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Proteins Leads (protein + lead)

Distribution by Scientific Domains

Life Sciences	57%
Medical Sciences	28%

Selected Abstracts

Actinobacillus actinomycetemcomitans induces apoptosis of T lymphocytes by the Fas and Fas ligand pathway

MOLECULAR ORAL MICROBIOLOGY, Issue 5 2002
A. Nalbant
Actinobacillus actinomycetemcomitans expresses a number of toxins capable of inducing apoptotic cell death of T lymphocytes. However, the exact mechanism(s) has not been elucidated. The present study investigated the involvement of the Fas (CD95)-mediated apoptotic pathway in A. actinomycetemcomitans -induced T-cell apoptosis. To that end, peripheral blood mononuclear cells (PBMC) were cultured with or without A. actinomycetemcomitans cell-free culture supernatant (CFCS) for 0,96 h. The cells were then labeled with specific monoclonal antibodies and flow cytometry was performed. Results demonstrated up-regulation of Fas and activation of caspase-3 in T cells in response to A. actinomycetemcomitans CFCS. Monocytes were the only cells analyzed to express Fas ligand (FasL) constitutively, and this was further up-regulated in response to A. actinomycetemcomitans CFCS, while T cells expressed FasL only after this stimulation. Depletion of monocytes prior to stimulation with A. actinomycetemcomitans CFCS led to a marked decline in apoptosis. Blocking of Fas,FasL interactions with anti-Fas monoclonal antibody or Fas:Fc fusion protein lead to a significant decline, but not abolition, of T-cell apoptosis. Nearly all T cells expressed Bcl-2 at the outset of culture, and Bcl-2 expression declined in T cells stimulated with A. actinomycetemcomitans CFCS. Collectively, these data provide evidence for the induction of T-cell apoptosis by A. actinomycetemcomitans via the Fas-mediated pathway, involving caspase-3 and Bcl- 2. Moreover, this apoptotic response was dependent on the presence of monocytes. [source]

Alteration of NF-,B activity leads to mitochondrial apoptosis after infection with pathological prion protein

CELLULAR MICROBIOLOGY, Issue 9 2007
Soizic Bourteele
Summary Nuclear factor kappa B (NF-,B) is a key regulator of the immune response, but in almost the same manner it is involved in induction of inflammation, proliferation and regulation of apoptosis. In the central nervous system activated NF-,B plays a neuroprotective role. While in some neurodegenerative disorders the role of NF-,B is well characterized, there is poor knowledge on the role of NF-,B in prion disease. We found binding but no transcriptional activity of the transcription factor in vitro. Characterizing the mechanism of cell death after infection with pathological prion protein increased caspase-9 and caspase-3 activity was detected and the lack of NF-,B activity resulted in the inability to activate target genes that usually play an important role in neuroprotection. Additionally, we investigated the role of NF-,B after prion infection of Nfkb1,/,, Nfkb2,/, and Bcl3,/, mice and central nervous system-specific p65-deleted mice revealing an accelerated prion disease in NF-,B2- and Bcl-3-deficient mice, which is in line with a reduced neuroprotective activity in prion infection. Based on our findings, we propose a model whereby the alteration of NF-,B activity at the early stages of infection with pathological prion protein leads to neuronal cell death mediated by mitochondrial apoptosis. [source]

PROTEIN, FIBRE AND BLOOD PRESSURE: POTENTIAL BENEFIT OF LEGUMES

CLINICAL AND EXPERIMENTAL PHARMACOLOGY AND PHYSIOLOGY, Issue 4 2008
Ya Ping Lee
SUMMARY 1Prevention of hypertension and improved blood pressure control can be achieved through dietary modification. In particular, population studies and randomised controlled trials have indicated a beneficial effect of both dietary protein and dietary fibre on level of blood pressure. 2A large population study indicates that an increase in 37 g/day of protein leads to a decrease in mean systolic and diastolic blood pressure by approximately 3 and 2.5 mmHg, respectively. This protective effect is independent of the source of dietary protein. 3Meta-analysis suggests that a fibre increase of approximately 17 g/day will decrease systolic blood pressure by 1.15 mmHg and diastolic blood pressure by 1.65 mmHg, with soluble fibre showing a stronger effect than insoluble fibre. 4Protein and dietary fibre may have additive effects to lower blood pressure. One feasible approach to increasing both protein and fibre in the daily diet could be through the incorporation of legumes, a protein- and fibre-rich food. 5This review assesses the evidence for effects of protein and fibre to reduce blood pressure and the potential of incorporation of legumes into the daily diet as a feasible approach to achieving such benefits for blood pressure. [source]

A GyrB-GyrA fusion protein expressed in yeast cells is able to remove DNA supercoils but cannot substitute eukaryotic topoisomerase II

GENES TO CELLS, Issue 3 2002
Sonia Trigueros
Background: Type II topoisomerases are a highly conserved class of enzymes which transport one double-stranded DNA segment through a transient break in another. Whereas the eukaryotic enzymes are homodimers of a single polypeptide, their bacterial homologues are homodimers of two independently coded protein subunits. Unlike eukaryotic topoisomerase II and bacterial topoisomerase IV, DNA gyrase is a bacterial type II topoisomerase which specializes in intramolecular DNA transport. Results: We have fused the Escherichia coli coding sequences for the proteins GyrB and GyrA, which comprise DNA gyrase. This fusion was expressed in yeast cells and yielded the expected full-length protein product. When it was expressed in ,top1- top2-4 yeast cells, the fusion protein compensated their slow growth and reverted their elevated chromosomal excision of ribosomal genes. Furthermore, it removed DNA positive supercoils. The fusion protein, however, was unable to complement the temperature-dependent lethality of top2-4 cells. Conclusion: Fusion of the E. coli GyrB and GyrA proteins leads to a catalytically active topoisomerase which compensates several phenotypic traits attributed to unconstrained DNA supercoiling in topoisomerase-deficient cells. However, since the fusion protein cannot substitute for topoisomerase II, it may be efficient in intramolecular but not intermolecular DNA passage, resembling the catalytic properties of DNA gyrase. [source]

Auxin-induced, SCFTIR1 -mediated poly-ubiquitination marks AUX/IAA proteins for degradation

THE PLANT JOURNAL, Issue 1 2009
Felipe Dos Santos Maraschin
Summary The plant hormone auxin (indole-3-acetic acid or IAA) regulates plant development by inducing rapid cellular responses and changes in gene expression. Auxin promotes the degradation of Aux/IAA transcriptional repressors, thereby allowing auxin response factors (ARFs) to activate the transcription of auxin-responsive genes. Auxin enhances the binding of Aux/IAA proteins to the receptor TIR1, which is an F-box protein that is part of the E3 ubiquitin ligase complex SCFTIR1. Binding of Aux/IAA proteins leads to degradation via the 26S proteasome, but evidence for SCFTIR1 -mediated poly-ubiquitination of Aux/IAA proteins is lacking. Here we used an Arabidopsis cell suspension-based protoplast system to find evidence for SCFTIR1 -mediated ubiquitination of the Aux/IAA proteins SHY2/IAA3 and BDL/IAA12. Each of these proteins showed a distinct abundance and repressor activity when expressed in this cell system. Moreover, the amount of endogenous TIR1 protein appeared to be rate-limiting for a proper auxin response measured by the co-transfected DR5::GUS reporter construct. Co-transfection with 35S::TIR1 led to auxin-dependent degradation, and excess of 35S::TIR1 even led to degradation of Aux/IAAs in the absence of auxin treatment. Expression of the mutant tir1-1 protein or the related F-box protein COI1, which is involved in jasmonate signaling, had no effect on Aux/IAA degradation. Our results show that SHY2/IAA3 and BDL/IAA12 are poly-ubiquitinated and degraded in response to increased auxin or TIR1 levels. In conclusion, our data provide experimental support for the model that SCFTIR1 -dependent poly-ubiquitination of Aux/IAA proteins marks these proteins for degradation by the 26S proteasome, leading to activation of auxin-responsive gene expression. [source]

Single amino acid variation in barley 14-3-3 proteins leads to functional isoform specificity in the regulation of nitrate reductase

THE PLANT JOURNAL, Issue 6 2005
Mark P. Sinnige
Summary The highly conserved family of 14-3-3 proteins function in the regulation of a wide variety of cellular processes. The presence of multiple 14-3-3 isoforms and the diversity of cellular processes regulated by 14-3-3 suggest functional isoform specificity of 14-3-3 isoforms in the regulation of target proteins. Indeed, several studies observed differences in affinity and functionality of 14-3-3 isoforms. However, the structural variation by which isoform specificity is accomplished remains unclear. Because other reports suggest that specificity is found in differential expression and availability of 14-3-3 isoforms, we used the nitrate reductase (NR) model system to analyse the availability and functionality of the three barley 14-3-3 isoforms. We found that 14-3-3C is unavailable in dark harvested barley leaf extract and 14-3-3A is functionally not capable to efficiently inhibit NR activity, leaving 14-3-3B as the only characterized isoform able to regulate NR in barley. Further, using site directed mutagenesis, we identified a single amino acid variation (Gly versus Ser) in loop 8 of the 14-3-3 proteins that plays an important role in the observed isoform specificity. Mutating the Gly residue of 14-3-3A to the alternative residue, as found in 14-3-3B and 14-3-3C, turned it into a potent inhibitor of NR activity. Using surface plasmon resonance, we show that the ability of 14-3-3A and the mutated version to inhibit NR activity correlates well with their binding affinity for the 14-3-3 binding motif in the NR protein, indicating involvement of this residue in ligand discrimination. These results suggest that both the availability of 14-3-3 isoforms as well as binding affinity determine isoform-specific regulation of NR activity. [source]

Structure,Activity Studies on Suramin Analogues as Inhibitors of NAD+ -Dependent Histone Deacetylases (Sirtuins)

CHEMMEDCHEM, Issue 10 2007
Johannes Trapp Dr.
Abstract Suramin is a symmetric polyanionic naphthylurea originally used for the treatment of trypanosomiasis and onchocerciasis. Suramin and diverse analogues exhibit a broad range of biological actions in,vitro and in,vivo, including, among others, antiproliferative and antiviral activity. Suramin derivatives usually target purinergic binding sites. Class,III histone deacetylases (sirtuins) are amidohydrolases that require nicotinamide adenine dinucleotide (NAD+) as a cofactor for their catalytic mechanism. Deacetylation of the target proteins leads to a change in conformation and alters the activity of the proteins in question. Suramin was reported to inhibit human sirtuin,1 (SIRT1). We tested a diverse set of suramin analogues to elucidate the inhibition of the NAD+ -dependent histone deacetylases SIRT1 and SIRT2 and discovered selective inhibitors of human sirtuins with potency in the two-digit nanomolar range. In addition, the structural requirements for the binding of suramin derivatives to sirtuins were investigated by molecular docking. The recently published X-ray crystal structure of human SIRT5 in complex with suramin and the human SIRT2 structure were used to analyze the interaction mode of the novel suramin derivatives. [source]