosa wherein compound PI3 exhibited maximum activity. In relation with microbial biofilm inhibition, we have observed reduction in bacterial motility, proteolytic activity and secreted exo-polysaccharide (EPS) from both Staph. aureus and Ps. aeruginosa when they were grown in presence of these compounds. While addressing the issue of toxicity on host, we have observed that these molecules exhibited minimum level of R.B.C degradation.

CONCLUSION

These findings establish the antibacterial and anti biofilm properties of 3-amino-4-aminoximidofurazan derivatives (PI1-4).

SIGNIFICANCE AND IMPACT OF THE STUDY

Therefore, our current findings demonstrate that 3-amino-4-aminoximidofurazan derivatives (PI1-4) may hold promise to be effective biofilm and microbial inhibitors that may be clinically significant.

Drosophila KASH-domain protein Klarsicht regulates microtubule stability and integrin receptor localization during collective cell migration

During collective migration of the Drosophila embryonic salivary gland, cells rearrange to form a tube of a distinct shape and size. Here, we report a novel role for the Drosophila Klarsicht-Anc-Syne Homology (KASH) domain protein Klarsicht (Klar) in the regulation of microtubule (MT) stability and integrin receptor localization during salivary gland migration. In wild-type salivary glands, MTs became progressively stabilized as gland migration progressed. In embryos specifically lacking the KASH domain containing isoforms of Klar, salivary gland cells failed to rearrange and migrate, and these defects were accompanied by decreased MT stability and altered integrin receptor localization. In muscles and photoreceptors, KASH isoforms of Klar work together with Klaroid (Koi), a SUN domain protein, to position nuclei; however, loss of Koi had no effect on salivary gland migration, suggesting that Klar controls gland migration through novel interactors. The disrupted cell rearrangement and integrin localization observed in klar mutants could be mimicked by overexpressing Spastin (Spas), a MT severing protein, in otherwise wild-type salivary glands. In turn, promoting MT stability by reducing spas gene dosage in klar mutant embryos rescued the integrin localization, cell rearrangement and gland migration defects. Klar genetically interacts with the Rho1 small GTPase in salivary gland migration and is required for the subcellular localization of Rho1. We also show that Klar binds tubulin directly in vitro. Our studies provide the first evidence that a KASH-domain protein regulates the MT cytoskeleton and integrin localization during collective cell migration.

Surface micropattern limits bacterial contamination

BACKGROUND

Bacterial surface contamination contributes to transmission of nosocomial infections. Chemical cleansers used to control surface contamination are often toxic and incorrectly implemented. Additional non-toxic strategies should be combined with regular cleanings to mitigate risks of human error and further decrease rates of nosocomial infections. The Sharklet micropattern (MP), inspired by shark skin, is an effective tool for reducing bacterial load on surfaces without toxic additives. The studies presented here were carried out to investigate the MP surfaces capability to reduce colonization of methicillin-sensitive Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) compared to smooth control surfaces.

METHODS

The MP and smooth surfaces produced in acrylic film were compared for remaining bacterial contamination and colonization following inoculation. Direct sampling of surfaces was carried out after inoculation by immersion, spray, and/or touch methods. Ultimately, a combination assay was developed to assess bacterial contamination after touch transfer inoculation combined with drying (persistence) to mimic common environmental contamination scenarios in the clinic or hospital environment. The combination transfer and persistence assay was then used to test antimicrobial copper beside the MP for the ability to reduce MSSA and MRSA challenge.

RESULTS

The MP reduced bacterial contamination with log reductions ranging from 87-99% (LR = 0.90-2.18; p < 0.05) compared to smooth control surfaces. The MP was more effective than the 99.9% pure copper alloy C11000 at reducing surface contamination of S. aureus (MSSA and MRSA) through transfer and persistence of bacteria. The MP reduced MSSA by as much as 97% (LR = 1.54; p < 0.01) and MRSA by as much as 94% (LR = 1.26; p < 0.005) compared to smooth controls. Antimicrobial copper had no significant effect on MSSA contamination, but reduced MRSA contamination by 80% (LR = 0.70; p < 0.005).

CONCLUSION

The assays developed in this study mimic hospital environmental contamination events to demonstrate the performance of a MP to limit contamination under multiple conditions. Antimicrobial copper has been implemented in hospital room studies to evaluate its impact on nosocomial infections and a decrease in HAI rate was shown. Similar implementation of the MP has potential to reduce the incidence of HAIs although future clinical studies will be necessary to validate the MP's true impact.

Microarray analysis of Mu transposition in Salmonella enterica, serovar Typhimurium: transposon exclusion by high-density DNA binding proteins

All organisms contain transposons with the potential to disrupt and rearrange genes. Despite the presence of these destabilizing sequences, some genomes show remarkable stability over evolutionary time. Do bacteria defend the genome against disruption by transposons? Phage Mu replicates by transposition and virtually all genes are potential insertion targets. To test whether bacteria limit Mu transposition to specific parts of the chromosome, DNA arrays of Salmonella enterica were used to quantitatively measure target site preference and compare the data with Escherichia coli. Essential genes were as susceptible to transposon disruption as non-essential ones in both organisms, but the correlation of transposition hot spots among homologous genes was poor. Genes in highly transcribed operons were insulated from transposon mutagenesis in both organisms. A 10 kb cold spot on the pSLT plasmid was near parS, a site to which the ParB protein binds and spreads along DNA. Deleting ParB erased the plasmid cold spot, and an ectopic parS site placed in the Salmonella chromosome created a new cold spot in the presence of ParB. Our data show that competition between cellular proteins and transposition proteins on plasmids and the chromosome is a dominant factor controlling the genetic footprint of transposons in living cells.

A gyrase mutant with low activity disrupts supercoiling at the replication terminus

When a mutation in an essential gene shows a temperature-sensitive phenotype, one usually assumes that the protein is inactive at nonpermissive temperature. DNA gyrase is an essential bacterial enzyme composed of two subunits, GyrA and GyrB. The gyrB652 mutation results from a single base change that substitutes a serine residue for arginine 436 (R436-S) in the GyrB protein. At 42 degrees C, strains with the gyrB652 allele stop DNA replication, and at 37 degrees C, such strains grow but have RecA-dependent SOS induction and show constitutive RecBCD-dependent DNA degradation. Surprisingly, the GyrB652 protein is not inactive at 42 degrees C in vivo or in vitro and it doesn't directly produce breaks in chromosomal DNA. Rather, this mutant has a low k(cat) compared to wild-type GyrB subunit. With more than twice the normal mean number of supercoil domains, this gyrase hypomorph is prone to fork collapse and topological chaos near the terminus of DNA replication.

Bacteriophage Mu targets the trinucleotide sequence CGG

Target specificity for bacteriophage Mu was studied using a new phage derivative that enabled cloning of Mu-host junctions from phage DNA. Insertions distributed throughout the chromosome showed no orientation bias with respect to transcription or replication polarity. Genes with a high frequency of the triplet CGG were preferred targets.

Microarray analysis of transposition targets in Escherichia coli: the impact of transcription

Transposable elements have influenced the genetic and physical composition of all modern organisms. Defining how different transposons select target sites is critical for understanding the biochemical mechanism of this type of recombination and the impact of mobile genes on chromosome structure and function. Phage Mu replicates in Gram-negative bacteria using an extremely efficient transposition reaction. Replicated copies are excised from the chromosome and packaged into virus particles. Each viral genome plus several hundred base pairs of host DNA covalently attached to the prophage right end is packed into a virion. To study Mu transposition preferences, we used DNA microarray technology to measure the abundance of >4,000 Escherichia coli genes in purified Mu phage DNA. Insertion hot- and cold-spot genes were found throughout the genome, reflecting >1,000-fold variation in utilization frequency. A moderate preference was observed for genes near the origin compared to terminus of replication. Large biases were found at hot and cold spots, which often include several consecutive genes. Efficient transcription of genes had a strong negative influence on transposition. Our results indicate that local chromosome structure is more important than DNA sequence in determining Mu target-site selection.

Mu and IS1 transpositions exhibit strong orientation bias at the Escherichia coli bgl locus

The region upstream of the Escherichia coli bgl operon is an insertion hot spot for several transposons. Elements as distantly related as Tn1, Tn5, and phage Mu home in on this location. To see what characteristics result in a high-affinity site for transposition, we compared in vivo and in vitro Mu transposition patterns near the bgl promoter. In vivo, Mu insertions were focused in two narrow zones of DNA near bgl, and both zones exhibited a striking orientation bias. Five hot spots upstream of the bgl cyclic AMP binding protein (CAP) binding site had Mu insertions exclusively with the phage oriented left to right relative to the direction of bgl transcription. One hot spot within the CAP binding domain had the opposite (right-to-left) orientation of phage insertion. The DNA segment lying between these two Mu hot-spot clusters is extremely A/T rich (80%) and is an efficient target for insertion sequences during stationary phase. IS1 insertions that activate the bgl operon resulted in a decrease in Mu insertions near the CAP binding site. Mu transposition in vitro differed significantly from the in vivo transposition pattern, having a new hot-spot cluster at the border of the A/T-rich segment. Transposon hot-spot behavior and orientation bias may relate to an asymmetry of transposon DNA-protein complexes and to interactions with proteins that produce transcriptionally silenced chromatin.

Phage Mu transposition immunity reflects supercoil domain structure of the chromosome

Transposition immunity is the negative influence that the presence of one transposon sequence has on the probability of a second identical element inserting in the same site or in sites nearby. A transposition-defective Mu derivative (MudJr1) produced transposition immunity in both directions from one insertion point in the Salmonella typhimurium chromosome. To control for the sequence preference of Mu transposition proteins, Tn10 elements were introduced as targets at various distances from an immunity-conferring MudJr1 element. Mu transposition into a Tn10 target was not detectable when the distance of separation from MudJr1 was 5 kb, and transposition was unencumbered when the separation was 25 kb. Between 5 kb and 25 kb, immunity decayed gradually with distance. Immunity decayed more sharply in a gyrase mutant than in a wild-type strain. We propose that Mu transposition immunity senses the domain structure of bacterial chromosomes.

How is osmotic regulation of transcription of the Escherichia coli proU operon achieved? A review and a model

The proU operon in enterobacteria encodes a binding-protein-dependent transporter for the active uptake of glycine betaine and L-proline, and serves an adaptive role during growth of cells in hyperosmolar environments. Transcription of proU is induced 400-fold under these conditions, but the underlying signal transduction mechanisms are incompletely understood. Increased DNA supercoiling and activation by potassium glutamate have each been proposed in alternative models as mediators of proU osmoresponsivity. We review here the available experimental data on proU regulation, and in particular the roles for DNA supercoiling, potassium glutamate, histone-like proteins of the bacterial nucleoid, and alternative sigma factors of RNA polymerase in such regulation. We also propose a new unifying model, in which the pronounced osmotic regulation of proU expression is achieved through the additive effects of at least three separate mechanisms, each comprised of a cis element [two promoters P1 and P2, and negative-regulatory-element (NRE) downstream of both promoters] and distinct trans-acting factors that interact with it: stationary-phase sigma factor RpoS with P1, nucleoid proteins HU and IHF with P2, and nucleoid protein H-NS with the NRE. In this model, potassium glutamate may activate proU expression through each of the three mechanisms whereas DNA supercoiling has a very limited role, if any, in the osmotic induction of proU transcription. We also suggest that proU may be a virulence gene in the pathogenic enterobacteria.

Use of epicardial pacing wires after coronary artery bypass surgery

OBJECTIVE

To replicate a previous study that described the incidence and characteristics of patients after coronary artery bypass graft surgery who required the use of epicardial pacing wires and to explore the reasons for epicardial pacing wire use in this patient population.

DESIGN

Ex post facto descriptive correlational.

SETTING

Cardiothoracic intensive care and step down units of a 500-bed medical center.

SUBJECTS

Convenience sample of 196 patients after coronary artery bypass graft surgery, 165 who did not use the epicardial pacing wires and 31 who used the epicardial pacing wires to augment cardiac output, diagnose dysrhythmias, suppress dysrhythmias, or treat heart block. Patients receiving other surgical techniques in combination with coronary artery bypass graft surgery were not included.

PROCEDURE

Recording of demographic and clinical data for all of the sample population, with additional data collected when the epicardial pacing wires were used.

DATA ANALYSIS

Independent t test and chi-square analysis were used to determine significance between the means and frequencies in the variables of the patients who used the epicardial pacing wires and those who did not. The significance level was set at 0.05.

RESULTS

There were no statistically significant differences between the groups in terms of age or previous or recent myocardial infarction, which was opposite of the replicated study's findings. A statistically significant difference (p < 0.001) was found between the groups for the use of inotropic support, which was also opposite of the findings of that study. The group requiring epicardial pacing wire utilization demonstrated a greater need for diuretics in the preoperative phase than those who did not (p < 0.01), as well as a higher use of digitalis therapy before surgery (p < 0.01). Additionally, those who were paced experienced a greater cardiac output (p = 0.013) and cardiac index (p = 0.018) after pacing was initiated.

CONCLUSIONS

The variation in findings between this study and the one replicated may be the result of variations in the patient populations, treatment practices, or preoperative condition. Replication of this study at a future date may reveal variables not identified here.

Evidence for involvement of proteins HU and RpoS in transcription of the osmoresponsive proU operon in Escherichia coli

Transcription of the proU operon of Escherichia coli is induced several hundred-fold upon growth at elevated osmolarity, but the underlying mechanisms are incompletely understood. Three cis elements appear to act additively to mediate proU osmoresponsivity: (i) sequences around a promoter, P1, which is situated 250 bp upstream of the first structural gene proV; (ii) sequences around another (sigma 70-dependent) promoter, P2, which is situated 60 bp upstream of proV; and (iii) a negative regulatory element present within the proV coding region. These three cis elements are designated, respectively, P1R, P2R, and NRE. trans-acting mutants with partially derepressed proU expression have been obtained earlier, and a vast majority of the mutations affect the gene encoding the nucleoid protein HNS. In this study we employed a selection for trans-acting mutants with reduced proU+ expression, and we obtained a derivative that had suffered mutations in two separate loci designated dpeA and dpeB. The dpeB mutation caused a marked reduction in promoter P1 expression and was allelic to rpoS, the structural gene for the stationary-phase-specific sigma factor of RNA polymerase. Expression from P1 was markedly induced, in an RpoS-dependent manner, in stationary-phase cultures. In contrast to the behavior of the isolated P1 promoter, transcription from a construct carrying the entire proU cis-regulatory region (P1R plus P2R plus NRE) was not significantly affected by either growth phase or RpoS. The dpeA locus was allelic to hupB, which along with hupA encodes the nucleoid protein HU. hupA hupB double mutants exhibited a pronounced reduction in proU osmotic inducibility. HU appears to affect proU regulation through the P2R mechanism, whereas the effect of HNS is mediated through the NRE.