198,607 research outputs found
Multiple interactions of HIV-1 Tat protein with size-defined heparin oligosaccharides
No full textTat protein, a transactivating factor of the human immunodeficiency virus type I, acts also as an extracellular molecule. Heparin affects the bioavailability and biological activity of extracellular Tat (Rusnati, M., Coltrini, D., Oreste, P., Zoppetti, G., Albini, A., Noonan, D., D'Adda di Fagagna, F., Giacca, M., and Presta, M. (1997) J. Biol. Chem. 272, 11313-11320). Here, a series of homogeneously sized, (3)H-labeled heparin fragments were evaluated for their capacity to bind to free glutathione S-transferase (GST)-Tat protein and to immobilized GST-Tat. Hexasaccharides represent the minimum sized heparin fragments able to interact with GST-Tat at physiological ionic strength. Also, the affinity of binding increases with increasing the molecular size of the oligosaccharides, with large fragments (>/=18 saccharides) approaching the affinity of full-size heparin. 6-Mer heparin binds GST-Tat with a dissociation constant (K(d)) equal to 0.7 +/- 0.4 microM and a molar oligosaccharide:GST-Tat ratio of about 1:1. Interaction of GST-Tat with 22-mer or full-size heparin is consistent instead with two-component binding. At subsaturating concentrations, a single molecule of heparin interacts with 4-6 molecules of GST-Tat with high affinity (K(d) values in the nanomolar range of concentration); at saturating concentrations, heparin binds GST-Tat with lower affinity (K(d) values in the micromolar range of concentration) and a molar oligosaccharide:GST-Tat ratio of about 1:1. In agreement with the binding data, a positive correlation exists between the size of heparin oligosaccharides and their capacity to inhibit cell internalization, long terminal repeat-transactivating activity of extracellular Tat in HL3T1 cells, and its mitogenic activity in murine adenocarcinoma T53 Tat-less cells. The data demonstrate that the modality of heparin-Tat interaction is strongly affected by the size of the saccharide chain. The possibility of establishing multiple interactions increases the affinity of large heparin fragments for Tat protein and the capacity of the glycosaminoglycan to modulate the biological activity of extracellular Tat
Prefazione
No full textIl libro presenta gli esiti di una ricerca partecipativa dedicata al coinvolgimento dei cittadini immigrati nella vita culturale della città
La "cassetta degli attrezzi" del Progetto Con nuove culture
No full textIl saggio presenta gli strumenti di analisi e di implementazione delle esperienze realizzate o progettate nell'ambito del Progetto Con nuove culture a Bolzano (progetto promosso dalla Provincia di Bolzano in convenzione con il Dipartimento di Scienze dell'Educazione dell'Università di Bologna). Si tratta di strumenti elaborati appositamente a supporto dell'attività di formazione e realizzazione di eventi culturali portati avanti dal Progetto
Culture in dialogo: storia, strumenti, analisi per ripensare al cultura nei contesti multiculturali
No full textIl saggio approfondisce le diverse fasi del Progetto Con nuove culture svoltosi a Bolzano tra il 2010 e il 2013 e avente l'obiettivo di coinvolgere i cittadini immigrati nella vita cultura delle istituzioni locali (musei, biblioteche, teatri); il saggio ripercorre la storia del progetto che ha seguito una metodologia partecipativa coinvolgendo operatori delle istituzioni culturali coinvolte e associazioni migranti presenti sul territorio; nelle diverse sue diverse fasi, il progetto ha elaborato una serie di strumenti di analisi di cui si riportano i dati quantitativi e qualitativi raccolti
Basic fibroblast growth factor is released from endothelial extracellular matrix in a biologically active form.
No full textBasic fibroblast growth factor (bFGF) binds to heparin-like molecules present in the extracellular matrix (ECM) of transformed fetal bovine aortic endothelial GM 7373 cells. Binding of bFGF to ECM can be competed by heparin or heparan sulfate, and ECM-bound bFGF can be released by treating the cells with heparinase or heparatinase. After binding to ECM, bFGF is slowly released into the medium in a biologically active form, as shown by its capacity to induce an increase of cell-associated plasminogen activator activity and cell proliferation. The increase is prevented upon removal of ECM-bound bFGF by a neutral 2 M NaCl wash. Soluble heparin and heparan sulfate reduce the amount of ECM-bound bFGF released into the medium, possibly competing with ECM polysaccharides for heparinase-like enzymes produced by endothelial cells, suggesting that these enzymes are involved in the mobilization of ECM-bound bFGF
The basic domain in HIV-1 Tat protein as a target for polysulfonated heparin-mimicking extracellular Tat antagonists
No full textHeparin binds extracellular HIV-1 Tat protein and modulates its HI long terminal repeat (LTR)-transactivating activity (M. Rusnati, D. Coltrini, P. Oreste, G. Zoppetti, A. Albini, D. Noonan, F. d'Adda di Fagagna, M. Giacca, and M. Presta (1997) J. Biol. Chem. 272, 11313-11320). On this basis, the glutathione S-transferase (GST)-Tat(R49/52/53/55/56/57A) mutant, in which six arginine residues within the basic domain of Tat were mutagenized to alanine residues, was compared with GSTTat for its capacity to bind immobilized heparin. Dissociation of the GST-Tat(R49/52/53/55/56/57A) · heparin complex occurred at ionic strength significantly lower than that required to dissociate the GST-Tat-heparin complex. Accordingly, heparin binds immobilized GST-Tat and GSTTat(R49/52/53/55/56/57A) with a dissociation constant equal to 0.3 and 1.0 μM, respectively. Also, the synthetic basic domain Tat-(41-60) competes with GST-Tat for heparin binding. Suramin inhibits [3H]heparin/Tat interaction, 125I-GST-Tat internalization, and the LTR-transactivating activity of extracellular Tat in HL3T1 cells and prevents 125I-GST-Tat binding and cell proliferation in Tat-overexpressing T53 cells. The suramin derivative 14CPNU 145156E binds immobilized GST-Tat with a dissociation constant 5 times higher than heparin and is unable to bind GST-Tat(R49-52/53/55/56/57A). Although heparin was an antagonist more potent than suramin, modifications of the backbone structure in selected suramin derivatives originated Tat antagonists whose potency was close to that shown by heparin. In conclusion, suramin derivatives bind the basic domain of Tat, prevent Tat/heparin and Tat/cell surface interactions, and inhibit the biological activity of extracellular Tat. Our data demonstrate that tailored polysulfonated compounds represent potent extracellular Tat inhibitors of possible therapeutic value
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