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1.

001-es BibID:BIBFORM054319
035-os BibID:PMID: 11453982
Első szerző:Koncz Gábor (biológus, immunológus)
Cím:Co-clustering of Fcγ and B cell receptors induces dephosphorylation of the Grb2-associated binder 1 docking protein / Gábor Koncz, Gábor K. Tóth, Gyöngyi Bökönyi, György Kéri, Israel Pecht, David Medgyesi, János Gergely, Gabriella Sármay
Dátum:2001
ISSN:0014-2956 1432-1033
Megjegyzések:The immunoreceptor tyrosine-based inhibitory motif (ITIM) of human type Ilb Fc gamma receptor (Fc gamma RIIb) is phosphorylated on its tyrosine upon co-clustering with the B cell receptor (BCR). The phosphorylated ITIM (p-ITIM) binds to the SH2 domains of polyphosphoinositol 5-phosphatase (SHIP) and the tyrosine phosphatase, SHP-2. We investigated the involvement of the molecular complex composed of the phosphorylated SHIP and Fc gamma RIIb in the activation of SHP-2. As a model compound, we synthesized a bisphosphopeptide, combining the sequences of p-ITIM and the N-terminal tyrosine phosphorylated motif of SHIP with a flexible spacer. This compound bound to the recombinant SH2 domains of SHP-2 with high affinity and activated the phosphatase in an in vitro assay. These data suggest that the phosphorylated Fc gamma RII-SHIP complexes formed in the intact cells may also activate SHP-2. Grb2-associated binder 1 (Gab1) is a multisite docking protein, which becomes tyrosine-phosphorylated in response to various types of signaling, including BCR. In turn it binds to the SH2 domains of SHP-2, SHIP and the p85 subunit of phosphatidyl inositol 3-kinase (PtdIns3-K) and may regulate their activity. Gab1 is a potential substrate of SHP-2, thus its binding to Fc gamma RIIb may modify the Gab1-bound signaling complex. We show here that Gab1 is part of the multiprotein complex assembled by Fc gamma RIIb upon its co-clustering with BCR. Gab1 may recruit SH2 domain-containing molecules to the phosphorylated Fc gamma RIIb. SHP-2, activated upon the binding to Fc gamma RIIb-SHIP complex, partially dephosphorylates Gab1, resulting in the release of PtdIns3-K and ultimately in the inhibition of downstream activation pathways in BCR/Fc gamma RIIb co-aggregated cells.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
B-lymphocytes
Fc gamma receptors IIb
signal transduction
Megjelenés:European Journal of Biochemistry. - 268 : 14 (2001), p. 3898-3906. -
További szerzők:Tóth Gábor K. Bökönyi Gyöngyi Kéri György Pecht, Israel Medgyesi Dávid Gergely János Sármay Gabriella
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2.

001-es BibID:BIBFORM054320
Első szerző:Kurucz István
Cím:Bacterially expressed human FcγRIIb is soluble and functionally active after in vitro refolding / István Kurucz, Ágnes Hilbert, Attila Kapus, Dávid Medgyesi, Gábor Koncz, Gabriella Sármay, Anna Erdei, János Gergely
Dátum:2000
ISSN:0165-2478
Megjegyzések:A recombinant soluble form of the human Fc gamma receptor was produced by engineering a cDNA construct containing the extracellular part of the mature protein. After expression in bacteria as inclusion body, the polypeptide was highly purified and was refolded in vitro with a method that was developed for the renaturation of immunoglobulin fragments. With this method oxidation of the disulfide bridges within the domains of the protein is done in the presence of an artificial 'chaperone' which protects the polypeptide molecules from unwanted protein-protein interactions thereby inhibiting the incorrect oxidation of the SH-groups, and misfolding of the protein. The refolded recombinant soluble Fc gamma RIIb showed several characteristics of the native receptor: (i) it was recognized by a series of monoclonal antibodies specific for, and in most cases produced against the native cell-surface receptor; (ii) it is bound to its ligand (the Fc-region of different immunoglobulins) under very diverse conditions; and (iii) it is competed strongly and specifically with the native cell surface receptor for both ligand and antibody binding in experiments with distinct read-outs; (iv) monoclonal antibodies produced against the recombinant protein specifically recognized Fc gamma RIIb on different cells. From these data it was concluded that the recombinant soluble Fc-receptor was in a native, functionally active form, and its function was not affected by the lack of glycosylation. (C) 2000 Elsevier Science B.V. All rights reserved.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
soluble Fc gamma receptors
bacterial expression
refolding
Megjelenés:Immunology Letters. - 75 : 1 (2000), p. 33-40. -
További szerzők:Hilbert Ágnes Kapus Attila Medgyesi Dávid Koncz Gábor (1970-) (biológus, immunológus) Sármay Gabriella Erdei Anna Gergely János
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3.

001-es BibID:BIBFORM054299
035-os BibID:PMID: 18950707
Első szerző:Maus Máté
Cím:Grb2 associated binder 2 couples B-cell receptor to cell survival / Máté Maus, Dávid Medgyesi, Dorottya Kövesdi, Dorottya Csuka, Gábor Koncz, Gabriella Sármay
Dátum:2009
ISSN:0898-6568
Megjegyzések:B-cell fate during maturation and the germinal center reaction is regulated through the strength and the duration of the B-cell receptor signal. Signaling pathways discriminating between apoptosis and survival in B cells are keys in understanding adaptive immunity. Gab2 is a member of the Gab/Dos adaptor protein family. It has been shown in several model systems that Gab/Dos family members may regulate both the anti-apoptotic PI3-K/Akt and the mitogenic Ras/MAPK pathways, still their role in B-cells have not been investigated in detail. Here we studied the role of Gab2 in B-cell receptor mediated signaling. We have shown that BCR crosslinking induces the marked phosphorylation of Gab2 through both Lyn and Syk kinases. Subsequently Gab2 recruits p85 regulatory subunit of PI3-K. and SHP-2. Our results revealed that Ig-alpha/Ig-beta, signal transducing unit of the B-cell receptor, may function as scaffold recruiting Gab2 to the signalosome. Overexpression of Gab2 in A20 cells demonstrated that Gab2 is a regulator of the PI3-K/Akt but not that of the Ras/MAPK pathway in B cells. Accordingly to the elevated Akt phosphorylation, overexpression of wild-type Gab2 in A20 cells suppressed Fas-mediated apoptosis, and enhanced BCR-mediated rescue from Fas-induced cell death. Although PH-domain has only a stabilizing effect on membrane recruitment of Gab2, it is indispensable in mediating its anti-apoptotic effect. (c) 2008 Elsevier Inc. All rights reserved.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
B-cell
Signaling
Gab2 adaptor/scaffolding protein
Phosphorylation
PH domain
Survival
Megjelenés:Cellular Signalling. - 21 : 2 (2009), p. 220-227. -
További szerzők:Medgyesi Dávid Kövesdi Dorottya Csuka Dorottya Koncz Gábor (1970-) (biológus, immunológus) Sármay Gabriella
Pályázati támogatás:OTKA-K60760
OTKA
GVOP-2004-05-3.1.1/3.00183
GVOP
NKFP-1-A/040/2004
Egyéb
CellKom REr/06
Egyéb
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4.

001-es BibID:BIBFORM054307
035-os BibID:PMID: 15081531
Első szerző:Medgyesi Dávid
Cím:Functional consequences of a MAPK docking site on human FcγRIIb / Dávid Medgyesi, Rita Sárközi, Gábor Koncz, Krisztina Arató, Györgyi Váradi, Gábor K. Tóth, Gabriella Sármay
Dátum:2004
ISSN:0165-2478
Megjegyzések:Type IIb Fcgamma receptors (FcgammaRIIb) have a major role in regulating B cell activation. Upon its co-aggregation with the B cell receptors (BCR) via immune complexes FcgammaRIIb become phosphorylated on tyrosine within its immunoreceptor tyrosine based inhibitory motif (MM) and in turn recruit protein- and inositol phosphatases, inhibiting thereby signal transduction. The intracellular domain of the human FcgammaRIIb has a membrane proximal motif that is very similar to those of MAPK docking site in MAPK-interacting molecules. Additionally, in contrast to the mouse, a serine residue is located next to this motif that is a potential phosphorylation site for Ser/Thr kinases. Our aim was to study the role of the putative MAPK docking motif on FcgammaRIIb mediated function. We report here that MAPKs bind to FcgammaRIIb affinity purified from the detergent extracts of anti-IgM activated and BCR-FcgammaRIIb co-clustered B cells. We detected extracellular signal regulated kinase (ERK) activity in FcgammaRIIb immunoprecipitates and identified the bound proteins as 85, 44 and 42 kDa ERKs by Western blots. Active ERKs bound to the synthetic peptide representing the putative docking site of FcgammaRIIb on a Ser/Thr phosphatase dependent manner. The FcgammaRIIb-associated ERKs may phosphorylate the membrane proximal serine of the receptor. We examined the consequences of serine phosphorylation by comparing the proteins that interact with synthetic peptides comprising the combined sequences of the MAPK docking site and the ITIM either in phosphorylated or in non-phosphorylated forms. The results indicate that phosphorylation on serine modifies the binding of Lyn to FcgammaRIIb, thus might negatively regulate phosphorylation of ITIM. (C) 2003 Elsevier B.V. All rights reserved.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
B cell
Fc gamma RIIb
MAPK docking site
regulation
signalling
Megjelenés:Immunology Letters. - 92 : 1-2 (2004), p. 83-90. -
További szerzők:Sárközi Rita Koncz Gábor (1970-) (biológus, immunológus) Arató Krisztina Váradi Györgyi Tóth Gábor K. Sármay Gabriella
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Intézményi repozitóriumban (DEA) tárolt változat
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5.

001-es BibID:BIBFORM054306
Első szerző:Medgyesi Dávid
Cím:Functional mapping of the FcγRII binding site on human IgG1 by synthetic peptides / Dávid Medgyesi, Katalin Uray, Krisztina Sallai, Ferenc Hudecz, Gábor Koncz, Jakub Abramson, Israel Pecht, Gabriella Sármay, János Gergely
Dátum:2004
ISSN:0014-2980
Megjegyzések:Receptors specific for the Fc part of IgG (FcgammaR) are expressed by several cell types and play diverse roles in immune responses. Impaired function of the activating and inhibitory FcgammaR may result in autoimmunity. Thus, the modulation of IgG-FcgammaR interaction can be a target for the development of treatments for some autoimmune and inflammatory diseases. This study addresses the localization and functional characterization of linear sequences in human IgG1 which bind to FcgammaRII. Peptides with overlapping sequences derived from the CH2 domain of human IgG1 between P(234) and S(298) were synthesized and used in binding and functional experiments. Binding of the peptides to FcgammaR was assayed in vitro and ex vivo, and peptides found to interact were functionally tested. The shortest effective peptide was T(216)-p(271) which bound to soluble recombinant Fc-gammaRIIb with K(d)=6x10(6) M(-1). The biotinylated peptides R(255)-p(271) and T(256)-p(271) complexed by avidin exhibited functional activity; they induced FcgammaRIIb-mediated inhibition of the BCR-triggered Ca(2+) response of human Burkitt lymphoma cells, and inflammatory cytokine production (TNF-alpha and IL-6) by the human monocyte cell line MonoMac. In conclusion, our results suggest that the selected peptides functionally represent the Fc-gammaRII-binding part of IgG1.
Tárgyszavak:Orvostudományok Elméleti orvostudományok idegen nyelvű folyóiratközlemény külföldi lapban
IgG
Fc gamma Re
fc peptide
binding site
Megjelenés:European Journal of Immunology. - 34 : 4 (2004), p. 1127-1135. -
További szerzők:Uray Katalin Sallai Krisztina Hudecz Ferenc Koncz Gábor (1970-) (biológus, immunológus) Abramson, Jakub Pecht, Israel Sármay Gabriella Gergely János
Pályázati támogatás:AKP 2000-40 3,3
MTA
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