Regulatory NK cells mediated between immunosuppressive monocytes and dysfunctional T cells in chronic HBV infection

BACKGROUND AND AIMS

HBV infection represents a major health problem worldwide, but the immunological mechanisms by which HBV causes chronic persistent infection remain only partly understood. Recently, cell subsets with suppressive features have been recognised among monocytes and natural killer (NK) cells. Here we examine the effects of HBV on monocytes and NK cells.

METHODS

Monocytes and NK cells derived from chronic HBV-infected patients and healthy controls were purified and characterised for phenotype, gene expression and cytokines secretion by flow cytometry, quantitative real-time (qRT)-PCR, ELISA and western blotting. Culture and coculture of monocytes and NK cells were used to determine NK cell activation, using intracellular cytokines staining.

RESULTS

In chronic HBV infection, monocytes express higher levels of PD-L1, HLA-E, interleukin (IL)-10 and TGF-β, and NK cells express higher levels of PD-1, CD94 and IL-10, compared with healthy individuals. HBV employs hepatitis B surface antigen (HBsAg) to induce suppressive monocytes with HLA-E, PD-L1, IL-10 and TGF-β expression via the MyD88/NFκB signalling pathway. HBV-treated monocytes induce NK cells to produce IL-10, via PD-L1 and HLA-E signals. Such NK cells inhibit autologous T cell activation.

CONCLUSIONS

Our findings reveal an immunosuppressive cascade, in which HBV generates suppressive monocytes, which initiate regulatory NK cells differentiation resulting in T cell inhibition.

Coimmunoprecipitation of reversibly glycosylated polypeptide with sucrose synthase from developing castor oilseeds

The sucrose synthase (SUS) interactome of developing castor oilseeds (COS; Ricinus communis) was assessed using coimmunoprecipitation (co-IP) with anti-(COS RcSUS1)-IgG followed by proteomic analysis. A 41-kDa polypeptide (p41) that coimmunoprecipitated with RcSUS1 from COS extracts was identified as reversibly glycosylated polypeptide-1 (RcRGP1) by LC-MS/MS and anti-RcRGP1 immunoblotting. Reciprocal Far-western immunodot blotting corroborated the specific interaction between RcSUS1 and RcRGP1. Co-IP using anti-(COS RcSUS1)-IgG and clarified extracts from other developing seeds as well as cluster (proteoid) roots of white lupin and Harsh Hakea consistently recovered 90 kDa SUS polypeptides along with p41/RGP as a SUS interactor. The results suggest that SUS interacts with RGP in diverse sink tissues to channel UDP-glucose derived from imported sucrose into hemicellulose and/or glycoprotein/glycolipid biosynthesis.

WSSV envelope protein VP51B links structural protein complexes and may mediate virus infection

White spot syndrome virus (WSSV), an enveloped double-stranded DNA virus, is the causative agent of a disease that has led to severe mortalities of cultured shrimps in Taiwan and many other countries. In the previous study, Penaeus monodon chitin-binding protein (CBP) and glucose transporter 1 (Glut1), two cell membrane proteins, were found to at least interact with other 10 WSSV envelope proteins including VP51B. These envelope proteins might form a protein complex. According to the known information, VP51B was used to identify its role in the protein complex. Western blotting of the intact viral particles and fractionation of the viral components confirmed that VP51B is one of WSSV envelope proteins. In this study, the protein-protein interaction between VP51B and other WSSV envelope proteins was identified by far-western blot experiment and VP51B was found to interact with VP24, VP31, VP32, VP39B and VP41A. Furthermore, the in vivo neutralization experiment using recombinant VP51B plus with VP39B showed the best inhibition. These data indicate that VP51B participates in the WSSV protein complex and plays an important role in WSSV infection.

Elevated GFAP induces astrocyte dysfunction in caudal brain regions: A potential mechanism for hindbrain involved symptoms in type II Alexander disease

Alexander Disease (AxD) is a "gliopathy" caused by toxic, dominant gain-of-function mutations in the glial fibrillary acidic protein (GFAP) gene. Two distinct types of AxD exist. Type I AxD affected individuals develop cerebral symptoms by 4 years of age and suffer from macrocephaly, seizures, and physical and mental delays. As detection and diagnosis have improved, approximately half of all AxD patients diagnosed have onset >4 years and brainstem/spinal cord involvement. Type II AxD patients experience ataxia, palatal myoclonus, dysphagia, and dysphonia. No study has examined a mechanistic link between the GFAP mutations and caudal symptoms present in type II AxD patients. We demonstrate that two key astrocytic functions, the ability to regulate extracellular glutamate and to take up K(+) via K+ channels, are compromised in hindbrain regions and spinal cord in AxD mice. Spinal cord astrocytes in AxD transgenic mice are depolarized relative to WT littermates, and have a three-fold reduction in Ba(2+) -sensitive Kir4.1 mediated currents and six-fold reduction in glutamate uptake currents. The loss of these two functions is due to significant decreases in Kir4.1 (>70%) and GLT-1 (>60%) protein expression. mRNA expression for KCNJ10 and SLC1A2, the genes that code for Kir4.1 and GLT-1, are significantly reduced by postnatal Day 7. Protein and mRNA reductions for Kir4.1 and GLT-1 are exacerbated in AxD models that demonstrate earlier accumulation of GFAP and increased Rosenthal fiber formation. These findings provide a mechanistic link between the GFAP mutations/overexpression and the symptoms in those affected with Type II AxD.

A mutant O-GlcNAcase as a probe to reveal global dynamics of protein O-GlcNAcylation during Drosophila embryonic development

O-GlcNAcylation is a reversible type of serine/threonine glycosylation on nucleocytoplasmic proteins in metazoa. Various genetic approaches in several animal models have revealed that O-GlcNAcylation is essential for embryogenesis. However, the dynamic changes in global O-GlcNAcylation and the underlying mechanistic biology linking them to embryonic development is not understood. One of the limiting factors towards characterizing changes in O-GlcNAcylation has been the limited specificity of currently available tools to detect this modification. In the present study, harnessing the unusual properties of an O-GlcNAcase (OGA) mutant that binds O-GlcNAc (O-N-acetylglucosamine) sites with nanomolar affinity, we uncover changes in protein O-GlcNAcylation as a function of Drosophila development.

Tanshinone IIA attenuates interleukin-17A-induced systemic sclerosis patient-derived dermal vascular smooth muscle cell activation via inhibition of the extracellular signal-regulated kinase signaling pathway

OBJECTIVE

Salvia miltiorrhiza has long been used to treat systemic sclerosis. Tanshinone IIA, one of the phytochemicals derived from the roots of Salvia miltiorrhiza, exhibits multiple biological activities. The present study aimed to investigate whether tanshinone IIA has an effect on the interleukin-17A-induced functional activation of systemic sclerosis patient-derived dermal vascular smooth muscle cells.

METHODS

Systemic sclerosis patient-derived dermal vascular smooth muscle cells were incubated with various dosages of tanshinone IIA in the presence of interleukin-17A or the serum of systemic sclerosis patients. Cell proliferation was assessed using Cell Counting Kit-8. The expression of collagen 1 and 3 in cells was evaluated by immunofluorescence. Cell migration was measured using a transwell assay. The expression of phospho-extracellular signal-regulated kinase was detected by Western blotting.

RESULTS

Our data demonstrate that tanshinone IIA exerts an inhibitory effect on interleukin-17A-induced systemic sclerosis patient-derived dermal vascular smooth muscle cell proliferation, collagen synthesis and migration.

CONCLUSION

These findings suggest that tanshinone IIA might serve as a promising therapeutic agent for the treatment of systemic sclerosis.

Oligomerization and phosphorylation dependent regulation of ArgBP2 adaptive capabilities and associated functions

ArgBP2 (Arg-Binding Protein 2/SORBS2) is an adaptor protein involved in cytoskeleton associated signal transduction, thereby regulating cell migration and adhesion. These features are associated with its antitumoral role in pancreatic cancer cells. Tyrosine phosphorylation of ArgBP2, mediated by c-Abl kinase and counterbalanced by PTP-PEST phosphatase, regulates many of its interactions. However, the exact mechanisms of action and of regulation of ArgBP2 remain largely unknown. We found that ArgBP2 has the capacity to form oligomers which are destabilized by tyrosine phosphorylation. We could show that ArgBP2 oligomerization involves the binding of one of its SH3 domains to a specific proline rich cluster. ArgBP2 self-association increases its binding to some of its molecular partners and decreased its affinity for others. Hence, the phosphorylation/oligomerization state of ArgBP2 directly regulates its functions by modulating its adaptive capabilities. Importantly, using a human pancreatic cancer cell model (MiaPaCa-2 cells), we could validate that this property of ArgBP2 is critical for its cytoskeleton associated functions. In conclusions, we describe a new mechanism of regulation of ArgBP2 where tyrosine phosphorylation of the protein interfere with a SH3 mediated self-interaction, thereby controlling its panel of interacting partners and related functions.

Functional characterization of a slow and tight-binding inhibitor of plasmin isolated from Russell's viper venom

BACKGROUND

Snake venoms are rich in Kunitz-type protease inhibitors that may have therapeutic applications. However, apart from trypsin or chymotrypsin inhibition, the functions of most of these inhibitors have not been elucidated. A detailed functional characterization of these inhibitors may lead to valuable drug candidates.

METHODS

A Kunitz-type protease inhibitor, named DrKIn-II, was tested for its ability to inhibit plasmin using various approaches such as far western blotting, kinetic analyses, fibrin plate assay and euglobulin clot lysis assay. In addition, the antifibrinolytic activity of DrKIn-II was demonstrated in vivo.

RESULTS

DrKIn-II potently decreased the amidolytic activity of plasmin in a dose-dependent manner, with a global inhibition constant of 0.2nM. Inhibition kinetics demonstrated that the initial binding of DrKIn-II causes the enzyme to isomerize, leading to the formation of a much tighter enzyme-inhibitor complex. DrKIn-II also demonstrated antifibrinolytic activity in fibrin plate assay and significantly prolonged the lysis of the euglobulin clot. Screening of DrKIn-II against a panel of serine proteases indicated that plasmin is the preferential target of DrKIn-II. Furthermore, DrKIn-II treatment prevented the increase of FDP in coagulation-stimulated mice and significantly reduced the bleeding time in a murine tail bleeding model.

CONCLUSION

DrKIn-II is a potent, slow and tight-binding plasmin inhibitor that demonstrates antifibrinolytic activity both in vitro and in vivo.

GENERAL SIGNIFICANCE

This is the first in-depth functional characterization of a plasmin inhibitor from a viperid snake. The potent antifibrinolytic activity of DrKIn-II makes it a potential candidate for the development of novel antifibrinolytic agents.

Anti-inflammatory effects of prosapogenin III from the dried roots of Liriope platyphylla in LPS-stimulated RAW264.7 cells

Liriope platyphylla has been reported to possess various biological activities, including anti-asthma, anti-inflammation, anti-diabetes, and neuriotogenic properties. In this study, we evaluated the effects of prosapogenin III isolated from the roots of L. platyphylla (Liriopis Tuber) on inflammatory responses in lipopolysaccharide (LPS) stimulated RAW264.7 mouse macrophages. We investigated LPS-induced production/expression of inflammatory mediators such as nitric oxide (NO), inducible nitric oxide synthase (iNOS), cyclooxigenase-2 (COX-2), and proinflammatory cytokines, including interleukin-1β (IL-1β) and interleukin (IL)-6 in RAW264.7 cells. We also performed Western blot analysis for determination of the phosphorylation of mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase (ERK) 1/2, p38, and c-Jun N-terminal kinase (JNK), and nuclear translocation of nuclear factor-κB (NF-κB) in LPS-stimulated cells. Treatment with prosapogenin III resulted in significant inhibition of NO production in LPS-stimulated Raw264.7 cells through suppression of iNOS expression. Treatment with prosapogenin III resulted in a significant decrease in expressions of COX-2, IL-1β, and IL-6 through down-regulation of their mRNA or protein in LPS-stimulated cells. In addition, treatment with prosapogenin III resulted in potently inhibited phosphorylation of three MAPKs, including ERK1/2, p38, and JNK in LPS-stimulated cells. Treatment with prosapogenin III also resulted in suppression of the nuclear translocation of NF-κB in LPS-stimulated cells. These results indicate that prosapogenin III of Liriopis Tuber has anti-inflammatory effects in activated macrophages through inhibition of production of inflammatory mediators by blockade of the MAPK/NF-κB pathway.

Heterogeneous interactome between Litopenaeus vannamei plasma proteins and Vibrio parahaemolyticus outer membrane proteins

A great loss has been suffered by microbial infectious diseases under intensive shrimp farming in recent years. In this background, the understanding of shrimp innate immunity becomes an importantly scientific issue, but little is known about the heterogeneous protein-protein interaction between pathogenic cells and hosts, which is a key step for the invading microbes to infect internet organs through bloodstream. In the present study, bacterial outer membrane (OM) protein array and pull-down approaches are used to isolate both Vibrio parahaemolyticus OM proteins that bind to shrimp serum proteins and the shrimp serum proteins that interact with bacterial cells, respectively. Three interacting shrimp serum proteins, hemocyanin, β-1,3-glucan binding protein and LV_HP_RA36F08r and thirty interacting OM proteins were determined. They form 63 heterogeneous protein-protein interactions. Nine out of the 30 OM proteins were randomly demonstrated to be up-regulated or down-regulated when bacterial cells were cultured with shrimp sera, indicating the biological significance of the network. The interesting findings uncover the complexity of struggle between host immunity and bacterial infection. Compared with our previous report on heterogeneous interactome between fish grill and bacterial OM proteins, the present study further extends the investigation from lower vertebrates to invertebrates and develops a bacterial OM protein array to identify the OM proteins bound with shrimp serum proteins, which elevates the frequencies of the bound OM proteins. Our results highlight the way to determine and understand the heterogeneous interaction between hosts and microbes.

The adaptor protein SAP directly associates with CD3ζ chain and regulates T cell receptor signaling

Mutations altering the gene encoding the SLAM associated protein (SAP) are responsible for the X-linked lymphoproliferative disease or XLP1. Its absence is correlated with a defective NKT cells development, a decrease in B cell functions and a reduced T cells and NK cells cytotoxic activities, thus leading to an immunodeficiency syndrome. SAP is a small 128 amino-acid long protein that is almost exclusively composed of an SH2 domain. It has been shown to interact with the CD150/SLAM family of receptors, and in a non-canonical manner with SH3 containing proteins such as Fyn, βPIX, PKCθ and Nck1. It would thus play the role of a minimal adaptor protein. It has been shown that SAP plays an important function in the activation of T cells through its interaction with the SLAM family of receptors. Therefore SAP defective T cells display a reduced activation of signaling events downstream of the TCR-CD3 complex triggering. In the present work, we evidence that SAP is a direct interactor of the CD3ζ chain. This direct interaction occurs through the first ITAM of CD3ζ, proximal to the membrane. Additionally, we show that, in the context of the TCR-CD3 signaling, an Sh-RNA mediated silencing of SAP is responsible for a decrease of several canonical T cell signaling pathways including Erk, Akt and PLCγ1 and to a reduced induction of IL-2 and IL-4 mRNA. Altogether, we show that SAP plays a central function in the T cell activation processes through a direct association with the CD3 complex.

Nucleolin interacts with US11 protein of herpes simplex virus 1 and is involved in its trafficking

Herpes simplex virus type 1 (HSV-1) infection induces profound nucleolar modifications at the functional and organizational levels, including nucleolar invasion by several viral proteins. One of these proteins is US11, which exhibits several different functions and displays both cytoplasmic localization and clear nucleolar localization very similar to that of the major multifunctional nucleolar protein nucleolin. To determine whether US11 interacts with nucleolin, we purified US11 protein partners by coimmunoprecipitations using a tagged protein, Flag-US11. From extracts of cells expressing Flag-US11 protein, we copurified a protein of about 100 kDa that was further identified as nucleolin. In vitro studies have demonstrated that nucleolin interacts with US11 and that the C-terminal domain of US11, which is required for US11 nucleolar accumulation, is sufficient for interaction with nucleolin. This association was confirmed in HSV-1-infected cells. We found an increase in the nucleolar accumulation of US11 in nucleolin-depleted cells, thereby revealing that nucleolin could play a role in US11 nucleocytoplasmic trafficking through one-way directional transport out of the nucleolus. Since nucleolin is required for HSV-1 nuclear egress, the interaction of US11 with nucleolin may participate in the outcome of infection.

The molecular assembly of amyloid aβ controls its neurotoxicity and binding to cellular proteins

Accumulation of β-sheet-rich peptide (Aβ) is strongly associated with Alzheimer's disease, characterized by reduction in synapse density, structural alterations of dendritic spines, modification of synaptic protein expression, loss of long-term potentiation and neuronal cell death. Aβ species are potent neurotoxins, however the molecular mechanism responsible for Aβ toxicity is still unknown. Numerous mechanisms of toxicity were proposed, although there is no agreement about their relative importance in disease pathogenesis. Here, the toxicity of Aβ 1–40 and Aβ 1–42 monomers, oligomers or fibrils, was evaluated using the N2a cell line. A structure-function relationship between peptide aggregation state and toxic properties was established. Moreover, we demonstrated that Aβ toxic species cross the plasma membrane, accumulate in cells and bind to a variety of internal proteins, especially on the cytoskeleton and in the endoplasmatic reticulum (ER). Based on these data we suggest that numerous proteins act as Aβ receptors in N2a cells, triggering a multi factorial toxicity.

Effects of estradiol on ischemic factor-induced astrocyte swelling and AQP4 protein abundance

In the early hours of ischemic stroke, cerebral edema forms as Na, Cl, and water are secreted across the blood-brain barrier (BBB) and astrocytes swell. We have shown previously that ischemic factors, including hypoxia, aglycemia, and arginine vasopressin (AVP), stimulate BBB Na-K-Cl cotransporter (NKCC) and Na/H exchanger (NHE) activities and that inhibiting NKCC and/or NHE by intravenous bumetanide and/or HOE-642 reduces edema and infarct in a rat model of ischemic stroke. Estradiol also reduces edema and infarct in this model and abolishes ischemic factor stimulation of BBB NKCC and NHE. There is evidence that NKCC and NHE also participate in ischemia-induced swelling of astrocytes. However, little is known about estradiol effects on astrocyte cell volume. In this study, we evaluated the effects of AVP (100 nM), hypoxia (7.5% O(2)), aglycemia, hypoxia (2%)/aglycemia [oxygen glucose deprivation (OGD)], and estradiol (1-100 nM) on astrocyte cell volume using 3-O-methyl-d-[(3)H]glucose equilibration methods. We found that AVP, hypoxia, aglycemia, and OGD (30 min to 5 h) each significantly increased astrocyte cell volume, and that estradiol (30-180 min) abolished swelling induced by AVP or hypoxia, but not by aglycemia or OGD. Bumetanide and/or HOE-642 also abolished swelling induced by AVP but not aglycemia. Abundance of aquaporin-4, known to participate in ischemia-induced astrocyte swelling, was significantly reduced following 7-day but not 2- or 3-h estradiol exposures. Our findings suggest that hypoxia, aglycemia, and AVP each contribute to ischemia-induced astrocyte swelling, and that the edema-attenuating effects of estradiol include reduction of hypoxia- and AVP-induced astrocyte swelling and also reduction of aquaporin-4 abundance.

Chlamydophila pneumoniae induces production of the defensin-like MIG/CXCL9, which has in vitro antichlamydial activity

CXC chemokines that lack the ELR motif, including the monokine induced by IFN-γ (MIG/CXCL9), the IFN-induced protein of 10 kDa (IP-10/CXCL10), and the IFN-inducible T-cell α-chemoattractant (I-TAC/CXCL11), have been shown to mediate the generation of type 1 immune responses and to possess defensin-like bactericidal effects. This study revealed that the infection of mice with Chlamydophila pneumoniae via the intranasal route resulted in the local expression of MIG/CXCL9, IP-10/CXCL10, and I-TAC/CXCL11. The expression of IP-10/CXCL10 and I-TAC/CXCL11 mRNA peaked on day 4. On day 7, the expression of MIG/CXCL9 mRNA in the infected lungs was increased 156-fold relative to that in the uninfected mouse lungs. MIG/CXCL9 was also detected at a protein level from day 1, with the highest concentration in the supernatants of the infected lungs on day 7. The expression of IFN-γ displayed similar kinetics. C. pneumoniae and its inactivated form also induced the production of MIG/CXCL9 in mouse fibroblasts and in the murine macrophage cell line J774A in vitro. Cotreatment of the tissue cultures with C. pneumoniae and different quantities of IFN-γ resulted in strong increases in MIG/CXCL9 production. Recombinant MIG/CXCL9 exerted dose-dependent antibacterial activity against C. pneumoniae. Significant antichlamydial activity of MIG/CXCL9 was observed after a 15-min incubation period. Chlamydial proteins at a molecular weight of 60 kDa were identified by Far-Western blot assay and liquid chromatography-tandem mass spectrometry as binding molecules of MIG/CXCL9. The results of these experiments suggest that MIG/CXCL9 might play an important role in the innate and acquired defense mechanisms against C. pneumoniae.

The helper-component protease transmission factor of tobacco etch potyvirus binds specifically to an aphid ribosomal protein homologous to the laminin receptor precursor

Potyviruses are plant pathogens transmitted by aphids in a non-persistent manner. During transmission, the virus-encoded factor helper-component protease (HCPro) is presumed to act as a molecular bridge, mediating the reversible retention of virions to uncharacterized binding sites in the vector mouthparts. Whilst the predicted interaction between HCPro and the coat protein (CP) of virions has been confirmed experimentally, the characterization of putative HCPro-specific receptors in aphids has remained elusive, with the exception of a report that described binding of HCPro of zucchini yellow mosaic virus to several cuticle proteins. To identify other aphid components that could play a role during transmission, this study used purified HCPro of tobacco etch virus (TEV) in far-Western blotting assays as bait to select interactors among proteins extracted from aphid heads. With this approach, new HCPro-interacting proteins were found, and several were identified after mass spectrometry analysis and searches in databases dedicated to aphid sequences. Among these interactors, a ribosomal protein S2 (RPS2) was chosen for further investigation due to its homology with the laminin receptor precursor, known to act as the receptor of several viruses. The specific interaction between RPS2 and TEV HCPro was confirmed after cloning and heterologous expression of the corresponding Myzus persicae gene. The possible involvement of RPS2 in the transmission process was further suggested by testing a variant of HCPro that was non-functional for transmission due to a mutation in the conserved KITC motif (EITC variant). This variant retained its ability to bind CP but failed to interact with RPS2.

Functional interaction between MutL and 3'-5' exonuclease X in Escherichia coli

Exonuclease X is a 3'-5' distributive exonuclease that functions in DNA recombination and repair. It undergoes multiple rounds of binding, hydrolysis, and release to degrade long substrate molecules and thus is very inefficient. In order to identify a cofactor that elevates the excision activity of ExoX, we screened many proteins involved in repair and recombination. We observed that MutL greatly promoted the exonuclease activity of ExoX, and then verified the interaction between MutL and ExoX using SPR and Far-Western analysis. This promotion is independent of ATP and the DNA-binding activity of MutL. We constructed two deletion mutants to analyze this interaction and its regulation of ExoX activity, and found that this functional interaction with ExoX is mainly due to ionic interactions with the N-terminus of MutL. This adds a new role to MutL and gives a clue to MutL's possible regulation on other DnaQ family exonuclease members.

A complex of Shc and Ran-GTPase localises to the cell nucleus

The three isoforms of the adaptor protein Shc play diverse roles in cell signalling. For example, the observation of p46 Shc in the nuclei of hepatocellular carcinoma cells suggests a function quite distinct from the better characterised cytoplasmic role. Ligands responsible for the transport of various Shc isoforms into organelles such as the nucleus have yet to be reported. To identify such ligands a far western approach was used to determine the p52 Shc interactome. The Ran-GTPase nuclear transport protein was identified and found to bind to p52 Shc in vitro with low micromolar affinity. Co-immunoprecipitation, pull down and fluorescence lifetime imaging microscopy experiments in stable cells confirmed cellular interaction and nuclear localisation. The nuclear transport factor protein NTF2, which functions in cohort with Ran, was shown to form a complex with both RAN and Shc, suggesting a mechanism for Shc entry into the nucleus as part of a tertiary complex.

Delineation of pulmonary airway fluid protein fractions with HRPO binding-avidity by far-Western ligand blot and mass spectrometry analyses: a model methodology for detecting mannose-binding protein expression profiles

BACKGROUND AND AIM OF WORK

Limited research to date has characterized the potential for HRPO to function as a primary molecular probe.

METHODS

Pulmonary airway fluid was developed by non-reducing far-Western (ligand) blot analyses utilizing conjugated HRPO-strepavidin or non-conjugated HRPO without the presence of primary immunoglobulin. Endogenous esterase-like biochemical activity of fractions within pulmonary airway fluid was inactivated to determine if they were capable of biochemically converting HRPO chemiluminescent substrate. Complementary analyses modified pulmonary fluid and HRPO with beta-galactosidase and alpha-mannosidase respectively, in addition to determining the influence of mannose and maltose competitive binding on HRPO far-Western (ligand) blot analyses. Identification of pulmonary fluid fractions detected by HRPO far-Western blot analyses was determined by mass spectrometry.

RESULTS

Modification of pulmonary fluid with beta-galactosidase, and HRPO with alpha-mannosidase in concert with maltose and mannose competitive binding analyses altered the intensity and spectrum of pulmonary fluid fractions detected by HRPO far-Western blot analysis. Identity of pulmonary airway fluid fractions detected by HRPO far-Western (ligand) blot analysis were transferrin, dynein, albumin precursor, and two 156 kDa equine peptide fragments.

CONCLUSIONS

HRPO can function as a partially-selective primary molecular probe when applied in either a conjugated or non-conjugated form. Some protein fractions can form complexes with HRPO through molecular mechanisms that involve physical interactions at the terminal alpha-mannose-rich regions of HRPO glycan side-chains. Based on its known molecular composition and structure, HRPO provides an opportunity for the development of diagnostics methodologies relevant to disease biomarkers that possess mannose-binding avidity.

Identification of novel Smad2 and Smad3 associated proteins in response to TGF-beta1

Transforming growth factor-beta 1 (TGF-beta1) is an important growth inhibitor of epithelial cells and insensitivity to this cytokine results in uncontrolled cell proliferation and can contribute to tumorigenesis. TGF-beta1 signals through the TGF-beta type I and type II receptors, and activates the Smad pathway via phosphorylation of Smad2 and Smad3. Since little is known about the selective activation of Smad2 versus Smad3, we set out to identify novel Smad2 and Smad3 interacting proteins in epithelial cells. A non-transformed human cell line was transduced with Myc-His(6)-Smad2 or Myc-His(6)-Smad3-expressing retrovirus and was treated with TGF-beta1. Myc-His(6)-Smad2 or Myc-His(6)-Smad3 was purified by tandem affinity purification, eluates were subject to SDS-PAGE and Colloidal Blue staining, and select protein bands were digested with trypsin. The resulting tryptic peptides were analyzed by liquid chromatography (LC) and tandem mass spectrometry (MS/MS) and the SEQUEST algorithm was employed to identify proteins in the bands. A number of proteins that are known to interact with Smad2 or Smad3 were detected in the eluates. In addition, a number of putative novel Smad2 and Smad3 associated proteins were identified that have functions in cell proliferation, apoptosis, actin cytoskeleton regulation, cell motility, transcription, and Ras or insulin signaling. Specifically, the interaction between Smad2/3 and the Cdc42 guanine nucleotide exchange factor, Zizimin1, was validated by co-immunoprecipitation. The discovery of these novel Smad2 and/or Smad3 associated proteins may reveal how Smad2 and Smad3 are regulated and/or uncover new functions of Smad2 and Smad3 in TGF-beta1 signaling.

Screening of LRRK2 interactants by yeast 2-hybrid analysis

OBJECTIVE

To isolate and identify the potential binding partners of LRRK2, a gene linked to both dominant familial form and sporadic form of Parkinson's disease, thus to further our knowledge of its function.

METHODS

We used a sequence containing full-length of COR domain and part of ROC and MAPKKK domain as bait. The bait amplified by polymerase chain reaction (PCR) was then cloned into a yeast expression plasmid pGBKT7. After being sequenced and analyzed, pGBKT7-bait was transformed into the yeast strain AH109. Western blot was performed to confirm the expression of pGBKT7-bait in AH109 yeast strain. Then human fetal brain cDNA library was transformed into that yeast strain, which could express pGBKT7-bait fusion protein. The yeast strain which contained pGBKT7-bait and human fetal brain cDNA library was plated on quadruple dropout medium (SD/-Trp/-Leu/-His/-Ade) containing X-alpha-gal. We retested these positive colonies using 2 independent yeast strains AH109 contained pGBKT7-bait or pGBKT7, respectively. At last, these plasmids isolated from these true positive colonies were analyzed by bioinformatics.

RESULTS

We obtained 9 true positive colonies, these colonies were sequenced, and we performed sequence Blast in GenBank. Three colonies of the 9 positive colonies were not in open reading-frames. Among other 6 colonies, there were known proteins including spermatid perinuclear RNA-binding protein (STRBP) and BCL2-associated athanogene 5 isoform b (BAG5), as well as unknown proteins including tyrosine phosphatase non-receptor type (PTPN23), l(3)mbt-like 3 isoform b (L3MBTL3), RALY RNA binding protein-like isoform 1 (RALYL), and Homo sapiens mRNA for KIAA1783 protein, partial cds (KIAA1783).

CONCLUSION

True positive colonies of LRRK2 are successfully obtained by the yeast 2-hybrid. Our screened proteins may provide a new research clue for revealing biological functions of LRRK2, pathogenesis of Parkinson's disease, and other neurodegerations.

Atrial natriuretic peptide production and natriuretic peptide receptors in the human uterus and their effect on myometrial relaxation

OBJECTIVE

The objective of the study was to identify the effect of atrial natriuretic peptide (ANP) on uterine contractility, production of ANP, and natriuretic peptide receptor (NPR) expression in human myometrial tissue.

STUDY DESIGN

In an institutional review board-approved study, gravid human myometrium was obtained from patients undergoing cesarean section. Uterine contractility was examined using isometric force tension studies. After regular uterine contractions were obtained with oxytocin, ANP was added in increasing concentrations. ANP concentration was measured from myometrial tissue using radioimmunoassay (RIA). Primary myometrial cell culture was performed and treated with nifedipine vs oxytocin. RIA was performed on these cells and the cell culture media. Western blot analysis was performed on uterine tissue samples for natriuretic peptide receptors.

RESULTS

With increasing concentration of ANP (starting at 3 pM), myometrial contraction frequency decreased. ANP was identified in primary cultured myometrial cells and cell culture media. Myometrial ANP concentration increased with advancing gestational age. The concentration of ANP decreased within myometrial cells treated with oxytocin. The amount of ANP in the cell culture media increased from cells treated with nifedipine. Western blot identified NPR-A, -B, and -C in myometrial tissue. NPR-A expression was significantly increased in preterm samples.

CONCLUSION

ANP has a dose dependent effect on uterine relaxation. ANP is present in human myometrial cells and appears to be secreted by myometrial cells. The concentration of ANP may vary with gestational age and modulators of uterine contractility. NPR-A, -B, and -C receptor proteins are present in myometrial tissue. NPR-A levels may correlate with gestational age.

The nucleocapsid protein of severe acute respiratory syndrome coronavirus inhibits cell cytokinesis and proliferation by interacting with translation elongation factor 1alpha

Severe acute respiratory syndrome coronavirus (SARS-CoV) is the etiological agent of SARS, an emerging disease characterized by atypical pneumonia. Using a yeast two-hybrid screen with the nucleocapsid (N) protein of SARS-CoV as a bait, the C terminus (amino acids 251 to 422) of the N protein was found to interact with human elongation factor 1-alpha (EF1alpha), an essential component of the translational machinery with an important role in cytokinesis, promoting the bundling of filamentous actin (F-actin). In vitro and in vivo interaction was then confirmed by immuno-coprecipitation, far-Western blotting, and surface plasmon resonance. It was demonstrated that the N protein of SARS-CoV induces aggregation of EF1alpha, inhibiting protein translation and cytokinesis by blocking F-actin bundling. Proliferation of human peripheral blood lymphocytes and other human cell lines was significantly inhibited by the infection of recombinant retrovirus expressing SARS-CoV N protein.

Aberrant Notch3 and Notch4 expression in human hepatocellular carcinoma

BACKGROUND

Notch signalling is altered in several solid tumours and it plays a role in growth inhibition and apoptosis of hepatocellular carcinoma (HCC)-derived cell lines, bile duct development and hepatocyte regeneration.

AIMS

This study aims to analyse the expression of Notch3, Notch4 and HES1 and HES6 as Notch-target genes in HCC, matched non-neoplastic tissue and HEPG2 cells.

RESULTS

Notch3 and Notch4 are not expressed in normal liver and in chronic hepatitis surrounding HCC. Cirrhotic tissue stains negative for Notch3, while Notch4 is expressed by hepatocytes at the edge of regenerative nodules and in cell planes adjacent to fibrous septa. HCC tissue displays Notch3 and Notch4 abnormal accumulation, respectively, in 78% and 68% of the cases. The endothelium of hepatic veins with neoplastic permeation is frequently Notch4 positive. An upregulation of Notch3 mRNA was found in 95% of HCCs vs cirrhosis (P=0.0001), while Notch4 mRNA was downregulated in 80% of HCCs. HES6 mRNA expression was higher in HCC tissue when compared with cirrhosis (P=0.007), paralleling Notch3 mRNA expression. The HEPG2 cell line displays high Notch3 and low Notch4 protein and mRNA levels.

CONCLUSIONS

These descriptive findings suggest an aberrant expression of Notch3 and Notch4 in HCC and allow the hypothesis of an activation of Notch signalling by Notch3.

Analysis of interactions between nutrient germinant receptors and SpoVA proteins ofBacillus subtilisspores

Yeast two-hybrid and Far Western analyses were used to detect interactions between Bacillus subtilis spores' nutrient germinant receptor proteins and proteins encoded by the spoVA operon, all of which are involved in spore germination and located in the spores' inner membrane. These analyses indicated that two subunits of the GerA nutrient germinant receptor interact, consistent with previous genetic data, and that some GerA proteins interact with SpoVAD and some with SpoVAE. SpoVA proteins appear to be involved in the release of the spore's dipicolinic acid during spore germination, an event triggered by the binding of nutrient germinants to their receptors. Consequently, these new findings suggest that nutrient germinant receptors physically contact SpoVA proteins, and presumably this is a route for signal transduction during spore germination.