Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0272170 (SDS)
 50,377 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

CD28 is a costimulatory receptor that can provide the second signal necessary for T-cell activation and function in response to stimulation through the T-cell antigen receptor/CD3 complex. We found that a distinct array of proteins was phosphorylated on tyrosine following stimulation with anti-CD28 monoclonal antibody, as detected by immune-complex kinase assays. Anti-CD28 stimulation of in vitro kinase activity was detergent-dependent, occurring in immune complexes prepared with Brij 96 but not Nonidet P-40. Pretreatment of cells with low concentrations of phorbol ester increased the activation-independent phosphorylation of proteins in CD28 immune complexes. Reimmunoprecipitation studies indicated that the cytoplasmic protein-tyrosine kinases Lck and Fyn were associated with CD28. CD28 itself was phosphorylated both in vitro and in vivo in an activation-dependent manner, as detected by nonreducing/reducing SDS/PAGE analyses. The activation-stimulated phosphorylation of CD28 may play a key role in signaling through this receptor.
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PMID:Activation-dependent phosphorylation of the T-lymphocyte surface receptor CD28 and associated proteins. 751 28

Previously we showed that a thiol-reactive heavy metal, HgCl2, crosslinked multiple cell surface receptors through a ligand-independent pathway, which produced massive aggregates of phosphotyrosine (PTYR)-containing proteins beneath plasma membrane [Nakashima et al. (1994): J Immunol 152: 1064-1071]. In this study we characterized these unique aggregates at the molecular level. The lysates in Brij 96 of thymocytes treated with HgCl2 were separated into the supernatant and pellet fractions by simple centrifugation. Selected PTYR-containing proteins and p56lck appeared in the pellet fraction as quickly as 5 s after exposure to HgCl2, and were further increased in amount by 5 min. Although the mechanism of triggering these events was redox-linked, the majority of proteins in the Brij 96-insoluble aggregates were dissociated in SDS-PAGE under nonreducing condition. This suggested that PTYR-containing proteins and p56lck themselves do not form dimer or polymer directly by thiol-mediated bond. The pellet fraction was further found to include some other signal delivery elements, such as GTPase activating protein, phosphatidylinositol 3 kinase, and mitogen-activated protein kinase. Finally, all of these signal elements and selected PTYR-containing proteins were collected in the same fraction by the sucrose density gradient centrifugation. These results suggest a unique redox-linked pathway of formation of a giant signal complex.
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PMID:Evidence of redox-linked signaling for producing a giant signal complex. 753 34

Necator americanus (Nematoda: Strongyloidea), a human hookworm parasite, is known to release considerable amounts of acetylcholinesterase (AChE) [Pritchard, D. I., Leggett K. V., Rogan, M. T., McKean, P. G. & Brown, A. (1991) Necator americanus secretory acetylcholinesterase and its purification from excretory/secretory products by affinity chromatography, Parasite Immunol. 13, 187-199]. The present study deals with AChE activity recovered in sequential somatic extracts, and excretory/secretory products, of the adult stage of the parasite. 97% of AChE was extractable in low-salt and high-salt detergent-free buffers, and only 3% was solubilised by a further extraction in the presence of Triton X-100. AChE in all three extracts was affected by the AChE inhibitors eserine, bis(4-allyldimethylammoniumphenyl)pentan-3-one dibromide and edrophonium chloride, but was resistant to the effects of tetramonoisopropylpyrophosphortetramide, a butyrylcholinesterase inhibitor. Sucrose density centrifugation revealed that AChE in all somatic extracts (low-salt, high-salt and detergent) resolved almost exclusively as a single peak between 6.9-7.5 S, while excretory/secretory products resolved at 8.2 S. These values are all compatible with dimers of catalytic subunits and no evidence was found for the presence of higher oligomers such as asymmetric forms. The only sample to show a shift in sedimentation following the inclusion of detergent (Triton X-100, Brij 96) in the gradient was a component of the detergent-soluble extract, indicating the existence of a minor amphiphilic form. In low-salt-soluble and high-salt-soluble extracts, AChE was solubilised as a hydrophilic globular form, probably a dimeric G2. The analysis of diisopropylfluorophosphate-labelled extracts by SDS/PAGE, and unlabelled extracts by immunoblotting using a polyvalent antiserum to N. americanus AChE, indicated that the AChE isolated in each extract was biochemically and immunologically similar. The banding patterns obtained were comparable to that seen when purified AChE was analysed by SDS/PAGE and immunoblotted. This suggests that the basic catalytic subunit has a mass of 66-70 kDa with the active site being located in a 30-kDa domain. All experimental data indicate the existence of only one AChE class in Necator homologous to AChE of class B from Caenorhabditis elegans. The solubility characteristics and globular nature of this hookworm AChE suggest that its major function is as an excretory or secretory product. This again raises the question of the true biological function of this 'non-cholinergenic' nematode secretion.
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PMID:The molecular forms of acetylcholinesterase from Necator americanus (Nematoda), a hookworm parasite of the human intestine. 830 98

Three distinct acetylcholinesterases were detected in the annelid oligochaete Dendrobaena veneta. Two enzymes (alpha, beta), copurified from a Triton-X-100-soluble extract of whole animals by affinity (edrophonium-Sepharose) chromatography, were separately eluted from a Sephadex G-200 column. Gel-filtration chromatography, sedimentation analysis and SDS/PAGE showed the alpha and beta forms to be a globular dimer (110 kDa, 7.0 S) and a hydrophilic monomer (58 kDa, 5.0 S) respectively, both weakly linked to the cell membrane. The third form (gamma), also purified to homogeneity by slower filtration through an edrophonium-Sepharose matrix, proved to be an amphiphilic globular dimer (133 kDa, 7.0 S) with a phosphatidylinositol anchor giving cell membrane insertion, detergent (Triton X-100, Brij 96) interaction and self-aggregation. The alpha acetylcholinesterase showed a fairly low substrate specificity: the beta form hydrolyzed propionylthiocholine at the highest rate and was inactive on butyrylthiocholine; the gamma acetylcholinesterase, showing a marked active-site specificity with differently sized substrates, was likely functional in cholinergic synapses. Studies with inhibitors showed incomplete inhibition of all three acetylcholinesterase by 1 mM eserine and different sensitivity for edrophonium or procainamide. The alpha and beta forms, sensitive to 1,5-bis(4-allyldimethylammoniumphenyl)-pentan-3-one dibromide, were unaffected by tetra(monoisopropyl)-pyrophosphortetramide, while both these agents inhibited the gamma enzyme. All three forms showed excess-substrate inhibition by acetylthiocholine. Enzyme activity was histochemically localized in the nerve ring and its minor branches. Monomeric acetylcholinesterase (beta) is likely the only form present in the ganglionic glial framework.
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PMID:Acetylcholinesterase in Dendrobaena veneta (Oligochaeta: Opisthopora) is present with forms sensitive and insensitive to phosphatidylinositol phospholipase C. Biochemical characterization and histochemical localization in the nervous system. 868 69

Receptors for the Fc portion of IgG (Fc gamma R) evoke a variety of immune responses upon attachment of the immune complex to this cell surface molecule. Enhancement of tumor cell cytotoxicity is one essential response mediated by Fc gamma Rs. We are studying two mAbs, G7 and PNK-E, which bind to a cytolytic triggering molecular complex on porcine NK cells and phagocytes and function in the enhancement and induction of tumor cell cytotoxicity, respectively. Through biochemical characterization and molecular cloning, we have identified the G7 molecule as the porcine homologue of human Fc gamma RIIIA alpha. The G7 and PNK-E molecules have previously been shown to exist as a complex on the cell surface, suggesting that PNK-E represents an Fc gamma RIIIA alpha-associated molecule in the porcine system. We used the mild detergent Brij 96 to identify associated molecules such as the gamma and zeta subunits. G7 and PNK-E mAbs immunoprecipitate the identical multimolecular complex which includes the gamma subunit on porcine PMN. In addition to the G7 molecule at 40 kDa and the gamma subunit at 7 kDa, Brij 96 immunoprecipitation with G7 mAb, PNK-E mAb, or anti-gamma Ab shows association of unidentified molecules of approximately 15, 20, and 25 kDa on reducing SDS-PAGE, none of which appear to be the zeta subunit. Large-scale immunoprecipitation of the G7 complex from porcine PMN will be performed to isolate sufficient quantities of these unidentified proteins to obtain amino acid sequences. Since these molecules seem to be distinct from Fc gamma R-associated subunits described to date, these studies may lead to the identification of unique Fc gamma R-associated molecules and suggest the presence of a novel Fc gamma RIIIA alpha molecular complex in the porcine system.
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PMID:Identification of a unique porcine Fc gamma RIIIA alpha molecular complex. 880 11

The following studies are the first to demonstrate the association of porcine FcgammaRIIIaalpha with a molecule that contains significant homology to the cathelin family of antimicrobial proteins. We performed immunoprecipitation of the porcine FcgammaRIIIaalpha multisubunit complex from Brij 96 lysates of polymorphonuclear leukocytes using the G7 mAb, which binds to FcgammaRIIIaalpha on the surface of porcine NK cells and phagocytes. Previous results indicate that the transmembrane alpha subunit of the FcgammaRIIIa complex is associated with the gamma subunit on the surface of porcine polymorphonuclear leukocytes and with several other unique proteins that surface iodinate and migrate at approximately 15, 20, and 25 kDa when analyzed by reducing SDS-PAGE. Through characterization of the porcine FcgammaRIIIa complex, we identified the 15-kDa molecule as a unique FcgammaR-associated protein that has not been described in other systems. We now report an association between FcgammaRIIIaalpha and a 15-kDa molecule that shares homology to cathelin, a protein of undetermined function initially identified in porcine leukocytes. A domain with a high degree of homology to cathelin is found in the proregions of a family of antibiotic proteins referred to as cathelicidins. The results of our studies indicate the presence of a novel FcgammaRIIIa complex in the porcine system, and may provide new insights into the function of this antimicrobial protein homologue in relation to the variety of responses mediated through FcgammaRs.
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PMID:Identification of a novel Fc gamma RIIIa alpha-associated molecule that contains significant homology to porcine cathelin. 1470 98