Distribution by Scientific Domains

Kinds of Immunoprecipitation

  • chromatin immunoprecipitation

  • Terms modified by Immunoprecipitation

  • immunoprecipitation analysis
  • immunoprecipitation experiment
  • immunoprecipitation studies

  • Selected Abstracts

    Re-oxygenation of hypoxic simian virus 40 (SV40)-infected CV1 cells causes distinct changes of SV40 minichromosome-associated replication proteins

    FEBS JOURNAL, Issue 9 2002
    Hans-Jörg Riedinger
    Hypoxia interrupts the initiation of simian virus 40 (SV40) replication in vivo at a stage situated before unwinding of the,origin region. After re-oxygenation, unwinding followed by a synchronous round of viral replication takes place. To,further characterize the hypoxia-induced inhibition of unwinding, we analysed the binding of several replication proteins to the viral minichromosome before and after re-oxygenation. T antigen, the 34-kDa subunit of replication protein A (RPA), topoisomerase I, the 48-kDa subunit of primase, the 125-kDa subunit of polymerase ,, and the 37-kDa subunit of replication factor C (RFC) were present at the viral chromatin already under hypoxia. The 70-kDa subunit of RPA, the 180-kDa subunit of polymerase ,, and proliferating cell nuclear antigen (PCNA) were barely detectable at the SV40 chromatin under hypoxia and significantly increased after re-oxygenation. Immunoprecipitation of minichromosomes with T antigen-specific antibody and subsequent digestion with micrococcus nuclease revealed that most of the minichromosome-bound T antigen was associated with the viral origin in hypoxic and in re-oxygenated cells. T antigen-catalysed unwinding of the SV40 origin occurred, however, only after re-oxygenation as indicated by (a) increased sensitivity of re-oxygenated minichromosomes against digestion with single-stranded DNA-specific nuclease P1; (b) stabilization of RPA-34 binding at the SV40 minichromosome; and (c) additional phosphorylations of RPA-34 after re-oxygenation, probably catalysed by DNA-dependent protein kinase. The results presented suggest that the subunits of the proteins necessary for unwinding, primer synthesis and primer elongation first assemble at the SV40 origin in form of stable, active complexes directly before they start to work. [source]

    Plk3 inhibits pro-apoptotic activity of p73 through physical interaction and phosphorylation

    GENES TO CELLS, Issue 7 2009
    Meixiang Sang
    Plk3, one of Polo-like kinase family members, is involved in the regulation of cell cycle progression and DNA damage response. In this study, we found that Plk3 inhibits pro-apoptotic activity of p73 through physical interaction and phosphorylation. During cisplatin (CDDP)-mediated apoptosis, Plk3 was transcriptionally induced, whereas its protein level was kept at basal level, suggesting that Plk3 might rapidly degrade in response to CDDP. Immunoprecipitation and in vitro pull-down experiments demonstrated that Plk3 interacts with p73. Luciferase reporter assays and RT-PCR experiments revealed that Plk3 inhibits p73-mediated transcriptional activity. Consistent with these results, pro-apoptotic activity of p73 was blocked by Plk3. Additionally, Plk3 decreased the stability of p73. Intriguingly, kinase-deficient Plk3 failed to inhibit p73 function, indicating that kinase activity of Plk3 is required for Plk3-mediated inhibition of p73. Indeed, in vitro kinase reaction showed that NH2 -terminal portion of p73 is phosphorylated by Plk3. In accordance with these observations, knocking down of Plk3 increased the stability of p73 and promoted CDDP-mediated apoptosis in association with up-regulation of p73. Collectively, our present findings suggest that Plk3 plays an important role in the regulation of cell fate determination in response to DNA damage through the inhibition of p73. [source]

    BIP, a BRAM-interacting protein involved in TGF-, signalling, regulates body length in Caenorhabditis elegans

    GENES TO CELLS, Issue 7 2001
    Katsura Sugawara
    Background The TGF-, superfamily has diverse biological activities and is involved in the early development of animals. We previously identified a novel family member, BMP receptor associated molecule (BRAM), which binds to the intracellular domain of BMP type IA receptor and is involved in the BMP signalling pathway. Results To identify novel molecules involved in TGF-, signalling pathways, we performed yeast two-hybrid screening using BRAM as bait. From a Xenopus cDNA library, we cloned a cDNA encoding 693 amino acids and containing the motif for an oxysterol binding protein (OSBP), which we designated BRAM interacting protein (BIP). We then isolated a BIP homologue from the Caenorhabditis elegans that encodes 733 amino acids and also contains the OSBP-like motif. Immunoprecipitation and Western blotting studies revealed that C. elegans BIP could interact with the C. elegans BRAM homologues BRA-1 and BRA-2. C. elegans BIP was expressed in pharyngeal muscle, hypodermis and several neuronal cells, an expression pattern overlaps with those of BRA-1 and BRA-2. Finally, we found that inhibition of BIP expression in C. elegans by double stranded RNA interference produces a Sma phenotype. Conclusions BIP was isolated using the yeast two-hybrid systems. BIP may function in the TGF-, pathway and regulate body length in C. elegans. [source]

    Potassium channel Kir4.1 macromolecular complex in retinal glial cells

    GLIA, Issue 2 2006
    Nathan C. Connors
    Abstract A major role for Müller cells in the retina is to buffer changes in the extracellular K+ concentration ([K+]o) resulting from light-evoked neuronal activity. The primary K+ conductance in Müller cells is the inwardly rectifying K+ channel Kir4.1. Since this channel is constitutively active, K+ can enter or exit Müller cells depending on the state of the [K+]o. This process of [K+]o buffering by Müller cells ("K+ siphoning") is enhanced by the precise accumulation of these K+ channels at discrete subdomains of Müller cell membranes. Specifically, Kir4.1 is localized to the perivascular processes of Müller cells in animals with vascular retinas and to the endfeet of Müller cells in all species examined. The water channel aquaporin-4 (AQP4) also appears to be important for [K+]o buffering and is expressed in Müller cells in a very similar subcellular distribution pattern to that of Kir4.1. To gain a better understanding of how Müller cells selectively target K+ and water channels to discrete membrane subdomains, we addressed the question of whether Kir4.1 and AQP4 associate with the dystrophin,glycoprotein complex (DGC) in the mammalian retina. Immunoprecipitation (IP) experiments were utilized to show that Kir4.1 and AQP4 are associated with DGC proteins in rat retina. Furthermore, AQP4 was also shown to co-precipitate with Kir4.1, suggesting that both channels are tethered together by the DGC in Müller cells. This work further defines a subcellular localization mechanism in Müller cells that facilitates [K+]o buffering in the retina. © 2005 Wiley-Liss, Inc. [source]

    ,IV tubulin is selectively expressed by oligodendrocytes in the central nervous system

    GLIA, Issue 3 2005
    Nobuo Terada
    Abstract Oligodendrocyte differentiation and myelination involve dramatic changes in cell signaling pathways, gene expression patterns, cell shape, and cytoskeletal organization. In a pilot study investigating CNS angiogenesis, oligodendrocytes were intensely labeled by antisera directed against the C-terminal of Tie-2, a 140-kDa transmembrane receptor for angiopoietin. Immunoprecipitation of rat brain proteins with Tie-2 C-terminal antisera, however, produced a single spot of ,55-kDa pI ,5 by two-dimensional (2D) electrophoresis, which was identified as ,-tubulin by mass spectrometry. Isotype-specific antibodies for ,IV tubulin selectively labeled oligodendrocytes. First detected in premyelinating oligodendrocytes, ,IV tubulin was abundant in myelinating oligodendrocyte perinuclear cytoplasm and processes extending to and along developing myelin internodes. ,IV tubulin-positive MTs were diffusely distributed in oligodendrocyte perinuclear cytoplasm and not organized around the centrosome. ,IV tubulin may play a role in establishing the oligodendrocyte MT network, which is essential for the transport of myelin proteins, lipids, and RNA during myelination. © 2005 Wiley-Liss, Inc. [source]

    Nuclear translocation of UDCA by the glucocorticoid receptor is required to reduce TGF-,1,induced apoptosis in rat hepatocytes,

    HEPATOLOGY, Issue 4 2005
    Susana Solá
    Ursodeoxycholic acid (UDCA) inhibits classical mitochondrial pathways of apoptosis by either directly stabilizing mitochondrial membranes or modulating specific upstream targets. Furthermore, UDCA regulates apoptosis-related genes from transforming growth factor ,1 (TGF-,1),induced hepatocyte apoptosis by a nuclear steroid receptor (NSR),dependent mechanism. In this study, we further investigated the potential role of the glucocorticoid receptor (GR) in the antiapoptotic function of UDCA. Our results with short interference RNA (siRNA) technology confirmed that UDCA significantly reduces TGF-,1,induced apoptosis of primary rat hepatocytes through a GR-dependent effect. Immunoprecipitation assays and confocal microscopy showed that UDCA enhanced free GR levels with subsequent GR nuclear translocation. Interestingly, when a carboxy-terminus deleted form of GR was used, UDCA no longer increased free GR and/or GR translocation, nor did it protect against TGF-,1,induced apoptosis. In co-transfection experiments with GR response element reporter and overexpression constructs, UDCA did not enhance the transactivation of GR with TGF-,1. Finally, using a flourescently labeled UDCA molecule, the bile acid appeared diffuse in the cytosol but was aggregated in the nucleus of hepatocytes. Both siRNA assays and transfection experiments with either wild-type or mutant forms of GR showed that nuclear trafficking occurs through a GR-dependent mechanism. In conclusion, these results further clarify the antiapoptotic mechanism(s) of UDCA and suggest that GR is crucial for the nuclear translocation of this bile acid for reducing apoptosis. (HEPATOLOGY 2005;42:925,934.) [source]

    Hyaluronan-binding peptide can inhibit tumor growth by interacting with Bcl-2

    Ninfei Liu
    Abstract Previous studies have indicated that proteins that bind hyaluronan can also inhibit the growth of tumor cells. To determine if synthetic peptides also possessed these properties, we tested a series of polypeptides containing structural motifs from different proteins for their ability to bind [3H]hyaluronan, and identified one compound termed P4 that had a particularly strong interaction. Further studies revealed that P4 also inhibited the growth of tumor cells in tissue culture as well as on the chorioallantoic membranes of chicken embryos. In addition, expression vectors for P4 caused tumor cells to grow slower in nude mice and reduced their vascularization. The P4 peptide also inhibited VEGF-induced angiogenesis in the chorioallantoic membranes of chicken embryos. Studies on cultured cells indicated that P4 induced apoptosis, which was blocked by a pan-caspase inhibitor. Confocal microscopy revealed that shortly after its uptake, P4 became associated with mitochondria. Immunoprecipitation indicated that P4 could bind to Bcl-2 and Bcl-xL, which are associated with mitochondria and regulate apoptosis. This was also supported by the fact that P4 induced the release of cytochrome c from preparations of mitochondria. Taken together, these results suggest that P4 binds to Bcl-2 and related proteins and this activates the apoptotic cascade. © 2003 Wiley-Liss, Inc. [source]

    Mutational Analysis and Functional Correlation With Phenotype in German Patients With Childhood-Type Hypophosphatasia

    Hideo Orimo
    Abstract The tissue-nonspecific alkaline phosphatase (TNSALP) gene from five German family members with childhood-type hypophosphatasia (HOPS) was analyzed using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP)-direct sequencing method. Four novel missense mutations (T51M, R54S, L258P, and R374H) and two that had been described previously (A160T and R206W) were detected in the respective patients. Mutation A160T was detected in 3 distinct patients, and a polymorphism V505A that had been described previously was detected in the same allele as L258P mutation in 1 patient and in 2 fathers whose V505A alleles were not transmitted to the probands. No other mutations were found in 2 patients. Transient expression of the mutant proteins in COS-1 cells showed that the four novel mutations and R206W were severe alleles, whereas A160T was a moderate allele. Analysis of its enzymatic activity and genetic transmission patterns confirmed that V505A was a polymorphism. Immunoprecipitation of the transiently expressed proteins showed that levels of the 80-kDa mature form of the enzyme were diminished or absent with the severe alleles; instead, levels of high-molecular mass disulfide-linked aggregates were increased. These results suggest that in compound heterozygotes, the combination of severe and moderate alleles may combine to cause the mild phenotype seen in childhood-type HOPS. [source]

    Nuclear and nuclear envelope localization of dystrophin Dp71 and dystrophin-associated proteins (DAPs) in the C2C12 muscle cells: DAPs nuclear localization is modulated during myogenesis

    R. González-Ramírez
    Abstract Dystrophin and dystrophin-associated proteins (DAPs) form a complex around the sarcolemma, which gives stability to the sarcolemma and leads signal transduction. Recently, the nuclear presence of dystrophin Dp71 and DAPs has been revealed in different non-muscle cell types, opening the possibility that these proteins could also be present in the nucleus of muscle cells. In this study, we analyzed by Immunofluorescence assays and Immunoblotting analysis of cell fractions the subcellular localization of Dp71 and DAPs in the C2C12 muscle cell line. We demonstrated the presence of Dp71, ,-sarcoglycan, ,-dystrobrevin, ,-dystroglycan and ,-syntrophin not only in plasma membrane but also in the nucleus of muscle cells. In addition, we found by Immunoprecipitation assays that these proteins form a nuclear complex. Interestingly, myogenesis modulates the presence and/or relative abundance of DAPs in the plasma membrane and nucleus as well as the composition of the nuclear complex. Finally, we demonstrated the presence of Dp71, ,-sarcoglycan, ,-dystroglycan, ,-dystrobrevin and ,-syntrophin in the C2C12 nuclear envelope fraction. Interestingly, ,-sarcoglycan and ,-dystroglycan proteins showed enrichment in the nuclear envelope, compared with the nuclear fraction, suggesting that they could function as inner nuclear membrane proteins underlying the secondary association of Dp71 and the remaining DAPs to the nuclear envelope. Nuclear envelope localization of Dp71 and DAPs might be involved in the nuclear envelope-associated functions, such as nuclear structure and modulation of nuclear processes. J. Cell. Biochem. 105: 735,745, 2008. © 2008 Wiley-Liss, Inc. [source]

    ,-cardiac actin (ACTC) binds to the band 3 (AE1) cardiac isoform

    Paulo Roberto Moura Lima
    Abstract The band 3 protein is the major integral protein present in the erythrocyte membrane. Two tissue-specific isoforms are also expressed in kidney alpha intercalated cells and in cardiomyocytes. It has been suggested that the cardiac isoform predominantly mediates the anion exchange in cardiomyocytes, but the role of the cytoplasmic domain of the band 3 (CDB3) protein in the cardiac tissue is unknown. In order to characterize novel associations of the CDB3 in the cardiac tissue, we performed the two-hybrid assay, using a bait comprising the region from leu 258 to leu 311 of the erythrocyte band 3, which must also be present in the cardiac isoform. The assay revealed two clones containing the C-terminal region of the ,-cardiac actin. Immunoprecipitation of whole rat heart using an anti-actin antibody, immunoblotted with anti-human band 3, showed that actin binds to band 3 which was confirmed in the reverse assay. The confocal microscopy showed band 3 in the intercalated discs. Thus, besides the in vivo physical interaction in the Saccharomyces cerevisiae cell, we demonstrated using immunopreciptation that there is a physical association of band 3 with ,-cardiac actin in cardiomyocyte, and we suggest that the binding occur "in situ," in the intercalated disc, a site of cell,cell contact and attachment of the sarcomere to the plasma membrane. © 2003 Wiley-Liss, Inc. [source]

    Role of surface promoter mutations in hepatitis B surface antigen production and secretion in occult hepatitis B virus infection,

    Sonali Sengupta
    Abstract The production, secretion, and localization of surface proteins of hepatitis B virus (HBV) and the ratio of large to small surface protein S was studied in HepG2 cells transfected with the wild-type and mutant pre-S1 and pre-S2/S promoters of HBV molecular clones 313.1 (GenBank accession no. AY161147) and 761.1 (GenBank accession no. AY161159) from two patients with occult HBV infection. Fusion constructs were made by in frame fusion of the wild-type surface gene to the mutant pre-S1 and pre-S2/S promoters and wild-type promoter so that the structural part of the small surface protein remains identical. HepG2 cells transfected transiently were used for analysis. HBV surface proteins production and secretion was determined by enzyme linked immuno assay (ELISA) and localization by immunofluorescence. Immunoprecipitation of the large, middle, and small surface protein was carried out in transient transfected and metabolically labeled cells to determine the ratio of the large to small surface protein. The results indicate that HepG2 cells transfected with mutant HBV promoters had reduced HBV surface proteins secretion compared to wild-type HBV. HepG2 cells transfected with mutant HBV pre-S1 and pre-S2/S promoters showed cytoplasmic aggregation of HBV surface proteins compared to wild-type HBV promoters, which showed diffuse cytoplasmic localization. In all cases, the HBV surface proteins localized to the endoplasmic reticulum. The ratio between the large and small surface protein was 1.89 and 0.56 with mutant HBV 313.1 and 761.1 pre-S1 and pre-S2/S promoters, respectively, compared to 0.17 in wild-type. Thus, the aggregation of surface proteins, altered ratio and secretion of surface proteins were possibly the causes of occult hepatitis B infection. J. Med. Virol. 79:220,228, 2007. © 2007 Wiley-Liss, Inc. [source]

    Csk-homologous kinase interacts with SHPS-1 and enhances neurite outgrowth of PC12 cells

    Hiroaki Mitsuhashi
    Abstract SHPS-1 is an immunoglobulin superfamily protein with four immunoreceptor tyrosine-based inhibitory motifs (ITIMs) in its cytoplasmic region. Various neurotrophic factors induce the tyrosine phosphorylation of SHPS-1 and the association of SHPS-1 with the protein tyrosine phosphatase SHP-2. Using a yeast two-hybrid screen, we identified a protein tyrosine kinase, Csk-homologous kinase (CHK), as an SHPS-1-interacting protein. Immunoprecipitation and pull-down assays using glutathione S -transferase (GST) fusion proteins containing the Src homology 2 (SH2) domain of CHK revealed that CHK associates with tyrosine-phosphorylated SHPS-1 via its SH2 domain. HIS3 assay in a yeast two-hybrid system using the tyrosine-to-phenylalanine mutants of SHPS-1 indicated that the first and second ITIMs of SHPS-1 are required to bind CHK. Over-expression of wild-type CHK, but not a kinase-inactive CHK mutant, enhanced the phosphorylation of SHPS-1 and its subsequent association with SHP-2. CHK phosphorylated each of four tyrosines in the cytoplasmic region of SHPS-1 in vitro. Co-expression of SHPS-1 and CHK enhanced neurite outgrowth in PC12 cells. Thus, CHK phosphorylates and associates with SHPS-1 and is involved in neural differentiation via SHP-2 activation. [source]

    Nitric Oxide-Sensitive Guanylyl Cyclase Activity Inhibition Through Cyclic GMP-Dependent Dephosphorylation

    Rut Ferrero
    Abstract: The soluble form of guanylyl cyclase (sGC) plays a pivotal role in the transduction of inter- and intracellular signals conveyed by nitric oxide. Here, a feedback inhibitory mechanism triggered by cyclic guanosine-3,,5,-monophosphate (cGMP)-dependent protein kinase (PKG) activation is described. Preincubation of chromaffin cells with C-type natriuretic peptide, which increased cGMP levels and activated PKG, or with cGMP-permeant analogue (which also activates PKG), in the presence of a broad-spectrum phosphodiesterase inhibitor, resulted in a decrease in subsequent sodium nitroprusside (SNP)-dependent cGMP elevations. This inhibitory effect was mimicked by activating a protein phosphatase and counteracted by the selective PKG inhibitor KT-5823 and by different protein phosphatase inhibitors. Immunoprecipitation of sGC from cells submitted to different treatments followed by immunodetection with antiphosphoserine antibodies (clone 4A9) showed changes in phosphorylation levels of the , subunit of sGC, and these changes correlated well with differences in SNP-elicited cGMP accumulations. Pretreatment of cells with several PKG inhibitors or protein phosphatase inhibitors produced an enhancement of SNP-stimulated cGMP rises without changing the SNP concentration required to produce half-maximal or maximal responses. Taken together, these results indicate that the catalytic activity of sGC is closely coupled to the phosphorylation state of its , subunit and that the tonic activity of PKG or its stimulation regulates sGC activity through dephosphorylation of the , subunit. [source]

    Markers of mRNA stabilization and degradation, and RNAi within astrocytoma GW bodies

    Joanna J. Moser
    Abstract GW bodies (GWBs) are unique cytoplasmic structures that contain the mRNA binding protein GW182 and other proteins involved in mRNA processing pathways. The rationale for this study arose from clinical studies indicating that 33% of patients with GWB autoantibodies have a motor/sensory neuropathy and/or ataxia. The novelty of this study is the identification of GWBs in astrocytes and astrocytoma cells within cell bodies and cytoplasmic projections. Astrocytoma GWBs exhibit complex heterogeneity with combinations of LSm4 and XRN1 as well as Ago2 and Dicer, key proteins involved in mRNA degradation and RNA interference, respectively. GWB subsets contained the mRNA transport and stabilization proteins SYNCRIP, hnRNPA1, and FMRP, not previously described as part of the GWB complex. Immunoprecipitation of astrocytoma GWBs suggested that Dicer, hDcp, LSm4, XRN1, SYNCRIP, and FMRP form a multiprotein complex. GWBs are likely involved in a number of regulatory mRNA pathways in astrocytes and astrocytoma cells. © 2007 Wiley-Liss, Inc. [source]

    Presenilin 1 is involved in the maturation of ,-site amyloid precursor protein-cleaving enzyme 1 (BACE1)

    Akira Kuzuya
    Abstract One of the pathologic hallmarks of Alzheimer's disease is the excessive deposition of ,-amyloid peptides (A,) in senile plaques. A, is generated when ,-amyloid precursor protein (APP) is cleaved sequentially by ,-secretase, identified as ,-site APP-cleaving enzyme 1 (BACE1), and ,-secretase, a putative enzymatic complex containing presenilin 1 (PS1). However, functional interaction between PS1 and BACE1 has never been known. In addition to this classical role in the generation of A, peptides, it has also been proposed that PS1 affects the intracellular trafficking and maturation of selected membrane proteins. We show that the levels of exogenous and endogenous mature BACE1 expressed in presenilin-deficient mouse embryonic fibroblasts (PS,/,MEFs) were reduced significantly compared to those in wild-type MEFs. Moreover, the levels of mature BACE1 were increased in human neuroblastoma cell line, SH-SY5Y, stably expressing wild-type PS1, compared to native cells. Conversely, the maturation of BACE1 was compromised under the stable expression of dominant,negative mutant PS1 overexpression. Immunoprecipitation assay showed that PS1 preferably interacts with proBACE1 rather than mature BACE1, indicating that PS1 can be directly involved in the maturation process of BACE1. Further, endogenous PS1 was immunoprecipitated with endogenous BACE1 in SH-SY5Y cells and mouse brain tissue. We conclude that PS1 is directly involved in the maturation of BACE1, thus possibly functioning as a regulator of both ,- and ,-secretase in A, generation. © 2006 Wiley-Liss, Inc. [source]

    Two Ser/Thr protein kinases essential for efficient aggregation and spore morphogenesis in Myxococcus xanthus

    Emily A. Stein
    Summary Myxococcus xanthus has a complex life cycle that involves vegetative growth and development. Previously, we described the espAB locus that is involved in timing events during the initial stages of fruiting body formation. Deletion of espA caused early aggregation and sporulation, whereas deletion of espB caused delayed aggregation and sporulation resulting in reduced spore yields. In this study, we describe two genes, pktA5 and pktB8, that flank the espAB locus and encode Ser/Thr protein kinase (STPK) homologues. Cells deficient in pktA5 or pktB8 formed translucent mounds and produced low spore yields, similar in many respects to espB mutants. Double mutant analysis revealed that espA was epistatic to pktA5 and pktB8 with respect to aggregation and fruiting body morphology, but that pktA5 and pktB8 were epistatic to espA with respect to sporulation efficiency. Expression profiles of pktA5,lacZ and pktB8,lacZ fusions and Western blot analysis showed that the STPKs are expressed under vegetative and developmental conditions. In vitro kinase assays demonstrated that the RD kinase, PktA5, autophosphorylated on threonine residue(s) and phosphorylated the artificial substrate, myelin basic protein. In contrast, autophosphorylation of the non-RD kinase, PktB8, was not observed in vitro; however, the phenotype of a pktB8 kinase-dead point mutant resembled the pktB8 deletion mutant, indicating that this residue was important for function and that it likely functions as a kinase in vivo. Immunoprecipitation of Tap-tagged PktA5 and PktB8 revealed an interaction with EspA during development in M. xanthus. These results, taken together, suggest that PktA5 and PktB8 are STPKs that function during development by interacting with EspA and EspB to regulate M. xanthus development. [source]

    Identification of in vitro phosphorylation sites in the Arabidopsis thaliana somatic embryogenesis receptor-like kinases

    Rumyana Karlova
    Abstract The Arabidopsis thaliana somatic embryogenesis receptor-like kinase (SERK) family consists of five leucine-rich repeat receptor-like kinases (LRR-RLKs) with diverse functions such as brassinosteroid insensitive 1 (BRI1)-mediated brassinosteroid perception, development and innate immunity. The autophosphorylation activity of the kinase domains of the five SERK proteins was compared and the phosphorylated residues were identified by LC-MS/MS. Differences in autophosphorylation that ranged from high activity of SERK1, intermediate activities for SERK2 and SERK3 to low activity for SERK5 were noted. In the SERK1 kinase the C-terminally located residue Ser-562 controls full autophosphorylation activity. Activation loop phosphorylation, including that of residue Thr-462 previously shown to be required for SERK1 kinase activity, was not affected. In vivo SERK1 phosphorylation was induced by brassinosteroids. Immunoprecipitation of CFP-tagged SERK1 from plant extracts followed by MS/MS identified Ser-303, Thr-337, Thr-459, Thr-462, Thr-463, Thr-468, and Ser-612 or Thr-613 or Tyr-614 as in vivo phosphorylation sites of SERK1. Transphosphorylation of SERK1 by the kinase domain of the main brassinosteroid receptor BRI1 occurred only on Ser-299 and Thr-462. This suggests both intra- and intermolecular control of SERK1 kinase activity. Conversely, BRI1 was transphosphorylated by the kinase domain of SERK1 on Ser-887. BRI1 kinase activity was not required for interaction with the SERK1 receptor in a pull down assay. [source]

    AMPA receptor antibodies in limbic encephalitis alter synaptic receptor location,

    ANNALS OF NEUROLOGY, Issue 4 2009
    Meizan Lai MD
    Objective To report the clinical and immunological features of a novel autoantigen related to limbic encephalitis (LE) and the effect of patients' antibodies on neuronal cultures. Methods We conducted clinical analyses of 10 patients with LE. Immunoprecipitation and mass spectrometry were used to identify the antigens. Human embryonic kidney 293 cells expressing the antigens were used in immunocytochemistry and enzyme-linked immunoabsorption assay. The effect of patients' antibodies on cultures of live rat hippocampal neurons was determined with confocal microscopy. Results Median age was 60 (38,87) years; 9 were women. Seven had tumors of the lung, breast, or thymus. Nine patients responded to immunotherapy or oncological therapy, but neurological relapses, without tumor recurrence, were frequent and influenced the long-term outcome. One untreated patient died of LE. All patients had antibodies against neuronal cell surface antigens that by immunoprecipitation were found to be the glutamate receptor 1 (GluR1) and GluR2 subunits of the ,-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor (AMPAR). Human embryonic kidney 293 cells expressing GluR1/2 reacted with all patients' sera or cerebrospinal fluid, providing a diagnostic test for the disorder. Application of antibodies to cultures of neurons significantly decreased the number of GluR2-containing AMPAR clusters at synapses with a smaller decrease in overall AMPAR cluster density; these effects were reversed after antibody removal. Interpretation Antibodies to GluR1/2 associate with LE that is often paraneoplastic, treatment responsive, and has a tendency to relapse. Our findings support an antibody-mediated pathogenesis in which patients' antibodies alter the synaptic localization and number of AMPARs. Ann Neurol 2009;65:424,434 [source]

    Defective phosphorylation of interleukin-18 receptor , causes impaired natural killer cell function in systemic-onset juvenile idiopathic arthritis

    ARTHRITIS & RHEUMATISM, Issue 9 2009
    Wilco de Jager
    Objective Systemic-onset juvenile idiopathic arthritis (JIA) is an autoimmune disease characterized by arthritis and systemic features. Its pathogenesis is still largely unknown. It is characterized immunologically by natural killer (NK) cell dysfunction and cytokine signatures that predominantly feature interleukin-1 (IL-1), IL-6, and IL-18. Since IL-18 can drive NK cell function, we examined how the high plasma levels of this cytokine are related to the documented NK cell failure in these patients. Methods The phenotype and function of NK cells from 10 healthy control subjects, 15 patients with polyarticular JIA, and 15 patients with systemic-onset JIA were characterized by staining and functional assays in vitro. IL-18 ligand binding was visualized by fluorescence microscopy. Phosphorylation of several MAP kinases and the IL-18 receptor , (IL-18R,) were visualized by Western blotting. Results IL-18 from the plasma of systemic-onset JIA patients stimulated the activation of NK cells from healthy controls and bound its cognate receptor. However, NK cells from systemic-onset JIA patients failed to up-regulate cell-mediated killing molecules, such as perforin and interferon-,, after IL-18 stimulation. Furthermore, treatment with IL-18 did not induce the phosphorylation of receptor-activated MAP kinases in NK cells. Alternate activation of NK cells by IL-12 induced NK cell cytotoxicity. We observed no additive effect of IL-18 in combination with IL-12 in systemic-onset JIA patients. Immunoprecipitation of IL-18R, showed that NK cells from systemic-onset JIA could not phosphorylate this receptor after IL-18 stimulation. Conclusion The mechanism of the impaired NK cell function in systemic-onset JIA involves a defect in IL-18R, phosphorylation. This observation has major implications for the understanding and, ultimately, the treatment of systemic-onset JIA. [source]

    Oncostatin M,induced CCL2 transcription in osteoblastic cells is mediated by multiple levels of STAT-1 and STAT-3 signaling: An implication for the pathogenesis of arthritis

    ARTHRITIS & RHEUMATISM, Issue 5 2009
    Sang-Heng Kok
    Objective To examine the roles of STATs 1 and 3 in CCL2 production in human osteoblastic cells and their influences on arthritis development. Methods The expression of CCL2 in primary human osteoblasts and U2OS human osteoblastic cells was examined by Northern blotting and enzyme-linked immunosorbent assay. The roles of STAT-1/3 and c-Fos were assessed using short hairpin RNAs (shRNA) to silence their functions. Serine phosphorylation of STATs was assessed by Western blotting. Promoter activities of c-Fos and CCL2 were assessed by chloramphenicol acetyltransferase and luciferase assays, respectively. Interactions of STAT-1, STAT-3, and c-Fos with DNA were evaluated by electrophoretic mobility shift assay (EMSA) and immunoprecipitation. The effect of the JAK inhibitor AG-490 on collagen-induced arthritis (CIA) in rats was examined using immunohistochemistry. Results Oncostatin M (OSM) stimulated CCL2 expression in primary human osteoblasts and U2OS cells. In U2OS cells, STAT-1 and STAT-3 were involved in OSM-stimulated CCL2 expression, and both the phosphatidylinositol 3-kinase/Akt and MEK/ERK pathways were implicated in the activation of these STATs. STAT-1 and STAT-3 modulated the expression of c-Fos and directly transactivated the CCL2 promoter. Moreover, EMSA showed formation of a DNA,protein complex containing STAT-1, STAT-3, and interestingly, c-Fos. Immunoprecipitation confirmed the binding between c-Fos and STAT-1/3. Reporter assay revealed synergistic attenuation of CCL2 promoter activity by shRNA targeting of STAT-1, STAT-3, and c-Fos. AG-490 suppressed OSM-stimulated activation of STAT-1/3 and synthesis of CCL2 in vitro and diminished the severity of CIA and the number of CCL2-synthesizing osteoblasts in vivo. Conclusion These findings show that multiple levels of STAT-1/3 signaling modulate OSM-stimulated CCL2 expression in human osteoblastic cells. Clinically, this pathway may be related to the pathogenesis of arthritis. [source]

    research paper: Role of the cold shock domain protein A in the transcriptional regulation of HBG expression

    Raffaella Petruzzelli
    Summary Impaired switching from fetal haemoglobin (HbF) to adult globin gene expression leads to hereditary persistence of fetal haemoglobin (HPFH) in adult life. This is of prime interest because elevated HbF levels ameliorate ,-thalassaemia and sickle cell anaemia. Fetal haemoglobin levels are regulated by complex mechanisms involving factors linked or not to the ,-globin gene (HBB) locus. To search for factors putatively involved in the expression of the ,-globin genes (HBG1, HBG2), we examined the reticulocyte transcriptome of three siblings who had different HbF levels and different degrees of ,-thalassaemia severity although they had the same ,BA - and ,,B cluster genotypes. By mRNA differential display we isolated the cDNA coding for the cold shock domain protein A (CSDA), also known as dbpA, previously reported to interact in vitro with the HBG2 promoter. Expression studies performed in K562 and in primary erythroid cells showed an inverse relationship between HBG and CSDA expression levels. Functional studies performed by Chromatin Immunoprecipitation and reporter gene assays in K562 cells demonstrated that CSDA is able to bind the HBG2 promoter and suppress its expression. Therefore, our study demonstrated that CSDA is a trans-acting repressor factor of HBG expression and modulates the HPFH phenotype. [source]

    Neuroprotection by donepezil against glutamate excitotoxicity involves stimulation of ,7 nicotinic receptors and internalization of NMDA receptors

    H Shen
    BACKGROUND AND PURPOSE Glutamate excitotoxicity may be involved in ischaemic injury to the CNS and some neurodegenerative diseases, such as Alzheimer's disease. Donepezil, an acetylcholinesterase (AChE) inhibitor, exerts neuroprotective effects. Here we demonstrated a novel mechanism underlying the neuroprotection induced by donepezil. EXPERIMENTAL APPROACH Cell damage in primary rat neuron cultures was quantified by lactate dehydrogenase release. Morphological changes associated with neuroprotective effects of nicotine and AChE inhibitors were assessed by immunostaining. Cell surface levels of the glutamate receptor sub-units, NR1 and NR2A, were analyzed using biotinylation. Immunoblot was used to measure protein levels of cleaved caspase-3, total NR1, total NR2A and phosphorylated NR1. Immunoprecipitation was used to measure association of NR1 with the post-synaptic protein, PSD-95. Intracellular Ca2+ concentrations were measured with fura 2-acetoxymethylester. Caspase 3-like activity was measured using enzyme substrate, 7-amino-4-methylcoumarin (AMC)-DEVD. KEY RESULTS Levels of NR1, a core subunit of the NMDA receptor, on the cell surface were significantly reduced by donepezil. In addition, glutamate-mediated Ca2+ entry was significantly attenuated by donepezil. Methyllycaconitine, an inhibitor of ,7 nicotinic acetylcholine receptors (nAChR), inhibited the donepezil-induced attenuation of glutamate-mediated Ca2+ entry. LY294002, a phosphatidyl inositol 3-kinase (PI3K) inhibitor, had no effect on attenuation of glutamate-mediated Ca2+ entry induced by donepezil. CONCLUSIONS AND IMPLICATIONS Decreased glutamate toxicity through down-regulation of NMDA receptors, following stimulation of ,7 nAChRs, could be another mechanism underlying neuroprotection by donepezil, in addition to up-regulating the PI3K-Akt cascade or defensive system. [source]

    Thrombin-induced platelet endostatin release is blocked by a proteinase activated receptor-4 (PAR4) antagonist

    Li Ma
    Endostatin is a potent endogenous inhibitor of angiogenesis that was recently shown to be stored in platelets and released in response to thrombin, but not ADP. In the present study, we have tested the hypothesis that thrombin-induced endostatin release from rat platelets is mediated via proteinase-activated receptor-4 (PAR4). Immunoprecipitation and Western blotting confirmed that endostatin is contained within rat platelets. Aggregation and release of endostatin could be elicited by thrombin (0.5 , 1.0 U ml,1) or by specific PAR4 agonist (AYPGKF-NH2; AY-NH2; 15 , 50 ,M). Significant release of endostatin could be induced by a dose of thrombin below that necessary for induction of aggregation. An adenosine diphosphate (ADP) scavenger, apyrase, inhibited the platelet aggregation induced by thrombin, but not the release of endostatin. In contrast, a selective PAR4 antagonist (trans-cinnamoyl-YPGKF-NH2; tcY-NH2) prevented endostatin release and aggregation induced by thrombin or by AY-NH2. We conclude that thrombin-induced endostatin release from rat platelets is PAR4-mediated via an ADP-independent mechanism that can occur independently of platelet aggregation. British Journal of Pharmacology (2001) 134, 701,704; doi:10.1038/sj.bjp.0704312 [source]

    2C4, a monoclonal antibody against HER2, disrupts the HER kinase signaling pathway and inhibits ovarian carcinoma cell growth

    CANCER, Issue 12 2005
    Noriyuki Takai M.D.
    Abstract BACKGROUND Human epidermal growth factor receptor 2 (HER2) is overexpressed in 25,30% of ovarian carcinoma cases and a correlation between increased HER2 expression and decreased survival has been demonstrated. HER2 is a ligand-less member of the HER family that functions as the preferred coreceptor for epidermal growth factor receptor (EGFR), HER3, and HER4. METHODS An approach was developed to target HER2's role as a coreceptor using a monoclonal antibody, 2C4, which sterically hinders HER2's recruitment into a functional HER complex. RESULTS HER2 was robustly expressed in all eight ovarian carcinoma cell lines; expression of EGFR and HER3 was variable. Even though four of the eight cell lines responded to EGF, 2C4 antibody moderately inhibited in vitro proliferation of only two cell lines (OVCA433 and SK-OV-3). Furthermore, ligand-stimulated p-MAPK expression was inhibited by 2C4 only in these two cell lines after exposure to EGF. Immunoprecipitation and eTag analysis revealed that OVCA433 expressed heterodimers of EGFR/HER2, and these heterodimers were disrupted after treatment with 2C4, whereas OVCA432 cells did not have these heterodimers. In murine xenograft experiments, the in vivo growth of OVCA433, but not of OVCA432, ovarian carcinoma cells was significantly inhibited by 2C4 treatment of the mice. CONCLUSION 2C4 is able to disrupt the HER signaling pathway and inhibit the in vitro and in vivo growth of ovarian carcinoma cell lines. The response appears limited to lines in which HER2 heterodimers were able to transduce proliferative signals. Our findings suggest a strong rationale to conduct clinical trials of 2C4 in a subset of patients with ovarian tumors. Cancer 2005. © 2005 American Cancer Society. [source]

    Therapeutic antitumor efficacy of monoclonal antibody against Claudin-4 for pancreatic and ovarian cancers

    CANCER SCIENCE, Issue 9 2009
    Masayo Suzuki
    Claudin-4 (CLDN4) is a tetraspanin transmembrane protein of tight junction structure and is highly expressed in pancreatic and ovarian cancers. In this study, we aimed to generate an anti-Claudin-4 monoclonal antibody (mAb) and evaluate its antitumor efficacy in vitro and in vivo. To isolate specific mAb, we generated CLDN3, 4, 5, 6, and 9, expressing Chinese hamster ovary (CHO) cells, and then used them as positive and negative targets through cell-based screening. As a result, we succeeded in isolating KM3900 (IgG2a), which specifically bound to CLDN4, from BXSB mice immunized with pancreatic cancer cells. Immunoprecipitation and flow cytometry analysis revealed that KM3900 recognized the conformational structure and bound to extracellular loop 2 of CLDN4. Furthermore, binding of KM3900 was detected on CLDN4-expressing pancreatic and ovarian cancer cells, but not on negative cells. Next, we made the mouse,human chimeric IgG1 (KM3934) and evaluated its antitumor efficacy. KM3934 induced dose-dependent antibody-dependent cellular cytotoxicity and complement-dependent cytotoxicity in vitro, and significantly inhibited tumor growth in MCAS or CFPAC-1 xenograft SCID mice in vivo (P < 0.05). These results suggest that mAb therapy against CLDN4 is promising for pancreatic and ovarian cancers. (Cancer Sci 2009; 100: 1623,1630) [source]

    Normoxic destabilization of ATF-4 depends on proteasomal degradation

    ACTA PHYSIOLOGICA, Issue 4 2010
    M. Wottawa
    Abstract Aim:, Hypoxia-inducible gene expression is an important physiological adaptive mechanism in response to a decreased oxygen supply. We have recently described an oxygen- and prolyl-4-hydroxylase (PHD)3-dependent stabilization of the activating transcription factor 4 (ATF-4). The aim of the present study was to examine if the normoxic destabilization of ATF-4 is regulated by oxygen-dependent proteasomal degradation. Methods:, We determined poly-ubiquitination of ATF-4 in normoxia compared to hypoxia by immunoprecipitation and immunoblots. Furthermore, we analysed the expression of the ATF-4 target gene GADD153 as a function of oxygen concentration. Results:, ATF-4 protein levels were not detectable in normoxia. Normoxic degradation correlated with an oxygen-dependent poly-ubiquitination of ATF-4, which was hindered by hypoxic incubation of the cells. As a result of hypoxia, GADD153 was expressed. The hypoxic GADD153 expression was attenuated or increased by transfecting the cells with ATF-4 siRNA or PHD3 siRNA respectively. Conclusion:, Our results demonstrate the involvement of oxygen-dependent proteasomal degradation of ATF-4 in the hypoxia-induced expression of GADD153. Taken together, hypoxia/PHD3-regulated stabilization of ATF-4 by hindering oxygen-dependent degradation may play a critical role in linking cell fate decisions to oxygen availability. [source]

    HOXA13 directly regulates EphA6 and EphA7 expression in the genital tubercle vascular endothelia

    Carley A. Shaut
    Abstract Hypospadias, a common defect affecting the growth and closure of the external genitalia, is often accompanied by gross enlargements of the genital tubercle (GT) vasculature. Because Hoxa13 homozygous mutant mice also exhibit hypospadias and GT vessel expansion, we examined whether genes playing a role in angiogenesis exhibit reduced expression in the GT. From this analysis, reductions in EphA6 and EphA7 were detected. Characterization of EphA6 and EphA7 expression in the GT confirmed colocalization with HOXA13 in the GT vascular endothelia. Analysis of the EphA6 and EphA7 promoter regions revealed a series of highly conserved cis -regulatory elements bound by HOXA13 with high affinity. GT chromatin immunoprecipitation confirmed that HOXA13 binds these gene-regulatory elements in vivo. In vitro, HOXA13 activates gene expression through the EphA6 and EphA7 gene-regulatory elements. Together these findings indicate that HOXA13 directly regulates EphA6 and EphA7 in the developing GT and identifies the GT vascular endothelia as a novel site for HOXA13-dependent expression of EphA6 and EphA7. Developmental Dynamics 236:951,960, 2007. © 2007 Wiley-Liss, Inc. [source]

    Direct role of NF-,B activation in Toll-like receptor-triggered HLA-DRA expression

    Keun-Wook Lee
    Abstract Microbial components, such as DNA containing immunostimulatory CpG motifs (CpG-DNA) and lipopolysaccharides (LPS), elicit the cell surface expression of MHC class II (MHC-II) through Toll-like receptor (TLR)/IL-1R. Here, we show that CpG-DNA and LPS induce expression of the HLA-DRA in the human B cell line, RPMI 8226. Ectopic expression of the dominant negative mutant of CIITA and RNA interference targeting the CIITA gene indicate that CIITA activation is not enough for the maximal MHC-II expression induced by CpG-DNA and LPS. Additionally, nuclear factor (NF)-,B activation is required for the CpG-DNA-activated and LPS-activated HLA-DRA expression, whereas IFN-,-induced MHC-II expression depends on CIITA rather than on NF-,B. Comprehensive mutant analyses, electrophoretic mobility shift assays and chromatin immunoprecipitation assays, reveal that the functional interaction of NF-,B with the promoter element is necessary for the TLR-mediated HLA-DRA induction by CpG-DNA and LPS. This novel mechanism provides the regulation of MHC-II gene expression with complexity and functional diversity. [source]

    Impaired IL-4 production by CD8+ T,cells in NOD mice is related to a defect of c-Maf binding to the IL-4 promoter

    Xiao-Ping Chen
    Abstract CD8+ T,cells play an important role in the induction of the autoimmune response in non-obese diabetic (NOD) mice. Here we describe abnormalities in the control of cytokine production by NOD CD8+ T,cells. NOD CD8+ T,cells had an increased propensity to produce IFN-, upon TCR activation, in both adult and 2-week-old mice. NOD CD8+ T,cells had a reduced capacity to produce IL-4 in type,2 conditions compared to CD8+ T,cells from the diabetes-resistant strains BALB/c and C57BL/6. Both GATA-3 and c-Maf, two positive transactivators for IL-4 gene expression, were expressed in type,2 conditions at comparable levels in NOD CD8+ T,cells. The GATA-3 was functional since normal levels of IL-5 were produced and the IL-4 promoter was hyperacetylated in NOD CD8+ T,cells. In contrast, c-Maf failed to bind to its responsive element as determined by chromatin immunoprecipitation (ChIP) assay. These results suggest that NOD CD8+ T,cells possess an increased propensity to produce IFN-, and impaired c-Maf-dependent DNA binding activities in vivo that lead to reduced IL-4 production following TCR activation. These defects may facilitate the development of the autoimmune response by inducing an overall type,1-biased immune response in NOD mice. [source]

    Immunolocalization of BK channels in hippocampal pyramidal neurons

    Claudia A. Sailer
    Abstract Neurons are highly specialized cells in which the integration and processing of electrical signals critically depends on the precise localization of ion channels. For large-conductance Ca2+ - activated K+ (BK) channels, targeting to presynaptic membranes in hippocampal pyramidal cells was reported; however, functional evidence also suggests a somatodendritic localization. Therefore we re-examined the subcellular distribution of BK channels in mouse hippocampus using a panel of independent antibodies in a combined approach of conventional immunocytochemistry on cultured neurons, pre- and postembedding electron microscopy and immunoprecipitation. In cultured murine hippocampal neurons, the colocalization of BK channels with both pre- and postsynaptic marker proteins was observed. Electron microscopy confirmed targeting of BK channels to axonal as well as dendritic membranes of glutamatergic synapses in hippocampus. A postsynaptic localization of BK channels was also supported by the finding that the channel coimmunoprecipitated with PSD95, a protein solely expressed in the postsynaptic compartment. These results thus demonstrate that BK channels reside in both post- and presynaptic compartments of hippocampal pyramidal neurons. [source]