Antisense suppression of the small chloroplast protein CP12 in tobacco: a transcriptional viewpoint

The chloroplast protein CP12 forms a multi-enzyme complex with the Calvin-Benson cycle enzymes phosphoribulokinase (PRK) and NADP-glyceraldehyde-3-phosphate dehydrogenase (GAPDH). PRK and GAPDH are inactivated when present in this complex, a process shown in vitro to be dependent upon oxidized CP12. Recently we reported on the importance of CP12 in vivo to higher plant metabolism using antisense suppression of CP12 in tobacco (Nicotiana tabacum). Our results indicated that while only minor changes in photosynthetic carbon fixation and in PRK and GAPDH activities were observed, striking changes in growth rates and morphology were seen. In this article we present data on the transcriptional changes observed in one of the antisense lines and we discuss the major findings in light of the metabolic phenotype described.

Surface display of Aeromonas hydrophila GAPDH in attenuated Vibrio anguillarum to develop a Noval multivalent vector vaccine

Displaying foreign antigens on the surface of attenuated or avirulent bacteria is an important strategy to develop live multivalent vector vaccines. In our previous work, several efficient surface display systems have been established based on outer membrane anchoring elements, which could successfully display heterologous proteins in attenuated Vibrio anguillarum. In this work, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) from pathogenic Aeromonas hydrophila LSA34 was fused to seven display systems and introduced into attenuated V. anguillarum strain MVAV6203 (AV) to get seven GAPDH-display strains. The strain AV/pN-gapA showed the best display efficacy of GAPDH and was tested as the multivalent vaccine candidate. Further immune protection evaluation of AV/pN-gapA in turbot (Scophtalmus maximus) demonstrated that the attenuated V. anguillarum with surface-displayed GAPDH of A. hydrophila LSA34 effectively protected turbot from the infections of A. hydrophila and V. anguillarum and showed potential value for further multivalent vaccine development.

Monilinia species causing brown rot of peach in China

In this study, 145 peaches and nectarines displaying typical brown rot symptoms were collected from multiple provinces in China. A subsample of 26 single-spore isolates were characterized phylogenetically and morphologically to ascertain species. Phylogenetic analysis of internal transcribed spacer (ITS) regions 1 and 2, glyceraldehyde-3-phosphate dehydrogenase (G3PDH), β-tubulin (TUB2) revealed the presence of three distinct Monilinia species. These species included Monilinia fructicola, Monilia mumecola, and a previously undescribed species designated Monilia yunnanensis sp. nov. While M. fructicola is a well-documented pathogen of Prunus persica in China, M. mumecola had primarily only been isolated from mume fruit in Japan. Koch's postulates for M. mumecola and M. yunnanensis were fulfilled confirming pathogenicity of the two species on peach. Phylogenetic analysis of ITS, G3PDH, and TUB2 sequences indicated that M. yunnanensis is most closely related to M. fructigena, a species widely prevalent in Europe. Interestingly, there were considerable differences in the exon/intron structure of the cytochrome b (Cyt b) gene between the two species. Morphological characteristics, including spore size, colony morphology, lesion growth rate, and sporulation, support the phylogenetic evidence suggesting the designation of M. yunnanensis as a new species. A new multiplex PCR method was developed to facilitate the detection of M. yunnanensis and differentiation of Monilinia spp. causing brown rot of peach in China.

GLUT1 enhances mTOR activity independently of TSC2 and AMPK

Enhanced GLUT1 expression in mesangial cells plays an important role in the development of diabetic nephropathy by stimulating signaling through several pathways resulting in increased glomerular matrix accumulation. Similarly, enhanced mammalian target of rapamycin (mTOR) activation has been implicated in mesangial matrix expansion and glomerular hypertrophy in diabetes. We sought to examine whether enhanced GLUT1 expression increased mTOR activity and, if so, to identify the mechanism. We found that levels of GLUT1 expression and mTOR activation, as evidenced by S6 kinase (S6K) and 4E-BP-1 phosphorylation, changed in tandem in cell lines exposed to elevated levels of extracellular glucose. We then showed that increased GLUT1 expression enhanced S6K phosphorylation by 1.7- to 2.9-fold in cultured mesangial cells and in glomeruli from GLUT1 transgenic mice. Treatment with the mTOR inhibitor, rapamycin, eliminated the GLUT1 effect on S6K phosphorylation. In cells lacking functional tuberous sclerosis complex (TSC) 2, GLUT1 effects on mTOR activity persisted, indicating that GLUT1 effects were not mediated by TSC. Similarly, AMP kinase activity was not altered by enhanced GLUT1 expression. Conversely, enhanced GLUT1 expression led to a 2.4-fold increase in binding of mTOR to its activator, Rheb, and a commensurate 2.1-fold decrease in binding of Rheb to glyceraldehyde 3-phosphate dehydrogenase (GAPDH) consistent with mediation of GLUT1 effects by a metabolic effect on GAPDH. Thus, GLUT1 expression appears to augment mesangial cell growth and matrix protein accumulation via effects on glycolysis and decreased GAPDH interaction with Rheb.

The S-nitrosylation of glyceraldehyde-3-phosphate dehydrogenase 2 is reduced by interaction with glutathione peroxidase 3 in Saccharomyces cerevisiae

Glutathione peroxidases (Gpxs) are the key anti-oxidant enzymes found in Saccharomyces cerevisiae. Among the three Gpx isoforms, glutathione peroxidase 3 (Gpx3) is ubiquitously expressed and modulates the activities of redox-sensitive thiol proteins involved in various biological reactions. By using a proteomic approach, glyceraldehyde-3-phosphate dehydrogenase 2 (GAPDH2; EC 1.2.1.12) was found as a candidate protein for interaction with Gpx3. GAPDH, a key enzyme in glycolysis, is a multi-functional protein with multiple intracellular localizations and diverse activities. To validate the interaction between Gpx3 and GAPDH2, immunoprecipitation and a pull-down assay were carried out. The results clearly showed that GAPDH2 interacts with Gpx3 through its carboxyl-terminal domain both in vitro and in vivo. Additionally, Gpx3 helps to reduce the S-nitrosylation of GAPDH upon nitric oxide (NO) stress; this subsequently increases cellular viability. On the basis of our findings, we suggest that Gpx3 protects GAPDH from NO stress and thereby contributes to the maintenance of homeostasis during exposure to NO stress.

Expression, purification and kinetic characterization of His-tagged glyceraldehyde-3-phosphate dehydrogenase from Trypanosoma cruzi

Trypanosomes are flagellated protozoa responsible for serious parasitic diseases that have been classified by the World Health Organization as tropical sicknesses of major importance. One important drug target receiving considerable attention is the enzyme glyceraldehyde-3-phosphate dehydrogenase from the protozoan parasite Trypanosoma cruzi, the causative agent of Chagas disease (T. cruzi Glyceraldehyde-3-phosphate dehydrogenase (TcGAPDH); EC 1.2.1.12). TcGAPDH is a key enzyme in the glycolytic pathway of T. cruzi and catalyzes the oxidative phosphorylation of D-glyceraldehyde-3-phosphate (G3P) to 1,3-bisphosphoglycerate (1,3-BPG) coupled to the reduction of oxidized nicotinamide adenine dinucleotide, (NAD(+)) to NADH, the reduced form. Herein, we describe the cloning of the T. cruzi gene for TcGAPDH into the pET-28a(+) vector, its expression as a tagged protein in Escherichia coli, purification and kinetic characterization. The His(6)-tagged TcGAPDH was purified by affinity chromatography. Enzyme activity assays for the recombinant His(6)-TcGAPDH were carried out spectrophotometrically to determine the kinetic parameters. The apparent Michaelis-Menten constant (K(M)(app)) determined for D-glyceraldehyde-3-phosphate and NAD(+) were 352±21 and 272±25 μM, respectively, which were consistent with the values for the untagged enzyme reported in the literature. We have demonstrated by the use of Isothermal Titration Calorimetry (ITC) that this vector modification resulted in activity preserved for a higher period. We also report here the use of response surface methodology (RSM) to determine the region of optimal conditions for enzyme activity. A quadratic model was developed by RSM to describe the enzyme activity in terms of pH and temperature as independent variables. According to the RMS contour plots and variance analysis, the maximum enzyme activity was at 29.1°C and pH 8.6. Above 37°C, the enzyme activity starts to fall, which may be related to previous reports that the quaternary structure begins a process of disassembly.

Brucella abortus L7/L12 recombinant protein induces strong Th1 response in acute brucellosis patients

BACKGROUND

Because of high morbidity of the brucellosis in humans and the potential use of the microorganism as an agent of biologic warfare, protection of effective vaccines and specific diagnostic reagents become necessary to eradicate brucellosis.

OBJECTIVE

In this study we aimed to investigate the cytokine responses and changes in peripheral blood lymphocyte subgroups of acute brucellosis patients in response to L7/L12 and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) recombinant proteins derived from Brucella abortus.

METHODS

levels of IFN-γ, IL-4 and IL-10 secreted from PBMCs of 25 acute brucellosis patients and 15 healthy controls, stimulated with Phytohemagglutinin (PHA), L7/L12 or GAPDH were measured by ELISA. Furthermore alterations in lymphocyte subgroups in response to these Brucella antigens were determined by flow cytometry.

RESULTS

Extracellular IFN-γ levels were found to be elevated after stimulation with L7/L12 in patients with acute brucellosis, whereas no significant changes were found in IL-4 and IL-10 levels. Similar data was also obtained with GAPDH, but the stimulation of IFN-γ production was not observed in all patients and was not as strong as that observed for L7/L12. Moreover, when the distribution of lymphocytes subgroups (CD3+, CD3+ CD4+, CD3+ CD8+, CD4+ CD25+, CD3+ CD69+ and CD3+ CD152+) was evaluated, it was found that the stimulation with L7/L12 and GAPDH only led to an increase in the percentage of CD3+ CD69+ lymphocytes.

CONCLUSION

These data indicate that Brucella abortus L7/L12 or GAPDH induce a Th1 type immune response in acute brucellosis patients. Additionally, these recombinant proteins, especially L7/L12, may be used in new vaccine preparations and diagnostic tests.

TRPV4 channels augment macrophage activation and ventilator-induced lung injury

We have previously implicated transient receptor potential vanilloid 4 (TRPV4) channels and alveolar macrophages in initiating the permeability increase in response to high peak inflation pressure (PIP) ventilation. Alveolar macrophages were harvested from TRPV4(-/-) and TRPV4(+/+) mice and instilled in the lungs of mice of the opposite genotype. Filtration coefficients (K(f)) measured in isolated perfused lungs after ventilation with successive 30-min periods of 9, 25, and 35 cmH(2)O PIP did not significantly increase in lungs from TRPV4(-/-) mice but increased >2.2-fold in TRPV4(+/+) lungs, TRPV4(+/+) lungs instilled with TRPV4(-/-) macrophages, and TRPV4(-/-) lungs instilled with TRPV4(+/+) macrophages after ventilation with 35 cmH(2)O PIP. Activation of TRPV4 with 4-alpha-phorbol didecanoate (4alphaPDD) significantly increased intracellular calcium, superoxide, and nitric oxide production in TRPV4(+/+) macrophages but not TRPV4(-/-) macrophages. Cross-sectional areas increased nearly 3-fold in TRPV4(+/+) macrophages compared with TRPV4(-/-) macrophages after 4alphaPDD. Immunohistochemistry staining of lung tissue for nitrotyrosine revealed increased amounts in high PIP ventilated TRPV4(+/+) lungs compared with low PIP ventilated TRPV4(+/+) or high PIP ventilated TRPV4(-/-) lungs. Thus TRPV4(+/+) macrophages restored susceptibility of TRPV4(-/-) lungs to mechanical injury. A TRPV4 agonist increased intracellular calcium and reactive oxygen and nitrogen species in harvested TRPV4(+/+) macrophages but not TRPV4(-/-) macrophages. K(f) increases correlated with tissue nitrotyrosine, a marker of peroxynitrite production.

Redox and electrophilic properties of vapor- and particle-phase components of ambient aerosols

Particulate matter (PM) has been the primary focus of studies aiming to understand the relationship between the chemical properties of ambient aerosols and adverse health effects. Size and chemical composition of PM have been linked to their oxidative capacity which has been postulated to promote or exacerbate pulmonary and cardiovascular diseases. But in the last few years, new studies have suggested that volatile and semi-volatile components may also contribute to many adverse health effects. The objectives of this study were: (i) assess for the first time the redox and electrophilic potential of vapor-phase components of ambient aerosols and (ii) evaluate the relative contributions of particle- and vapor-fractions to the hazard of a given aerosol. To achieve these objectives vapor- and particle-phase samples collected in Riverside (CA) were subjected to three chemical assays to determine their redox and electrophilic capacities. The results indicate that redox active components are mainly associated with the particle-phase, while electrophilic compounds are found primarily in the vapor-phase. Vapor-phase organic extracts were also capable of inducing the stress responding protein, heme-oxygenase-1 (HO-1), in RAW264.7 murine macrophages. These results demonstrate the importance of volatile components in the overall oxidative and electrophilic capacity of aerosols, and point out the need for inclusion of vapors in future health and risk assessment studies.

Plastidial glyceraldehyde-3-phosphate dehydrogenase deficiency leads to altered root development and affects the sugar and amino acid balance in Arabidopsis

Glycolysis is a central metabolic pathway that, in plants, occurs in both the cytosol and the plastids. The glycolytic glyceraldehyde-3-phosphate dehydrogenase (GAPDH) catalyzes the conversion of glyceraldehyde-3-phosphate to 1,3-bisphosphoglycerate with concomitant reduction of NAD(+) to NADH. Both cytosolic (GAPCs) and plastidial (GAPCps) GAPDH activities have been described. However, the in vivo functions of the plastidial isoforms remain unresolved. In this work, we have identified two Arabidopsis (Arabidopsis thaliana) chloroplast/plastid-localized GAPDH isoforms (GAPCp1 and GAPCp2). gapcp double mutants display a drastic phenotype of arrested root development, dwarfism, and sterility. In spite of their low gene expression level as compared with other GAPDHs, GAPCp down-regulation leads to altered gene expression and to drastic changes in the sugar and amino acid balance of the plant. We demonstrate that GAPCps are important for the synthesis of serine in roots. Serine supplementation to the growth medium rescues root developmental arrest and restores normal levels of carbohydrates and sugar biosynthetic activities in gapcp double mutants. We provide evidence that the phosphorylated pathway of Ser biosynthesis plays an important role in supplying serine to roots. Overall, these studies provide insights into the in vivo functions of the GAPCps in plants. Our results emphasize the importance of the plastidial glycolytic pathway, and specifically of GAPCps, in plant primary metabolism.

NAD+-dependent post-translational modification of Escherichia coli glyceraldehyde-3-phosphate dehydrogenase

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a multifunctional housekeeping protein reported to be a target of several covalent modifications in many organisms. In a previous study, enterohemorrhagic (EHEC) and enteropathogenic (EPEC) Escherichia coli strains were shown to secrete GAPDH and the protein to bind human plasminogen and fibrinogen. Here we report that GAPDH of these pathogens is ADP-ribosylated either in the cytoplasm or in the extracellular medium. GAPDH catalyzes its own modification, which involves Cys-149 at the active site. ADP-ribosylation of extracellular GAPDH may play an important role in the host-pathogen interaction, as also proposed in other pathogens.

The glyceraldehyde-3-phosphate dehydrogenase and the small GTPase Rab 2 are crucial for Brucella replication

The intracellular pathogen Brucella abortus survives and replicates inside host cells within an endoplasmic reticulum (ER)-derived replicative organelle named the “Brucella-containing vacuole” (BCV). Here, we developed a subcellular fractionation method to isolate BCVs and characterize for the first time the protein composition of its replicative niche. After identification of BCV membrane proteins by 2 dimensional (2D) gel electrophoresis and mass spectrometry, we focused on two eukaryotic proteins: the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the small GTPase Rab 2 recruited to the vacuolar membrane of Brucella. These proteins were previously described to localize on vesicular and tubular clusters (VTC) and to regulate the VTC membrane traffic between the endoplasmic reticulum (ER) and the Golgi. Inhibition of either GAPDH or Rab 2 expression by small interfering RNA strongly inhibited B. abortus replication. Consistent with this result, inhibition of other partners of GAPDH and Rab 2, such as COPI and PKC ι, reduced B. abortus replication. Furthermore, blockage of Rab 2 GTPase in a GDP-locked form also inhibited B. abortus replication. Bacteria did not fuse with the ER and instead remained in lysosomal-associated membrane vacuoles. These results reveal an essential role for GAPDH and the small GTPase Rab 2 in B. abortus virulence within host cells.

A key determinant for intracellular pathogenic bacteria to ensure their virulence within host cells is their ability to bypass the endocytic pathway and to reach a safe replication niche. Brucella bacteria reach the endoplasmic reticulum (ER) to create their replicating niche called the Brucella-containing vacuole (BCV). The ER is a suitable strategic place for pathogenic Brucella. Bacteria can be hidden from host cell defences to persist within the host, and can take advantage of the membrane reservoir delivered by the ER to replicate. Interactions between BCV and the ER lead to the presence of ER proteins on the BCV membrane. Currently, no other proteins (eukaryotic or prokaryotic) have yet been associated with the BCV membrane. Here we show that non-ER related proteins are also present on the BCV membrane, in particular, the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the small GTPase Rab 2 known to be located on secretory vesicles that traffic between the ER and the Golgi apparatus. GAPDH and the small GTPase Rab 2 are involved in Brucella replication at late post-infection. Similarly, integrity of secretory vesicle trafficking is also necessary for Brucella replication. Here, we show that recruitment of the two eukaryotic proteins GAPDH and Rab 2 on BCV membranes is necessary for the establishment of the replicative niche by sustaining interactions between the ER and secretory membrane vesicles.

Hydrolase regulates NAD+ metabolites and modulates cellular redox

Although the classical redox functions of co-enzyme NAD(+) are firmly established in metabolism, there are numerous enzymes that catalyze cleavage of NAD(+) to yield free ADP-ribose (ADPr) or related metabolites, whose functions remain largely unknown. Here we show that the Nudix (nucleoside diphosphate linked to another moiety X) hydrolase Ysa1 from Saccharomyces cerevisiae is a major regulator of cellular ADPr and O-acetyl-ADP-ribose (OAADPr). OAADPr is the direct product of NAD(+)-dependent protein deacetylases (sirtuins) and is readily converted to ADPr. Ysa1 cleaves ADPr/OAADPr into ribose phosphate/acetyl-ribose phosphate and AMP. In cells lacking Ysa1 (Deltaysa1), ADPr and OAADPr levels increased approximately 50%, with a corresponding decrease in AMP. Strikingly, Deltaysa1 cells display higher resistance to exogenous reactive oxygen species (ROS) and 40% lower basal levels of endogenous ROS, compared with wild type. The biochemical basis for these differences in ROS-related phenotypes was investigated, and the results provide evidence that increased ADPr/OAADPr levels protect cells via the following two pathways: (i) lower ROS production through inhibition of complex I of the mitochondrial electron transport chain, and (ii) generation of higher levels of NADPH to suppress ROS damage. The latter occurs through diverting glucose into the pentose phosphate pathway by ADPr inhibition of glyceraldehyde-3-phosphate dehydrogenase, a central enzyme of glycolysis.

Interfering with glycolysis causes Sir2-dependent hyper-recombination of Saccharomyces cerevisiae plasmids

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key metabolic regulator implicated in a variety of cellular processes. It functions as a glycolytic enzyme, a protein kinase, and a metabolic switch under oxidative stress. Its enzymatic inactivation causes a major shift in the primary carbohydrate flux. Furthermore, the protein is implicated in regulating transcription, ER-to-Golgi transport, and apoptosis. We found that Saccharomyces cerevisiae cells null for all GAPDH paralogues (Tdh1, Tdh2, and Tdh3) survived the counter-selection of a GAPDH-encoding plasmid when the NAD(+) metabolizing deacetylase Sir2 was overexpressed. This phenotype required a fully functional copy of SIR2 and resulted from hyper-recombination between S. cerevisiae plasmids. In the wild-type background, GAPDH overexpression increased the plasmid recombination rate in a growth-condition dependent manner. We conclude that GAPDH influences yeast episome stability via Sir2 and propose a model for the interplay of Sir2, GAPDH, and the glycolytic flux.

A novel method for isolation of human lung T cells from lung resection tissue reveals increased expression of GAPDH and CXCR6

Lung T lymphocytes are important in pulmonary immunity and inflammation. It has been difficult to study these cells due to contamination with other cell types, mainly alveolar macrophages. We have developed a novel method for isolating lung T cells from lung resection tissue, using a combination of approaches. Firstly the lung tissue was finely chopped and filtered through a nylon mesh. Lymphocytic cells were enriched by Percoll density centrifugation and the T cells purified using human CD3 microbeads, resulting in 90.5%+/-1.9% (n=11) pure lymphocytes. The T cell yield from the crude cell preparation was 10.8+/-2.1% and viability, calculated using propidium iodide (PI) staining and trypan blue, was typically over 95%. The purification process did not affect expression of CD69 or CD103, nor was there a difference in the proportion of CD4 and CD8 cells between the starting population and the purified cells. Microarray analysis and real time RT-PCR revealed upregulation of GAPDH and CXCR6 of the lung T cells as compared to blood-derived T cells. This technique highly enriches lung T cells to allow detailed investigation of the biology of these cells.

Regulation of plant cytosolic glyceraldehyde 3-phosphate dehydrogenase isoforms by thiol modifications

Cytosolic NAD-dependent glyceraldehyde 3-P dehydrogenase (GAPDH; GapC; EC 1.2.1.12) catalyzes the oxidation of triose phosphates during glycolysis in all organisms, but additional functions of the protein has been put forward. Because of its reactive cysteine residue in the active site, it is susceptible to protein modification and oxidation. The addition of GSSG, and much more efficiently of S-nitrosoglutathione, was shown to inactivate the enzymes from Arabidopsis thaliana (isoforms GapC1 and 2), spinach, yeast and rabbit muscle. Inactivation was fully or at least partially reversible upon addition of DTT. The incorporation of glutathione upon formation of a mixed disulfide could be shown using biotinylated glutathione ethyl ester. Furthermore, using the biotin-switch assay, nitrosylated thiol groups could be shown to occur after treatment with nitric oxide donors. Using mass spectrometry and mutant proteins with one cysteine lacking, both cysteines (Cys-155 and Cys-159) were found to occur as glutathionylated and as nitrosylated forms. In preliminary experiments, it was shown that both GapC1 and GapC2 can bind to a partial gene sequence of the NADP-dependent malate dehydrogenase (EC 1.2.1.37; At5g58330). Transiently expressed GapC-green fluorescent protein fusion proteins were localized to the nucleus in A. thaliana protoplasts. As nuclear localization and DNA binding of GAPDH had been shown in numerous systems to occur upon stress, we assume that such mechanism might be part of the signaling pathway to induce increased malate-valve capacity and possibly other protective systems upon overreduction and initial formation of reactive oxygen and nitrogen species as well as to decrease and protect metabolism at the same time by modification of essential cysteine residues.

Tomato bushy stunt virus co-opts the RNA-binding function of a host metabolic enzyme for viral genomic RNA synthesis

Tomato bushy stunt virus (TBSV), a plus-stranded [(+)] RNA plant virus, incorporates the host metabolic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) into the viral replicase complex. Here, we show that, during TBSV replication in yeast, the yeast GAPDH Tdh2p moves from the cytosol to the peroxisomal membrane surface, the site of viral RNA synthesis. In yeast cells lacking Tdh2p, decreasing the levels of its functionally redundant homolog Tdh3p inhibited TBSV replication and resulted in equivalent levels of (+) and minus-stranded [(-)] viral RNA, in contrast to the hallmark excess of (+)RNA. Tdh2p specifically bound an AU pentamer sequence in the (-)RNA, suggesting that GAPDH promotes asymmetric RNA synthesis by selectively retaining the (-)RNA template in the replicase complex. Downregulation of GAPDH in a natural plant host decreased TBSV genomic RNA accumulation. Thus, TBSV co-opts the RNA-binding function of a metabolic protein, helping convert the host cell into a viral factory.

Purification and characterization of glyceraldehyde-3-phosphate dehydrogenase from European pilchard Sardina pilchardus

The NAD+-dependent cytosolic glyceralehyde-3-phosphate dehydrogenase (GAPDH; EC 1.2.1.12) was purified from the skeletal muscle of European pilchard Sardina pilchardus and its physicochemical and kinetic properties were investigated. The purification method consisted of two steps, ammonium sulfate fractionation followed by Blue Sepharose CL-6B chromatography, resulting in an approximately 78-fold increase in specific activity and a final yield of approximately 25%. The Michaelis constants (K(m)) for NAD+ and D-glyceraldehyde-3-phosphate were 92.0 microM and 73.4 microM, respectively. The maximal velocity (V(max)) of the purified enzyme was estimated to be 37.6 U/mg. Under the assay conditions, the optimum pH and temperature were 8.0 and 30 degrees C. The molecular weight of the purified enzyme was 37 kDa determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Non-denaturing polyacrylamide gels yielding a molecular weight of 154 kDa suggested that the enzyme is a homotetramer. Polyclonal antibodies against the purified enzyme were used to recognize the enzyme in different sardine tissues by Western blot analysis. The isoelectric point, obtained by an isoelectric focusing system in polyacrylamide slab gels, revealed only one GAPDH isoform (pI 7.9).

A mutation in human VAP-B–MSP domain, present in ALS patients, affects the interaction with other cellular proteins

Amyotrophic Lateral Sclerosis (ALS) is the most common adult-onset Motor Neuron Disease (MND), characterized by motor neurons death in the cortex, brainstem and spinal cord. Ten loci linked to Familial ALS have been mapped. ALS8 is caused by a substitution of a proline by a serine in the Vesicle-Associated Membrane Protein-Associated protein-B/C (VAP-B/C). VAP-B belongs to a highly conserved family of proteins implicated in Endoplasmic Reticulum-Golgi and intra-Golgi transport and microtubules stabilization. Previous studies demonstrated that the P56S mutation disrupts the subcellular localization of VAP-B and that this position would be essential for Unfolded Protein Response (UPR) induced by VAP-B. In the present work we expressed and purified recombinant wild-type and P56S mutant VAP-B-MSP domain for the analysis of its interactions with other cellular proteins. Our findings suggest that the P56S mutation may lead to a less stable interaction of this endoplasmic reticulum protein with at least two other proteins: tubulin and GAPDH. These two proteins have been previously related to other forms of neurodegenerative diseases and are potential key points to understand ALS8 pathogenesis and other forms of MND. Understanding the role of these protein interactions may help the treatment of this devastating disease in the future.

Pyridine nucleotide redox abnormalities in diabetes

In addition to hyperglycemia, diabetes is associated with increased levels of circulating free fatty acids, lactate, and branched chain amino acids, all of which produce an excessive reduced form of pyridine nucleotides NADH (reductive stress) in the cytosol and mitochondria. Our studies suggest that cytosolic NADH reductive stress under high glucose is largely caused by increased flux of glucose through polyol (sorbitol) pathway consisting of aldose reductase and sorbitol dehydrogenase. Inhibition of aldose reductase that blocks the polyol pathway has been shown to ameliorate diabetic neuropathy in humans. Cytosolic NADH reductive stress is predicted to increase production of diglycerides, reactive oxygen species, and methylglyoxal. Recent studies indicate that increasing NADH affects gene expression through the NADH activating transcriptional co-repressor, C-terminal binding protein (CtBP). In addition, it has been shown that the NADH utilizing enzyme, glyceraldehyde-3-phosphate dehydrogenase, participates as transcriptional regulator. These findings testify to the importance of NADH redox balance in cell biology and pathogenesis of diabetes and its complications. For example, through CtBP, the high NADH to NAD(+) ratio decreases an expression of SirT1, the protein inducing longevity and anti-apoptosis. This review covers metabolic cascades causing reductive stress and oxidative stress in diabetes after a brief introduction of the redox concept.

pH-dependent association of enolase and glyceraldehyde-3-phosphate dehydrogenase of Lactobacillus crispatus with the cell wall and lipoteichoic acids

The plasminogen-binding proteins enolase and glyceraldehyde-3-phosphate dehydrogenase of Lactobacillus crispatus were localized on the cell surface at pH 5 but released into the medium at an alkaline pH. These proteins bound to lipoteichoic acids at a pH below their isoelectric point. The results indicate that lactobacilli rapidly modify their surface properties in response to changes in pH.

Rapid and intermittent cotransport of slow component-b proteins

After synthesis in neuronal perikarya, proteins destined for synapses and other distant axonal sites are transported in three major groups that differ in average velocity and protein composition: fast component (FC), slow component-a (SCa), and slow component-b (SCb). The FC transports mainly vesicular cargoes at average rates of approximately 200-400 mm/d. SCa transports microtubules and neurofilaments at average rates of approximately 0.2-1 mm/d, whereas SCb translocates approximately 200 diverse proteins critical for axonal growth, regeneration, and synaptic function at average rates of approximately 2-8 mm/d. Several neurodegenerative diseases are characterized by abnormalities in one or more SCb proteins, but little is known about mechanisms underlying SCb compared with FC and SCa. Here, we use live-cell imaging to visualize and quantify the axonal transport of three SCb proteins, alpha-synuclein, synapsin-I, and glyceraldehyde-3-phosphate dehydrogenase in cultured hippocampal neurons, and directly compare their transport to synaptophysin, a prototypical FC protein. All three SCb proteins move rapidly but infrequently with pauses during transit, unlike synaptophysin, which moves much more frequently and persistently. By simultaneously visualizing the transport of proteins at high temporal and spatial resolution, we show that the dynamics of alpha-synuclein transport are distinct from those of synaptophysin but similar to other SCb proteins. Our observations of the cotransport of multiple SCb proteins in single axons suggest that they move as multiprotein complexes. These studies offer novel mechanistic insights into SCb and provide tools for further investigating its role in disease processes.

A novel internally controlled real-time reverse transcription-PCR assay for HIV-1 RNA targeting the pol integrase genomic region

Given the worldwide increasing spread of HIV-1 genetic variants, it is mandatory that assays used for nucleic acid testing for HIV-1 detect all existing groups and subtypes of HIV-1. In this report the development and evaluation of a quantitative real-time HIV-1 RT-PCR assay that targets a conserved region within the pol integrase domain is described. As an internal control reaction, endogenous glyceraldehyde-3-phosphate-dehydrogenase transcripts were detected in a multiplex configuration. The detection limit (95% cut-off value) was determined by probit analysis and calculated as 281 IU/ml of HIV-1 RNA. Within-run and between-run coefficients of variation were below 15 and 27%, respectively, indicating high reproducibility. The described assay detected all tested HIV-1 isolates representing groups M, O and N. Within group M, quantitative test results correlated well with viral loads as determined by the automated Abbott RealTime HIV-1 assay. Based on the testing of 1206 confirmed HIV-1 RNA negative blood donor samples, assay specificity was found to be 100%. The rate of inhibition was 0.37%. The described HIV-1 real-time RT-PCR was validated according to regulatory guidelines and is applicable to the screening of blood donors as well as the determination of HIV-1 viral load.

Regulation of apoptosis by protein S-nitrosylation

S-nitrosylation/denitrosylation of critical cysteine residues on proteins serves as a redox switch that regulates the function of a wide array of proteins. A key signaling pathway that is regulated by S-nitrosylation is apoptotic cell death. Here we will review the proteins in apoptotic pathways that are known to be S-nitrosylated by endogenous NO production. The targets and functional consequences of S-nitrosylation during apoptosis are multifaceted, allowing cells to fine tune their response to apoptotic signals.