FhCaBP4: A Fasciola hepatica calcium binding protein with EF-hand and dynein light chain domains

In trematodes, there is a family of proteins which combine EF-hand-containing domains with dynein light chain (DLC)-like domains. A member of this family from the liver fluke, Fasciola hepatica-FhCaBP4-has been identified and characterised biochemically. FhCaBP4 has an N-terminal domain containing two imperfect EF-hand sequences and a C-terminal dynein light chain-like domain. Molecular modelling predicted that the two domains are joined by a flexible linker. Native gel electrophoresis demonstrated that FhCaBP4 binds to calcium, manganese, barium and strontium ions, but not to magnesium or zinc ions. The hydrophobic, fluorescent probe 8-anilinonaphthalene-1-sulphonate bound more tightly to FhCaBP4 in the presence of calcium ions. This suggests that the protein undergoes a conformational change on ion binding which increases the number of non-polar residues on the surface. FhCaBP4 was protected from limited proteolysis by the calmodulin antagonist W7, but not by trifluoperazine or praziquantel. Protein-protein cross-linking experiments showed that FhCaBP4 underwent calcium ion-dependent dimerisation. Since DLCs are commonly dimeric, it is likely that FhCaBP4 dimerises through this domain. The molecular model reveals that the calcium ion-binding site is located close to a key sequence in the DLC-like domain, suggesting a plausible mechanism for calcium-dependent dimerisation.

FhCaBP3: A Fasciola hepatica calcium binding protein with EF-hand and dynein light chain domains

A DNA sequence encoding a protein with predicted EF-hand and dynein light chain binding domains was identified in a Fasciola hepatica EST library. Sequence analysis of the encoded protein revealed that the most similar known protein was the Fasciola gigantica protein FgCaBP3 and so this newly identified protein was named FhCaBP3. Molecular modelling of FhCaBP3 predicted a highly flexible N-terminal region, followed by a domain containing two EF-hand motifs the second of which is likely to be a functioning divalent ion binding site. The C-terminal domain of the protein contains a dynein light chain like region. Interestingly, molecular modelling predicts that calcium ion binding to the N-terminal domain destabilises the ß-sheet structure of the C-terminal domain. FhCaBP3 can be expressed in, and purified from, Escherichia coli. The recombinant protein dimerises and the absence of calcium ions appeared to promote dimerisation. Native gel shift assays demonstrated that the protein bound to calcium and manganese ions, but not to magnesium, barium, zinc, strontium, nickel, copper or cadmium ions. FhCaBP3 interacted with the calmodulin antagonists trifluoperazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide and chlorpromazine as well as the myosin regulatory light chain-binding drug praziquantel. Despite sequence and structural similarities to other members of the same protein family from F. hepatica, FhCaBP3 has different biochemical properties to the other well characterised family members, FH22 and FhCaBP4. This suggests that each member of this trematode calcium-binding family has discrete functional roles within the organism.

Vitamin D binding protein isoforms as candidate predictors of disease extension in childhood arthritis

Introduction: Juvenile idiopathic arthritis (JIA) comprises a poorly understood group of chronic autoimmune diseases with variable clinical outcomes. We investigated whether the synovial fluid (SF) proteome could distinguish a subset of patients in whom disease extends to affect a large number of joints.

Methods: SF samples from 57 patients were obtained around time of initial diagnosis of JIA, labeled with Cy dyes and separated by two-dimensional electrophoresis. Multivariate analyses were used to isolate a panel of proteins which distinguish patient subgroups. Proteins were identified using MALDI-TOF mass spectrometry with expression verified by immunochemical methods. Protein glycosylation status was confirmed by hydrophilic interaction liquid chromatography.

Results: A truncated isoform of vitamin D binding protein (VDBP) is present at significantly reduced levels in the SF of oligoarticular patients at risk of disease extension, relative to other subgroups (p < 0.05). Furthermore, sialylated forms of immunopurified synovial VDBP were significantly reduced in extended oligoarticular patients (p < 0.005).

Conclusion: Reduced conversion of VDBP to a macrophage activation factor may be used to stratify patients to determine risk of disease extension in JIA patients.

Single-stranded DNA-binding protein hSSB1 is critical for genomic stability

Single-strand DNA (ssDNA)-binding proteins (SSBs) are ubiquitous and essential for a wide variety of DNA metabolic processes, including DNA replication, recombination, DNA damage detection and repair. SSBs have multiple roles in binding and sequestering ssDNA, detecting DNA damage, stimulating nucleases, helicases and strand-exchange proteins, activating transcription and mediating protein-protein interactions. In eukaryotes, the major SSB, replication protein A (RPA), is a heterotrimer. Here we describe a second human SSB (hSSB1), with a domain organization closer to the archaeal SSB than to RPA. Ataxia telangiectasia mutated (ATM) kinase phosphorylates hSSB1 in response to DNA double-strand breaks (DSBs). This phosphorylation event is required for DNA damage-induced stabilization of hSSB1. Upon induction of DNA damage, hSSB1 accumulates in the nucleus and forms distinct foci independent of cell-cycle phase. These foci co-localize with other known repair proteins. In contrast to RPA, hSSB1 does not localize to replication foci in S-phase cells and hSSB1 deficiency does not influence S-phase progression. Depletion of hSSB1 abrogates the cellular response to DSBs, including activation of ATM and phosphorylation of ATM targets after ionizing radiation. Cells deficient in hSSB1 exhibit increased radiosensitivity, defective checkpoint activation and enhanced genomic instability coupled with a diminished capacity for DNA repair. These findings establish that hSSB1 influences diverse endpoints in the cellular DNA damage response.

Lipopolysaccharide-binding protein and CD14 are increased in the bronchoalveolar lavage fluid of smokers

Lipopolysaccharide-binding protein (LBP) and CD14 contribute to the recognition of pathogens by cells, which triggers the activation of defence responses. Smoking is a risk factor for the development of chronic obstructive pulmonary disease (COPD) and respiratory infections. The current authors theorised that levels of LBP and CD14 in the lungs of smokers would be higher than those in the lungs of never-smokers. These elevated levels could affect host responses upon infection. LBP, soluble CD14 (sCD14) and interleukin (IL)-8 were detected by ELISA. Nuclear factor (NF)- ?B, p38 and the inhibitor I?Ba were studied by immunoassays. Gene expression was assessed by RT-PCR. Bronchoalveolar lavage levels of LBP and CD14 were significantly higher in smokers and COPD patients than in never-smokers, whereas levels of both proteins were not significantly different between smokers and COPD patients. IL-6, IL-1ß5 and cigarette smoke condensate induced the expression of LBP and CD14 by airway epithelial cells. LBP and sCD14 inhibited the nontypeable Haemophilus influenzae (NTHi)-dependent secretion of IL-8 and the activation of NF-?B and p38 mitogen-activated protein kinase signalling pathways but they increased the internalisation of NTHi by airway epithelial cells. Thus, in the inflamed airways of smokers both proteins could contribute to inhibit bacteria-dependent cellular activation without compromising the internalisation of pathogens by airway cells. Copyright©ERS Journals Ltd 2009.

Complement factor H is a serum-binding protein for adrenomedullin, and the resulting complex modulates the bioactivities of both partners

Adrenomedullin (AM) is an important regulatory peptide involved in both physiological and pathological states. We have previously demonstrated the existence of a specific AM-binding protein (AMBP-1) in human plasma. In the present study, we developed a nonradioactive ligand blotting assay, which, together with high pressure liquid chromatography/SDS-polyacrylamide gel electrophoresis purification techniques, allowed us to isolate AMBP-1 to homogeneity. The purified protein was identified as human complement factor H. We show that AM/factor H interaction interferes with the established methodology for quantification of circulating AM. Our data suggest that this routine procedure does not take into account the AM bound to its binding protein. In addition, we show that factor H affects AM in vitro functions. It enhances AM-mediated induction of cAMP in fibroblasts, augments the AM-mediated growth of a cancer cell line, and suppresses the bactericidal capability of AM on Escherichia coli. Reciprocally, AM influences the complement regulatory function of factor H by enhancing the cleavage of C3b via factor I. In summary, we report on a potentially new regulatory mechanism of AM biology, the influence of factor H on radioimmunoassay quantification of AM, and the possible involvement of AM as a regulator of the complement cascade.

Insulin-like growth factor binding protein-3 mediates vascular repair by enhancing nitric oxide generation

Insulin-like growth factor binding protein (IGFBP)-3 modulates vascular development by regulating endothelial progenitor cell (EPC) behavior, specifically stimulating EPC cell migration. This study was undertaken to investigate the mechanism of IGFBP-3 effects on EPC function and how IGFBP-3 mediates cytoprotection following vascular injury.

The Arabidopsis RNA-binding protein FCA requires a lysine-specific demethylase 1 homolog to downregulate FLC.

A repressor of the transition to flowering in Arabidopsis is the MADS box protein FLOWERING LOCUS C (FLC). FCA, an RNA-binding protein, and FY, a homolog of the yeast RNA 3' processing factor Pfs2p, downregulate FLC expression and therefore promote flowering. FCA/FY physically interact and alter polyadenylation/3' processing to negatively autoregulate FCA. Here, we show that FCA requires FLOWERING LOCUS D (FLD), a homolog of the human lysine-specific demethylase 1 (LSD1) for FLC downregulation. FCA also partially depends on DICER-LIKE 3, involved in chromatin silencing. fca mutations increased levels of unspliced sense FLC transcript, altered processing of antisense FLC transcripts, and increased H3K4 dimethylation in the central region of FLC. These data support a close association of FCA and FLD in mediating H3K4 demethylation and thus transcriptional silencing of FLC and reveal roles for antisense RNA processing and DCL3 function in this regulation.

Identification of a high-risk haplotype for the dystrobrevin binding protein 1 (DTNBP1) gene in the Irish study of high-density schizophrenia families

A recent report showed significant associations between several SNPs in a previously unknown EST cluster with schizophrenia. (1). The cluster was identified as the human dystrobrevin binding protein 1 gene (DTNBP1) by sequence database comparisons and homology with mouse DTNBP1. (2). However, the linkage disequilibrium (LD) among the SNPs in DTNBP1 as well as the pattern of significant SNP-schizophrenia association was complex. This raised several questions such as the number of susceptibility alleles that may be involved and the size of the region where the actual disease mutation(s) could be located. To address these questions, we performed different single-marker tests on the 12 previously studied and 2 new SNPs in DTNBP1 that were re-scored using an improved procedure, and performed a variety of haplotype analyses. The sample consisted of 268 Irish multiplex families selected for high density of schizophrenia. Results suggested a simple structure where the LD in the target region could be explained by 6 haplotypes that together accounted for 96% of haplotype diversity in the whole sample. From these six, a single high-risk haplotype was identified that showed a significant association with schizophrenia and explained the pattern of significant findings in the analyses with individual markers. This haplotype was 30 kb long, had a large effect, could be measured with two tag SNPs only, had a frequency of 6% in our sample, seemed to be of relatively recent origin in evolutionary terms, and was equally distributed over Ireland. Implications of these findings for follow-up and replication studies are discussed.

Simvastatin decreases the level of heparin-binding protein in patients with acute lung injury

Heparin-binding protein is released by neutrophils during inflammation and disrupts the integrity of the alveolar and capillary endothelial barrier implicated in the development of acute lung injury and systemic organ failure. We sought to investigate whether oral administration of simvastatin to patients with acute lung injury reduces plasma heparin-binding protein levels and improves intensive care unit outcome.

Unspliced X-box-binding Protein 1 (XBP1) Protects Endothelial Cells from Oxidative Stress through Interaction with Histone Deacetylase 3

It is well-known that atherosclerosis occurs geographically at branch points where disturbed flow predisposes to the development of plaque via triggering of oxidative stress and inflammatory reactions. In this study, we found that disturbed flow activated anti-oxidative reactions via up-regulating heme oxygenase 1 (HO-1) in an X-box binding protein 1 (XBP1) and histone deacetylase 3 (HDAC3)-dependent manner. Disturbed flow concomitantly up-regulated the unspliced XBP1 (XBP1u) and HDAC3 in a vascular endothelial growth factor receptor (VEGFR) and PI3K/Akt dependent manner. The presence of XBP1 was essential for the up-regulation of HDAC3 protein. Over-expression of XBP1u and/or HDAC3 activated Akt1 phosphorylation, Nrf2 protein stabilization and nuclear translocation, and HO-1 expression. Knockdown of XBP1u decreased the basal level and disturbed flow-induced Akt1 phosphorylation, Nrf2 stabilization and HO-1 expression. Knockdown of HDAC3 ablated XBP1u-mediated effects. The mammalian target of rapamycin complex 2 (mTORC2) inhibitor, AZD2014, ablated XBP1u or HDAC3 or disturbed flow-mediated Akt1 phosphorylation, Nrf2 nuclear translocation and HO-1 expression. Neither actinomycin D nor cycloheximide affected disturbed flow-induced up-regulation of Nrf2 Protein. Knockdown of Nrf2 abolished XBP1u or HDAC3 or disturbed flow-induced HO-1 up-regulation. Co-immunoprecipitation assays demonstrated that XBP1u physically bound to HDAC3 and Akt1. The region of amino acids 201 to 323 of the HDAC3 protein was responsible for the binding to XBP1u. Double immunofluorescence staining revealed that the interactions between Akt1 and mTORC2, Akt1 and HDAC3, Akt1 and XBP1u, HDAC3 and XBP1u occurred in the cytosol. Thus, we demonstrate that XBP1u and HDAC3 exert a protective effect on disturbed flow-induced oxidative stress via up-regulation of mTORC2-dependent Akt1 phosphorylation and Nrf2-mediated HO-1 expression.

CCAAT/enhancer binding protein α predicts poorer prognosis and prevents energy starvation-induced cell death in hepatocellular carcinoma

CCAAT enhancer binding protein α (C/EBPα) plays an essential role in cellular differentiation, growth, and energy metabolism. Here, we investigate the correlation between C/EBPα and hepatocellular carcinoma (HCC) patient outcomes and how C/EBPα protects cells against energy starvation. Expression of C/EBPα protein was increased in the majority of HCCs examined (191 pairs) compared with adjacent nontumor liver tissues in HCC tissue microarrays. Its upregulation was correlated significantly with poorer overall patient survival in both Kaplan-Meier survival (P = 0.017) and multivariate Cox regression (P = 0.028) analyses. Stable C/EBPα-silenced cells failed to establish xenograft tumors in nude mice due to extensive necrosis, consistent with increased necrosis in human C/EBPα-deficient HCC nodules. Expression of C/EBPα protected HCC cells in vitro from glucose and glutamine starvation-induced cell death through autophagy-involved lipid catabolism. Firstly, C/EBPα promoted lipid catabolism during starvation, while inhibition of fatty acid beta-oxidation significantly sensitized cell death. Secondly, autophagy was activated in C/EBPα-expressing cells, and the inhibition of autophagy by ATG7 knockdown or chloroquine treatment attenuated lipid catabolism and subsequently sensitized cell death. Finally, we identified TMEM166 as a key player in C/EBPα-mediated autophagy induction and protection against starvation.

CONCLUSION: The C/EBPα gene is important in that it links HCC carcinogenesis to autophagy-mediated lipid metabolism and resistance to energy starvation; its expression in HCC predicts poorer patient prognosis.

Susceptibility to Invasive Meningococcal Disease: Polymorphism of Complement System Genes and Neisseria meningitidis Factor H Binding Protein

BACKGROUND: Neisseria meningitidis can cause severe infection in humans. Polymorphism of Complement Factor H (CFH) is associated with altered risk of invasive meningococcal disease (IMD). We aimed to find whether polymorphism of other complement genes altered risk and whether variation of N. meningitidis factor H binding protein (fHBP) affected the risk association.

METHODS: We undertook a case-control study with 309 European cases and 5,200 1958 Birth Cohort and National Blood Service cohort controls. We used additive model logistic regression, accepting P<0.05 as significant after correction for multiple testing. The effects of fHBP subfamily on the age at infection and severity of disease was tested using the independent samples median test and Student's T test. The effect of CFH polymorphism on the N. meningitidis fHBP subfamily was investigated by logistic regression and Chi squared test.

RESULTS: Rs12085435 A in C8B was associated with odds ratio (OR) of IMD (0.35 [95% CI 0.19-0.67]; P = 0.03 after correction). A CFH haplotype tagged by rs3753396 G was associated with IMD (OR 0.56 [95% CI 0.42-0.76], P = 1.6x10-4). There was no bacterial load (CtrA cycle threshold) difference associated with carriage of this haplotype. Host CFH haplotype and meningococcal fHBP subfamily were not associated. Individuals infected with meningococci expressing subfamily A fHBP were younger than those with subfamily B fHBP meningococci (median 1 vs 2 years; P = 0.025).

DISCUSSION: The protective CFH haplotype alters odds of IMD without affecting bacterial load for affected heterozygotes. CFH haplotype did not affect the likelihood of infecting meningococci having either fHBP subfamily. The association between C8B rs12085435 and IMD requires independent replication. The CFH association is of interest because it is independent of known functional polymorphisms in CFH. As fHBP-containing vaccines are now in use, relationships between CFH polymorphism and vaccine effectiveness and side-effects may become important.

HPV16 Down-Regulates the Insulin-Like Growth Factor Binding Protein 2 to Promote Epithelial Invasion in Organotypic Cultures

Cervical cancer is a multi-stage disease caused by human papillomaviruses (HPV) infection of cervical epithelial cells, but the mechanisms regulating disease progression are not clearly defined. Using 3-dimensional organotypic cultures, we demonstrate that HPV16 E6 and E7 proteins alter the secretome of primary human keratinocytes resulting in local epithelial invasion. Mechanistically, absence of the IGF-binding protein 2 (IGFBP2) caused increases in IGFI/II signalling and through crosstalk with KGF/FGFR2b/AKT, cell invasion. Repression of IGFBP2 is mediated by histone deacetylation at the IGFBP2 promoter and was reversed by treatment with histone deacetylase (HDAC) inhibitors. Our in vitro findings were confirmed in 50 invasive cancers and 79 cervical intra-epithelial neoplastic lesions caused by HPV16 infection, where IGFBP2 levels were reduced with increasing disease severity. In summary, the loss of IGFBP2 is associated with progression of premalignant disease, and sensitises cells to pro-invasive IGF signalling, and together with stromal derived factors promotes epithelial invasion.