Eporter for normalization. Cells were stimulated with anti-CD3 plus anti-CD28 Abs 24 h after transfection for the last 6 h. Cells were lysed then and processed to measure the LUC activity with the Dual Luciferase system (Promega, CA USA) according to the manufacturer’s instructions.3PO Plasmids and MutagenesisStandard molecular biology techniques were used to generate the different constructions used in this study. Site-directed 38916-34-6 manufacturer mutagenesis was done with the QuickChange Mutagenesis Kit (Agilent-Stratagene, CA, USA) following the manufacturer instructions. All constructions and mutations were verified by nucleotide sequencing.Flow Cytometry and ImmunohistochemistryJurkat cells were stimulatd with soluble anti-CD3 plus antiCD28 Abs for 24 hours and were stained with Phycoerythrin (PE)labeled anti-CD25 or PE-IgG2b isotype control (Immunostep, Salamanca, Spain). Data were acquired on a Gallios Flow Cytometer instrument (Beckman Coulter, Inc. CA, USA) and analysis was carried out with WinMDI software.Cell Culture and TransfectionsHEK293 were maintained at 37uC in Dulbecco’s modified Eagle’s medium supplemented with 10 FBS, 2 mM L-glutamine, 100 U/ml penicillin G, and 100 mg/ml streptomycin. Transient transfection of HEK293 cells was carried out using the calcium phosphate precipitation method [18]. JCam1.6, P116 and Jurkat T leukemia cells were kept at logarithmic growth in RPMI 1640 medium supplemented with 10 FBS, 2 mM Lglutamine, 1 mM sodium pyruvate, non essential aa, 100 U/ml penicillin G, and 100 mg/ml streptomycin. Transfection of Jurkat T cells was performed by electroporation as described previously [19]. PBLs were isolated from buffy coats of healthy donors obtained from the regional blood bank, with approval of its ethical committee, by centrifugation on Ficoll-Hypaque (GE Healthcare, Buckinghamshire, UK.) cushions. Monocytes/macrophages were eliminated by adherence to plastic for at least 1 h at 37uC.Results LYP/CSK Binding in Human T Cells is Induced Upon T Cell StimulationTo verify the validity of the Pep/Csk cooperative model [6] for LYP/CSK interaction, we first tested in HEK293 cells the association of CSK with Arg620 and Trp620 LYP variants, in an active or inactive state (D195A substrate trapping mutant, referred throughout this paper as DA). In contrast with previous data for Pep [9,21], we found that LYPW did bind CSK (Figure 1A), in agreement with data obtained for LYP [10,14]. Thereafter, we tested whether cell activation could affect this interaction. Treatment of cells with pervanadate (PV), a potent PTP inhibitor, increased the binding of CSK and LYP either active or inactive, but the interaction of CSK with LYPW was always lower than with LYPR (Figure 1A). To confirm these results in a cell line more relevant to LYP function, we expressed LYP variants along with CSK in Jurkat cells, a well-known model for the study of early TCR signaling. In these cells, LYPW also interacted with CSK (Figure 1B) and, as before, this interaction was increased after PV treatment. IP of either LYP or CSK in Jurkat cells resulted in a very low co-precipitation of the other protein in resting cells (Figure 1C, upper panel); however, this association augmented after PV treatment (Figure 1C, middle panel) or TCR stimulation (Figure 1C, lower panel). Additionally, we verified that LYP/CSK interaction between endogenous proteins was increased upon CD3 and CD28 co-stimulation in PBLs (Figure 1D). The efficiency of stimulation in these cells wa.Eporter for normalization. Cells were stimulated with anti-CD3 plus anti-CD28 Abs 24 h after transfection for the last 6 h. Cells were lysed then and processed to measure the LUC activity with the Dual Luciferase system (Promega, CA USA) according to the manufacturer’s instructions.Plasmids and MutagenesisStandard molecular biology techniques were used to generate the different constructions used in this study. Site-directed mutagenesis was done with the QuickChange Mutagenesis Kit (Agilent-Stratagene, CA, USA) following the manufacturer instructions. All constructions and mutations were verified by nucleotide sequencing.Flow Cytometry and ImmunohistochemistryJurkat cells were stimulatd with soluble anti-CD3 plus antiCD28 Abs for 24 hours and were stained with Phycoerythrin (PE)labeled anti-CD25 or PE-IgG2b isotype control (Immunostep, Salamanca, Spain). Data were acquired on a Gallios Flow Cytometer instrument (Beckman Coulter, Inc. CA, USA) and analysis was carried out with WinMDI software.Cell Culture and TransfectionsHEK293 were maintained at 37uC in Dulbecco’s modified Eagle’s medium supplemented with 10 FBS, 2 mM L-glutamine, 100 U/ml penicillin G, and 100 mg/ml streptomycin. Transient transfection of HEK293 cells was carried out using the calcium phosphate precipitation method [18]. JCam1.6, P116 and Jurkat T leukemia cells were kept at logarithmic growth in RPMI 1640 medium supplemented with 10 FBS, 2 mM Lglutamine, 1 mM sodium pyruvate, non essential aa, 100 U/ml penicillin G, and 100 mg/ml streptomycin. Transfection of Jurkat T cells was performed by electroporation as described previously [19]. PBLs were isolated from buffy coats of healthy donors obtained from the regional blood bank, with approval of its ethical committee, by centrifugation on Ficoll-Hypaque (GE Healthcare, Buckinghamshire, UK.) cushions. Monocytes/macrophages were eliminated by adherence to plastic for at least 1 h at 37uC.Results LYP/CSK Binding in Human T Cells is Induced Upon T Cell StimulationTo verify the validity of the Pep/Csk cooperative model [6] for LYP/CSK interaction, we first tested in HEK293 cells the association of CSK with Arg620 and Trp620 LYP variants, in an active or inactive state (D195A substrate trapping mutant, referred throughout this paper as DA). In contrast with previous data for Pep [9,21], we found that LYPW did bind CSK (Figure 1A), in agreement with data obtained for LYP [10,14]. Thereafter, we tested whether cell activation could affect this interaction. Treatment of cells with pervanadate (PV), a potent PTP inhibitor, increased the binding of CSK and LYP either active or inactive, but the interaction of CSK with LYPW was always lower than with LYPR (Figure 1A). To confirm these results in a cell line more relevant to LYP function, we expressed LYP variants along with CSK in Jurkat cells, a well-known model for the study of early TCR signaling. In these cells, LYPW also interacted with CSK (Figure 1B) and, as before, this interaction was increased after PV treatment. IP of either LYP or CSK in Jurkat cells resulted in a very low co-precipitation of the other protein in resting cells (Figure 1C, upper panel); however, this association augmented after PV treatment (Figure 1C, middle panel) or TCR stimulation (Figure 1C, lower panel). Additionally, we verified that LYP/CSK interaction between endogenous proteins was increased upon CD3 and CD28 co-stimulation in PBLs (Figure 1D). The efficiency of stimulation in these cells wa.
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