Effects of immunoglobulin D on expression of IgD receptor and protein tyrosine kinase signaling in human CD4+ T cells / 中国药理学与毒理学杂志

OBJECTIVE To observe whether human CD4 + T cells could be activated by immuno-globulin D (IgD) via IgD receptor(IgDR)-Lck. METHODS Human CD4+ T cells were purified from peripheral blood mononuclear cells (PBMCs) with microbeads. The viability of T cells were detected by CCK-8. The binding affinity and expression of IgDR on T cells were detected by flow cytometry. The protein expression of IgDR, Lck and P-Lck were analyzed by western blot. RESULTS IgD could concentration-dependent bind to IgDR on CD4+ T cells. The expression of IgDR was increased in response to treatment with IgD in a time- dependent and concentration- dependent manner. Stimulating by IgD resulted in enhanced phosphorylation of Lck compared with that in the medium control sample. The expression of Lck was not changed. As inhibitor of PTK, Herbimycin A or A770041, which combined with IgD could significantly inhibit phosphorylation of Lck(Tyr394). The proliferation promoting effect of IgD was blocked by Herbimycin A or A770041. IgD could stimulate CD4+ T cell activation and proliferation through upreg?ulating activating tyrosine residue of Lck (Tyr394) phosphorylation. CONCLUSION These results demon?strate that IgD exaggerates CD4+T cell activities, which may be through promoting Lck phosphorylation.

The effect of siRNA inhibited tyrosine protein kinase Lck on the function of T cells in asthmatic mice / 中国医师杂志

Objective Using the technology of siRNA to inhibit gene expression of T cells'nonreceptor tyrosine protein kinase Lck in asthmatic mice,and to study the effect of siRNA inhibited Lck to the function of T cells in asthmatic mice.Methods The 21 - 23 bp RNA fragments of mouse T cell Lck were made by chemosynthesis.INTERFERinTMsiRNA Transfection Reagent was used as transfection reagent to transfect the siRNA into the spleen T cells of asthmatic mice for 48 hours.Then T cells were mixed with bone marrow dendritic cells (DC) of asthmatic mice for another 48 hours.Cell culture suspension was collected and the level of IL-4,IL-13,IL-2,INF-γ were detected with respondent ELISA kits; Western Blot was used to identify if the expression of Lck was blocked.Results The expression of Lck in T cells almost could not be detected in siRNA interference group.The levels of IL-4 and IL-13 in siRNA interference group( 10.19 ± 1.66,12.34 ±0.79) were lower than no-siRNA interference(28.06 ±2.88,27.87 ± 1.61 )and control group ( 22.07 ± 2.5 1,20.47 ± 2.37 ),and the difference was statistical significant ( P ＜0.01 ).Conclusions Special siRNA could block the expression of special gene,and Lck specific siRNA could block the activation and differentiation of T cells and reduce the secretion of inflammatory cytokines in asthmatic mice.

In vivo study of tyrosine protein kinase Lck inhibited by siRNA in T cells of asthmatic mice / 中国医师杂志

ObjectiveUsing the technology of siRNA to inhibit the gene expression of no-receptor　tyrosine protein kinase Lck in T cells of asthmatic mice,and to study the therapeutic effect of Lck specific　siRNA in asthmatic mice.MethodsReceptor tyrosine protein kinase Lck specific siRNA fragments were　taken from chemosynthesis.In vivo-jetPEITM was used to transfect the siRNA into mice body through tail　vein injection.The mice were killed 48 hours later,and the levels of IL-4,IL-17 in bronchoalveolar lavage　fluid (BALF) were detected with respondent ELISA kits.The change of inflammatory histopathology in lung　was observed with H.E.staining.The expression of Lck in lung was detected with immunohistochemistry　(IHC),and the level of Lck in lung tissue homogenate was detected with Western Blot.Results Compared with asthmatic group[ (234.68 ± 11.15 ) pg/ml,( 96.76 ± 8.28 ) pg/ml],the levels of IL-4,IL-17　[ (234.68 ± 11.15)pg/ml,(96.76 ±8.28) pg/ml] in the BALF of siRNA interference group decreased,　and the inflammation in the lung relieved.IHC indicated that the expression of Lck in lung decreased and　the level of Lck in lung tissue homogenate decreased ( P ＜ 0.05 ).Conclusions Lck specific siRNA　could reduce the level of IL-4,IL-17 in the lung tissues of asthmatic mice,and relieve the inflammatory reaction in lung.

Transmembrane Adaptor Proteins Positively Regulating the Activation of Lymphocytes

Engagement of the immunoreceptors initiates signaling cascades resulting in lymphocyte activation and differentiation to effector cells, which are essential for the elimination of pathogens from the body. For the transduction of these immunoreceptor-mediated signals, several linker proteins termed transmembrane adaptor proteins (TRAPs) were shown to be required. TRAPs serve as platforms for the assembly and membrane targeting of the specific signaling proteins. Among seven TRAPs identified so far, LAT and LIME were shown to act as a positive regulator in TCR-mediated signaling pathways. In this review, we will discuss the functions of LAT and LIME in modulating T cell development, activation and differentiation.

Expression of Lck in renal tubule epithelial cells of lupus nephritis / 中华风湿病学杂志

Objective To investigate the Lymphocyte-specific protein-tyrosine kinase(Lck)gene ex- pression in the renal tubule epithelial cells(TECs)of lupus nephritis,and the effect of interlenkin-2(IL-2) stimulation on its expression.Methods Proximal TECs derived from 6 weeks old spontaneous systemic lupus erythematosus(SLE)BXSB mice were exposed to IL-2(100 U/ml),the expression of Lck mRNA and protein was examined by reverse transcription-polymerase chain reaction(RT-PCR)and immunoblotting respectively. The difference of Lck gene expression before and after IL-2 stimulation was investigated.The expression of Lck protein in TECs of renal tissues of BXSB mice and human with lupus nephritis was observed through im- munohistochemistry.Results The expression of Lck mRNA and protein was very low in cultured TECs of 6 weeks old BXSB mice,but increased sharply after IL-2 stimulation(P

Regulation of chicken protein tyrosine phosphatase 1 and human protein tyrosine phosphatase 1B activity by casein kinase II- and p56lck-mediated phosphorylation

Protein tyrosine phosphorylation and dephosphorylation are important in the regulation of cell proliferation and signaling cascade. In order to examine whether phosphatase activity of CPTP1 and HPTP1B, typical nontransmembrane protein tyrosine phosphatase, could be controlled by phosphorylation, affinity-purified PTPs were phosphorylated by CKII and p56lck in vitro. Phosphoamino acid analysis revealed that CPTP1 was phosphorylated on both serine and threonine residues by CKII, and tyrosine residue by p56lck. Phosphatase activity of CPTP1 was gradually increased by three-fold concomitant with phosporylation by CKII. Phosphorylation of HPTP1B by CKII resulted in quick two-fold enhancement of its phosphatase activity within 5 min of incubation and remained in that state. In the presence of CKII inhibitor, heparin or poly(Glu.Tyr), both phosphorylation and enhancement of phosphatase activity of CPTP1 and HPTP1B were mostly blocked. p56lck catalyzed tyrosine phosphorylation of CPTP1 and HPTP1B was only observed by inhibiting the intrinsic tyrosine phosphatase activity. Taken together, these results indicate that CPTP1 or HPTP1B possesses a capability to regulate its phosphatase activity through phosphorylation processes and may participate in the cellular signal cascades.

Cross-linking of CD4 induces cytoskeletal association of CD4 and p56lck

A membrane glycoprotein CD4 functions as a co-receptor of a T lymphocyte. The co-receptor function has been attributed to a protein tyrosine kinase, p56lck, which is activated upon CD4 binding to MHC molecule. In this study, we present evidences that one of the pathways through which CD4 transmits its signal is cytoskeleton association of p56lck tyrosine kinase as well as CD4 itself. Cytoskeletal association of both proteins is inhibited by a tyrosine kinase inhibitor, genistein, indicating that tyrosine protein kinase activation is important for cytoskeletal association of CD4 and p56lck. Cytoskeletal association of these proteins by CD4 cross-linking is not affected by inhibitors of protein kinase C nor PI3-kinase. Taken together, these results suggest that CD4 cross-linking activates a tyrosine kinase which then induces the simultaneous association of CD4 and p56lck with cytoskeleton.