Improved analytical sensitivity reveals the occurrence of gender-related variability in diamine oxidase enzyme activity in healthy individuals

OBJECTIVES

Serum diamine oxidase (DAO; EC 1.4.3.6) activity is often employed as a clinical indicator of the integrity of intestinal mucosa. However, interindividual variation in enzyme activity and reference values for healthy women and men have not been studied.

DESIGN AND METHODS

DAO activity was measured by using cadaverine coupled to O-dianisidine oxidation in 50 healthy individuals.

RESULTS

The mean activity was 7.59+/-3.67 U/L for women and 2.38+/-0.71 U/L for men (p<0.001).

CONCLUSIONS

Gender is a major determinant for DAO activity in healthy subjects.

Localization of the TIG3 transglutaminase interaction domain and demonstration that the amino-terminal region is required for TIG3 function as a keratinocyte differentiation regulator

Tazarotene-induced gene 3 (TIG3) regulates keratinocyte terminal differentiation by activating type I transglutaminase (TG1). TIG3 consists of an amino-terminal (N-terminal) segment, that encodes several conserved motifs, and a carboxy-terminal (C-terminal) membrane-anchoring domain. By producing a series of truncation mutants that remove segments of the N-terminal region, and monitoring the ability of each mutant to co-precipitate TG1, function as a TG1 substrate, or functionally localize with TG1 in cells, we show that the TIG3 domain that interacts with TG1 is located within a TIG3 segment spanning amino acids 112-164. Although they bind TG1, TIG3 mutants lacking the conserved N-terminal region drive apoptosis-like cell death characterized by cell rounding, membrane blebbing, cytochrome c release, procaspase-3 and poly(ADP-ribose)polymerase (PARP) cleavage, and reduced p53 and p21 levels. Compared with TIG3, these truncated mutants have an increased tendency to associate with membranes. A mutant lacking the C-terminal membrane-anchoring domain is inactive. These findings suggest that TIG3 interaction with TG1 does not require the N-terminal conserved domains, that the TIG3 N-terminal region is required for TIG3-dependent keratinocyte differentiation, that its removal converts TIG3 into a proapoptotic protein, and that this change in action of TIG3 is associated with an intracellular redistribution.

The first agmatine/cadaverine aminopropyl transferase: biochemical and structural characterization of an enzyme involved in polyamine biosynthesis in the hyperthermophilic archaeon Pyrococcus furiosus

We report here the characterization of the first agmatine/cadaverine aminopropyl transferase (ACAPT), the enzyme responsible for polyamine biosynthesis from an archaeon. The gene PF0127 encoding ACAPT in the hyperthermophile Pyrococcus furiosus was cloned and expressed in Escherichia coli, and the recombinant protein was purified to homogeneity. P. furiosus ACAPT is a homodimer of 65 kDa. The broad substrate specificity of the enzyme toward the amine acceptors is unique, as agmatine, 1,3-diaminopropane, putrescine, cadaverine, and sym-nor-spermidine all serve as substrates. While maximal catalytic activity was observed with cadaverine, agmatine was the preferred substrate on the basis of the k(cat)/K(m) value. P. furiosus ACAPT is thermoactive and thermostable with an apparent melting temperature of 108 degrees C that increases to 112 degrees C in the presence of cadaverine. Limited proteolysis indicated that the only proteolytic cleavage site is localized in the C-terminal region and that the C-terminal peptide is not necessary for the integrity of the active site. The crystal structure of the enzyme determined to 1.8-A resolution confirmed its dimeric nature and provided insight into the proteolytic analyses as well as into mechanisms of thermal stability. Analysis of the polyamine content of P. furiosus showed that spermidine, cadaverine, and sym-nor-spermidine are the major components, with small amounts of sym-nor-spermine and N-(3-aminopropyl)cadaverine (APC). This is the first report in Archaea of an unusual polyamine APC that is proposed to play a role in stress adaptation.

A structural insight into the inhibition of human and Leishmania donovani ornithine decarboxylases by 1-amino-oxy-3-aminopropane

The critical role of polyamines in key processes such as cell growth, differentiation and macromolecular synthesis makes the enzymes involved in their synthesis potential targets in the treatment of certain types of cancer and parasitic diseases. Here we present a study on the inhibition of human and Leishmania donovani ODC (ornithine decarboxylase), the first committed enzyme in the polyamine biosynthesis pathway, by APA (1-amino-oxy-3-aminopropane). The present study shows APA to be a potent inhibitor of both human and L. donovani ODC with a K(i) value of around 1.0 nM. We also show that L. donovani ODC binds the substrate, the co-enzyme pyridoxal 5'-phosphate and the irreversible inhibitor alpha-difluoromethylornithine (a curative agent of West African sleeping sickness) with less affinity than human ODC. We have also determined the three-dimensional structure of human ODC in complex with APA, which revealed the mode of the inhibitor binding to the enzyme. In contrast with earlier reports, the structure showed no indication of oxime formation between APA and PLP (pyridoxal 5'-phosphate). Homology modelling suggests a similar mode of binding of APA to L. donovani ODC. A comparison of the ODC-APA-PLP structure with earlier ODC structures also shows that the protease-sensitive loop (residues 158-168) undergoes a large conformational change and covers the active site of the protein. The understanding of the structural mode of APA binding may constitute the basis for the development of more specific inhibitors of L. donovani ODC.

Identification of substrates for transglutaminase in Physarum polycephalum, an acellular slime mold, upon cellular mechanical damage

Transglutaminases are Ca(2+)-dependent enzymes that post-translationally modify proteins by crosslinking or polyamination at specific polypeptide-bound glutamine residues. Physarum polycephalum, an acellular slime mold, is the evolutionarily lowest organism expressing a transglutimase whose primary structure is similar to that of mammalian transglutimases. We observed transglutimase reaction products at injured sites in Physarum macroplasmodia upon mechanical damage. With use of a biotin-labeled primary amine, three major proteins constituting possible transglutimase substrates were affinity-purified from the damaged slime mold. The purified proteins were Physarum actin, a 40 kDa Ca(2+)-binding protein with four EF-hand motifs (CBP40), and a novel 33 kDa protein highly homologous to the eukaryotic adenine nucleotide translocator, which is expressed in mitochondria. Immunochemical analysis of extracts from the damaged macroplasmodia indicated that CBP40 is partly dimerized, whereas the other proteins migrated as monomers on SDS/PAGE. Of the three proteins, CBP40 accumulated most significantly around injured areas, as observed by immunofluoresence. These results suggested that transglutimase reactions function in the response to mechanical injury.

Cadaverine protects Vibrio vulnificus from superoxide stress

An electron paramagnetic resonance (EPR) signal characteristic of the 5,5'-dimethyl-1-pyrroline-N-oxide (DMPO)-OH spin adduct, which is formed from the reaction of DMPO with superoxide radicals generated by xanthine oxidase-mediated reaction, was significantly reduced by the cadaverine or Escherichia coli Mn-containing superoxide dismutase (MnSOD). Likewise, cytochrome c reduction by superoxide was inhibited by cadaverine, and the inhibition level increased in proportion to the level of cadaverine. The cadA mutant of Vibrio vulnificus, which does not produce cadaverine because of the lack of lysine decarboxylase, exhibits less tolerance to superoxide stress in comparison with wild type. The results indicate that cadaverine scavenges superoxide radicals, and protects cells from oxidative stress.

The impact of Cu treatment on phenolic and polyamine levels in plant material regenerated from embryos obtained in anther culture of carrot

The influence of copper sulphate on the regeneration of carrot (Daucus carota L.) androgenic embryos and changes in the levels of phenolic substances and polyamines that might be indicative of the response to oxidative stress were investigated. The cultivation on the regeneration medium supplemented with Cu(2+) at the concentrations 1 and 10 microM for 15 weeks resulted in significant dose-dependent inhibition of the growth and organogenic ability of carrot embryos. The total content of phenolic acids (represented by the sum of all soluble and insoluble fractions) in the Cu(2+)-treated carrot cultures did not change in comparison with the control (0.1 microM Cu(2+)). However, the levels of phenolic acids in the individual fractions showed significant differences. The cultivation in the presence of increased Cu(2+) evoked first of all the rise of free chlorogenic and caffeic acids, and the increase in soluble ester-bound ferulic acid. Marked dose-dependent decline in the amount of ferulic acid incorporated into the cell walls of the Cu(2+)-treated carrot cultures was partly compensated by the increase in the content of p-hydroxybenzoic acid. Decline in the total polyamine contents in the carrot tissues cultivated in the presence of increased Cu(2+) concentrations was observed. The most abundant polyamine, both in a free and PCA-soluble conjugated forms, was putrescine, the least abundant was spermine, which occurred in free form only. While the levels of free polyamines slightly decreased in a dose-dependent manner in the Cu(2+)-treated cultures, those of PCA-soluble conjugates markedly rose (enhancement to 135 and 170% in 1 and 10 microM Cu(2+), respectively, compared with the control). The decline in the total polyamine contents was caused mainly by the decline in the levels of PCA-insoluble conjugates. The decrease observed in this fraction was approximately to 70 and 50% in 1 and 10 microM Cu(2+)-treated cultures, respectively, when compared with the control. The role of phenolic acids and polyamines in preventing Cu(2+)stress in the carrot tissues is discussed.

Lysine decarboxylase expression by Vibrio vulnificus is induced by SoxR in response to superoxide stress

Lysine decarboxylase expression by Vibrio vulnificus, which is up-regulated by CadC in response to acid stress, is also induced by SoxR in response to superoxide stress. SoxR binds to the promoter region of the cadBA operon, coding for a lysine-cadaverine antiporter (CadB) and a lysine decarboxylase (CadA). The induction of cadBA transcription by SoxR is independent of CadC. Cadaverine, which neutralizes the external medium, also appears to scavenge superoxide radicals, since increasing cellular cadaverine by elevating the gene dosage of cadBA significantly diminished the induction of Mn-containing superoxide dismutase under methyl viologen-induced oxidative stress. Consistently, a lack of cadaverine caused by mutation in cadA resulted in low tolerance to oxidative stress compared with that of the wild type.

A Rapid Transglutaminase Assay for High-Throughput Screening Applications

Transglutaminases (TGs) are widely distributed enzymes that catalyze posttranslational modification of proteins by Ca2+-dependent cross-linking reactions. The family members of TGs participate in many significant processes of biological functions such as tissue regeneration, cell differentiation, apoptosis, and certain pathologies. A novel technique for TG activity assay was developed in this study. It was based on the rapid capturing, fluorescence quenching, and fast separation of the unreacted fluorescent molecules from the macromolecular product with magnetic dextran-coated charcoal. As few as 3 ng of guinea pig liver transglutaminase (gpTG) could be detected by the method; activities of 96 TG samples could be measured within an hour. The Km of gpTG determined by this method for monodansylcadaverine (dansyl-CAD) and N, N-dimethylcasein was 14 and 5 μM, respectively. A typical competitive inhibition pattern of cystamine on dansyl-CAD for gpTG activity was also demonstrated. The application of this technique is not limited to the use of dansyl-CAD as the fluorescent substrate of TG; other small fluor-labeled TG substrates may substitute dansyl-CAD. Finally, this method is rapid, highly sensitive, and inexpensive. It is suitable not only for high-throughput screening of enzymes or enzyme inhibitors but also for enzyme kinetic analysis.

Cross linking to tissue transglutaminase and collagen favours gliadin toxicity in coeliac disease

BACKGROUND AND AIMS

Intestinal inflammation in coeliac disease is driven by the gluten fraction of wheat proteins. Deamidation or cross linking of gluten peptides by tissue transglutaminase (tTG), the coeliac disease autoantigen, creates potent T cell stimulatory peptides. Therefore, our aim was to identify the reaction patterns of gluten peptides, intestinal extracellular matrix proteins, and tTG.

METHODS

tTG activity was analysed by incorporation of monodansyl cadaverine into gliadins. Fluorescence labelled tTG reactive short gliadin peptides were used to demonstrate their deamidation and explore their cross linking patterns with tTG itself or extracellular matrix proteins. Patient sera and controls were checked for autoantibodies to matrix proteins.

RESULTS

Gliadins alpha1-alpha11, gamma1-gamma6, omega1-omega3, and omega5 were substrates for tTG. tTG catalysed the cross linking of gliadin peptides with interstitial collagen types I, III, and VI. Coeliac patients showed increased antibody titres against the collagens I, III, V, and VI.

CONCLUSIONS

tTG formed high molecular weight complexes with all tested gliadins. As all tested gliadins were substrates for tTG, the tTG catalysed modifications were not restricted to single gliadin types and epitopes. Furthermore, haptenisation and long term immobilisation of gliadin peptides by tTG catalysed binding to abundant extracellular matrix proteins could be instrumental in the perpetuation of intestinal inflammation and some associated autoimmune diseases in coeliac disease.

Purification and partial characterization of the plasma clotting protein from the pink shrimp Farfantepenaeus paulensis

A clotting protein (CP) was purified from the plasma of the pink shrimp Farfantepenaeus paulensis by sequential anion-exchange chromatography. The shrimp CP was able to form stable clots in vitro in the presence of hemocyte lysate and Ca2+, suggesting that the clotting reaction is catalyzed by a Ca2+-dependent transglutaminase present in shrimp hemocytes. Dansylcadaverine was incorporated into the shrimp CP in the presence of endogenous transglutaminase (hemocyte lysate), confirming that the shrimp purified CP is the substrate for the transglutaminase enzyme. The molecular mass of the CP was determined by gel filtration to be 341 kDa and 170 kDa by SDS-PAGE under reducing conditions. These results suggest that the shrimp CP consists of two identical subunits, covalently linked by disulphide bonds. The amino acid sequence at the N-terminus was 100% identical to that of the penaeids Litopenaeus vannamei and Penaeus monodon and 66% to 80% identical to the CPs of other decapods. This is the first report of a CP characterization in an Atlantic penaeid species. Further studies, including a molecular cloning approach would enable to detect which tissues express the gene of the clotting protein. It would be also useful to understand the mechanism by which the coagulation time is delayed in shrimps under stress conditions.

Pathoadaptive mutation that mediates adherence of shiga toxin-producing Escherichia coli O111

The adherence of pathogenic Escherichia coli strains to intestinal epithelium is essential for initiation of infection. The cad operon encodes the lysine decarboxylase (LDC) system responsible for metabolizing lysine, and this operon has been proposed as an antivirulence mechanism in enteroinvasive E. coli and Shigella flexneri and as a factor mediating E. coli O157:H7 adherence. We sought to determine whether the LDC activity was present in a phylogenetically characterized collection of diarrheagenic E. coli (DEC) strains and to establish whether its expression was associated with their adherence to tissue culture cells. LDC activity was found in most of the pathogenic E. coli strains tested and was absent from Shiga toxin-producing E. coli (STEC) O111 strains (DEC pathotype 8). Analysis of the cad region in these O111 strains indicates that the operon has been rearranged and some of the genes are either missing or disrupted. A similar rearrangement was found in an E. coli O111:H8 strain recently isolated from an outbreak in Texas. Complementation of the LDC-negative strains with the cad operon in trans restored the LDC activity and resulted in a reduction in adherence to tissue culture cells. Initial analysis of the protein profiles on the surface of the O111 strains indicates that the LDC activity has an effect on the expression of the adhesin intimin. Cadaverine had a slight effect on LDC-negative strain adhesion but none on intimin expression. Our data suggest that this pathoadaptive mutation is an important mechanism to control functions potentially implicated in the pathogenesis of these organisms.

Hoxb13 up-regulates transglutaminase activity and drives terminal differentiation in an epidermal organotypic model

Hox genes act to differentiate and pattern embryonic structures by promoting the proliferation of specific cell types. An exception is Hoxb13, which functions as a proapoptotic and antiproliferative protein during development of the caudal spinal cord and tail vertebrae and has also been implicated in adult cutaneous wound repair. The adult epidermis, which expresses several Hox genes including Hoxb13, is continually renewed in a program of growth arrest, differentiation, and a specialized form of apoptosis (cornification). Yet little is known about the function(s) of these genes in skin. Based on its role during embryogenesis, Hoxb13 is an attractive candidate to be involved in the regulation of epidermal differentiation. Here, we demonstrate that Hoxb13 overexpression in an adult organotypic epidermal model recapitulates actions of Hoxb13 reported in embryonic development. Epidermal cell proliferation is decreased, apoptosis increased, and excessive terminal differentiation observed, as characterized by enhanced transglutaminase activity and excessive cornified envelope formation. Overexpression of Hoxb13 also produces abnormal phenotypes in the epidermal tissue that resemble certain pathological features of dysplastic skin diseases. Our results suggest that Hoxb13 functions to promote epidermal differentiation, a critical process for skin regeneration and for the maintenance of normal barrier function.

Transglutaminase activity is present in highly purified nonsynaptosomal mouse brain and liver mitochondria

Several active transglutaminase (TGase) isoforms are known to be present in human and rodent tissues, at least three of which, namely, TGase 1, TGase 2 (tissue transglutaminase), and TGase 3, are present in the brain. TGase activity is known to be present in the cytosolic, nuclear, and extracellular compartments of the brain. Here, we show that highly purified mouse brain nonsynaptosomal mitochondria and mouse liver mitochondria and mitoplast fractions derived from these preparations possess TGase activity. Western blotting and experiments with TGase 2 knock-out (KO) mice ruled out the possibility that most of the mitochondrial/mitoplast TGase activity is due to TGase 2, the TGase isoform responsible for the majority of the activity ([14C]putrescine-binding assay) in whole brain and liver homogenates. The identity of the mitochondrial/mitoplast TGase(s) is not yet known. Possibly, the activity may be due to one of the other TGase isoforms or perhaps to a protein that does not belong to the classical TGase family. This activity may play a role in regulation of mitochondrial function both in normal physiology and in disease. Its nature and regulation deserve further study.

The dynamics of autophagy visualized in live cells: from autophagosome formation to fusion with endo/lysosomes

Autophagy has been implicated in a range of disorders and hence is of major interest. However, imaging autophagy in real time has been hampered by lack of suitable markers. We have compared the potential of monodansylcadaverine, widely used as an autophagosomal marker, and the Atg8 homologue LC3, to follow autophagy by fluorescence microscopy whilst labelling late endosomes and lysosomes simultaneously using EGFP-CD63. Monodansylcadaverine labelled only acidic CD63-positive compartments in response to a range of autophagic inducers in various live or post-fixed cells, staining being identical in atg5(+/+) and atg5(-/-) MEFs in which autophagosome formation is disabled. Monodansylcadaverine staining was essentially indistinguishable from that of LysoTracker Red, LAMP-1 or LAMP-2. In contrast, 60-90% of EGFP-LC3-positive punctate organelles did not colocalise with LAMP-1/LAMP-2/CD63 and were monodansylcadaverine-negative while EGFP-LC3 puncta that did colocalise with LAMP-1/LAMP-2/CD63 were also monodansylcadaverine-positive. Hence monodansylcadaverine is no different from other markers of acidic compartments and it cannot be used to follow autophagosome formation. In contrast, fusion of mRFP-LC3-labelled autophagosomes with EGFP-CD63-positive endosomes and lysosomes and sequestration of dsRed-labelled mitochondria by EGFP-LC3- and EGFP-CD63-positive compartments could be visualized in real time. Moreover, transition of EGFP-LC3-I (45 kDa) to EGFP-LC3-II (43 kDa)-traced by immunoblotting and verified by [(3)H]ethanolamine labelling-revealed novel insights into the dynamics of autophagosome homeostasis, including the rapid activation of autophagy by the apoptotic inducer staurosporine prior to apoptosis proper. Use of fluorescent LC3 and a counter-fluorescent endosomal/lysosomal protein clearly allows the entire autophagic process to be followed by live cell imaging with high fidelity.

Binding and uptake of wheat germ agglutinin-grafted PLGA-nanospheres by caco-2 monolayers

PURPOSE

The Caco-2 association of lectin-grafted PLGA-nanospheres was investigated compared to plain and BSA-coated spheres.

METHODS

Nanospheres made from fluorescent-labeled PLGA were coated with wheat germ agglutinin (WGA) or BSA and incubated with Caco-2 monolayers varying the concentration of nanospheres, the time, and the temperature. The tests were performed in a static horizontal as well as an aerated vertical setup to find out the system most appropriate for estimation of bioadhesion.

RESULTS

Due to bioadhesive effects, WGA-modified particles exhibited highest association to the cells as compared to plain and BSA-coated ones. The amount of associated spheres increased with time and concentration of the nanosphere suspension. Whereas the binding of lectin-coated spheres was independent from energy, their uptake was energy consuming as opposed to BSA and plain nanospheres, which exhibited nonspecific, energy independent binding and uptake. Although more particles were associated with the monolayer in the horizontal setup than in the vertical system, the vertical system reflects true bioadhesion due to circulation of the spheres which inhibits the influence of sedimentation.

CONCLUSIONS

Immobilization of WGA considerably enhances the binding as well as the uptake of PLGA-nanospheres by Caco-2 monolayers. For bioadhesion studies, the vertical setup is recommended instead of the horizontal setup.

Characterization of a transglutaminase from scallop hemocyte and identification of its intracellular substrates

Scallop hemocytes contain a transglutaminase (TGase) that is electrophoretically different from the TGase in the adductor muscle. The optimum temperature of the hemocyte TGase was lower (about 15 degrees C), compared with the muscle TGase (35-40 degrees C). Other properties, such as the high sodium chloride (NaCl) and CaCl2 concentrations required for activation, instability in salt solutions, and the Km values against monodansylcadaverine (MDC) and succinylated casein, were similar for both enzymes. When hemocyte homogenate was incubated with MDC at 10 degrees C, MDC was incorporated into the 230 k and 100 k proteins of the hemocytes. The 100 k protein was only detected in the supernatant, the 230 k protein was insoluble, and the 210 k protein was detected in both fractions. In the absence of MDC, the 230 k, 210 k, and 100 k proteins were cross-linked by endogenous transglutaminase. The 230 k protein was most quickly cross-linked and formed huge polymers within 5 min. These results suggest that if scallop tissues are injured, hemocyte transglutaminase may be activated, initially cross-linking the insoluble hemocyte 230 k protein, followed by the 210 k and 100 k proteins, to form a cross-linked protein matrix with inter cross-linking of hemocyte sheets, to stop the bleeding.

A Zea mays 39-kDa thylakoid transglutaminase catalyses the modification by polyamines of light-harvesting complex II in a light-dependent way

A transglutaminase (TGase; EC 2.3.2.13) activity, which shared many properties with the TGase activity of the Helianthus tuberosus chloroplast, was observed in the Zea mays L. chloroplast and in its fractions. This activity was found to be prevalent in thylakoids; bis-(glutamyl) spermidine and bis-(glutamyl) putrescine were the main polyamine conjugates formed. Light stimulated the endogenous thylakoid activity. Putrescine, spermidine and spermine were conjugated to the isolated light-harvesting complex of photosystem II (LHCII) with different degrees of efficiency, spermine being the polyamine most efficiently conjugated. A TGase with a light-sensitive activity was identified in the photosystem II-enriched fraction. Its partial purification on a sucrose gradient allowed the separation of a 39-kDa band, which was immunorecognised by two anti-TGase antibodies (Ab-3 and rat prostatic gland-TGase). Both a colorimetric and a radiometric assay for TGase activity, the former carried out in the presence of biotinylated cadaverine and the latter in the presence of polyamines labelled with radioactive isotopes and resulting in the isolation of glutamyl-polyamines, further confirmed that the thylakoid enzyme is indeed a calcium-dependent transglutaminase (Thyl-TGase). At variance with guinea pig liver and erythrocyte TGases, which are insensitive to light, the activity of the thylakoid transglutaminase is affected by light. Moreover, this enzyme, when tested with purified LHCII as substrate, catalysed the production of mono- and bis-glutamyl-polyamines in equal amounts, whereas the 'animal' enzymes produced mainly mono-derivatives. Herein, it is discussed whether this light sensitivity is due to the enzyme or the substrate.

Identification of Factor XIIIa-Reactive Glutamine Acceptor and Lysine Donor Sites within Fibronectin-Binding Protein (FnbA) from Staphylococcus aureus

Staphylococcal fibronectin-binding protein (FnbA) is a surface-associated receptor responsible for the reversible binding of bacteria to human fibronectin and fibrin(ogen). Recently we have shown that FnbA serves as a substrate for coagulation factor XIIIa and undergoes covalent cross-linking to its ligands, resulting in the formation of heteropolymers (Matsuka, Y. V., Anderson, E. T., Milner-Fish, T., Ooi, P., and Baker, S. (2003) Staphylococcus aureus fibronectin-binding protein serves as a substrate for coagulation factor XIIIa: Evidence for factor XIIIa-catalyzed covalent cross-linking to fibronectin and fibrin, Biochemistry 42, 14643-14652). Factor XIIIa also catalyzes the incorporation in FnbA of fluorescent probes dansylcadaverine and glutamine-containing synthetic peptide patterned on the NH(2)-terminal segment of fibronectin. In this study, the above probes were utilized for site-specific labeling and identification of reactive Gln and Lys residues targeted by factor XIIIa in rFnbA. Probe-decorated rFnbA samples were subjected to trypsin or Glu-C digestion, followed by separation of labeled peptides using reversed phase HPLC. Sequencing and mass spectral analyses of isolated probe-modified peptides have been employed for the identification of factor XIIIa-reactive Gln and Lys residues. Analysis of dansylcadaverine-labeled peptides resulted in the identification of one major, Gln103, and three minor, Gln105, Gln783, and Gln830, amine acceptor sites. The labeling procedure with dansyl-PGGQQIV probe revealed that Lys157, Lys503, Lys620, and Lys762 serve as amine donor sites. The identified reactive glutamine acceptor and lysine donor sites of FnbA may participate in transglutaminase-mediated cross-linking reactions resulting in the covalent attachment of pathogenic Staphylococcus aureus to human host proteins.

Interaction of Chlamydia trachomatis serovar L2 with the host autophagic pathway

Chlamydiae are obligate intracellular pathogens that replicate within a membrane-bound compartment (the inclusion) and are associated with important human diseases, such as trachoma, pneumonia, and atherosclerosis. We have examined the interaction of the host autophagic pathway with Chlamydia trachomatis serovar L2 by using the specific autophagosomal stain monodansylcadaverine, antibodies to autophagosome-associated markers, and traditionally used autophagic inhibitors, particularly 3-methyladenine and amino acids. Chlamydial inclusions did not sequester monodansylcadaverine, suggesting absence of fusion with autophagosomes. Interestingly, exposure of cultures infected for 19 h to 3-methyladenine or single amino acids until the end of infection (44 h) caused various degrees of abnormalities in the inclusion maturation and in the progeny infectivity. Incubation of host cells with chemicals throughout the entire period of infection modulated the growth of Chlamydia even more dramatically. Remarkably, autophagosomal markers MAP-LC3 and calreticulin were redistributed to the inclusion of Chlamydia, a process that appears to be sensitive to 3-methyladenine and some amino acids. The present data indicate the lack of autophagosomal fusion with the inclusion because it was devoid of monodansylcadaverine and no distinct rim of autophagosomal protein-specific staining around the inclusion could be observed. However, high sensitivity of Chlamydia to conditions that could inhibit host autophagic pathway and the close association of MAP-LC3 and calreticulin with the inclusion membrane still suggest a potential role of host autophagy in the pathogenesis of Chlamydia.

Excretion and uptake of cadaverine by CadB and its physiological functions in Escherichia coli

The functions of the putative cadaverine transport protein CadB were studied in Escherichia coli. CadB had both cadaverine uptake activity, dependent on proton motive force, and cadaverine excretion activity, acting as a cadaverine-lysine antiporter. The Km values for uptake and excretion of cadaverine were 20.8 and 303 microM respectively. Both cadaverine uptake and cadaverine-lysine antiporter activities of CadB were functional in cells. Cell growth of a polyamine-requiring mutant was stimulated slightly at neutral pH by the cadaverine uptake activity and greatly at acidic pH by the cadaverine-lysine antiporter activity. At acidic pH, the operon containing cadB and cadA, encoding lysine decarboxylase, was induced in the presence of lysine. This caused neutralization of the extracellular medium and made possible the production of CO(2) and cadaverine and aminopropylcadaverine instead of putrescine and spermidine. The induction of the cadBA operon also generated a proton motive force. When the cadBA operon was not induced, the expression of the speF-potE operon, encoding inducible ornithine decarboxylase and a putrescine-ornithine antiporter, was increased. The results indicate that the cadBA operon plays important roles in cellular regulation at acidic pH.

Characterization of Liposomal Tacrolimus in Lung Surfactant-like Phospholipids and Evaluation of Its Immunosuppressive Activity†

Tacrolimus (FK506) is a hydrophobic immunosuppressive agent that rapidly penetrates the plasmatic membrane and inhibits the signal transduction cascade of T lymphocytes. The objective of this study was the characterization of liposomal FK506 with surfactant-like phospholipids to be administered intratracheally after lung transplantation or in inflammatory lung diseases. We evaluated the optimal incorporation of FK506 in dipalmitoylphosphatidylcholine (DPPC) and DPPC/1-palmitoyl-2-oleoylphosphatidylglycerol (POPG) monolayers and bilayers and the effects of FK506 on the physical properties of DPPC and DPPC/POPG (8:2 w/w) vesicles. In addition, we assessed the immunosuppressive effects of surfactant-like phospholipid vesicles containing different amounts of FK506 on T-cell proliferation and interleukin 2 production. From surface pressure measurements of FK506/DPPC and FK506/DPPC/POPG mixed monolayers, we determined that FK506 was embedded into these monolayers up to an FK506 concentration of about 0.4 mol %. Beyond this concentration, FK506 was not quantitatively incorporated into the monolayer, suggesting possible concentration-dependent aggregation of tacrolimus. The incorporation of FK506 into DPPC monolayers, at concentrations <or= 5 microM, occurred with a partition coefficient of (3.9 +/- 0.3) x 10(3) at the bilayer equivalence pressure. FK506 was incorporated in DPPC bilayers up to an FK506 concentration of about 0.7-1 mol %, which was about double that obtained via the monolayer technique. FK506 hardly affected the transition enthalpy, the T(m), and cooperativity of the phase transition of DPPC and DPPC/POPG vesicles as determined by differential scanning calorimetry and steady-state 1,6-diphenyl-1,3,5-hexatriene anisotropy. Finally, this study provides evidence that liposomal FK506 retains the immunosuppressive efficacy of the drug.

Molecular cloning and characterization of a maize transglutaminase complementary DNA

Two related complementary DNA clones, TGZ15 and TGZ21, encoding active maize transglutaminase (TGase) have been isolated for the first time in plants by molecular cloning (Patent Pending PCT/ES03/00247). Southern and northern blot analyses indicate that the two cDNAs probably corresponded to two different single-copy genes in the maize genome. Northern blot analyses revealed that the transcript is expressed preferentially in young leaves and differentiated embryogenic maize callus. This expression is dependent on light exposure time. TGase activity of the proteins encoded by clones TGZ15 and TGZ21 was detected in bacterial extracts overexpressing them, using two enzymatic assays. TGase activity was significantly higher than that of the empty-phagemid bacterial extracts. As in other TGases, this activity was inhibited by monodansyl cadaverine (MDC), GTP and the absence of exogenous Ca(2+). Likewise, light-stimulated Ca(2+)-dependent TGase activity was detected in thylakoids and grana of maize chloroplast, which was inhibited by MDC, GTP, DIECA and Diuron.

Analyses of Galpha-interacting protein and activator of G-protein-signaling-3 functions in macroautophagy

Macroautophagy or autophagy is an ubiquitous and conserved degradative pathway of cytosolic components, macromolecules or organelles, into the lysosome. By using biochemical and microscopic methods, which allow one to measure the rate of autophagy, the role of two regulators of Gi3 protein activity, activator of G-protein-signaling-3 (AGS3) and Galpha-interacting protein (GAIP), was studied in the control of autophagy in human colon cancer HT-29 cells. In HT-29 cells, autophagy is under the control of the Gi3 protein and, when bound to the GTP, the Galphai3 protein inhibits autophagy, whereas it stimulates autophagy when bound to the GDP. GAIP, which enhances the intrinsic GTPase-activating protein activity of the Galphai3 protein, stimulates autophagy by favoring the GDP-bound form of Galphai3. We showed that GAIP is phosphorylated on its serine 151 and that this phosphorylation is dependent on the presence of amino acids that modulate Raf-1 activity, the kinase upstream of Erk1/2. AGS3, a guanine nucleotide dissociation inhibitor, stimulates autophagy by binding Galphai3 proteins. The intracellular localization of AGS3 (Golgi apparatus and endoplasmic reticulum, two membranes known to be at the origin of autophagosomes) is consistent with its role in autophagy.

Patch-clamp experiments with porins extracted from a marine bacterium (Photobacterium profundum strain SS9) and reconstituted in liposomes

The reconstitution of bacterial porins in liposome bilayers for patch-clamp recording is well established. However, the solutions used in the dehydration, rehydration, and osmotic swelling of the liposomes have been developed for porins from enteric bacteria. Porins from marine bacteria normally function in contact with seawater whose ionic composition and osmotic pressure would appear to be incompatible with the established methods. Here, we show that, contrary to expectation, an established reconstitution and patch-clamp method works well with porins, mainly OmpH and OmpL, extracted from the deep-sea marine bacterium Photobacterium profundum strain SS9 and that seawater can be introduced at a supplementary stage.

Importance of tissue transglutaminase in repair of extracellular matrices and cell death of dermal fibroblasts after exposure to a solarium ultraviolet A source

Investigations were undertaken to study the role of the protein cross-linking enzyme tissue transglutaminase in changes associated with the extracellular matrix and in the cell death of human dermal fibroblasts following exposure to a solarium ultraviolet A source consisting of 98.8% ultraviolet A and 1.2% ultraviolet B. Exposure to nonlethal ultraviolet doses of 60 to 120 kJ per m2 resulted in increased tissue transglutaminase activity when measured either in cell homogenates, "in situ" by incorporation of fluorescein-cadaverine into the extracellular matrix or by changes in the epsilon(gamma-glutamyl) lysine cross-link. This increase in enzyme activity did not require de novo protein synthesis. Incorporation of fluorescein-cadaverine into matrix proteins was accompanied by the cross-linking of fibronectin and tissue transglutaminase into nonreducible high molecular weight polymers. Addition of exogenous tissue transglutaminase to cultured cells mimicking extensive cell leakage of the enzyme resulted in increased extracellular matrix deposition and a decreased rate of matrix turnover. Exposure of cells to 180 kJ per m2 resulted in 40% to 50% cell death with dying cells showing extensive tissue transglutaminase cross-linking of intracellular proteins and increased cross-linking of the surrounding extracellular matrix, the latter probably occurring as a result of cell leakage of tissue transglutaminase. These cells demonstrated negligible caspase activation and DNA fragmentation but maintained their cell morphology. In contrast, exposure of cells to 240 kJ per m2 resulted in increased cell death with caspase activation and some DNA fragmentation. These cells could be partially rescued from death by addition of caspase inhibitors. These data suggest that changes in cross-linking both in the intracellular and extracellular compartments elicited by tissue transglutaminase following exposure to ultraviolet provides a rapid tissue stabilization process following damage, but as such may be a contributory factor to the scarring process that results.

Glutamate-induced increases in transglutaminase activity in primary cultures of astroglial cells

Glutamate exposure of astroglial cells caused ligand-gated channel receptor activation, associated with excitotoxic cell response. We investigated the effects of 24 h glutamate exposure on transglutaminase in astrocytes primary cultures at 7, 14, and 21 days in vitro (DIV). Increases in enzyme activity were observed as a function of cell differentiation stage in glutamate-treated cultures. These effects were significantly reduced when GYKI 52466, an AMPA/KA receptors inhibitor, was added to the culture medium prior to incubation with glutamate. Microscopy observation on transglutaminase-mediated, fluorescent dansylcadaverine incorporation in living cells was consistent with these results. Western blotting analysis with monoclonal antibody showed that glutamate also up-regulated tissue transglutaminase expression, which reached the highest values in 14 DIV cultures. Confocal laser scanning microscopy analysis of immunostained astroglial cells showed a mainly cytoplasmic localisation of the enzyme both in control and treated cultures; nevertheless, counterstaining with the nuclear dye acridine orange demonstrated the presence of tissue transglutaminase also into the nucleus of glutamate-exposed and 21 DIV cells. The increases in enzyme expression and localisation in the nucleus of glutamate-treated astroglial cells may be part of biochemical alterations induced by excitotoxic stimulus.

Polyamines as olfactory stimuli in the goldfish Carassius auratus

Electrophysiological responses of goldfish olfactory receptor neurons (ORNs) and goldfish behavioral responses to polyamines were investigated in vivo. Electro-olfactogram (EOG) recordings indicated that polyamines (putrescine, cadaverine and spermine) are potent olfactory stimuli for goldfish with estimated electrophysiological thresholds of 10(-8)-10(-7) mol l(-1), similar to that for L-arginine, the most stimulatory amino acid. Although thresholds were similar, the magnitude of the EOG responses to intermediate (10(-5)-10(-4) mol l(-1)) and high (10(-3) mol l(-1)) concentrations of polyamines dwarfed the responses to amino acids and related single amine containing compounds (amylamine and butylamine). The EOG responses to 0.1 mmol l(-1) putrescine, cadaverine and spermine were, respectively, 4.2x, 4.3x and 10.3x the response of the standard, 0.1 mmol l(-1) L-arginine. Electrophysiological cross-adaptation experiments indicated that polyamine receptor sites are independent from those to L-amino acids (alanine, arginine, glutamate, lysine, methionine and ornithine), bile salts (sodium taurocholate and taurolithocholate), the single amine containing compounds (amylamine and butylamine) and ATP. Further, the cross-adaptation experiments revealed the existence of independent receptor sites for the different polyamines tested. Pharmacological experiments suggested that polyamine odorant transduction does not primarily involve the cyclic AMP and IP(3) second messenger pathways. Behavioral assays indicated that polyamines are attractants that elicit feeding behavior similar to that elicited by L-amino acids.

Cross-linking of cellular proteins by tissue transglutaminase during necrotic cell death: a mechanism for maintaining tissue integrity

Tissue transglutaminase (tTG) is a Ca(2+)-dependent enzyme which cross-links proteins via epsilon(gamma-glutamyl)lysine bridges. There is increasing evidence that tTG is involved in wound repair and tissue stabilization, as well as in physiological mechanisms leading to cell death. To investigate the role of this enzyme in tissue wounding leading to loss of Ca(2+) homoeostasis, we initially used a model involving electroporation to reproduce cell wounding under controlled conditions. Two cell models were used whereby tTG expression is regulated either by antisense silencing in ECV 304 cells or by using transfected Swiss 3T3 cells in which tTG expression is under the control of the tet regulatory system. Using these cells, loss of Ca(2+) homoeostasis following electroporation led to a tTG-dependent formation of highly cross-linked proteinaceous shells from intracellular proteins. Formation of these structures is dependent on elevated intracellular Ca(2+), but it is independent of intracellular proteases and is near maximal after only 20 min post-wounding. Using labelled primary amines as an indicator of tTG activity within these 'wounded cells', we demonstrate that tTG modifies a wide range of proteins that are present in both the perinuclear and intranuclear spaces. The demonstration of entrapped DNA within these shell structures, which showed limited fragmentation, provides evidence that the high degree of transglutaminase cross-linking results in the prevention of DNA release, which may serve to dampen any subsequent inflammatory response. Comparable observations were shown when monolayers of cells were mechanically wounded by scratching. In this second model of cell wounding, redistribution of tTG activity to the extracellular matrix was also demonstrated, an effect which may serve to stabilize tissues post-trauma, and thus contribute to the maintenance of tissue integrity.

Impairment of the cytotoxic and oxidative activities of 7 beta-hydroxycholesterol and 7-ketocholesterol by esterification with oleate

Atherosclerosis involves inflammatory processes, as well as cytotoxic and oxidative reactions. In atherosclerotic plaques, these phenomena are revealed by the presence of dead cells, oxidized lipids, and oxidative DNA damage, but the molecules triggering these events are still unknown. As 7 beta-hydroxycholesterol and 7-ketocholesterol, which are present at elevated concentrations in atherosclerotic lesions, are strongly cytotoxic and pro-oxidative, their effects were determined on cell death, superoxide anion and nitric oxide production, lipid peroxidation, and oxidative DNA damage. 7-Ketocholesterol- and 7 beta-hydroxycholesterol-induced cell death leads to a loss of mitochondrial potential, to increased permeability to propidium iodide, and to morphological nuclear changes (swelling, fragmentation, and/or condensation of nuclei). These effects are preceded by the formation of cytoplasmic monodansylcadaverine-positive structures and are associated with a rapid enhancement of cells overproducing superoxide anions, a decrease in cells producing nitric oxide, lipid peroxidation (formation of malondialdehyde and 4-hydroxynonenal adducts, low ratio of [unsaturated fatty acids]/[saturated fatty acids]) as well as oxidative DNA damage (8-oxoguanine formation). Noteworthy, none of the cytotoxic features previously observed with 7 beta-hydroxycholesterol and 7-ketocholesterol were noted with cholesterol, 7 beta-hydroxycholesteryl-3-oleate and 7-ketocholesteryl-3-oleate, with the exception of a slight increase in superoxide anion production with 7 beta-hydroxycholesteryl-3-oleate. This finding supports the theory that 7 beta-hydroxycholesterol and 7-ketocholesterol could induce cytotoxic and oxidative processes observed in atherosclerotic lesions and that esterification of these compounds may contribute to reducing atherosclerosis progression.

Time profile of putrescine, cadaverine, indole and skatole in human saliva

The concentrations of putrescine, cadaverine, indole and skatole were determined in the saliva of healthy human volunteers upon waking and at time points during the day. Putrescine was found to be the most abundant of the amines studied, followed by cadaverine then indole. Skatole could not be detected in the saliva samples at any time point. The amines were found in the highest concentrations immediately upon waking (mean concentrations (microg/ml): putrescine 33.0+/-19.0, cadaverine 17.6+/-16.7 and indole 0.4+/-0.4) with a rapid decrease following consumption of breakfast and brushing their teeth (mean concentrations (microg/ml): putrescine 7.0+/-6.4, cadaverine 3.1+/-4.7 and indole 0.04+/-0.09). Putrescine and cadaverine then increased in concentration during the day apart from a decrease post-lunch caused by increased salivary flow and mechanical cleaning due to mastication. An analytical method based on high performance liquid chromatography and fluorescence detection has been developed to quantify amines in human saliva. Sodium fluoride has been shown to be an effective inhibitor of amine formation in saliva at room temperature allowing samples to be collected and kept without requiring cold storage.

Inhibition of Salmonella typhimurium enteropathogenicity by piperidine, a metabolite of the polyamine cadaverine

Piperidine is a 1-ring heterocyclic compound formed from the polyamine cadaverine in the human intestine. Because heterocyclic compounds are routinely used in the promotion of antimicrobial treatment strategies, it was considered whether piperidine could be used against infection with enteric pathogens. This study demonstrates that piperidine treatment prevented the invasion of Salmonella typhimurium into model intestinal epithelium by nearly 95%. In vivo studies also revealed that it increased mouse survival and reduced S. typhimurium translocation into and colonization of various organs and tissues. Initial evaluations demonstrated that piperidine reduced the S. typhimurium-induced polymorphonuclear leukocyte transepithelial migration response in vitro by inhibiting activation of protein kinase C. Piperidine did not affect the ability of S. typhimurium to elicit interleukin-8 secretion by epithelial cells or to activate extracellular-regulated kinase signal transduction pathways. These results show that piperidine does not exhibit paninhibitory activity and suggest that piperidine may be useful in down-regulating active inflammation at mucosal surfaces.

Induction of autophagy causes dramatic changes in the subcellular distribution of GFP-Rab24

Rab GTPases comprises a large family of proteins, with more than 50 gene products localized in distinct subcellular compartments. Rab24 is a member of this family whose function is not presently known. In order to elucidate the role of this protein we have generated a GFP-tagged Rab24 and studied the distribution of this chimera by fluorescence microscopy. GFP-Rab24 showed a perinuclear reticular localization that often encircled the nucleus. This reticular pattern partially overlapped with ER markers, cis-Golgi, and the ER-Golgi intermediate compartment. Surprisingly, when GFP-Rab24-transfected cells were starved to induce autophagy the distribution of the protein changed dramatically. GFP-Rab24 localized in large dots, cup-shaped structures and ring-shaped vesicles. Some of these vesicles were labeled with monodansylcadaverine, a specific autophagosome marker. In the presence of vinblastine, an agent that induces the formation of very large autophagic vesicles, GFP-Rab24 accumulated in the large vacuoles that were also labeled by monodansylcadaverine. Furthermore, Rab24 colocalized with LC3, a mammalian homolog of the yeast protein Apg8/Aut7, an essential gene for autophagy. This is the first report indicating that Rab24 localizes on autophagosomes, suggesting that this Rab protein is involved in the autophagic pathway.

Invasion of HeLa cells by Enterococcus faecalis clinical isolates

We examined the in vitro ability of Enterococcus faecalis clinical isolates to adhere to and to invade HeLa cells, suggested to be a valuable model system to study bacteria-directed endocytosis. Using a variety of compounds that act on eukaryotic cell structures, both microtubules and microfilaments were found to be involved in enterococcal entry into cells. Two distinct modes of interaction were observed: in one, a close proximity of bacteria with the cell membrane was observed, possibly leading to direct engulfment of the bacterial cell. In the other mode, cellular pseudopodal formation seemed to be stimulated by vicinity of bacterial cells; in some cases, such associations involved formation of clathrin-coated-like vesicles before internalizing enterococci. The above-mentioned experimental data together with the use of monodansylcadaverine, amiloride and NH4Cl, all involved in cytosol acidification and inhibition of receptor-mediated endocytosis (RME), led us to conclude that E. faecalis is internalized within HeLa cells by more than one invasion pathway. One, sensitive to amiloride, is most likely a macropinocytic, actin-dependent uptake mechanism, which determines the production of large smooth-membrane vacuoles engulfing enterococci. The other is RME, in which entry is dependent on both microfilament and microtubule structural integrity.

Involvement of tissue transglutaminase in the stabilisation of biomaterial/tissue interfaces important in medical devices

Tissue transglutaminase (tTG) has recently been established as a novel cell surface adhesion protein that binds with high affinity to fibronectin in the pericellular matrix. In this study, we have made use of this property to enhance the biocompatibility of poly(epsilon-caprolactone) (PCL), a biomaterial currently used in bone repair. Poly(epsilon-caprolactone) discs were first coated with fibronectin and then tTG. The surface localisation of the two proteins was confirmed using ELISA and the tTG shown to be active on the surface by incorporation of biotin cadaverine into the fibronectin coating. When human osteoblasts (HOBs) were seeded onto the coated polymer surfaces in serum free medium, the surface coated with fibronectin and then tTG showed an increase in the spreading of the cells as compared to the surface coated with fibronectin alone, when analysed using environmental scanning electron microscopy. The presence of tTG had no effect on HOB cell differentiation when analysed by determining alkaline phosphatase activity. The use of tTG as a novel adhesion protein in this way may therefore have considerable potential in forming a stable tissue/biomaterial interface for application in medical devices.

Polyamine-nucleic acid interactions and the effects on structure in oriented DNA fibers

Fibrous oriented calf thymus DNA containing the natural polyamines spermidine (Spd) and putrescine (Put), and the degradation polyamines cadaverine (Cad) and 1,3-diaminopropane (DAP), have been investigated at different water contents using nuclear magnetic resonance (NMR) methods, fiber X-ray diffraction and gravimetric measurements. When judged by X-ray only the DAP and Spd samples seem to undergo a B-A-form transition at reduced water activity. Solid-state two-dimensional rotor-synchronized magic angle spinning (2D-syncMAS) 31P-NMR, however, shows the A-form to be present also in the Put sample, and it appears that the separation between the amine units of diamines is correlated with the amount of A-form present. In addition, the solid-state NMR data show the polyamine-bound DNA samples to have a significant deviation from the ordinary B-form DNA structure, displaying similar amounts of BI and BII nucleotide conformations. The low water content of the samples suggest that the polyamines themselves act as hydrators of DNA. Water 2H-NMR results are in agreement with this observation. The quadrupolar splittings of the polyamine 2H signals for samples at low water content indicate some preferential spatial orientations of the polyamines in the ordered DNA environment. The polyamines show relatively fast macroscopic diffusion as detected by NMR self-diffusion measurements.

A novel assay to study autophagy: regulation of autophagosome vacuole size by amino acid deprivation

Autophagy is a normal degradative pathway that involves the sequestration of cytoplasmic portions and intracellular organelles in a membrane vacuole called the autophagosome. These vesicles fuse with lysosomes and the sequestered material is degraded. Owing to the complexity of the autophagic pathway and to its inaccessibility to external probes, little is known about the molecular mechanisms that regulate autophagy in higher eukaryotic cells. We used the autofluorescent drug monodansylcadaverine (MDC), a specific autophagolysosome marker to analyze at the molecular level the machinery involved in the autophagic process. We have developed a morphological and biochemical assay to study authophagy in living cells based on the incorporation of MDC. With this assay we observed that the accumulation of MDC was specifically induced by amino acid deprivation and was inhibited by 3-methlyadenine, a classical inhibitor of the autophagic pathway. Additionally, wortmannin, an inhibitor of PI3-kinases that blocks autophagy at an early stage, inhibited the accumulation of MDC in autophagic vacuoles. We also found that treatment of the cells with N-ethylmaleimide (NEM), an agent known to inhibit several vesicular transport events, completely blocked the incorporation of MDC, suggesting that an NEM-sensitive protein is required for the formation of autophagic vacuoles. Conversely, vinblastine, a microtubule depolymerizing agent that induces the accumulation of autophagic vacuoles by preventing their degradation, increased the accumulation of MDC and altered the distribution and size of the autophagic vacuoles. Our results indicate that in the presence of vinblastine very large MDC-vacuoles accumulated mainly under starvation conditions, indicating that the expansion of autophagosomes is upregulated by amino acid deprivation. Furthermore, these MDC-vacuoles were labeled with LC3, one of the mammalian homologues of the yeast protein Apg8/Aut7 that plays an important role in autophagosome formation.

Characterization of tissue transglutaminase in human osteoblast-like cells

Tissue transglutaminase (tTG) is a calcium-dependent and guanosine 5'-triphosphate (GTP) binding enzyme, which catalyzes the post-translational modification of proteins by forming intermolecular epsilon(gamma-glutamyl)lysine cross-links. In this study, human osteoblasts (HOBs) isolated from femoral head trabecular bone and two osteosarcoma cell lines (HOS and MG-63) were studied for their expression and localization of tTG. Quantitative evaluation of transglutaminase (TG) activity determined using the [1,4 14C]-putrescine incorporation assay showed that the enzyme was active in all cell types. However, there was a significantly higher activity in the cell homogenates of MG-63 cells as compared with HOB and HOS cells (p < 0.001). There was no significant difference between the activity of the enzyme in HOB and HOS cells. All three cell types also have a small amount of active TG on their surface as determined by the incorporation of biotinylated cadaverine into fibronectin. Cell surface-related tTG was further shown by preincubation of cells with tTG antibody, which led to inhibition of cell attachment. Western blot analysis clearly indicated that the active TG was tTG and immunocytochemistry showed it be situated in the cytosol of the cells. In situ extracellular enzyme activity also was shown by the cell-mediated incorporation of fluorescein cadaverine into extracellular matrix (ECM) proteins. These results clearly showed that MG-63 cells have high extracellular activity, which colocalized with the ECM protein fibronectin and could be inhibited by the competitive primary amine substrate putrescine. The contribution of tTG to cell surface/matrix interactions and to the stabilization of the ECM of osteoblast cells therefore could by an important factor in the cascade of events leading to bone differentiation and mineralization.

The use of an in vitro submerged keratinocyte model to predict induction of squamous metaplasia

An in vitro submerged keratinocyte model of squamous metaplasia (SQ) in epithelia is being developed to assess the risk associated with exposure to certain environmental agents. Tracheobronchial epithelium (TBE) in vivo can respond to airborne environmental insult by becoming squamous. Epidemiological evidence suggests that cigarette smoke is capable of inducing this change. Retinoic acid has been shown to maintain cells in the mucociliary state. SQ is considered protective and adaptive but potentially preneoplastic if unrelenting and is used histologically in the diagnosis of squamous cell carcinoma. SQ is characterised by upregulation of the expression of transglutaminase I (TGI), TGI activity leading to the formation of isopeptide cross-linked envelopes and replacement of the mucociliary cell type with non-polar squamous cells out of contact with the basal lamina. The ability of the in vitro keratinocyte submerged model to predict the squamous metaplastic response in vivo has been investigated in vitro using TG catalysed fluorescein cadaverine incorporation as a measure of cross-linked envelope formation, Alamar blue conversion to measure viability and Coomassie blue incorporation to measure total cellular protein. The modulation of the squamous condition by retinoic acid (RA), cigarette smoke condensate (CSC) and nicotine has been assessed in keratinocytes cultured in Green's medium. RA inhibited FC incorporation by 95% at 1 x 10(-5) M and simultaneously increased cell viability providing evidence to support its role in the regulation of the non-differentiated state. Nicotine (0-1 mg/ml) induced a dose-dependent increase in viability at 6 days, a response that was accompanied by an increase in FC incorporation at 12 days. CSC (0-5 microg/ml) increased FC incorporation after 12 days. Hence, nicotine modulated the squamous condition by up-regulating TGI activity following a period of hyperactivity. CSC induced a gradual change to the differentiated state and RA served to maintain the cells in an undifferentiated state.

A Sensitive Fluorometric Assay for Tissue Transglutaminase

We have devised a highly sensitive fluorometric well plate assay for tissue transglutaminase that is suitable for multiple kinetic analyses/high-throughput screening of chemical inventories for inhibitors of this enzyme. The procedure measures the rate of fluorescence enhancement (lambda(exc) 260 nm, lambda(em) 538 nm) when 1-N-(carbobenzoxy-l-glutaminylglycyl)-5-N-(5'N'N'-dimethylaminonaphthalenesulfonyl)diamidopentane (glutaminyl substrate) is cross-linked to dansyl cadaverine (amine substrate). The assay procedure can be used to measure the activity of as little as 60 microU of purified guinea pig liver tissue transglutaminase (4.2 ng or 54 fmol of enzyme).

Polyamine and thiol metabolism in Trypanosoma granulosum: similarities with Trypanosoma cruzi

Concentrations of free polyamines were investigated in Trypanosoma granulosum cultured in a semidefined medium containing traces of polyamines. Spermidine content peaked in early logarithmic growth while putrescine was not detectable. Unlike African trypanosomes and Leishmania, spermine was measured at equivalent amounts to spermidine in mid to late logarithmic stage cells. Addition of d,l-alpha-difluoromethylornithine to cultures did not decrease polyamine content nor was ornithine decarboxylase activity detected. In contrast, incubation of parasites with tritiated putrescine showed rapid uptake and subsequent conversion to spermidine and spermine. At late logarithmic growth, parasites contained glutathione (77% of total sulphydryl groups) and ovothiol A as major low molecular mass thiols with glutathionylpolyamine conjugates undetectable. However, the addition of exogenous putrescine elevated trypanothione and glutathionylspermidine content to 48% of total sulphydryl groups. Correspondingly, the addition of exogenous cadaverine increased homotrypanothione content. This first report of polyamines and low molecular mass thiols in Trypanosoma granulosum indicates intriguing similarities with the metabolism of the human pathogen Trypanosoma cruzi.

Protein-glutaminase from Chryseobacterium proteolyticum, an enzyme that deamidates glutaminyl residues in proteins. Purification, characterization and gene cloning

A novel protein-deamidating enzyme was purified to homogeneity from Chryseobacterium proteolyticum and the gene encoding it was cloned. The enzyme is a monomer with a pI of 10.0, a measured M(r) of approximately 20,000 and a calculated M(r) of 19,860. Extensive comparison with Streptoverticillium transglutaminase showed that the protein-deamidating enzyme lacked transglutaminase activity in terms of hydroxamate-formation between benzyloxycarbonyl-Gln-Gly and hydroxylamine, or monodansylcadaverine incorporation into casein. The enzyme deamidated the two glutaminyl residues in the oxidized insulin A chain and deamidated both casein and the oxidized insulin B chain with higher catalytic efficiencies (k(cat)/K(m)) than with short peptides. The enzyme was active against several proteins, including insoluble wheat gluten, but did not deamidate asparaginyl residues in peptides, free glutamine or other amides. The enzyme was therefore named protein-glutaminase (EC 3.5.1). The gene encoding the protein was cloned and, when expressed in Escherichia coli, the protein product had protein-glutaminase activity and cross-reacted with antiserum raised against the purified enzyme. The protein-glutaminase was shown to be expressed as a prepro-protein with a putative signal peptide of 21 amino acids and a pro-sequence of 114 amino acids. The amino-acid sequence had no obvious homology to any published sequence and is therefore a novel protein-glutaminase.

Conformational changes in the nucleosome followed by the selective accessibility of histone glutamines in the transglutaminase reaction: effects of ionic strength

Transglutaminases, the enzymes that catalyze the acyl-transfer reaction between glutamine and primary amines, have been used to introduce probes into proteins in order to perform structural studies using physical techniques. Here we use an original approach in which the increasing accessibility of the glutamines of core histones to TGase is used to monitor the salt-induced conformational changes of the nucleosome. The rationale of this strategy is that the accessibility of a glutamine to transglutaminase depends on the blockage due to the presence of either other histones or DNA. At low ionic strength, only glutamines on the N-terminal tails of H2B and H3 are labeled with monodansylcadaverine when core particles are incubated with transglutaminase. The partial unfolding that occurs when going to higher ionic strength values results in an increase in the number of reactive glutamines up to a maximum value of 16 per nucleosome. Labeling of some residues (e.g., Gln(104) and Gln(112) of H2A) requires the unwinding of DNA and the dissociation of the H2A--H2B dimers. Gln(76) of H3 is labeled in the H3--H4 tetramer only when the H2A--H2B dimers are dissociated. Interestingly, the labeling of Gln(95) of H2B exclusively depends on the unwinding of DNA. The accurate analysis of these results indicates that the ionic-dependent unwinding of the DNA may occur following a two-state model.

Binding sites of the polyamines putrescine, cadaverine, spermidine and spermine on A- and B-DNA located by simulated annealing

Molecular dynamics simulations with simulated annealing are performed on polyamine-DNA systems in order to determine the binding sites of putrescine, cadaverine, spermidine and spermine on A- and B-DNA. The simulations either contain no additional counterions or sufficient Na+ ions, together with the charge on the polyamine, to provide 73% neutralisation of the charges on the DNA phosphates. The stabilisation energies of the complexes indicate that all four polyamines should stabilise A-DNA in preference to B-DNA, which is in agreement with experiment in the case of spermine and spermidine, but not in the case of putrescine or cadaverine. The major groove is the preferred binding site on A-DNA of all the polyamines. Putrescine and cadaverine tend to bind to the sugar-phosphate backbone of B-DNA, whereas spermidine and spermine occupy more varied sites, including binding along the backbone and bridging both the major and minor grooves.

Binding sites of the polyamines putrescine, cadaverine, spermidine and spermine on A- and B-DNA located by simulated annealing

Molecular dynamics simulations with simulated annealing are performed on polyamine-DNA systems in order to determine the binding sites of putrescine, cadaverine, spermidine and spermine on A- and B-DNA. The simulations either contain no additional counterions or sufficient Na+ ions, together with the charge on the polyamine, to provide 73% neutralisation of the charges on the DNA phosphates. The stabilisation energies of the complexes indicate that all four polyamines should stabilise A-DNA in preference to B-DNA, which is in agreement with experiment in the case of spermine and spermidine, but not in the case of putrescine or cadaverine. The major groove is the preferred binding site on A-DNA of all the polyamines. Putrescine and cadaverine tend to bind to the sugar-phosphate backbone of B-DNA, whereas spermidine and spermine occupy more varied sites, including binding along the backbone and bridging both the major and minor grooves.

Inward potassium channel in guard cells as a target for polyamine regulation of stomatal movements

A number of studies show that environmental stress conditions such as drought, high salt, and air pollutants increase polyamine levels in plant cells. However, little is understood about the physiological function of elevated polyamine levels. We report here that polyamines regulate the voltage-dependent inward K(+) channel in the plasma membrane of guard cells and modulate stomatal aperture, a plant "sensor" to environmental changes. All natural polyamines, including spermidine, spermine, cadaverine, and putrescine, strongly inhibited opening and induced closure of stomata. Whole-cell patch-clamp analysis showed that intracellular application of polyamines inhibited the inward K(+) current across the plasma membrane of guard cells. Single-channel recording analysis indicated that polyamine regulation of the K(+) channel requires unknown cytoplasmic factors. In an effort to identify the target channel at the molecular level, we found that spermidine inhibited the inward K(+) current carried by KAT1 channel that was functionally expressed in a plant cell model. These findings suggest that polyamines target KAT1-like inward K(+) channels in guard cells and modulate stomatal movements, providing a link between stress conditions, polyamine levels, and stomatal regulation.

Binding of a fluorescent dansylcadaverine-substance P analogue to negatively charged phospholipid membranes

We have investigated the binding of a new dansylcadaverine derivative of substance P (DNC-SP) with negatively charged small unilamellar vesicles composed of a mixture of phosphatidylcholine (PC) and either phosphatidylglycerol (PG) or phosphatidylserine (PS) using fluorescence spectroscopic techniques. The changes in fluorescence properties were used to obtain association isotherms at variable membrane negative charges and at different ionic strengths. The experimental association isotherms were analyzed using two binding approaches: (i) the Langmuir adsorption isotherm and the partition equilibrium model, that neglect the activity coefficients; and (ii) the partition equilibrium model combined with the Gouy-Chapman formalism that considers electrostatic effects. A consistent quantitative analysis of each DNC-SP binding curve at different lipid composition was achieved by means of the Gouy-Chapman approach using a peptide effective interfacial charge (v) value of (0.95 +/- 0.02), which is lower than the physical charge of the peptide. For PC/PG membranes, the partition equilibrium constant were 7.8 x 10(3) M(-1) (9/1, mol/mol) and 6.9 x 10(3) M(-1) (7/3, mol/mol), whereas for PC/PS membranes an average value of 6.8 x 10(3) M(-1) was estimated. These partition equilibrium constants were similar to those obtained for the interaction of DNC-SP with neutral PC membranes (4.9 x 10(3) M(-1)), as theoretically expected. We demonstrate that the v parameter is a determinant factor to obtain a unique value of the binding constant independently of the surface charge density of the vesicles. Also, the potential of fluorescent dansylated SP analogue in studies involving interactions with cell membranes is discussed.

Induction of tissue transglutaminase in the trabecular meshwork by TGF-beta1 and TGF-beta2

PURPOSE

To study whether human trabecular meshwork (HTM) cells are capable of expressing and secreting tissue transglutaminase (tTgase), an enzyme cross-linking extracellular matrix (ECM) proteins, and whether tTgase and synthesis of cross-linked fibronectin are increased after treatment of HTM cells with transforming growth factor (TGF)-beta1 or -beta2.

METHODS

Anterior segments of six normal human eyes were stained with antibodies to tTgase. Tissues from three eyes were analyzed for tTgase using Western blot analysis. Monolayer cultures of HTM cells from eyes of five human donors were treated with 1.0 ng/ml TGF-beta1, -beta2, or 5 X 10(-7) M dexamethasone (DEX) for 12 to 96 hours. Induction of tTgase was investigated by Western and Northern blot analysis. External tTgase activity was measured by the ability to form polymerized fibronectin and the incorporation of biotinylated cadaverine into fibronectin.

RESULTS

Labeling for tTgase was observed throughout the entire HTM. Cultured HTM cells expressed tTgase intra- and extracellularly. Treatment of cultured HTM cells with TGF-beta1 and -beta2 increased the tTgase mRNA and protein levels, whereas DEX had no effect. TGF-beta-treated HTM cells showed a significant increase in polymerized and unpolymerized fibronectin. Incorporation of biotinylated cadaverine was markedly increased when HTM cells were treated with TGF-beta for 24 hours before seeding.

CONCLUSIONS

The enzyme tTgase is expressed in the HTM and is inducible by TGF-beta1 or -beta2 in cultured HTM cells. Extracellular tTgase is able to polymerize fibronectin. Increased levels of TGF-beta2 in the aqueous humor may lead to an increase of tTgase expression and activity in the HTM, causing an increase of irreversibly cross-linked ECM proteins. This mechanism might play a role for the increased outflow resistance seen in glaucomatous eyes.

The lysosomotropic agent monodansylcadaverine also acts as a solvent polarity probe

The autofluorescent substance monodansylcadaverine has recently been reported as a specific in vivo marker for autophagic vacuoles. However, the mechanism for this specific labeling remained unclear. Our results reveal that the common model of ion trapping in acidic compartments cannot completely account for the observed autophagic vacuole staining. Because autophagic vacuoles are characterized by myelin-like membrane inclusions, we tested whether this lipid-rich environment is responsible for the staining properties of monodansylcadaverine. In in vitro experiments using either liposomes or solvents of different polarity, monodansylcadaverine showed an increased relative fluorescence intensity in a hydrophobic environment as well as a Stokes shift dependent on the solvent polarity. To test the effect of autophagic vacuoles or autophagic vacuole lipids on monodansylcadaverine fluorescence, we isolated autophagic vacuoles and purified autophagic vacuole lipids depleted of proteins. Entire autophagic vacuoles and autophagic vacuole lipids had the same effect on monodansylcadaverine fluorescence properties, suggesting lipids as the responsible component. Our results suggest that the in vivo fluorescence properties of monodansylcadaverine do not depend exclusively on accumulation in acidic compartments by ion trapping but also on an effective interaction of this molecule with autophagic vacuole membrane lipids. (J Histochem Cytochem 48:251-258, 2000)