Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.1.3.16 (calcineurin)
17,112 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Regulation of the avidity of LFA-1 (CD11a/CD18, alpha L beta 2) for its ligand ICAM-1 (CD54) was studied in human B cells by evaluating the effects of a phorbol ester, anti-IgM antibodies, staurosporine, and okadaic acid. We monitored changes in LFA-1 avidity by quantifying binding of cells to an immobilized rICAM-1 fusion protein. In this assay, the protein kinase C-activating phorbol ester PDB and anti-IgM antibodies, as well as the protein kinase inhibitor, staurosporine, were able to induce LFA-1-dependent binding to ICAM-1. This demonstrates that the high avidity state of LFA-1 can be induced by a protein kinase C-dependent and by a protein kinase C-independent pathway. Furthermore, treatment of the cells with the protein phosphatase inhibitor, okadaic acid, inhibited binding to ICAM-1. Treatment with staurosporine before addition of okadaic acid not only induced enhanced binding of cells to ICAM-1, but also dramatically reduced the ability of okadaic acid to inhibit binding. These results suggest a critical role for a protein phosphatase in inducing the high avidity state of LFA-1 as well as a role for a protein kinase in inducing the low avidity state of LFA-1.
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PMID:Regulation of LFA-1 avidity in human B cells. Requirements for dephosphorylation events for high avidity ICAM-1 binding. 135 24

The immunosuppressive macrolide, rapamycin, impedes the G1 to S cell cycle progression in cytokine-stimulated normal lymphocytes and in certain autonomously proliferating cell lines. Here, we found that the rapamycin-induced growth arrest augments homotypic aggregation in the YAC-1 T cell lymphoma. The growth arrest and increased aggregation were both blocked by the rapamycin antagonist, L-685,818, which interacts with the intracellular binding proteins mediating rapamycin's biochemical action. Moreover, rapamycin-induced aggregation was not seen in YAC-1 cells mutants selected for resistance to the drug's antiproliferative effect. Although the inhibition of G1/S progression induced by serum deprivation also resulted in increased cellular aggregation, cell cycle blockade in late G1 by mimosine, early S phase by hydroxyurea, or G2/M by nocodazole all failed to do so. Furthermore, the aggregation induced by rapamycin was blocked by antibodies to the alpha (CD11a) or beta (CD18) subunits of the integrin, LFA-1, or to its ligands, ICAM-1 and ICAM-2, and did not occur in LFA-1-deficient YAC mutants. However, the surface expression of LFA-1, ICAM-1, or ICAM-2 was not augmented in cells aggregated by rapamycin. Finally, the serine/threonine protein phosphatase inhibitor, okadaic acid, was found to abrogate rapamycin-induced aggregation. Therefore, rapamycin's impairment of YAC-1 cell growth in G1 is accompanied by enhanced LFA-1-mediated homotypic cell adhesion that may reflect an increase of the integrin's avidity for its ligands and may involve protein phosphorylation/dephosphorylation events. This suggests the existence of a link between cell cycle progression and "inside-out" LFA-1 signaling, possibly regulated by rapamycin's biochemical targets.
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PMID:Increased LFA-1-mediated homotypic cell adhesion is associated with the G1 growth arrest induced by rapamycin in a T cell lymphoma. 754 51

The authors compared the phosphorylation-dependent signal transduction pathways involved in the regulation of adhesiveness of integrin LFA-1 with that of alpha 4 integrins binding to VCAM-1. The authors developed an in vitro method to monitor changes in adhesiveness using a VCAM-1 fusion protein coupled to magnetic beads. For LFA-1, a similar method has previously been established using an ICAM-1 fusion protein. Binding of cells was monitored and found to be strictly integrin alpha 4 and VCAM-1 dependent. The serine/threonine phosphatase inhibitors okadaic acid and calyculin A were equally potent in inhibiting binding to VCAM-1 as to ICAM-1, and inhibition of protein phosphatase-1 (PP1) is proposed to be the important denominator. Similarly, the phorbol ester PDBu, potentially stimulating protein phosphatase-1 and staurosporine, an inhibitor of serine/threonine kinases, enhanced adhesion to VCAM-1 as has previously been shown for ICAM-1. A major difference was that a significant portion of the binding to VCAM-1 was not susceptible to inhibition by drugs while binding to ICAM-1 could be completely inhibited. We propose that the adhesiveness of the alpha 4 integrins for VCAM-1 and of LFA-1 for ICAM-1 is regulated by similar or identical protein kinases and phosphatases.
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PMID:Regulation of alpha 4 integrin avidity in human B cells: requirement for dephosphorylation events for high avidity VCAM-1 binding. 879 17

The development of immunosuppressive agents reflects the progress in understanding the cellular and molecular mechanisms which mediate allograft rejection. Six paradigms represent the evolution of immunosuppressive strategies for organ transplantation. The proliferation paradigm advances agents which interrupt lymphocyte cell division (azathioprine, cyclophosphamide, mycophenolic acid). The depletion paradigm conscripts drugs that bind to lymphocyte cell surface markers, thereby producing cell lysis and/or inactivation (polyclonal ATGAM and thymoglobulin, and monoclonal OKT3 antilymphocyte antibodies). The cytokine paradigm uses agents that interrupt lymphocyte maturational events; eg, synthesis (calcineurin inhibitors: cyclosporine/tacrolimus), binding to surface receptors (anti-CD25 mAbs), or signal transduction phases of cytokine stimulation (sirolimus). The introduction of calcineurin inhibitors markedly reduces the rate of acute rejection episodes and increases short-term graft survival rates; nephrotoxicity and chronic allograft attrition remain as unanswered challenges. The cyclosporine A (CsA) sparing property of sirolimus permits the use of lower exposure to calcineurin agents, allows for early withdrawal of steroid therapy, and may delay allograft senescence. Furthermore, the combination of SRL with anti-IL-2R mAbs proffers an induction approach which allows prolonged periods of holiday from calcineurin inhibitors. To address the tissue nonselectivity of the calcineurin and mTOR inhibitors, which presumably causes the drug toxicities, new agents are being developed to selectively inhibit the T cell target Janus Kinase 3. In the costimulation paradigm, the accessory signals generated by antigen-presenting cells are interrupted by distinct agents: the receptor conjugate CTLA4-immunoglobulin and anti-B7 or anti-CD40 ligand mAbs. Another set of drugs (selectin blocking agents, anti-ICAM-1 antisense deoxy oligonucleotides, and the lymphocyte homing inhibitor FTY720) seeks to modulate the ischemia-reperfusion injury, which exacerbates cytokine-mediated events in the donor and the subsequent procurement injury and may also accelerate the progression of transplant senescence. Finally, the transplantation tolerance paradigm is based on the development of strategies which distort alloimmune recognition by antigen reactive cells (MHC peptides or proteins), produce anergy (costimulation blockers), functional inactivation, or deletion of antigen-reactive cells (donor bone marrow infusions and gene therapy). Presently, the optimal immunosuppressive strategy uses combinations of agents that act in synergistic fashion to provide the potency, freedom from toxic reactions, convenience of administration, and cost appropriate for the individual patient.
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PMID:Immunosuppressive agents in organ transplantation: past, present, and future. 1074 55

In clinical transplantation, the occurrence of cyclosporin A (CsA)-resistant production of IL-2 in vitro correlates with graft rejection in vivo. In this study we investigated the role of the costimulatory molecules CD28 and LFA-1 in this process in the setting of TCR-induced proliferation of primary T lymphocytes in vitro. Co-stimulation with ICAM-1 and B7.2 led to strong and CsA-resistant proliferation, which was found to be largely IL-2 dependent. All of the known calcineurin-dependent events, such as induction of NF-AT and NF-kappaB or stress-activated protein kinase activation, were markedly modulated by CsA independently of costimulation. In contrast, both ICAM-1 and B7.2 enhanced the half-life of the inducible IL-2 transcript in a CsA-resistant manner. LFA-1- but not CD28-induced IL-2 mRNA stabilization required the integrity of the actin-based cytoskeleton, suggesting that the two costimulatory molecules impact on qualitatively different signaling pathways. This is further suggested by the demonstration that LFA-1 and CD28 acted synergistically to confer CsA resistance in a model of co-stimulation using superantigen-pulsed dendritic cells. We propose that IL-2 transcript accumulation and subsequent T cell proliferation at the low transcriptional rate imposed by CsA are the result of co-stimulation-dependent stabilization of IL-2 mRNA.
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PMID:CD28 and LFA-1 contribute to cyclosporin A-resistant T cell growth by stabilizing the IL-2 mRNA through distinct signaling pathways. 1076 Aug 3

The authors previously showed that monocytes treated with calcium ionophore (CI) acquire characteristics of mature dendritic cells (DC) in part through a calcineurin-dependent pathway. In this study, the authors evaluated the ability of granulocyte-macrophage colony stimulating factor (GM-CSF), interleukin-2 (IL-2), and interleukin-12 (IL-12) alone or in combination with CI to induce DC characteristics in peripheral blood monocytes. Monocytes obtained by leukapheresis and countercurrent centrifugal elutriation were cultured with calcium, cytokines, or both, profiled by flow cytometry, and assessed for antigen uptake and sensitization of autologous CD8+ T cells to antigen. Monocytes treated with the combination of GM-CSF, IL-2, and IL-12 resulted in immunophenotypic and antigen uptake profiles typical of immature DC, including loss of surface CD14 expression, de novo low-level expression of B7.1, negligible CD83 expression, marked enhancement of CD40 and ICAM-1, and high major histocompatibility complex class I and II levels. A high level of antigen uptake by macro-pinocytosis was observed. In contrast, CI treatment significantly up-regulates B7.1, B7.2, CD40, CD54, and CD83 and substantially down-regulates CD14 and macro-pinocytosis, a profile consistent with mature DC. Many CI-induced modulations, but none resulting from cytokine treatment alone, were inhibited by the calcineurin phosphatase inhibitor cyclosporin A. Compared with monocytes treated with CI alone, combined treatment of monocytes with GM-CSF, IL-2, IL-12, and CI augmented B7.1 and CD83 expression and enhanced sensitization of autologous CD8+ T cells to melanoma-antigen-derived peptides. These results suggest that several independent pathways of DC activation can cooperatively enhance the function of monocyte-derived DC.
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PMID:Granulocyte-macrophage colony-stimulating factor, interleukin-2, and interleukin-12 synergize with calcium ionophore to enhance dendritic cell function. 1083 60

Using an in vitro co-culture assay we found that a rat medullary thymic epithelial cell (TEC) line (TE-R2.5) induces apoptosis of the BWRT8 thymocyte hybridoma (TH) (CD4(hi)CD8(low) alphabetaTCR(hi)). TH apoptosis induced by this TEC line was predominantly mediated by direct cell-cell contacts and was potentiated by cross-linking of the T cell receptor (TCR) by R73 monoclonal antibody (mAb). Dexamethasone (Dx) also triggered TH apoptosis but inhibited death of these cells induced by TE-R2.5 cells or immobilized R73 mAb. The TEC-induced apoptosis was independent of the LFA-1/ICAM-1 interaction but partly depended on a novel 29 kDa molecule expressed on TE-R2.5 cells. All three types of TH apoptosis were followed by the cleavage of poly-(ADP-ribose)-polymerase and were blocked by a caspase inhibitor Z-Val-Ala-Asp(OMe)-CH(2)F.PKC stimulation by phorbol myristate acetate interfered with the TH apoptosis induced by TE-R2.5 and Dx, but did not modulate the effect of R73 mAb. On the contrary, inhibition of calcineurin with cyclosporine A did not influence the apoptosis induced by TE-R2.5 and Dx, but completely prevented the R73-triggered TH cell death. The TE-R2.5-mediated BWRT8 apoptosis was suppressed by Na-orthovanadate, an inhibitor of protein tyrosine phosphatases (PTP) as well as by genistein, a protein tyrosine kinase (PTK) inhibitor, while both compounds potentiated the effect of Dx. Blocking PTP, but not PTK decreased the proapoptotic effect of R73 mAb. These results, including those using a BWRT8 subclone (BWRT8-MDP.2) which is resistant to TCR-triggered apoptosis, but sensitive to apoptosis stimulated by TE-R2.5 and Dx, indicate that TE-R2.5-induced TH apoptosis in our model is different from apoptosis in other TEC co-culture models, published so far.
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PMID:Comparison of signaling pathways involved in apoptosis of a thymocyte hybridoma triggered by a rat thymic medullary epithelial cell line, dexamethasone or T-cell receptor cross-linking. 1084 42

Mature dendritic cells (DCs), in addition to providing costimulation, can define the Th1, in contrast to the Th2, nature of a T-cell response through the production of cytokines and chemokines. Because calcium signaling alone causes rapid DC maturation of both normal and transformed myeloid cells, it was evaluated whether calcium-mobilized DCs polarize T cells toward a Th1 or a Th2 phenotype. After human monocytes were cultured for 24 hours in serum-free medium and granulocyte-macrophage colony-stimulating factor to produce immature DCs, additional overnight culture with either calcium ionophore (CI) or interferon gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), and soluble CD40L resulted in phenotypically mature DCs that produced interleukin-8 (IL-8) and displayed marked expression of CD80, CD86, CD40, CD54, CD83, DC-LAMP, and RelB. DCs matured by IFN-gamma, TNF-alpha, and soluble CD40L were additionally distinguished by undetectable CD4 expression, marked secretion of IL-12, IL-6, and MIP-1beta, and preferential ability to promote Th1/Tc1 characteristics during T-cell sensitization. In contrast, DCs matured by CI treatment were distinguished by CD4 expression, modest or absent levels of IL-12, IL-6, and MIP-1beta, and preferential ability to promote Th2/Tc2 characteristics. Calcium signaling selectively antagonized IL-12 production by mature DCs activated with IFN-gamma, TNF-alpha, and soluble CD40L. Although the activation of DCs by calcium signals is largely mediated through calcineurin phosphatase, the inhibition of IL-12 production by calcium signaling was independent of this enzyme. Naturally occurring calcium fluxes in immature DCs, therefore, negatively regulate Dc1 differentiation while promoting Dc2 characteristics and Th2/Tc2 polarization. Calcium-mobilized DCs may have clinical usefulness in treating disease states with excessive Th1/Tc1 activity, such as graft-versus-host disease or autoimmunity.
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PMID:Calcium signaling inhibits interleukin-12 production and activates CD83(+) dendritic cells that induce Th2 cell development. 1158 47

Experimental autoimmune myositis (EAM) is a good model of human inflammatory myopathy. We induced EAM in SJL/J mice by injection with myosin and treated inflammatory changes with FK506. The mice developed inflammatory changes after the fifth myosin injection. After treatment with FK506, inflammation was suppressed and central nuclei of the muscle fibers increased. These findings indicate that FK506 is effective in the treatment of EAM. The data suggests that FK506 inhibits interaction with calcineurin. Intercellular adhesion molecule-1 (ICAM-1) positive cells were present in the inflammatory and non-inflammatory areas of EAM. The FK506-treated group stained more weakly for ICAM-1 than the untreated EAM group.
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PMID:FK506 suppressed the inflammatory change of EAM in SJL/J mice. 1171 43

Chronic rejection remains a major complication in solid organ transplantation. Host alloreactive T cells (TC) can be activated by donor dendritic cells (DCs; direct allorecognition) or by recipient DCs (indirect allorecognition). A fundamental aspect of DC function is vascular invasion to present donor antigens to recipient naive TC in secondary lymphoid organs. We investigated the impact of calcineurin inhibitors on DC binding and transmigration to allogeneic human microvascular endothelial cells (ECs) with and without blocking of specific adhesion molecules. Recipient immature DCs were generated by culturing CD14 human peripheral blood monocytes with GM-CSF and IL-4. DC adhesion and transmigration were investigated on allogeneic ECs preincubated with increasing concentrations of cyclosporine and tacrolimus. Experiments were repeated in the presence of blocking antibodies against LFA-1, PECAM-1, VCAM-1, and ICAM-1. Endothelial stimulation with cyclosporine A (100 and 300 ng/mL) and tacrolimus (15 ng/mL) significantly enhanced DC-EC adhesion and transmigration (P<0.01). LFA-1 blockade on DCs significantly reduced cyclosporine- and tacrolimus-induced DC adhesion (P<0.001). VCAM-1 blockade on ECs partially reversed cyclosporine-induced DC adhesion (P<0.001), whereas DC adhesion under tacrolimus exposure was significantly decreased by ICAM-1 (P<0.01) and PECAM-1 (P<0.001) blockade. DC binding and transmigration on allogeneic ECs exposed to calcineurin inhibitors is concentration-dependently increased. Different adhesion molecule patterns on ECs are responsible for enhanced DC invasion under cyclosporine and tacrolimus exposure. We speculate that long-term immunosuppression mediates enhanced invasion of recipient DCs to the donor organ and therefore may aggravate chronic rejection.
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PMID:Dendritic cell adhesion is enhanced on endothelial cells preexposed to calcineurin inhibitors. 1611 27


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