UV radiation promotes melanoma dissemination mediated by the sequential reaction axis of cathepsins-TGF-ß1-FAP-α.

BACKGROUND: Ultraviolet radiation (UVR) is the major risk factor for development of malignant melanoma. Fibroblast activation protein (FAP)-α is a serine protease expressed on the surface of activated fibroblasts, promoting tumour invasion through extracellular matrix (ECM) degradation. The signalling mechanism behind the upregulation of FAP-α is not yet completely revealed. METHODS: Expression of FAP-α was analysed after UVR exposure in in vitro co-culture systems, gene expression arrays and artificial skin constructs. Cell migration and invasion was studied in relation to cathepsin activity and secretion of transforming growth factor (TGF)-ß1. RESULTS: Fibroblast activation protein-α expression was induced by UVR in melanocytes of human skin. The FAP-α expression was regulated by UVR-induced release of TGF-ß1 and cathepsin inhibitors prevented such secretion. In melanoma cell culture models and in a xenograft tumour model of zebrafish embryos, FAP-α mediated ECM degradation and facilitated tumour cell dissemination. CONCLUSIONS: Our results provide evidence for a sequential reaction axis from UVR via cathepsins, TGF-ß1 and FAP-α expression, promoting cancer cell dissemination and melanoma metastatic spread.

Capillary electrophoresis with laser-induced fluorescence detection as a tool for enzyme characterization and inhibitor screening.

An effective, rapid and economical CE/LIF (capillary electrophoresis/laser-induced fluorescence) method was developed and applied to the characterization of signal peptidase (SPase) enzyme, which is a target for the screening of new drug candidates. In this method, CE separates the product from the substrate and LIF selectively detects the fluorescence-labeled product and substrate. By measuring the increase of the product as a function of time, one can monitor the progression of the enzyme reaction. The progression curves were also used for screening inhibitors for this enzyme. The effects of various reaction conditions were also studied and discussed. In addition, this CE/LIF method was applied to the determination of the enzyme activity, the quality control of the substrate and/or enzymes, and the cross-reactivity of inhibitors to the enzyme. It can be concluded that this method is suitable for high throughput screening (HTS) assays because it can deliver fast, sensitive, quantitative, and reliable results.

Assessment of microwave-assisted enzymatic digestion by measuring glycated hemoglobin A1c by mass spectrometry.

Enzymatic digestion of proteins and analysis of the resulting peptides by mass spectrometry is an established approach in proteomics and in clinical and environmental chemistry. The long digestion times of several hours prevent the fast turnover of samples and results. Qualitative applications showed that microwave radiation profoundly shortens enzymatic digestion. However, its usefulness for quantitative applications had not been assessed. In this study, the microwave-assisted enzymatic digestion of hemoglobin at different temperatures, buffer concentrations, and digestion times was assessed and compared with conventional digestion for the proteolytic enzymes trypsin and Glu-C. A microwave-assisted enzymatic digestion method optimized for digestion time and temperature was applied for the analysis of glycated hemoglobin HbA1c and compared with a reference method. Using trypsin, complete digestion was obtained at 50 degrees C within 20 min. Under these conditions, the digestion efficiency was 20% higher than with conventional trypsin digestion. These effects were not observed with Glu-C as enzyme, probably because of the decreased stability of Glu-C at elevated temperatures in comparison with the trypsin used. The comparison of the optimized microwave-assisted digestion method using trypsin with the reference method for HbA1c using Glu-C gave a close correlation in the results (R2: 0.996). A significant bias of 0.33% HbA1c was observed, with higher values obtained with the microwave-assisted tryptic digest; this finding might have resulted from the use of a different enzyme. This study showed that microwave-assisted enzymatic digestion can substantially reduce digestion times to minutes and can be used in qualitative as well as quantitative applications.

Expression of lexA targeted ribozyme in Escherichia coli BL-21 (DE3) cells.

Coding sequences for a hammerhead ribozyme designed to cleave lexA mRNA in a targeted manner was cloned under phage T7 promoter and expressed in E. coli strain BL-21 (DE3) expressing T7 RNA polymerase under the control of IPTG-inducible lac UV-5 promoter. Ribozyme expression in vivo was demonstrated by RNase protection assay. Also, total RNA extracted from these transformed cells following induction by IPTG, displays site-specific cleavage of labeled lexA RNA in an in vitro reaction. The result demonstrates the active ribozyme in extracts of cell transformed with a recombinant cassette and goes beyond the earlier demonstration of the stability of in vitro synthesized ribozyme in cell extracts. The observed rise in lexA mRNA rules out any role for protease activity or resulting fragments of lexA protein in de-repression of RNA.

Effect of ultrasound on activation of serine proteases precursors.

The effect of ultrasound (US) (26.4 kHz, 26 W/cm2) on the activation process of a mixture of chymotrypsinogen and trypsinogen was studied. US led to a significant decrease in proteolytic activity, as well as inhibition of the activation process in general. It was shown that inhibition of proteinase activity under US influence was a consequence of inhibition of chymotrypsinogen-chymotrypsin transformation and the complete proteolytic trypsin degradation in the proenzymes mixture.

Replication restart in UV-irradiated Escherichia coli involving pols II, III, V, PriA, RecA and RecFOR proteins.

In Escherichia coli, UV-irradiated cells resume DNA synthesis after a transient inhibition by a process called replication restart. To elucidate the role of several key proteins involved in this process, we have analysed the time dependence of replication restart in strains carrying a combination of mutations in lexA, recA, polB (pol II), umuDC (pol V), priA, dnaC, recF, recO or recR. We find that both pol II and the origin-independent primosome-assembling function of PriA are essential for the immediate recovery of DNA synthesis after UV irradiation. In their absence, translesion replication or 'replication readthrough' occurs approximately 50 min after UV and is pol V-dependent. In a wild-type, lexA+ background, mutations in recF, recO or recR block both pathways. Similar results were obtained with a lexA(Def) recF strain. However, lexA(Def) recO or lexA(Def) recR strains, although unable to facilitate PriA-pol II-dependent restart, were able to perform pol V-dependent readthrough. The defects in restart attributed to mutations in recF, recO or recR were suppressed in a recA730 lexA(Def) strain expressing constitutively activated RecA (RecA*). Our data suggest that in a wild-type background, RecF, O and R are important for the induction of the SOS response and the formation of RecA*-dependent recombination intermediates necessary for PriA/Pol II-dependent replication restart. In con-trast, only RecF is required for the activation of RecA that leads to the formation of pol V (UmuD'2C) and facilitates replication readthrough.

HtrA2 promotes cell death through its serine protease activity and its ability to antagonize inhibitor of apoptosis proteins.

Inhibitor of apoptosis (IAP) proteins inhibit caspases, a function counteracted by IAP antagonists, insect Grim, HID, and Reaper and mammalian DIABLO/Smac. We now demonstrate that HtrA2, a mammalian homologue of the Escherichia coli heat shock-inducible protein HtrA, can bind to MIHA/XIAP, MIHB, and baculoviral OpIAP but not survivin. Although produced as a 50-kDa protein, HtrA2 is processed to yield an active serine protease with an N terminus similar to that of Grim, Reaper, HID, and DIABLO/Smac that mediates its interaction with XIAP. HtrA2 is largely membrane-associated in healthy cells, with a significant proportion observed within the mitochondria, but in response to UV irradiation, HtrA2 shifts into the cytosol, where it can interact with IAPs. HtrA2 can, like DIABLO/Smac, prevent XIAP inhibition of active caspase 3 in vitro and is able to counteract XIAP protection of mammalian NT2 cells against UV-induced cell death. The proapoptotic activity of HtrA2 in vivo involves both IAP binding and serine protease activity. Mutations of either the N-terminal alanine of mature HtrA2 essential for IAP interaction or the catalytic serine residue reduces the ability of HtrA2 to promote cell death, whereas a complete loss in proapoptotic activity is observed when both sites are mutated.

Acute myeloblastic leukemic cells acquire cellular cytotoxicity under genotoxic stress: implication of granzyme B and perforin.

Granzyme B (GrB) and perforin (PFN) are the major components of cytoplasmic granules contained in immune cellular effectors. The granule secretory pathway is one of the mechanisms by which these cells exert their cellular cytotoxicity. Recently, it has been reported that GrB and PFN are also present in circulating hemopoietic CD34(+) progenitor cells mobilized by chemotherapy and granulocyte-colony stimulating factor, whereas these proteins are undetected in steady-state peripheral CD34(+) cells. In this study, we hypothesized that anticancer agents may increase GrB and PFN expression in immature myeloid leukemic cells and that these treated leukemic cells become cellular effectors through a granule-dependent mechanism. Our results show that KG1a, HEL, and TF-1 CD34(+) acute myeloblastic leukemia cells expressed both GrB and PFN. Moreover, ionizing radiation, aracytine, and etoposide not only increase GrB and PFN expression but also conferred potent cellular cytotoxicity to these cells toward various cellular targets. Cellular cytotoxicity required cell-cell contact, was not influenced by anti-tumor necrosis factor alpha or anti-Fas blocking antibodies, and was abrogated by GrB inhibitors or antisense. These results suggest that, when exposed to genotoxic agents, immature leukemic cells acquire potent GrB- and PFN-dependent cellular cytotoxicity that can be potentially directed against normal residual myeloid progenitors or immune effectors. (Blood. 2000;96:1914-1920)

Importance of heptameric ring integrity for activity of Escherichia coli ClpP.

Radiation target analysis has been used to identify the minimal functional unit for expression of activity of ClpP, the proteolytic component of the ATP-dependent ClpAP protease. Radiation target sizes determined for small peptide hydrolysis, for ClpA activated and nucleotide-activated oligopeptide cleavage, and for ClpA-activated ATP-dependent protein degradation were 154, 118, and 160 kDa, respectively. Thus, the hydrolytic activity of ClpP, subunit M, 21,500, is dependent on the native oligomeric structure. The quaternary structure of ClpP determined by electron microscopy and hydrodynamic studies consists of two face-to-face seven-membered rings. The radiation target sizes are consistent with a requirement for conformational integrity of an entire ring for expression of hydrolytic activity. Radiation damage led to disruption of inter-ring contacts, giving rise to isolated rings of ClpP. Thus, contacts between rings of ClpP are less stable and more easily disrupted than contacts between subunits within the rings. Our data suggest that cooperative interactions between subunits within the ClpP rings are important for maintaining the active conformation of the proteolytic active site.

[The effect of electromagnetic field on the biosynthesis and various properties of extracellular proteinase and lectin from Bacillus subtilis 316 M]. / Vliianie élektromagnitnogo polia na biosintez i nekotorye svoistva vnekletochnoi proteinazy i lektina Bacillus subtils 316 M.

The promoting effect of electromagnetic field (EMF) on biosynthesis and activity of extracellular proteinase and lectin in B. subtilis 316 M was observed. It caused 1.5- and 4-fold increase of the metabolites yield respectively. The EMF stimulated a 2-fold activation of lectin, rise of the enzyme activity and a shift of it pI from 11.4-11.5 to 9.2-9.3.

Study of the photochemical immobilization of alkaline proteinase and chymotrypsin on the solid phase of O-hydroxyethylcellulose.

Stability of the photochemically immobilized alkaline proteinase (E.C. 3.4.21.14) and chymotrypsin (E.C. 3.4.21.1.) onto the gel of O-hydroxyethylcellulose has been studied. For the purpose of immobilization the photochemical generation of nitrene radicals caused by the photolysis of an azido group of bifunctional 4,4'-bis-azidostilbene-2,2'-disodium-sulphate and the newly synthetized O-(3-azidophthaloyl)-O-hydroxyethylcellulose have been employed. The immobilized alkaline proteinase demonstrated a decreased ability of denaturation and an increased laboratory stability.