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Title / Authors / Details Open Access Download

Identification of two highly sialylated human tear-fluid DMBT1 isoforms: the major high-molecular-mass glycoproteins in human tears.
Schulz BL, Oxley D, Packer NH, Karlsson NG

Human open eye tear fluid was separated by low-percentage SDS/PAGE to detect high-molecular-mass protein components. Two bands were found with apparent molecular masses of 330 and 270 kDa respectively. By peptide-mass fingerprinting after tryptic digestion, the proteins were found to be isoforms of the DMBT1 gene product, with over 30% of the predicted protein covered by the tryptic peptides. By using gradient SDS/agarose/polyacrylamide composite gel electrophoresis and staining for glycosylation, it was shown that the two isoforms were the major high-molecular-mass glycoproteins of >200 kDa in human tear fluid. Western blotting showed that the proteins expressed sialyl-Le(a). After the release of oligosaccharides by reductive beta-elimination from protein blotted on to PVDF membrane, it was revealed by liquid chromatography-MS that the O-linked oligosaccharides were comprised mainly of highly sialylated oligosaccharides with up to 16 monosaccharide units. A majority of the oligosaccharides could be described by the formula dHex(0-->2)NeuAc(1-->)(x)Hex(x)HexNAc(x)(-ol), x=1-6, where Hex stands for hexose, dHex for deoxyhexose, HexNAc for N-acetylhexosamine and NeuAc for N-acetylneuraminate. The number of sialic acids in the formula is less than 5. Interpretation of collision-induced fragmentation tandem MS confirmed the presence of sialic acid and suggested the presence of previously undescribed structures carrying the sialyl-Le(a) epitopes. Small amounts of neutral and sulphated species were also present. This is the first time that O-linked oligosaccharides have been detected and described from protein variant of the DMBT1 gene.

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The Biochemical journal, 366, 0264-6021, 2002

PMID: 12015815

P-Rex1, a PtdIns(3,4,5)P3- and Gbetagamma-regulated guanine-nucleotide exchange factor for Rac.
Welch HC, Coadwell WJ, Ellson CD, Ferguson GJ, Andrews SR, Erdjument-Bromage H, Tempst P, Hawkins PT, Stephens LR

Rac, a member of the Rho family of monomeric GTPases, is an integrator of intracellular signaling in a wide range of cellular processes. We have purified a PtdIns(3,4,5)P3-sensitive activator of Rac from neutrophil cytosol. It is an abundant, 185 kDa guanine-nucleotide exchange factor (GEF), which we cloned and named P-Rex1. The recombinant enzyme has Rac-GEF activity that is directly, substantially, and synergistically activated by PtdIns(3,4,5)P3 and Gbetagammas both in vitro and in vivo. P-Rex1 antisense oligonucleotides reduced endogenous P-Rex1 expression and C5a-stimulated reactive oxygen species formation in a neutrophil-like cell line. P-Rex1 appears to be a coincidence detector in PtdIns(3,4,5)P3 and Gbetagamma signaling pathways that is particularly adapted to function downstream of heterotrimeric G proteins in neutrophils.

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Cell, 108, 0092-8674, 2002

PMID: 11955434

Open Access

Antigen-stimulated activation of phospholipase D1b by Rac1, ARF6, and PKCalpha in RBL-2H3 cells.
DJ Powner, MN Hodgkin, MJ Wakelam

Phospholipase D (PLD) activity can be detected in response to many agonists in most cell types; however, the pathway from receptor occupation to enzyme activation remains unclear. In vitro PLD1b activity is phosphatidylinositol 4,5-bisphosphate dependent via an N-terminal PH domain and is stimulated by Rho, ARF, and PKC family proteins, combinations of which cooperatively increase this activity. Here we provide the first evidence for the in vivo regulation of PLD1b at the molecular level. Antigen stimulation of RBL-2H3 cells induces the colocalization of PLD1b with Rac1, ARF6, and PKCalpha at the plasma membrane in actin-rich structures, simultaneously with cooperatively increasing PLD activity. Activation is both specific and direct because dominant negative mutants of Rac1 and ARF6 inhibit stimulated PLD activity, and surface plasmon resonance reveals that the regulatory proteins bind directly and independently to PLD1b. This also indicates that PLD1b can concurrently interact with a member from each regulator family. Our results show that in contrast to PLD1b's translocation to the plasma membrane, PLD activation is phosphatidylinositol 3-kinase dependent. Therefore, because inactive, dominant negative GTPases do not activate PLD1b, we propose that activation results from phosphatidylinositol 3-kinase-dependent stimulation of Rac1, ARF6, and PKCalpha.

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Molecular biology of the cell, 13, 4, 2002

PMID: 11950936

The tyrosine kinase Lyn is required for B cell development beyond the T1 stage in the spleen: rescue by over-expression of Bcl-2.
Meade J, Fernandez C, Turner M

We have analyzed the effects of deficiency in the tyrosine kinase Lyn on B cell development using transgenic mice that express a B cell antigen receptor (BCR) of defined specificity (3-83,anti-H-2K(k or b)). In the absence of Lyn, immature B cells are abundant in the bone marrow and spleen up until the T1 stage (IgM(hi) IgD(-) CD21(-)CD23(-)), after which B cell development is severely impaired. The small number of mature B cells that do develop in Lyn-deficient mice express normal levels of the transgenic BCR and lack expression of CD80 and CD86, suggesting they are not activated. In Lyn-deficient animals the presence of a Bcl-2 transgene leads to a dramatic increase in B cell numbers and restores T2 stage (IgM(hi) IgD(hi) CD21(hi) CD23(int)) and mature populations. In 3-83 lyn-/- Bcl-2 Tg mice, a population of lambda-positive cells that also express the 383 idiotype is evident, suggesting that in the absence of lyn isotype exclusion by the transgenic BCR is less efficient. The results indicate that Lyn plays a positive role in the selection and survival of mature B cells in addition to its previously documented negative role in tolerance and B cell activation.

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European journal of immunology, 32, 0014-2980, 2002

PMID: 11920569

Natural cytotoxicity uncoupled from the Syk and ZAP-70 intracellular kinases.
Colucci F, Schweighoffer E, Tomasello E, Turner M, Ortaldo JR, Vivier E, Tybulewicz VL, Di Santo JP

The intracellular signals that trigger natural cytotoxicity have not been clearly determined. The Syk and ZAP-70 tyrosine kinases are essential for cellular activation initiated by B and T cell antigen receptors and may drive natural killer (NK) cell cytotoxicity via receptors bearing immunoreceptor tyrosine-based activation motifs (ITAMs). However, we found that, unlike B and T cells, NK cells developed in Syk-/-ZAP-70-/- mice and, despite their nonfunctional ITAMs, lysed various tumor targets in vitro and eliminated tumor cells in vivo, including those without NKG2D ligands. The simultaneous inhibition of phosphatidyl inositol 3 kinase and Src kinases abrogated the cytolytic activity of Syk-/-ZAP-70-/- NK cells and strongly reduced that of wild-type NK cells. This suggests that distinct and redundant signaling pathways act synergistically to trigger natural cytotoxicity.

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Nature immunology, 3, 1529-2908, 2002

PMID: 11836527

Wallerian degeneration of injured axons and synapses is delayed by a Ube4b/Nmnat chimeric gene.
TG Mack, M Reiner, B Beirowski, W Mi, M Emanuelli, D Wagner, D Thomson, T Gillingwater, F Court, L Conforti, FS Fernando, A Tarlton, C Andressen, K Addicks, G Magni, RR Ribchester, VH Perry, MP Coleman

Axons and their synapses distal to an injury undergo rapid Wallerian degeneration, but axons in the C57BL/WldS mouse are protected. The degenerative and protective mechanisms are unknown. We identified the protective gene, which encodes an N-terminal fragment of ubiquitination factor E4B (Ube4b) fused to nicotinamide mononucleotide adenylyltransferase (Nmnat), and showed that it confers a dose-dependent block of Wallerian degeneration. Transected distal axons survived for two weeks, and neuromuscular junctions were also protected. Surprisingly, the Wld protein was located predominantly in the nucleus, indicating an indirect protective mechanism. Nmnat enzyme activity, but not NAD+ content, was increased fourfold in WldS tissues. Thus, axon protection is likely to be mediated by altered ubiquitination or pyridine nucleotide metabolism.

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Nature neuroscience, 4, 12, 2001

PMID: 11770485

NaAGP4 is an arabinogalactan protein whose expression is suppressed by wounding and fungal infection in Nicotiana alata.
Gilson P, Gaspar YM, Oxley D, Youl JJ, Bacic A

Arabinogalactan proteins (AGPs) are proteoglycans secreted by plant cells that have been implicated in plant growth and development. Most AGPs cloned to date possess highly labile glycosylphosphatidylinositol (GPI) lipid anchors. These anchors transiently attach AGPs to the plasma membrane before they are released into the cell wall following GPI anchor hydrolysis. We have isolated and partially sequenced the protein core of an AGP purified from styles of Nicotiana alata. The protein sequence data were utilised to clone the AGP's gene, NaAGP4. This AGP shares about 78% sequence identity with the tomato AGP LeAGP-1. RNA gel blot analyses of different plant organs indicate that NaAGP4 is expressed in the same tissues and at similar levels as LeAGP-1. Furthermore, NaAGP4 like LeAGP-1 is rapidly suppressed by tissue wounding and by pathogen infection. We believe NaAGP4 and LeAGP-1 are the first described examples of orthologous AGPs from different plant species. In contrast, another AGP from N. alata, NaAGP1, is comparatively unaffected by wounding and pathogen infection, although this AGP is expressed in similar tissues and at similar levels as NaAGP4.

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Protoplasma, 215, 0033-183X, 2001

PMID: 11732052

Vav is required for cyclin D2 induction and proliferation of mouse B lymphocytes activated via the antigen Receptor.
Glassford J, Holman M, Banerji L, Clayton E, Klaus GG, Turner M, Lam EW

B lymphocytes from mice null for the Rho-family guanine-nucleotide exchange factor, Vav, are defective in their ability to proliferate in response to BCR cross-linking, but are able to proliferate normally in response to LPS. In addition, they have a depletion of CD5(+) (B1) lymphocytes and defective IgG class switching. This phenotype is reminiscent of that observed in mice null for the cell cycle regulatory protein, cyclin D2. We demonstrate here that the inability of vav(-/-) B cells to proliferate in response to BCR ligation is due to an inability to induce cyclin D2. In addition, we show that the proliferative defect of these cells occurs after the cells have entered early G1 phase. Analyses of potential down-stream signaling intermediates revealed differential activation of the stress-activated MAP kinases in the absence of Vav, normal activation of the ERK, MAPK, and phosphatidylinositol 3-kinase pathways, and defective intracellular calcium mobilization. We further demonstrate that intracellular calcium homeostasis is required for cyclin D2 induction, implicating a possible link with the defective calcium response of vav(-/-) B cells and their inability to induce cyclin D2.

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The Journal of biological chemistry, 276, 0021-9258, 2001

PMID: 11546804

Open Access

Rat natural killer cell receptor systems and recognition of MHC class I molecules.
Rolstad B, Naper C, Løvik G, Vaage JT, Ryan JC, Bäckman-Petersson E, Kirsch RD, Butcher GW

Rat natural killer (NK) cells recognize MHC-I molecules encoded by both the classical (RT1-A) and non-classical (RT1-C/E/M) MHC class I (MHC-I) regions. We have identified a receptor, the STOK2 antigen, which belongs to the Ly-49 family of killer cell lectin-like receptors, and we have localized the gene encoding it to the rat natural killer cell gene complex. We have also shown that it inhibits NK cytotoxicity when recognizing its cognate MHC-I ligand RT1-A1c on a target cell. This is the first inhibitory Ly-49-MHC-I interaction identified in the rat and highlights the great similarity between rat and mouse Ly-49 receptors and their MHC ligands. However, the mode of rat NK-cell recognition of target cells indicates that positive recognition of allo-MHC determinants, especially those encoded by the RT1-C/E/M region, is a prevalent feature. NK cells recruited to the peritoneum as a consequence of alloimmunization display positive recognition of allodeterminants. In one case, NK cells activated in this way have been shown to be specific for the immunizing, non-classical class I molecule RT1-Eu. These findings show that allospecific NK cells sometimes show features reminiscent of the adaptive immune response.

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Immunological reviews, 181, 0105-2896, 2001

PMID: 11513136

PtdIns(3)P regulates the neutrophil oxidase complex by binding to the PX domain of p40(phox).
CD Ellson, S Gobert-Gosse, KE Anderson, K Davidson, H Erdjument-Bromage, P Tempst, JW Thuring, MA Cooper, ZY Lim, AB Holmes, PR Gaffney, J Coadwell, ER Chilvers, PT Hawkins, LR Stephens

The production of reactive oxygen species (ROS) by neutrophils has a vital role in defence against a range of infectious agents, and is driven by the assembly of a multi-protein complex containing a minimal core of five proteins: the two membrane-bound subunits of cytochrome b(558) (gp91(phox) and p22(phox)) and three soluble factors (GTP-Rac, p47(phox) and p67(phox) (refs 1, 2). This minimal complex can reconstitute ROS formation in vitro in the presence of non-physiological amphiphiles such as SDS. p40(phox) has subsequently been discovered as a binding partner for p67(phox) (ref. 3), but its role in ROS formation is unclear. Phosphoinositide-3-OH kinases (PI(3)Ks) have been implicated in the intracellular signalling pathways coordinating ROS formation but through an unknown mechanism. We show that the addition of p40(phox) to the minimal core complex allows a lipid product of PI(3)Ks, phosphatidylinositol 3-phosphate (PtdIns(3)P), to stimulate specifically the formation of ROS. This effect was mediated by binding of PtdIns(3)P to the PX domain of p40(phox). These results offer new insights into the roles for PI(3)Ks and p40(phox) in ROS formation and define a cellular ligand for the orphan PX domain.

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Nature cell biology, 3, 7, 2001

PMID: 11433301

Peptide binding characteristics of the non-classical class Ib MHC molecule HLA-E assessed by a recombinant random peptide approach.
Stevens J, Joly E, Trowsdale J, Butcher GW

Increasing evidence suggests that the effect of HLA-E on Natural Killer (NK) cell activity can be affected by the nature of the peptides bound to this non-classical, MHC class Ib molecule. However, its reduced cell surface expression, and until recently, the lack of specific monoclonal antibodies hinder studying the peptide-binding specificity HLA-E.

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BMC immunology, 2, 1471-2172, 2001

PMID: 11432755

Open Access

Functional dichotomy in natural killer cell signaling: Vav1-dependent and -independent mechanisms.
Colucci F, Rosmaraki E, Bregenholt S, Samson SI, Di Bartolo V, Turner M, Vanes L, Tybulewicz V, Di Santo JP

The product of the protooncogene Vav1 participates in multiple signaling pathways and is a critical regulator of antigen-receptor signaling in B and T lymphocytes, but its role during in vivo natural killer (NK) cell differentiation is not known. Here we have studied NK cell development in Vav1-/- mice and found that, in contrast to T and NK-T cells, the absolute numbers of phenotypically mature NK cells were not reduced. Vav1-/- mice produced normal amounts of interferon (IFN)-gamma in response to Listeria monocytogenes and controlled early infection but showed reduced tumor clearance in vivo. In vitro stimulation of surface receptors in Vav1-/- NK cells resulted in normal IFN-gamma production but reduced tumor cell lysis. Vav1 was found to control activation of extracellular signal-regulated kinases and exocytosis of cytotoxic granules. In contrast, conjugate formation appeared to be only mildly affected, and calcium mobilization was normal in Vav1-/- NK cells. These results highlight fundamental differences between proximal signaling events in T and NK cells and suggest a functional dichotomy for Vav1 in NK cells: a role in cytotoxicity but not for IFN-gamma production.

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The Journal of experimental medicine, 193, 0022-1007, 2001

PMID: 11413196

Open Access

Signal transduction through Vav-2 participates in humoral immune responses and B cell maturation.
Doody GM, Bell SE, Vigorito E, Clayton E, McAdam S, Tooze R, Fernandez C, Lee IJ, Turner M

B and T lymphocytes develop normally in mice lacking the guanine nucleotide exchange factor Vav-2. However, the immune responses to type II thymus-independent antigen as well as the primary response to thymus-dependent (TD) antigen are defective. Vav-2-deficient mice are also defective in their ability to switch immunoglobulin class, form germinal centers and generate secondary immune responses to TD antigens. Mice lacking both Vav-1 and Vav-2 contain reduced numbers of B lymphocytes and display a maturational block in the development of mature B cells. B cells from Vav-1(-/-)Vav-2(-/-) mice respond poorly to antigen receptor triggering, both in terms of proliferation and calcium release. These studies show the importance of Vav-2 in humoral immune responses and B cell maturation.

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Nature immunology, 2, 1529-2908, 2001

PMID: 11376342

Rat tapasin: cDNA cloning and identification as a component of the class I MHC assembly complex.
Deverson EV, Powis SJ, Morrice NA, Herberg JA, Trowsdale J, Butcher GW

During the assembly of major histocompatibility complex (MHC) class I molecules transient associations are formed with the endoplasmic reticulum resident chaperones calnexin and calreticulin, ERp57 oxidoreductase, and also with tapasin, the latter mediating binding of the class I molecules to the transporter associated with antigen processing (TAP). We report here the isolation of a cDNA encoding rat tapasin from a DA (RT1av1) library. The cDNA encodes a proline-rich (11.3%) polypeptide of 464 residues with a potential ER-retention KK motif at its COOH-terminus, and a predicted molecular mass of 48 kDa. Matrix-assisted laser-desorption ionisation (MALDI) mass spectrometry of peptides derived from in-gel tryptic digestion of a TAP-associated protein match regions of the predicted translation product. A species of the correct molecular mass and predicted pl was also identified in association with radiolabelled immunoprecipitates of the rat TAP complex analysed by two-dimensional gel electrophoresis. This confirms rat tapasin as a component of the rat MHC class I assembly complex.

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Genes and immunity, 2, 1466-4879, 2001

PMID: 11294569

Two different, highly exposed, bulged structures for an unusually long peptide bound to rat MHC class I RT1-Aa.
Speir JA, Stevens J, Joly E, Butcher GW, Wilson IA

The rat MHC class Ia molecule RT1-Aa has the unusual capacity to bind long peptides ending in arginine, such as MTF-E, a thirteen-residue, maternally transmitted minor histocompatibility antigen. The antigenic structure of MTF-E was unpredictable due to its extraordinary length and two arginines that could serve as potential anchor residues. The crystal structure of RT1-Aa-MTF-E at 2.55 A shows that both peptide termini are anchored, as in other class I molecules, but the central residues in two independent pMHC complexes adopt completely different bulged conformations based on local environment. The MTF-E epitope is fully exposed within the putative T cell receptor (TCR) footprint. The flexibility demonstrated by the MTF-E structures illustrates how different TCRs may be raised against chemically identical, but structurally dissimilar, pMHC complexes.

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Immunity, 14, 1074-7613, 2001

PMID: 11163232

Open Access

Structural organization of the mouse phosphatidylinositol 3-kinase p110d gene.
Clayton E, McAdam S, Coadwell J, Chantry D, Turner M

Phosphatidylinositol 3-kinases are a family of dual specificity lipid/protein kinases. The products of PI3K's, phosphatidylinositol(3,4,5) triphosphate and phosphatidylinositol(3,4) bisphosphate, act as second messengers connecting activated transmembrane receptors to signaling pathways that control gene transcription, proliferation, transformation, programmed cell death, adhesion, migration and vesicular transport. There is evidence that different isoforms of PI3K's activate specific signaling pathways and are thus responsible for integrating cellular responses. The elucidation of the genomic structure of the catalytic subunits is a necessary step for the investigation of the function of PI3K isoforms by inactivation of the gene in vivo. The structural organization of p110alpha, beta, and gamma genes has been previously reported. Here we report the cloning, sequencing, and structural organization of the mouse p110delta gene from a murine 129/Sv genomic library. The p110delta gene consists of 22 exons and spans over 13 kb. Comparison of the genomic structure with that of p110alpha, beta, and gamma demonstrates that the p110delta gene shares its exon structure with p110beta, the most closely related PI3K at the amino acid level.

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Biochemical and biophysical research communications, 280, 0006-291X, 2001

PMID: 11162674

A locust type 1 ADP-ribosylation factor (lARF1)* is 100% identical in amino acid sequence to Drosophila ARF1 despite obvious DNA sequence divergence.
F Hannan, PD Evans

The cDNA of a type 1 ADP-ribosylation factor (ARF) from the desert locust, Locusta migratoria was cloned, sequenced and compared to ARF1 genes of other species. The locust ARF1 protein is 100% identical with the ARF1 protein of the fruit fly Drosophila melanogaster even though the DNA sequences are only 79% identical. The significance of this finding in relation to the considerable evolutionary distance between hemimetabolous and holometabolous insects is discussed.

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Insect molecular biology, 9, 6, 2000

PMID: 11122465

Vav-2 controls NFAT-dependent transcription in B- but not T-lymphocytes.
Doody GM, Billadeau DD, Clayton E, Hutchings A, Berland R, McAdam S, Leibson PJ, Turner M

We show here that Vav-2 is tyrosine phosphorylated following antigen receptor engagement in both B- and T-cells, but potentiates nuclear factor of activated T cells (NFAT)-dependent transcription only in B cells. Vav-2 function requires the N-terminus, as well as functional Dbl homology and SH2 domains. More over, the enhancement of NFAT-dependent transcription by Vav-2 can be inhibited by a number of dominant-negative GTPases. The ability of Vav-2 to potentiate NFAT-dependent transcription correlates with its ability to promote a sustained calcium flux. Thus, Vav-2 augments the calcium signal in B cells but not T cells, and a truncated form of Vav-2 can neither activate NFAT nor augment calcium signaling. The CD19 co-receptor physically interacts with Vav-2 and synergistically enhances Vav-2 phosphorylation induced by the B-cell receptor (BCR). In addition, we found that Vav-2 augments CD19-stimulated NFAT- dependent transcription, as well as transcription from the CD5 enhancer. These data suggest a role for Vav-2 in transducing BCR signals to the transcription factor NFAT and implicate Vav-2 in the integration of BCR and CD19 signaling.

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The EMBO journal, 19, 0261-4189, 2000

PMID: 11080163

Open Access

A comparison of agonist-specific coupling of cloned human alpha(2)-adrenoceptor subtypes.
JE Rudling, J Richardson, PD Evans

The agonist-specific coupling properties of the three cloned human alpha(2)-adrenoceptor subtypes have been compared, when expressed at similar levels in Chinese hamster ovary (CHO) cell lines, using noradrenaline and (+/-)-meta-octopamine as agonists. Noradrenaline can couple the receptor to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production in all three receptor subtypes, with the relative strength of the coupling to the pathways varying for each of the receptor subtypes. meta-Octopamine selectively couples the alpha(2A)-adrenoceptor only to the inhibition of forskolin-stimulated cyclic AMP production. However, meta-octopamine couples the alpha(2B)- and alpha(2C)-adrenoceptors to both the inhibition and stimulation of forskolin-stimulated cyclic AMP production. The relative potency of meta-octopamine to noradrenaline varies between the different alpha(2)-adrenoceptor subtypes. The effects of meta-octopamine are around two orders of magnitude less potent than those of noradrenaline on both the alpha(2A)- and alpha(2B)-adrenoceptor subtypes. In contrast, in the case of the alpha(2C)-adrenoceptor, meta-octopamine is only one order of magnitude less potent than noradrenaline in the stimulation of forskolin-stimulated cyclic AMP production and, in addition, is equipotent with noradrenaline in the inhibition of forskolin-stimulated cyclic AMP production and has an increased maximal response. This raises the possibility that meta-octopamine may have physiologically important actions via alpha(2C)-adrenoceptors in vivo. The results show that the modulation of cyclic AMP production occurs in both a subtype- and agonist-specific manner for alpha(2A)-adrenoceptors and in a subtype specific manner for alpha(2B)- and alpha(2C)-adrenoceptors.

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British journal of pharmacology, 131, 5, 2000

PMID: 11053214

Development of T-leukaemias in CD45 tyrosine phosphatase-deficient mutant lck mice.
Baker M, Gamble J, Tooze R, Higgins D, Yang FT, O'Brien PC, Coleman N, Pingel S, Turner M, Alexander DR

The CD45 tyrosine phosphatase lowers T-cell antigen receptor signalling thresholds by its positive actions on p56(lck) tyrosine kinase function. We now show that mice expressing active lck(F505) at non-oncogenic levels develop aggressive thymic lymphomas on a CD45(-/-) background. CD45 suppresses the tumorigenic potential of the kinase by dephosphorylation of the Tyr394 autophosphorylation site. In CD45(-/-) thymocytes the kinase is switched to a hyperactive oncogenic state, resulting in increased resistance to apoptosis. Transformation occurs in early CD4(-)CD8(-) thymocytes during the process of TCR-beta chain rearrangement by a recombinase-independent mechanism. Our findings represent the first example in which a tyrosine phosphatase in situ prevents the oncogenic actions of a SRC: family tyrosine kinase.

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The EMBO journal, 19, 0261-4189, 2000

PMID: 10970857

Open Access

Peptide specificity of RT1-A1(c), an inhibitory rat major histocompatibility complex class I natural killer cell ligand.
Stevens J, Jones RC, Bordoli RS, Trowsdale J, Gaskell SJ, Butcher GW, Joly E

The rat major histocompatibility complex class Ia allelomorph RT1-A1(c) is a potent ligand for the recently identified inhibitory rLy-49 receptor, STOK-2. With the ultimate objective of studying the interactions of these molecules using structural and functional methods, we undertook a detailed study of its peptide specificity. The study revealed that designing an "ideal peptide" by choosing the most abundant residues in the "binding motif" obtained by pool sequencing does not necessarily yield an optimal binding peptide. For RT1-A1(c), as many as four positions, P2, P4, P5, and P9, were detected as putative anchors. Since this molecule displays a preference for highly hydrophobic peptides, we tested binding of peptides derived from the known leader peptide sequences of other rat histocompatibility complex class I molecules. One such peptide, found to bind well, requiring 1.6 microm peptide to achieve 50% stabilization, was searched for in vivo. Natural RT1-A1(c) binding peptides were purified from rat splenocytes and characterized by mass spectrometry using a combined matrix-assisted laser desorption ionization/time-of-flight and quadrupole time-of-flight approach. Results showed that the signal sequence-derived peptide was not detectable in the purified peptide pool, which was composed of a complex spectrum of peptides. Seven of these self-peptides were successfully sequenced.

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The Journal of biological chemistry, 275, 0021-9258, 2000

PMID: 10856297

Open Access

Self-MHC class Ia (RT1-A(n)) protects cells co-expressing the activatory allogeneic MHC class Ib molecule (RT1-E(u)) from NK lysis.
Bäckman-Petersson E, Butcher GW, Hedlund G

We have previously shown activation of NK cells via recognition of an allogeneic, non-classical MHC class I molecule, RT1-E(u). In this study we investigated whether a self-MHC class I molecule could protect the allogeneic targets from being recognized and killed by the alloreactive NK (allo NK) cells. NK cells from BN (RT1 n) rats, primed in vivo by immunization with RT1(u)-expressing cells, manifested cytolytic activity against RT1(u)- as well as RT1(u/lv1)-expressing targets, but not against RT1(u/n)-expressing targets. The absence of cytolytic activity against semiallogeneic targets, i.e. targets expressing self-allotypes, was also valid for allo NK cells from alloimmunized F344 (RT1 (lv1)) rats. To analyze the ability of a distinct MHC class I molecule to protect target cells from NK lysis, Rat2 cells transfected with the activating allogeneic MHC class Ib, RT1-E(u) molecule were also transfected with the self-MHC class Ia, RT1-A1(n) molecule. The allo NK cells from BN rats immunized with RT1(u)-expressing cells were cytolytic against Rat2 transfected with the RT1-E(u) molecule. However, the allo NK cells manifested no cytolytic activity against double-transfected Rat2 cells, expressing the RT1-E(u) as well as the RT1-A1(n) molecule. We conclude that expression of a self-MHC class Ia (RT1-A) molecule protects targets from allo NK killing. Furthermore, the NK inhibition via recognition of the self-MHC class Ia molecule dominates over the activation via recognition of the allogeneic MHC class Ib molecule, RT1-E.

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International immunology, 12, 0953-8178, 2000

PMID: 10837412

Open Access

A panel of monoclonal antibodies to ovine placental lactogen.
Forsyth IA, Hutchings A, Butcher GW

A panel of 11 rat monoclonal antibodies (mAbs) has been raised to ovine placental lactogen (PL). By competitive enzyme-linked immunoabsorbent assay (ELISA), confirmed by two-site ELISA, the antibodies were shown to recognize six antigenic determinants on the ovine PL molecule, two of which overlap. One antigenic determinant (designated 1) was shared by other members of the prolactin/growth hormone (GH)/PL family in ruminants, humans and rodents. The binding of (125)I-labelled ovine PL to crude receptor preparations from sheep liver (somatotrophic) or rabbit mammary gland (lactogenic) was inhibited by mAbs recognizing antigenic determinants 2-6. Both types of receptor preparation were affected similarly. In the local in vivo pigeon crop sac assay, mAbs directed against determinants 3 and 6 enhanced the biological activity of ovine PL.

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The Journal of endocrinology, 165, 0022-0795, 2000

PMID: 10810307

Open Access

A new look at Syk in alpha beta and gamma delta T cell development using chimeric mice with a low competitive hematopoietic environment.
Colucci F, Guy-Grand D, Wilson A, Turner M, Schweighoffer E, Tybulewicz VL, Di Santo JP

The Syk protein tyrosine kinase (PTK) is essential for B, but not T or NK, cell development, although certain T cell subsets (i.e., gamma delta T cells of intestine and skin) appear to be dependent on Syk. In this report, we have re-evaluated the role of Syk in T cell development in hematopoietic chimeras generated by using Syk-deficient fetal liver hematopoietic stem cells (FL-HSC). We found that Syk-/- FL-HSC were vastly inferior to wild-type FL-HSC in reconstituting T cell development in recombinant-activating gene 2 (RAG2)-deficient mice, identifying an unexpected and nonredundant role for Syk in this process. This novel function of Syk in T cell development was mapped to the CD44-CD25+ stage. According to previous reports, development of intestinal gamma delta T cells was arrested in Syk-/- -->RAG2-/- chimeras. In striking contrast, when hosts were the newly established alymphoid RAG2 x common cytokine receptor gamma-chain (RAG2/gamma c) mice, Syk-/- chimeras developed intestinal gamma delta T cells as well as other T cell subsets (including alpha beta T cells, NK1.1+ alpha beta T cells, and splenic and thymic gamma delta T cells). However, all Syk-deficient T cell subsets were reduced in number, reaching about 25-50% of controls. These results attest to the utility of chimeric mice generated in a low competitive hematopoietic environment to evaluate more accurately the impact of lethal mutations on lymphoid development. Furthermore, they suggest that Syk intervenes in early T cell development independently of ZAP-70, and demonstrate that Syk is not essential for the intestinal gamma delta T cell lineage to develop.

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Journal of immunology (Baltimore, Md. : 1950), 164, 0022-1767, 2000

PMID: 10799872

Open Access