Identification of APOH polymorphisms as common genetic risk factors for venous thrombosis in the Chinese population

BACKGROUND

Venous thrombosis (VT) is a worldwide medical problem. In order to identify individuals at high risk early, it is necessary to find more genetic risk factors. Nowadays, the studies on genetic factors of thrombosis are mainly focused on coagulation and anticoagulation factors. The exploration of other proteins involved in thrombosis and hemostasis may lead to a breakthrough.

OBJECTIVES

We used APOH as a candidate gene to investigate the existence of genetic variation that could increase the risk of thrombosis.

METHODS/RESULTS

In the current study, with a resequencing method followed by a case-control study, four polymorphisms (c.-32C>A, c.422T>C, c.461G>A, and c.1004G>C) in APOH (encoding β2 -glycoprotein I) were found to be in high linkage disequilibrium, which could result in three haplotypes. The H2 heterozygotes and H3 homozygotes had approximately 1.5-fold and seven-fold increased risks for VT, respectively. The minor allele frequency in the general population was ~ 10%. In addition, H3 individuals showed a significantly decreased level of β2 -glycoprotein I, but an increased level of thrombin generation. Functional tests indicated that the mutant β2 -glycoprotein I had a significantly lower capacity to extend thrombin clotting time and increase thrombin generation potential.

CONCLUSIONS

This study revealed APOH as a new candidate gene associated with thrombosis, and further genetic research on this gene in patients in whom the cause of thrombophilia is unknown is therefore warranted.

CD147 promotes melanoma progression through hypoxia-induced MMP2 activation

Hypoxia enhances MMP2 expression and the invasion and metastatic potential of melanoma cells. CD147 has been shown to induce MMP2 in multiple cancers. To investigate the role of CD147 in hypoxiainduced MMP2 activation, we performed immunohistochemistry (IHC) staining in 206 normal and melanoma tissue samples, and analyzed the correlation between HIF1α and CD147. ChIP (chromosome Immunoprecipitation) in melanoma cell lines supports that HIF1α directly binds to CD147 promoter. Moreover, we made a series of deletion mutants of CD147 promoter, and identified a conserved HIF1α binding site. Point mutation in this site significantly decreased CD147 response to hypoxia. Importantly, knocking down CD147 attenuates MMP2 response to hypoxia in melanoma cell lines. MMP2 could not be efficiently activated by hypoxia in CD147 depletion cells. ELISA data showed that MMP2 secretion was reduced in CD147 depletion cells than control under hypoxia condition. To verify the data from cell culture model, we performed in vivo mouse xenograft experiment. IHC staining showed reduced MMP2 level in CD147 depleted xenografts compared to the control group, with the HIF1α level being comparable. Our study demonstrates a novel pathway mediated by CD147 to promote the MMP2 activation induced by hypoxia, and helps to understand the interplay between hypoxia and melanoma progression.

Sodium and potassium competition in potassium-selective and non-selective channels

Potassium channels selectively conduct K⁺, primarily to the exclusion of Na⁺, despite the fact that both ions can bind within the selectivity filter. Here we perform crystallographic titration and single-channel electrophysiology to examine the competition of Na⁺ and K⁺ binding within the filter of two NaK channel mutants; one is the potassium-selective NaK2K mutant and the other is the non-selective NaK2CNG, a CNG channel pore mimic. With high-resolution structures of these engineered NaK channel constructs, we explicitly describe the changes in K⁺ occupancy within the filter upon Na⁺ competition by anomalous diffraction. Our results demonstrate that the non-selective NaK2CNG still retains a K⁺-selective site at equilibrium, whereas the NaK2K channel filter maintains two high-affinity K⁺ sites. A double-barrier mechanism is proposed to explain K⁺ channel selectivity at low K⁺ concentrations.

K⁺ channels are selective for K⁺ despite the fact that Na⁺ can bind and conduct through the selectivity filter. Sauer et al. show that a K⁺-selective NaK2K channel has two high-affinity K⁺-binding sites, whereas a non-selective NaK2CNG channel has one, and propose a double-barrier mechanism for ion selectivity.

Ionic interactions of Ba2+ blockades in the MthK K+ channel

The movement and interaction of multiple ions passing through in single file underlie various fundamental K(+) channel properties, from the effective conduction of K(+) ions to channel blockade by Ba(2+) ions. In this study, we used single-channel electrophysiology and x-ray crystallography to probe the interactions of Ba(2+) with permeant ions within the ion conduction pathway of the MthK K(+) channel. We found that, as typical of K(+) channels, the MthK channel was blocked by Ba(2+) at the internal side, and the Ba(2+)-blocking effect was enhanced by external K(+). We also obtained crystal structures of the MthK K(+) channel pore in both Ba(2+)-Na(+) and Ba(2+)-K(+) environments. In the Ba(2+)-Na(+) environment, we found that a single Ba(2+) ion remained bound in the selectivity filter, preferably at site 2, whereas in the Ba(2+)-K(+) environment, Ba(2+) ions were predominantly distributed between sites 3 and 4. These ionic configurations are remarkably consistent with the functional studies and identify a molecular basis for Ba(2+) blockade of K(+) channels.

The conserved potassium channel filter can have distinct ion binding profiles: structural analysis of rubidium, cesium, and barium binding in NaK2K

The ion-binding profile in NaK2K is distinct from that in KcsA, even though the selectivity filter has been conserved.

Potassium channels are highly selective for K⁺ over the smaller Na⁺. Intriguingly, they are permeable to larger monovalent cations such as Rb⁺ and Cs⁺ but are specifically blocked by the similarly sized Ba²⁺. In this study, we used structural analysis to determine the binding profiles for these permeant and blocking ions in the selectivity filter of the potassium-selective NaK channel mutant NaK2K and also performed permeation experiments using single-channel recordings. Our data revealed that some ion binding properties of NaK2K are distinct from those of the canonical K⁺ channels KcsA and MthK. Rb⁺ bound at sites 1, 3, and 4 in NaK2K, as it does in KcsA. Cs⁺, however, bound predominantly at sites 1 and 3 in NaK2K, whereas it binds at sites 1, 3, and 4 in KcsA. Moreover, Ba²⁺ binding in NaK2K was distinct from that which has been observed in KcsA and MthK, even though all of these channels show similar Ba²⁺ block. In the presence of K⁺, Ba²⁺ bound to the NaK2K channel at site 3 in conjunction with a K⁺ at site 1; this led to a prolonged block of the channel (the external K⁺-dependent Ba²⁺ lock-in state). In the absence of K⁺, however, Ba²⁺ acts as a permeating blocker. We found that, under these conditions, Ba²⁺ bound at sites 1 or 0 as well as site 3, allowing it to enter the filter from the intracellular side and exit from the extracellular side. The difference in the Ba²⁺ binding profile in the presence and absence of K⁺ thus provides a structural explanation for the short and prolonged Ba²⁺ block observed in NaK2K.

αNAC inhibition of the FADD-JNK axis plays anti-apoptotic role in multiple cancer cells

Nascent polypeptide-associated complex α (αNAC) is reportedly overexpressed in several types of cancers and regulates cell apoptosis under hypoxic conditions in HeLa cells. The aim of our study was to investigate the apoptotic function of αNAC in cancer progression. First, we observed the cellular effects of αNAC depletion. Mouse αNAC was used to restore the protein level and verify the effect. An Annexin V assay, a caspase activity reporter assay, an apoptotic molecular marker, and a colony formation assay were used as markers to investigate the mechanisms of cell death caused by αNAC depletion. The Cancer 10-pathway reporter assay was used to screen downstream pathways. PCR site-directed deletion based on the functional domains of αNAC was used to construct deletion mutants. Those functional domain deletion mutants were used to recover the apoptotic phenotype caused by αNAC depletion. Finally, the role of αNAC in TNF-related apoptosis-inducing ligand (TRAIL) treatment was investigated in vitro. We found that depletion of αNAC in multiple types of cancer cells induce typical apoptotic cell death. This anti-apoptotic function is mediated by the FADD/c-Jun N-terminal kinase pathway. Intact αNAC is required for the direct binding of FADD as well as its anti-apoptosis function. Either αNAC depletion or the deletion of the ubiquitin-associated domain of αNAC sensitizes L929 cancer cells to mTRAIL treatment. Our study revealed a αNAC anti-apoptotic function in multiple types of cancer cells and suggested its potential in cancer therapy.

The histone methyltransferase ESET is required for the survival of spermatogonial stem/progenitor cells in mice

Self-renewal and differentiation of spermatogonial stem cells (SSCs) are the foundation of spermatogenesis throughout a male's life. SSC transplantation will be a valuable solution for young male patients to preserve their fertility. As SSCs in the collected testis tissue from the patients are very limited, it is necessary to expansion the SSCs in vitro. Previous studies suggested that histone methyltransferase ERG-associated protein with SET domain (ESET) represses gene expression and is essential for the maintenance of the pool of embryonic stem cells and neurons. The objective of this study was to determine the role of ESET in SSCs using in vitrocell culture and germ cell transplantation. Cell transplantation assay showed that knockdown of ESET reduced the number of seminiferous tubules with spermatogenesis when compared with that of the control. Knockdown of ESET also upregulated the expression of apoptosis-associated genes (such as P53, Caspase9, Apaf1), whereas inhibited the expression of apoptosis-suppressing genes (such as Bcl2l1, X-linked inhibitor of apoptosis protein). In addition, suppression of ESET led to increase in expression of Caspase9 and activation of Caspase3 (P17) as well as cleavage of poly (ADP-ribose) polymerase. Among the five ESET-targeting genes (Cox4i2, spermatogenesis and oogenesis Specific Basic Helix-Loop-Helix 2, Nobox, Foxn1 and Dazl) examined by ChIP assay, Cox4i2 was found to regulate SSC apoptosis by the rescue experiment. BSP analyses further showed that DNA methylation in the promoter loci of Cox4i2was influenced by ESET, indicating that ESET also regulated gene expression through DNA methylation in addition to histone methylation. In conclusion, we found that ESET regulated SSC apoptosis by suppressing of Cox4i2 expression through histone H3 lysine 9 tri-methylation and DNA methylation. The results obtained will provide unique insights that would broaden the research on SSC biology and contribute to the treatment of male infertility.

Diagnostic exome sequencing identifies two novel IQSEC2 mutations associated with X-linked intellectual disability with seizures: implications for genetic counseling and clinical diagnosis

Intellectual disability is a heterogeneous disorder with a wide phenotypic spectrum. Over 1,700 OMIM genes have been associated with this condition, many of which reside on the X-chromosome. The IQSEC2 gene is located on chromosome Xp11.22 and is known to play a significant role in the maintenance and homeostasis of the brain. Mutations in IQSEC2 have been historically associated with nonsyndromic X-linked intellectual disability. Case reports of affected probands show phenotypic overlap with conditions associated with pathogenic MECP2, FOXG1, CDKL5, and MEF2C gene mutations. Affected individuals, however, have also been identified as presenting with additional clinical features including seizures, autistic-behavior, psychiatric problems, and delayed language skills. To our knowledge, only 5 deleterious mutations and 2 intragenic duplications have been previously reported in IQSEC2. Here we report two novel IQSEC2 de novo truncating mutations identified through diagnostic exome sequencing in two severely affected unrelated male probands manifesting developmental delay, seizures, hypotonia, plagiocephaly, and abnormal MRI findings. Overall, diagnostic exome sequencing established a molecular diagnosis for two patients in whom traditional testing methods were uninformative while expanding on the mutational and phenotypic spectrum. In addition, our data suggests that IQSEC2 may be more common than previously appreciated, accounting for approximately 9 % (2/22) of positive findings among patients with seizures referred for diagnostic exome sequencing. Further, these data supports recently published data suggesting that IQSEC2 plays a more significant role in the development of X-linked intellectual disability with seizures than previously anticipated.

Biochemical parameters of Saccharopolyspora erythraea during feeding ammonium sulphate in erythromycin biosynthesis phase

The physiology of feeding ammonium sulphate in erythromycin biosynthesis phase of Saccharopolyspora erythraea on the regulation of erythromycin A (Er-A) biosynthesis was investigated in 50 L fermenter. At an optimal feeding ammonium sulphate rate of 0.03 g/L per h, the maximal Er-A production was 8281 U/mL at 174 h of growth, which was increased by 26.3% in comparison with the control (6557 U/mL at 173 h). Changes in cell metabolic response of actinomycete were observed, i.e. there was a drastic increase in the level of carbon dioxide evolution rate and oxygen consumption. Assays of the key enzyme activities and organic acids of S. erythraea and amino acids in culture broth revealed that cell metabolism was enhanced by ammonium assimilation, which might depend on the glutamate transamination pathway. The enhancement of cell metabolism induced an increase of the pool of TCA cycle and the metabolic flux of erythromycin biosynthesis. In general, ammonium assimilation in the erythromycin biosynthesis phase of S. erythraea exerted a significant impact on the carbon metabolism and formation of precursors of the process for dramatic regulation of secondary metabolites biosynthesis.

Recombinant PTD-Cu/Zn SOD attenuates hypoxia-reoxygenation injury in cardiomyocytes

BACKGROUND

Oxidative stress plays a pivotal role in myocardial ischemia-reperfusion injury. Increasing the protein expression of intracellular Cu/Zn SOD, which is the major endogenous antioxidant enzyme, may attenuate or prevent hypoxia-reoxygenation injury (HRI) in cultured cardiomyocytes. However, ectogenic Cu/Zn-SOD can hardly be transferred into cells to exert biological effects. In this study, we constructed PTD-Cu/Zn SOD plasmid with a kind of translocation structure-Protein transduction domain (PTD) and detected its transmembrane ability and antioxidant effects in H9c2 rat cardiomyocytes subjected to hypoxia/reoxygenation injury (HRI).

METHODS

We constructed the pET-PTD-Cu/Zn SOD (CDs) prokaryotic expression vectors in plasmid that were inserted into E. coli BL21 to induce the protein expression of PTD-Cu/Zn SOD. H9c2 cardiomyocyte HRI was achieved by exposing cardiomyocytes to 12 h hypoxia followed by 2 h reoxygenation. Protein expression of PTD-Cu/Zn SOD in cardiomyocytes was assayed by Western blot and their enzyme activities were investigated by immunohistochemistry and flow cytometry.

RESULTS

In cultured cardiomyocytes hypoxia-reoxygenation injury model, exogenous PTD-Cu/Zn SOD could penetrate cell membrane to clear superoxide anion and decrease hydrogen peroxide level in H9c2 cardiomyocytes subjected to HRI. The level of mitochondrial membrane potential was restored to normal, and the cell apoptosis was reduced in cardiomyocytes with PTD-Cu/Zn SOD treatment during HRI.

CONCLUSION

Recombinant PTD-Cu/Zn SOD could scavenge intracellular-free superoxide anion, protect mitochondria from damages, and attenuate the hypoxia-reoxygenation injury in cultured cardiomyocytes.

Abstract P4-05-01: Oncolytic Herpes Simplex Virus Vector G47Δ Effectively Targets Breast Cancer Stem Cells

Breast tumors can be classified according to their gene-expression profiles into different molecular subtypes with distinct biological and clinical features. Moreover, different subtypes show distinct responses to different therapeutic regimens, thereby resulting in markedly different outcomes. Recently, accumulating evidence has suggested that breast cancer originates from cancer stem cells (CSCs), which comprise a small percentage of the overall tumor but are highly tumorigenic and pluripotent with unlimited proliferation potential. Furthermore, cancer stem cells are highly resistant to conventional treatment, which potentially explains certain difficulties in treating cancer with current therapy options. The use of oncolytic viruses is a relatively new strategy in cancer therapy, oncolytic herpes simplex virus (oHSV) has been shown to be a safe and effective therapeutic approach for a variety of different cancers.

In this study, different types of breast cancer cell lines were cultured in anchorage-independent conditions, the cells typically form mammospheres within 10 days of anchorage-independent culture, which showed properties of CSCs. The mammospheres are capable of being passaged indefinitely and single dissociated mammosphere cells were able to regenerate spheres. Moreover, compared to the parental cell lines, mammoshpere cells were enriched for CD44+CD24− cells and highly expression of the alternative breast cancer stem cell marker ALDH-1.

The third generation oHSV vector G47Δ effectively killed different subtypes of breast cancer cells in vitro, with more than 98% of the tumor cells killed by day 5, even at multiplicities of infection(MOI) 0.01. Moreover, G47Δ equally targeted non-cancer stem cells (NCSCs) and CSCs which showed resistance to paclitaxel. We also demonstrated that G47Δ effectively replicated and spread among CSCs. Moreover, G47Δ impaired the self-renewal ability of CSCs, as the viable cells unable to form secondary tumor spheres. We also showed that G47Δ was able to induce the regression of tumor xenografts in BALB/c nude mice and demonstrated the ability of G47Δ to synergize with paclitaxel for killing both NCSCs and CSCs. This is the first report that oHSV effectively targets different breast cancer NCSCs and CSCs, thereby suggesting that oHSV may be an effective treatment modality for patients with breast cancer.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-05-01.

Distinct gating mechanisms revealed by the structures of a multi-ligand gated K(+) channel

The gating ring-forming RCK domain regulates channel gating in response to various cellular chemical stimuli in eukaryotic Slo channel families and the majority of ligand-gated prokaryotic K⁺ channels and transporters. Here we present structural and functional studies of a dual RCK-containing, multi-ligand gated K⁺ channel from Geobacter sulfurreducens, named GsuK. We demonstrate that ADP and NAD⁺ activate the GsuK channel, whereas Ca²⁺ serves as an allosteric inhibitor. Multiple crystal structures elucidate the structural basis of multi-ligand gating in GsuK, and also reveal a unique ion conduction pore with segmented inner helices. Structural comparison leads us to propose a novel pore opening mechanics that is distinct from other K⁺ channels.

DOI:http://dx.doi.org/10.7554/eLife.00184.001

Most cells are surrounded by a semipermeable membrane, and although this membrane allows very few molecules to pass through it, cells can use transmembrane proteins to overcome this barrier. Some of these proteins import glucose, amino acids and other nutrients into the cell, while others transport ions into or out of the cell. Ion transport across the cell membrane is essential for a wide variety of biological processes, including signal transduction and the generation of electrical impulses in nerve cells.

The pores that allow ions to travel through the cell membrane are known as ion channels, and most channels allow only one type of ion—usually sodium, calcium or potassium (K⁺) ions—to pass through them. There are many different types of ion channels and they are classified according to the type of ion they allow to pass through them, and by the gating mechanism that is used to open and close the channel. For example, ligand-gated K⁺ channels facilitate the passage of potassium ions and are opened and closed by ligands binding and unbinding to and from the channel.

Most K⁺ channels are made up of four identical subunits, and in the majority of ligand-gated K⁺ channels in prokaryotes, each of these subunits will have one or two ligand-binding RCK domains (where RCK stands for regulating the conductance of K⁺). This is also true for some K⁺ channels in eukaryotes. While it is known that RCK domains are responsible for regulating the transport of potassium ions across the cell membranes of diverse organisms, little is known about the structure or gating mechanisms of K⁺ channels that are gated by more than one ligand.

Kong et al. have studied a ligand-gated K⁺ channel called GsuK that has two RCK domains per subunit and is found in the bacterium G. sulfurreducens. They found that the opening process was mediated by a ligand that contains adenine, such as NAD⁺ or ADP, and the channel was closed by the presence of calcium ions. And by determining multiple crystal structures, Kong et al. were able to understand, from a structural point of view, how these ligands regulate this channel, and to propose a gating mechanism that is distinct from the mechanisms that are known to control other potassium channels.

DOI:http://dx.doi.org/10.7554/eLife.00184.002

[Experimental study of targeting MMP-9 deoxyribozyme role of adhesion and migration in human lung adenocarcinoma cancer cell.]

BACKGROUND

Deoxyribozyme has high biocatalytic activity and sequence specificity against the target mRNA and inhibits gene expression at mRNA level. The aim of this study is to investigate the impact of targeting MMP-9 deoxyribozyme to cell adhesion and migration in human lung adenocarcinoma cell line A549.

METHODS

The targeting MMP-9 deoxyribozyme was designed by oligofectamine into human lung adenocarcinoma cell line A549. The expression of MMP-9 in cell was detected by Western blot. The cell adhesion and migration after the intervention of deoxyribozyme was observed.

RESULTS

After targeting MMP-9 deoxyribozyme intervention, the expression of MMP-9 in the cells compared with the control group was significantly lower (P <0.01), at the same time, the rate of cell adhesion and migration were significantly decreased.

CONCLUSIONS

Targeting MMP-9 deoxyribozyme inhibited the expression of MMP-9 in human lung adenocarcinoma cell line A549 and effectively prevent cell adhesion and migration.

The correlation of HLA allele frequencies and HLA antibodies in sensitized kidney transplantation candidates

BACKGROUND

The clinical importance of the HLA system is as a transplant antigen. However, correlations between the development and strength of the immune response and HLA genes or specific foreign antigens are not clear.

OBJECTIVES

The objectives of this study were to detect HLA-A, -B, and -DRB1 allele frequencies and HLA antibodies in sensitized patients, and to investigate the correlation between the HLA alleles and HLA sensitization.

METHODS

This study included 383 sensitized patients and 1000 unsensitized patients awaiting kidney transplantation from 2001-2010. HLA -A, -B, and -DRB1 typing was performed using sequence-specific primer-polymerase chain reactions (SSP-PCR). Arlequin statistical analysis software was used to calculate the HLA allele frequencies among the 2 groups. The anti-HLA-specific antibodies of sensitized patients were identified and analyzed using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The numbers of identified HLA -A, -B, and -DRB1 alleles were 20, 43, and 14, respectively. The 5 most frequent HLA alleles in the 2 groups were not different: A-02, 11, 24, 33, 26; B-46, 60, 13, 75, 58; and DR-9, 15, 12, 4, 14. Among the sensitized group, the most frequent HLA-specific antibodies were as follows: A-2, 24, 68, 23, 32; B-27, 56, 57, 7, 60; and DR-7, 4, 9, 13, 17.

CONCLUSIONS

There was little correlation between HLA sensitization and HLA alleles of oneself. High frequency alleles and the specificity of high-frequency HLA antibodies were not consistent.

Structural insight into the ion-exchange mechanism of the sodium/calcium exchanger

Sodium/calcium (Na(+)/Ca(2+)) exchangers (NCX) are membrane transporters that play an essential role in maintaining the homeostasis of cytosolic Ca(2+) for cell signaling. We demonstrated the Na(+)/Ca(2+)-exchange function of an NCX from Methanococcus jannaschii (NCX_Mj) and report its 1.9 angstrom crystal structure in an outward-facing conformation. Containing 10 transmembrane helices, the two halves of NCX_Mj share a similar structure with opposite orientation. Four ion-binding sites cluster at the center of the protein: one specific for Ca(2+) and three that likely bind Na(+). Two passageways allow for Na(+) and Ca(2+) access to the central ion-binding sites from the extracellular side. Based on the symmetry of NCX_Mj and its ability to catalyze bidirectional ion-exchange reactions, we propose a structure model for the inward-facing NCX_Mj.