International Journal of Biochemistry & Cell Biology, 2010
Store-operated calcium channels are plasma membrane Ca 2+ channels that are activated by depletio... more Store-operated calcium channels are plasma membrane Ca 2+ channels that are activated by depletion of intracellular Ca 2+ stores, resulting in an increase in intracellular Ca 2+ concentration, which is maintained for prolonged periods in some cell types. Increases in intracellular Ca 2+ concentration serve as signals that activate a number of cellular processes, however, little is known about the regulation of these channels. We have characterized the immuno-suppressant compound BTP, which blocks store-operated channel mediated calcium influx into cells. Using an affinity purification scheme to identify potential targets of BTP, we identified the actin reorganizing protein, drebrin, and demonstrated that loss of drebrin protein expression prevents store-operated channel mediated Ca 2+ entry, similar to BTP treatment. BTP also blocks actin rearrangements induced by drebrin. While actin cytoskeletal reorganization has been implicated in store-operated calcium channel regulation, little is known about actin-binding proteins that are involved in this process, or how actin regulates channel function. The identification of drebrin as a mediator of this process should provide new insight into the interaction between actin rearrangement and store-operated channel mediated calcium influx.
T cells with a memory-like phenotype and possessing innate immune function have been previously i... more T cells with a memory-like phenotype and possessing innate immune function have been previously identified as CD8+CD44hi cells. These cells rapidly secrete IFN-γ upon stimulation with IL-12/IL-18 and are involved in innate responses to infection with Listeria monocytogenes. The signals regulating these cells are unclear. The Tec kinase Itk regulates T cell activation and we report here that a majority of the CD8+ T cells in Itk null mice have a phenotype of CD44hi similar to memory-like innate T cells. These cells are observed in mice carrying an Itk mutant lacking the kinase domain, indicating that active Tec kinase signaling suppresses their presence. These cells carry preformed message for and are able to rapidly produce IFN-γ upon stimulation in vitro with IL-12/IL-18, and endow Itk null mice the ability to effectively respond to infection with L. monocytogenes or exposure to lipopolysaccharides by secretion of IFN-γ. Transfer of these cells rescues the ability of IFN-γ null mice to reduce bacterial burden following L. monocytogenes infection, indicating that these cells are functional CD8+CD44hi T cells previously detected in vivo. These results indicate that active signals from Tec kinases regulate the development of memory-like CD8+ T cells with innate function.
International Journal of Biochemistry & Cell Biology, 2005
Natural killer T (NKT) cells are a subset of T cells that share properties of natural killer cell... more Natural killer T (NKT) cells are a subset of T cells that share properties of natural killer cells and conventional T cells. They are involved in immediate immune responses, tumor rejection, immune surveillance and control of autoimmune diseases. Most NKT cells express both an invariant T cell antigen receptor and the NK cell receptor NK1.1, and are referred to as invariant NKT cells. This invariant T cell receptor is restricted to interactions with glycolipids presented by the non-classical MHC, CD1d. These NKT cells rapidly produce high levels of interleukin (IL)-2, IFN-gamma, TNF-alpha, and IL-4 upon stimulation through their TCR. Most also have cytotoxic activity similar to NK cells. NKT cells are involved in a number of pathological conditions, and have been shown to regulate viral infections in vivo, and control tumor growth. They may also play both protective and harmful roles in the progression of certain autoimmune diseases, such as diabetes, lupus, atherosclerosis, and allergen-induced asthma.
Interleukin-2-inducible T cell kinase (ITK) is a non-receptor tyrosine kinase expressed in T cell... more Interleukin-2-inducible T cell kinase (ITK) is a non-receptor tyrosine kinase expressed in T cells, NKT cells and mast cells which plays a crucial role in regulating the T cell receptor (TCR), CD28, CD2, chemokine receptor CXCR4 and FcεR mediated signaling pathways. In T cells, ITK is an important mediator for actin reorganization, activation of PLCγ, mobilization of calcium, and activation of the NFAT transcription factor. ITK plays an important role in the secretion of IL-2, but more critically, also has a pivotal role in the secretion of Th2 cytokines, IL-4, IL-5 and IL-13. As such, ITK has been shown to regulate the development of effective Th2 response during allergic asthma as well as infections against parasitic worms. This ability of ITK to regulate Th2 responses, along with it's pattern of expression, has led to the proposal that it would represent an excellent target for Th2 mediated inflammation. We discuss here the possibilities and pitfalls of targeting ITK for inflammatory disorders.
NKT cells are a heterogeneous population characterized by the ability to rapidly produce cytokine... more NKT cells are a heterogeneous population characterized by the ability to rapidly produce cytokines, such as interleukin 2 (IL-2), IL-4, and gamma interferon (IFN-␥) in response to infections by viruses, bacteria, and parasites. The bacterial superantigen staphylococcal enterotoxin B (SEB) interacts with T cells bearing the V3, -7, or -8 T-cell receptors, inducing their expansion and cytokine secretion, leading to death in some cases due to cytokine poisoning. The majority of NKT cells bear the V7 or -8 T-cell receptor, suggesting that they may play a role in regulating this response. Using mice lacking NKT cells (CD1d ؊/؊ and J␣18 ؊/؊ mice), we set out to identify the role of these cells in T-cell expansion, cytokine secretion, and toxicity induced by exposure to SEB. We find that V8 ؉ CD4 ؉ T
T helper 17 (Th17) cells play major roles in autoimmunity and bacterial infections, yet how T cel... more T helper 17 (Th17) cells play major roles in autoimmunity and bacterial infections, yet how T cell receptor (TCR) signaling affects Th17 cell differentiation is relatively unknown. We demonstrate that CD4 + T cells lacking Itk, a tyrosine kinase required for full TCR-induced phospholipase C-g (PLC-g1) activation, exhibit decreased interleukin-17A (IL-17A) expression in vitro and in vivo, despite relatively normal expression of retinoic acid receptor-related orphan receptor-gT (ROR-gT) and IL-17F. IL-17A expression was rescued by pharmacologically induced Ca 2+ influx or constitutively activated nuclear factor of activated T cells (NFAT). Conversely, decreased TCR stimulation or calcineurin inhibition preferentially reduced IL-17A expression. We further found that the promoter of Il17a but not Il17f has a conserved NFAT binding site that bound NFATc1 in wild-type but not Itk-deficient cells, even though both exhibited open chromatin conformations. Finally, Itk À/À mice also showed differential regulation of IL-17A and IL-17F in vivo. Our results suggest that Itk specifically couples TCR signaling to Il17a expression and the differential regulation of Th17 cell cytokines through NFATc1.
Background: Exposure to Staphylococcal Enterotoxin B (SEB), a bacterial superantigen secreted by ... more Background: Exposure to Staphylococcal Enterotoxin B (SEB), a bacterial superantigen secreted by the Gram-positive bacteria Staphyloccocus aureus, results in the expansion and eventual clonal deletion and anergy of Vβ8 + T cells, as well as massive cytokine release, including Interleukin-2 (IL-2). This IL-2 is rapidly secreted following exposure to SEB and may contribute to the symptoms seen following exposure to this bacterial toxin. The Tec family kinase ITK has been shown to be important for the production of IL-2 by T cells stimulated in vitro and may represent a good target for blocking the production of this cytokine in vivo. In order to determine if ITK represents such a target, mice lacking ITK were analyzed for their response to SEB exposure.
The Tec family kinases are critical downstream regulators of antigen receptor signals in lymphocy... more The Tec family kinases are critical downstream regulators of antigen receptor signals in lymphocytes. As kinases, they act on critical substrates to regulate signals such as calcium increase leading to activation of transcription factors such as NFAT, NFjB and SRF. We now show here that ITK, a member of the Tec family of tyrosine kinases, has a kinase independent function. Mutants of ITK that lack kinase activity or a kinase domain can rescue cells lacking Tec family kinases for antigen receptor induced SRF activation, but not for NFAT, AP-1 or NFjB activation. Furthermore, expression of these mutants in WT cells enhanced SRF activation. This kinase independent function required the SH2 domain since a mutant lacking both the kinase and SH2 domains was much less effective at rescuing SRF activation. This kinase-deleted mutant could partially rescue ERK activation, and interact with multiple tyrosine phosphorylated proteins during antigen receptor signaling, suggesting that ITK uses a scaffolding function that regulates signals leading to specific regulation of SRF activation.
Patients with allergic asthma have symptoms of a predominant TH2 response, including airway eosin... more Patients with allergic asthma have symptoms of a predominant TH2 response, including airway eosinophilic inflammation and increased mucous production in the lungs. This accompanies increased airways responsiveness, which can be life threatening. Because TH2 cells and cytokines have been implicated in contributing to these symptoms, pathways that control the development of these cells or that regulate their cytokine production represent good targets for controlling this disease.We have previously shown that mice lacking the tyrosine kinase inducible T-cell kinase (ITK) have drastically reduced airway inflammation in a model of allergic asthma. However, it was not clear whether this translated into reduced airways hyperresponsiveness. We have analyzed tracheal responsiveness and airways hyperresponsiveness of wild-type (WT) and ITK null mice during induction of experimental allergic asthma.Experimental allergic asthma was induced in WT and ITK knockout mice. Tracheal responses to carbachol, acetylcholine, and potassium chloride were analyzed. Airways hyperresponsiveness to methacholine challenge was also analyzed in allergen-challenged mice, along with lung and bronchoalveolar lavage fluid TH2 cytokine message and protein.ITK null mice have reduced tracheal responses to cholinergic challenge in vitro before as well as after allergen challenge. These mice also have reduced airways hyperresponsiveness in response to allergen challenge, which could be rescued by transferring WT splenocytes or purified WT CD4+ T cells. This reduced airways response was preferentially accompanied by reduced expression of TH2 cytokines in the lungs.Our results indicate that the tyrosine kinase ITK and its function in T cells represent an attractive target for antiasthmatic drugs.Modulating the expression or activity of ITK may be a novel strategy to block allergic airway inflammation.
Mice lacking the vitamin D receptor (VDR) are resistant to airway inflammation. Pathogenic immune... more Mice lacking the vitamin D receptor (VDR) are resistant to airway inflammation. Pathogenic immune cells capable of transferring experimental airway inflammation to wildtype (WT) mice are present and primed in the VDR KO mice. Furthermore, the VDR KO immune cells homed to the WT lung in sufficient numbers to induce symptoms of asthma. Conversely, WT splenocytes, Th2 cells and hematopoetic cells induced some symptoms of experimental asthma when transferred to VDR KO mice, but the severity was less than that seen in the WT controls. Interestingly, experimentally induced vitamin D deficiency failed to mirror the VDR KO phenotype suggesting there might be a difference between absence of the ligand and VDR deficiency. Lipopolysaccharide (LPS) induced
International Journal of Biochemistry & Cell Biology, 2002
ITK and Rlk/Txk are the predominant Tec family of tyrosine kinases expressed in T cells, and are ... more ITK and Rlk/Txk are the predominant Tec family of tyrosine kinases expressed in T cells, and are involved in T cell antigen receptor mediated activation of T cells. These kinases require prior activation of Lck, Zap-70 and PI3-kinase for efficient activation. They share major substrates with both Lck and Zap-70, however the pathways they regulate are unclear. Recent evidence suggests that these kinases may not activate unique pathways, but instead serve as amplifiers for the upstream kinases Lck and Zap-70. This review will discuss the evidence for this view.
Polymerization of the actin cytoskeleton has been found to be essential for B cell activation. We... more Polymerization of the actin cytoskeleton has been found to be essential for B cell activation. We show here however, that stimulation of BCR induces a rapid global actin depolymerization in a BCR signal strength dependent manner, followed by polarized actin repolymerization. Depolymerization of actin enhances, and blocking actin depolymerization inhibits BCR signaling leading to altered BCR and lipid raft clustering, ERK activation and transcription factor activation. Furthermore actin depolymerization by itself induces altered lipid raft clustering and ERK activation, suggesting that F-actin may play a role in separating lipid rafts and in setting the threshold for cellular activation.
Inducible T-cell kinase (ITK) is a member of the Tec family of tyrosine kinases that are involved... more Inducible T-cell kinase (ITK) is a member of the Tec family of tyrosine kinases that are involved in signals emanating from cytokine receptors, antigen receptors and other lymphoid cell surface receptors. Stimulation of tyrosine phosphorylation and activation of ITK by the T-cell antigen receptor, CD28 and CD2 requires the presence of the Src family kinase Lck in T-cells. We have previously demonstrated that the activation of ITK by Src family kinases uses a phosphatidylinositol 3-kinase pathway, which recruits ITK to the membrane via its pleckstrin homology (PH) domain where it is acted upon by Src. We have further explored the mechanism of this requirement for Src family kinases in the activation of ITK. We found that deletion of the proline rich sequence found in the Tec homology domain of ITK results in reduced basal activity of ITK approximately 50%. These di¡erences in the basal activity of ITK were observed when the PH domain was deleted or when the kinase was membrane targeted. Furthermore, this deletion reduces the ability of the Src family kinase Lck to activate ITK, as well as to induce the ITK mediated tyrosine phosphorylation of its substrate PLCQ Q1. By contrast, deletion of the SH3 domain of ITK resulted in a two-fold increase in the basal activity of ITK, and allowed this mutant to have an enhanced response to Lck. These results suggest that the proline rich region within the Tec homology domain of ITK regulates its basal activity and its response to Src family kinase signals. ß
The eosinophil has been perceived as a terminal effector cell in allergic airway diseases. Howeve... more The eosinophil has been perceived as a terminal effector cell in allergic airway diseases. However, recent work has shown that this multifunctional cell could be more involved in the initial stages of allergic disease development than was previously thought, particularly with regard to the ability of the eosinophil to modulate T-cell responses. In this review, we discuss recent advances that suggest that eosinophils can present antigen to naïve as well as to antigen-experienced T cells, induce T helper 2 cell development, cytokine production or both, and affect T-cell migration to sites of inflammation. These findings are changing the way that eosinophil function in disease is perceived, and represent a shift in the dogma of allergic disease development.
Murine models of allergic asthma have been used to understand the mechanisms of development and p... more Murine models of allergic asthma have been used to understand the mechanisms of development and pathology in this disease. In addition, knockout mice have contributed significantly to our understanding of the roles of specific molecules and cytokines in these models. However, results can vary significantly depending on the mouse strain used in the model, and in particularly in understanding the effect of specific knockouts. For example, it can be equivocal as to whether specific gene knockouts affect the susceptibility of the mice to developing the disease, or lead to resistance. Here we used a house dust mite model of allergic airway inflammation to examine the response of two strains of mice (C57BL/6 and BALB/c) which differ in their responses in allergic airway inflammation. We demonstrate an algorithm that can facilitate the understanding of the behavior of these models with regards to susceptibility (to allergic airway inflammation) (S aai ) or resistance (R aai ) in this model. We verify that both C57BL/6 and BALB/c develop disease, but BALB/c mice have higher S aai for development. We then use this approach to show that the absence of the Tec family kinase Itk, which regulates the production of Th2 cytokines, leads to R aai in the C57BL/6 background, but decreases S aai on the BALB/c background. We suggest that the use of such approaches could clarify the behavior of various knockout mice in modeling allergic asthma.
International Journal of Biochemistry & Cell Biology, 2010
Store-operated calcium channels are plasma membrane Ca 2+ channels that are activated by depletio... more Store-operated calcium channels are plasma membrane Ca 2+ channels that are activated by depletion of intracellular Ca 2+ stores, resulting in an increase in intracellular Ca 2+ concentration, which is maintained for prolonged periods in some cell types. Increases in intracellular Ca 2+ concentration serve as signals that activate a number of cellular processes, however, little is known about the regulation of these channels. We have characterized the immuno-suppressant compound BTP, which blocks store-operated channel mediated calcium influx into cells. Using an affinity purification scheme to identify potential targets of BTP, we identified the actin reorganizing protein, drebrin, and demonstrated that loss of drebrin protein expression prevents store-operated channel mediated Ca 2+ entry, similar to BTP treatment. BTP also blocks actin rearrangements induced by drebrin. While actin cytoskeletal reorganization has been implicated in store-operated calcium channel regulation, little is known about actin-binding proteins that are involved in this process, or how actin regulates channel function. The identification of drebrin as a mediator of this process should provide new insight into the interaction between actin rearrangement and store-operated channel mediated calcium influx.
T cells with a memory-like phenotype and possessing innate immune function have been previously i... more T cells with a memory-like phenotype and possessing innate immune function have been previously identified as CD8+CD44hi cells. These cells rapidly secrete IFN-γ upon stimulation with IL-12/IL-18 and are involved in innate responses to infection with Listeria monocytogenes. The signals regulating these cells are unclear. The Tec kinase Itk regulates T cell activation and we report here that a majority of the CD8+ T cells in Itk null mice have a phenotype of CD44hi similar to memory-like innate T cells. These cells are observed in mice carrying an Itk mutant lacking the kinase domain, indicating that active Tec kinase signaling suppresses their presence. These cells carry preformed message for and are able to rapidly produce IFN-γ upon stimulation in vitro with IL-12/IL-18, and endow Itk null mice the ability to effectively respond to infection with L. monocytogenes or exposure to lipopolysaccharides by secretion of IFN-γ. Transfer of these cells rescues the ability of IFN-γ null mice to reduce bacterial burden following L. monocytogenes infection, indicating that these cells are functional CD8+CD44hi T cells previously detected in vivo. These results indicate that active signals from Tec kinases regulate the development of memory-like CD8+ T cells with innate function.
International Journal of Biochemistry & Cell Biology, 2005
Natural killer T (NKT) cells are a subset of T cells that share properties of natural killer cell... more Natural killer T (NKT) cells are a subset of T cells that share properties of natural killer cells and conventional T cells. They are involved in immediate immune responses, tumor rejection, immune surveillance and control of autoimmune diseases. Most NKT cells express both an invariant T cell antigen receptor and the NK cell receptor NK1.1, and are referred to as invariant NKT cells. This invariant T cell receptor is restricted to interactions with glycolipids presented by the non-classical MHC, CD1d. These NKT cells rapidly produce high levels of interleukin (IL)-2, IFN-gamma, TNF-alpha, and IL-4 upon stimulation through their TCR. Most also have cytotoxic activity similar to NK cells. NKT cells are involved in a number of pathological conditions, and have been shown to regulate viral infections in vivo, and control tumor growth. They may also play both protective and harmful roles in the progression of certain autoimmune diseases, such as diabetes, lupus, atherosclerosis, and allergen-induced asthma.
Interleukin-2-inducible T cell kinase (ITK) is a non-receptor tyrosine kinase expressed in T cell... more Interleukin-2-inducible T cell kinase (ITK) is a non-receptor tyrosine kinase expressed in T cells, NKT cells and mast cells which plays a crucial role in regulating the T cell receptor (TCR), CD28, CD2, chemokine receptor CXCR4 and FcεR mediated signaling pathways. In T cells, ITK is an important mediator for actin reorganization, activation of PLCγ, mobilization of calcium, and activation of the NFAT transcription factor. ITK plays an important role in the secretion of IL-2, but more critically, also has a pivotal role in the secretion of Th2 cytokines, IL-4, IL-5 and IL-13. As such, ITK has been shown to regulate the development of effective Th2 response during allergic asthma as well as infections against parasitic worms. This ability of ITK to regulate Th2 responses, along with it's pattern of expression, has led to the proposal that it would represent an excellent target for Th2 mediated inflammation. We discuss here the possibilities and pitfalls of targeting ITK for inflammatory disorders.
NKT cells are a heterogeneous population characterized by the ability to rapidly produce cytokine... more NKT cells are a heterogeneous population characterized by the ability to rapidly produce cytokines, such as interleukin 2 (IL-2), IL-4, and gamma interferon (IFN-␥) in response to infections by viruses, bacteria, and parasites. The bacterial superantigen staphylococcal enterotoxin B (SEB) interacts with T cells bearing the V3, -7, or -8 T-cell receptors, inducing their expansion and cytokine secretion, leading to death in some cases due to cytokine poisoning. The majority of NKT cells bear the V7 or -8 T-cell receptor, suggesting that they may play a role in regulating this response. Using mice lacking NKT cells (CD1d ؊/؊ and J␣18 ؊/؊ mice), we set out to identify the role of these cells in T-cell expansion, cytokine secretion, and toxicity induced by exposure to SEB. We find that V8 ؉ CD4 ؉ T
T helper 17 (Th17) cells play major roles in autoimmunity and bacterial infections, yet how T cel... more T helper 17 (Th17) cells play major roles in autoimmunity and bacterial infections, yet how T cell receptor (TCR) signaling affects Th17 cell differentiation is relatively unknown. We demonstrate that CD4 + T cells lacking Itk, a tyrosine kinase required for full TCR-induced phospholipase C-g (PLC-g1) activation, exhibit decreased interleukin-17A (IL-17A) expression in vitro and in vivo, despite relatively normal expression of retinoic acid receptor-related orphan receptor-gT (ROR-gT) and IL-17F. IL-17A expression was rescued by pharmacologically induced Ca 2+ influx or constitutively activated nuclear factor of activated T cells (NFAT). Conversely, decreased TCR stimulation or calcineurin inhibition preferentially reduced IL-17A expression. We further found that the promoter of Il17a but not Il17f has a conserved NFAT binding site that bound NFATc1 in wild-type but not Itk-deficient cells, even though both exhibited open chromatin conformations. Finally, Itk À/À mice also showed differential regulation of IL-17A and IL-17F in vivo. Our results suggest that Itk specifically couples TCR signaling to Il17a expression and the differential regulation of Th17 cell cytokines through NFATc1.
Background: Exposure to Staphylococcal Enterotoxin B (SEB), a bacterial superantigen secreted by ... more Background: Exposure to Staphylococcal Enterotoxin B (SEB), a bacterial superantigen secreted by the Gram-positive bacteria Staphyloccocus aureus, results in the expansion and eventual clonal deletion and anergy of Vβ8 + T cells, as well as massive cytokine release, including Interleukin-2 (IL-2). This IL-2 is rapidly secreted following exposure to SEB and may contribute to the symptoms seen following exposure to this bacterial toxin. The Tec family kinase ITK has been shown to be important for the production of IL-2 by T cells stimulated in vitro and may represent a good target for blocking the production of this cytokine in vivo. In order to determine if ITK represents such a target, mice lacking ITK were analyzed for their response to SEB exposure.
The Tec family kinases are critical downstream regulators of antigen receptor signals in lymphocy... more The Tec family kinases are critical downstream regulators of antigen receptor signals in lymphocytes. As kinases, they act on critical substrates to regulate signals such as calcium increase leading to activation of transcription factors such as NFAT, NFjB and SRF. We now show here that ITK, a member of the Tec family of tyrosine kinases, has a kinase independent function. Mutants of ITK that lack kinase activity or a kinase domain can rescue cells lacking Tec family kinases for antigen receptor induced SRF activation, but not for NFAT, AP-1 or NFjB activation. Furthermore, expression of these mutants in WT cells enhanced SRF activation. This kinase independent function required the SH2 domain since a mutant lacking both the kinase and SH2 domains was much less effective at rescuing SRF activation. This kinase-deleted mutant could partially rescue ERK activation, and interact with multiple tyrosine phosphorylated proteins during antigen receptor signaling, suggesting that ITK uses a scaffolding function that regulates signals leading to specific regulation of SRF activation.
Patients with allergic asthma have symptoms of a predominant TH2 response, including airway eosin... more Patients with allergic asthma have symptoms of a predominant TH2 response, including airway eosinophilic inflammation and increased mucous production in the lungs. This accompanies increased airways responsiveness, which can be life threatening. Because TH2 cells and cytokines have been implicated in contributing to these symptoms, pathways that control the development of these cells or that regulate their cytokine production represent good targets for controlling this disease.We have previously shown that mice lacking the tyrosine kinase inducible T-cell kinase (ITK) have drastically reduced airway inflammation in a model of allergic asthma. However, it was not clear whether this translated into reduced airways hyperresponsiveness. We have analyzed tracheal responsiveness and airways hyperresponsiveness of wild-type (WT) and ITK null mice during induction of experimental allergic asthma.Experimental allergic asthma was induced in WT and ITK knockout mice. Tracheal responses to carbachol, acetylcholine, and potassium chloride were analyzed. Airways hyperresponsiveness to methacholine challenge was also analyzed in allergen-challenged mice, along with lung and bronchoalveolar lavage fluid TH2 cytokine message and protein.ITK null mice have reduced tracheal responses to cholinergic challenge in vitro before as well as after allergen challenge. These mice also have reduced airways hyperresponsiveness in response to allergen challenge, which could be rescued by transferring WT splenocytes or purified WT CD4+ T cells. This reduced airways response was preferentially accompanied by reduced expression of TH2 cytokines in the lungs.Our results indicate that the tyrosine kinase ITK and its function in T cells represent an attractive target for antiasthmatic drugs.Modulating the expression or activity of ITK may be a novel strategy to block allergic airway inflammation.
Mice lacking the vitamin D receptor (VDR) are resistant to airway inflammation. Pathogenic immune... more Mice lacking the vitamin D receptor (VDR) are resistant to airway inflammation. Pathogenic immune cells capable of transferring experimental airway inflammation to wildtype (WT) mice are present and primed in the VDR KO mice. Furthermore, the VDR KO immune cells homed to the WT lung in sufficient numbers to induce symptoms of asthma. Conversely, WT splenocytes, Th2 cells and hematopoetic cells induced some symptoms of experimental asthma when transferred to VDR KO mice, but the severity was less than that seen in the WT controls. Interestingly, experimentally induced vitamin D deficiency failed to mirror the VDR KO phenotype suggesting there might be a difference between absence of the ligand and VDR deficiency. Lipopolysaccharide (LPS) induced
International Journal of Biochemistry & Cell Biology, 2002
ITK and Rlk/Txk are the predominant Tec family of tyrosine kinases expressed in T cells, and are ... more ITK and Rlk/Txk are the predominant Tec family of tyrosine kinases expressed in T cells, and are involved in T cell antigen receptor mediated activation of T cells. These kinases require prior activation of Lck, Zap-70 and PI3-kinase for efficient activation. They share major substrates with both Lck and Zap-70, however the pathways they regulate are unclear. Recent evidence suggests that these kinases may not activate unique pathways, but instead serve as amplifiers for the upstream kinases Lck and Zap-70. This review will discuss the evidence for this view.
Polymerization of the actin cytoskeleton has been found to be essential for B cell activation. We... more Polymerization of the actin cytoskeleton has been found to be essential for B cell activation. We show here however, that stimulation of BCR induces a rapid global actin depolymerization in a BCR signal strength dependent manner, followed by polarized actin repolymerization. Depolymerization of actin enhances, and blocking actin depolymerization inhibits BCR signaling leading to altered BCR and lipid raft clustering, ERK activation and transcription factor activation. Furthermore actin depolymerization by itself induces altered lipid raft clustering and ERK activation, suggesting that F-actin may play a role in separating lipid rafts and in setting the threshold for cellular activation.
Inducible T-cell kinase (ITK) is a member of the Tec family of tyrosine kinases that are involved... more Inducible T-cell kinase (ITK) is a member of the Tec family of tyrosine kinases that are involved in signals emanating from cytokine receptors, antigen receptors and other lymphoid cell surface receptors. Stimulation of tyrosine phosphorylation and activation of ITK by the T-cell antigen receptor, CD28 and CD2 requires the presence of the Src family kinase Lck in T-cells. We have previously demonstrated that the activation of ITK by Src family kinases uses a phosphatidylinositol 3-kinase pathway, which recruits ITK to the membrane via its pleckstrin homology (PH) domain where it is acted upon by Src. We have further explored the mechanism of this requirement for Src family kinases in the activation of ITK. We found that deletion of the proline rich sequence found in the Tec homology domain of ITK results in reduced basal activity of ITK approximately 50%. These di¡erences in the basal activity of ITK were observed when the PH domain was deleted or when the kinase was membrane targeted. Furthermore, this deletion reduces the ability of the Src family kinase Lck to activate ITK, as well as to induce the ITK mediated tyrosine phosphorylation of its substrate PLCQ Q1. By contrast, deletion of the SH3 domain of ITK resulted in a two-fold increase in the basal activity of ITK, and allowed this mutant to have an enhanced response to Lck. These results suggest that the proline rich region within the Tec homology domain of ITK regulates its basal activity and its response to Src family kinase signals. ß
The eosinophil has been perceived as a terminal effector cell in allergic airway diseases. Howeve... more The eosinophil has been perceived as a terminal effector cell in allergic airway diseases. However, recent work has shown that this multifunctional cell could be more involved in the initial stages of allergic disease development than was previously thought, particularly with regard to the ability of the eosinophil to modulate T-cell responses. In this review, we discuss recent advances that suggest that eosinophils can present antigen to naïve as well as to antigen-experienced T cells, induce T helper 2 cell development, cytokine production or both, and affect T-cell migration to sites of inflammation. These findings are changing the way that eosinophil function in disease is perceived, and represent a shift in the dogma of allergic disease development.
Murine models of allergic asthma have been used to understand the mechanisms of development and p... more Murine models of allergic asthma have been used to understand the mechanisms of development and pathology in this disease. In addition, knockout mice have contributed significantly to our understanding of the roles of specific molecules and cytokines in these models. However, results can vary significantly depending on the mouse strain used in the model, and in particularly in understanding the effect of specific knockouts. For example, it can be equivocal as to whether specific gene knockouts affect the susceptibility of the mice to developing the disease, or lead to resistance. Here we used a house dust mite model of allergic airway inflammation to examine the response of two strains of mice (C57BL/6 and BALB/c) which differ in their responses in allergic airway inflammation. We demonstrate an algorithm that can facilitate the understanding of the behavior of these models with regards to susceptibility (to allergic airway inflammation) (S aai ) or resistance (R aai ) in this model. We verify that both C57BL/6 and BALB/c develop disease, but BALB/c mice have higher S aai for development. We then use this approach to show that the absence of the Tec family kinase Itk, which regulates the production of Th2 cytokines, leads to R aai in the C57BL/6 background, but decreases S aai on the BALB/c background. We suggest that the use of such approaches could clarify the behavior of various knockout mice in modeling allergic asthma.
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