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Boyle AJ, Lindberg A, Tong J, Zhai D, Liu F, Vasdev N. Preliminary PET imaging of [ 11C]evobrutinib in mouse models of colorectal cancer, SARS-CoV-2, and lung damage: Radiosynthesis via base-aided palladium-NiXantphos-mediated 11C-carbonylation. J Labelled Comp Radiopharm 2024; 67:235-244. [PMID: 37691152 DOI: 10.1002/jlcr.4062] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Revised: 07/25/2023] [Accepted: 08/24/2023] [Indexed: 09/12/2023]
Abstract
Evobrutinib is a second-generation, highly selective, irreversible Bruton's tyrosine kinase (BTK) inhibitor that has shown efficacy in the autoimmune diseases arthritis and multiple sclerosis. Its development as a positron emission tomography (PET) radiotracer has potential for in vivo imaging of BTK in various disease models including several cancers, severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2), and lipopolysaccharide (LPS)-induced lung damage. Herein, we report the automated radiosynthesis of [11C]evobrutinib using a base-aided palladium-NiXantphos-mediated 11C-carbonylation reaction. [11C]Evobrutinib was reliably formulated in radiochemical yields of 5.5 ± 1.5% and a molar activity of 34.5 ± 17.3 GBq/μmol (n = 12) with 99% radiochemical purity. Ex vivo autoradiography studies showed high specific binding of [11C]evobrutinib in HT-29 colorectal cancer mouse xenograft tissues (51.1 ± 7.1%). However, in vivo PET/computed tomography (CT) imaging with [11C]evobrutinib showed minimal visualization of HT-29 colorectal cancer xenografts and only a slight increase in radioactivity accumulation in the associated time-activity curves. In preliminary PET/CT studies, [11C]evobrutinib failed to visualize either SARS-CoV-2 pseudovirus infection or LPS-induced injury in mouse models. In conclusion, [11C]evobrutinib was successfully synthesized by 11C-carbonylation and based on our preliminary studies does not appear to be a promising BTK-targeted PET radiotracer in the rodent disease models studied herein.
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Affiliation(s)
- Amanda J Boyle
- Azrieli Centre for Neuro-Radiochemistry, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, Ontario, Canada
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
| | - Anton Lindberg
- Azrieli Centre for Neuro-Radiochemistry, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, Ontario, Canada
| | - Junchao Tong
- Azrieli Centre for Neuro-Radiochemistry, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, Ontario, Canada
| | - Dongxu Zhai
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, Ontario, Canada
| | - Fang Liu
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, Ontario, Canada
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
- Department of Physiology, University of Toronto, Toronto, Ontario, Canada
| | - Neil Vasdev
- Azrieli Centre for Neuro-Radiochemistry, Centre for Addiction and Mental Health, Toronto, Ontario, Canada
- Brain Health Imaging Centre, Centre for Addiction and Mental Health, Campbell Family Mental Health Research Institute, Toronto, Ontario, Canada
- Department of Psychiatry, University of Toronto, Toronto, Ontario, Canada
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Krämer J, Bar-Or A, Turner TJ, Wiendl H. Bruton tyrosine kinase inhibitors for multiple sclerosis. Nat Rev Neurol 2023; 19:289-304. [PMID: 37055617 PMCID: PMC10100639 DOI: 10.1038/s41582-023-00800-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 35.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/09/2023] [Indexed: 04/15/2023]
Abstract
Current therapies for multiple sclerosis (MS) reduce both relapses and relapse-associated worsening of disability, which is assumed to be mainly associated with transient infiltration of peripheral immune cells into the central nervous system (CNS). However, approved therapies are less effective at slowing disability accumulation in patients with MS, in part owing to their lack of relevant effects on CNS-compartmentalized inflammation, which has been proposed to drive disability. Bruton tyrosine kinase (BTK) is an intracellular signalling molecule involved in the regulation of maturation, survival, migration and activation of B cells and microglia. As CNS-compartmentalized B cells and microglia are considered central to the immunopathogenesis of progressive MS, treatment with CNS-penetrant BTK inhibitors might curtail disease progression by targeting immune cells on both sides of the blood-brain barrier. Five BTK inhibitors that differ in selectivity, strength of inhibition, binding mechanisms and ability to modulate immune cells within the CNS are currently under investigation in clinical trials as a treatment for MS. This Review describes the role of BTK in various immune cells implicated in MS, provides an overview of preclinical data on BTK inhibitors and discusses the (largely preliminary) data from clinical trials.
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Affiliation(s)
- Julia Krämer
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, Münster, Germany
| | - Amit Bar-Or
- Center for Neuroinflammation and Neurotherapeutics, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
- Department of Neurology, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA, USA
| | | | - Heinz Wiendl
- Department of Neurology with Institute of Translational Neurology, University Hospital Münster, Münster, Germany.
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Nyhoff LE, Griffith AS, Clark ES, Thomas JW, Khan WN, Kendall PL. Btk Supports Autoreactive B Cell Development and Protects against Apoptosis but Is Expendable for Antigen Presentation. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2021; 207:2922-2932. [PMID: 34799428 PMCID: PMC9117567 DOI: 10.4049/jimmunol.2000558] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Accepted: 09/29/2021] [Indexed: 11/19/2022]
Abstract
Bruton's tyrosine kinase (Btk) propagates B cell signaling, and BTK inhibitors are in clinical trials for autoimmune disease. Although autoreactive B cells fail to develop in the absence of Btk, its role in mature cells is unknown. To address this issue, a model of conditional removal (Btk flox/Cre-ERT2 ) was used to excise Btk from mature transgenic B cells that recognize the pathophysiologic autoantigen insulin. Anti-insulin B cells escape central tolerance and promote autoimmune diabetes, mimicking human autoreactive cells. Lifelong Btk deficiency was previously shown to eliminate 95% of anti-insulin B cells, but in this model, mature anti-insulin B cells survived for weeks after targeted Btk deletion, even when competing with a polyclonal repertoire. BCR-stimulated cells could still signal via Syk, PLCy2, and CD22, but failed to upregulate the antiapoptotic protein Bcl-xL, and proliferation was impaired. Surprisingly, Btk-depleted anti-insulin B cells could still present Ag and activate T cells, a critical function in promoting T cell-mediated islet cell destruction. Thus, pharmacologic targeting of Btk may be most effective by blocking expansion of established autoreactive cells, and preventing emergence of new ones.
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Affiliation(s)
- Lindsay E Nyhoff
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN
- Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
| | - Amber S Griffith
- Division of Allergy and Immunology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
| | - Emily S Clark
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL; and
| | - James W Thomas
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN
- Division of Rheumatology, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
| | - Wasif N Khan
- Department of Microbiology and Immunology, Miller School of Medicine, University of Miami, Miami, FL; and
| | - Peggy L Kendall
- Department of Pathology, Microbiology and Immunology, Vanderbilt University School of Medicine, Nashville, TN;
- Division of Allergy, Pulmonary and Critical Care, Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN
- Division of Allergy and Immunology, Department of Medicine, Washington University School of Medicine, St. Louis, MO
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4
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Good L, Benner B, Carson WE. Bruton's tyrosine kinase: an emerging targeted therapy in myeloid cells within the tumor microenvironment. Cancer Immunol Immunother 2021; 70:2439-2451. [PMID: 33818636 PMCID: PMC8019691 DOI: 10.1007/s00262-021-02908-5] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2020] [Accepted: 03/02/2021] [Indexed: 12/15/2022]
Abstract
Bruton’s tyrosine kinase (BTK) is a non-receptor kinase belonging to the Tec family of kinases. The role of BTK in B cell receptor signaling is well defined and is known to play a key role in the proliferation and survival of malignant B cells. Moreover, BTK has been found to be expressed in cells of the myeloid lineage. BTK has been shown to contribute to a variety of cellular pathways in myeloid cells including signaling in the NLRP3 inflammasome, receptor activation of nuclear factor-κβ and inflammation, chemokine receptor activation affecting migration, and phagocytosis. Myeloid cells are crucial components of the tumor microenvironment and suppressive myeloid cells contribute to cancer progression, highlighting a potential role for BTK inhibition in the treatment of malignancy. The increased interest in BTK inhibition in cancer has resulted in many preclinical studies that are testing the efficacy of using single-agent BTK inhibitors. Moreover, the ability of tumor cells to develop resistance to single-agent checkpoint inhibitors has resulted in clinical studies utilizing BTK inhibitors in combination with these agents to improve clinical responses. Furthermore, BTK regulates the immune response in microbial and viral infections through B cells and myeloid cells such as monocytes and macrophages. In this review, we describe the role that BTK plays in supporting suppressive myeloid cells, including myeloid-derived suppressor cells (MDSC) and tumor-associated macrophages (TAM), while also discussing the anticancer effects of BTK inhibition and briefly describe the role of BTK signaling and BTK inhibition in microbial and viral infections.
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Affiliation(s)
- Logan Good
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA
| | - Brooke Benner
- Comprehensive Cancer Center, The Ohio State University, Columbus, OH, USA
| | - William E Carson
- Department of Surgery, Division of Surgical Oncology, Tzagournis Medical Research Facility, The Ohio State University, Columbus, OH, USA.
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Kanagaratham C, El Ansari YS, Lewis OL, Oettgen HC. IgE and IgG Antibodies as Regulators of Mast Cell and Basophil Functions in Food Allergy. Front Immunol 2020; 11:603050. [PMID: 33362785 PMCID: PMC7759531 DOI: 10.3389/fimmu.2020.603050] [Citation(s) in RCA: 87] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 10/22/2020] [Indexed: 12/15/2022] Open
Abstract
Food allergy is a major health issue, affecting the lives of 8% of U.S. children and their families. There is an urgent need to identify the environmental and endogenous signals that induce and sustain allergic responses to ingested allergens. Acute reactions to foods are triggered by the activation of mast cells and basophils, both of which release inflammatory mediators that lead to a range of clinical manifestations, including gastrointestinal, cutaneous, and respiratory reactions as well as systemic anaphylaxis. Both of these innate effector cell types express the high affinity IgE receptor, FcϵRI, on their surface and are armed for adaptive antigen recognition by very-tightly bound IgE antibodies which, when cross-linked by polyvalent allergen, trigger degranulation. These cells also express inhibitory receptors, including the IgG Fc receptor, FcγRIIb, that suppress their IgE-mediated activation. Recent studies have shown that natural resolution of food allergies is associated with increasing food-specific IgG levels. Furthermore, oral immunotherapy, the sequential administration of incrementally increasing doses of food allergen, is accompanied by the strong induction of allergen-specific IgG antibodies in both human subjects and murine models. These can deliver inhibitory signals via FcγRIIb that block IgE-induced immediate food reactions. In addition to their role in mediating immediate hypersensitivity reactions, mast cells and basophils serve separate but critical functions as adjuvants for type 2 immunity in food allergy. Mast cells and basophils, activated by IgE, are key sources of IL-4 that tilts the immune balance away from tolerance and towards type 2 immunity by promoting the induction of Th2 cells along with the innate effectors of type 2 immunity, ILC2s, while suppressing the development of regulatory T cells and driving their subversion to a pathogenic pro-Th2 phenotype. This adjuvant effect of mast cells and basophils is suppressed when inhibitory signals are delivered by IgG antibodies signaling via FcγRIIb. This review summarizes current understanding of the immunoregulatory effects of mast cells and basophils and how these functions are modulated by IgE and IgG antibodies. Understanding these pathways could provide important insights into innovative strategies for preventing and/or reversing food allergy in patients.
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Affiliation(s)
- Cynthia Kanagaratham
- Division of Immunology, Department of Pediatrics, Boston Children’s Hospital, Boston, MA, United States
- Department of Pediatrics, Harvard Medical School, Boston, MA, United States
| | - Yasmeen S. El Ansari
- Division of Immunology, Department of Pediatrics, Boston Children’s Hospital, Boston, MA, United States
- Institute of Laboratory Medicine, Philipps University Marburg, Marburg, Germany
| | - Owen L. Lewis
- Division of Immunology, Department of Pediatrics, Boston Children’s Hospital, Boston, MA, United States
| | - Hans C. Oettgen
- Division of Immunology, Department of Pediatrics, Boston Children’s Hospital, Boston, MA, United States
- Department of Pediatrics, Harvard Medical School, Boston, MA, United States
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Impact of amino acid substitution in the kinase domain of Bruton tyrosine kinase and its association with X-linked agammaglobulinemia. Int J Biol Macromol 2020; 164:2399-2408. [PMID: 32784026 DOI: 10.1016/j.ijbiomac.2020.08.057] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Revised: 08/02/2020] [Accepted: 08/03/2020] [Indexed: 02/06/2023]
Abstract
X-linked agammaglobulinemia (XLA) is a rare disease that affects the immune system, characterized by a serial development of bacterial infection from the onset of infantile age. Bruton tyrosine kinase (BTK) is a non-receptor cytoplasmic kinase that plays a crucial role in the B-lymphocyte maturation. The altered expression, mutation and/or structural variations of BTK are responsible for causing XLA. Here, we have performed extensive sequence and structure analyses of BTK to find deleterious variations and their pathogenic association with XLA. First, we screened the pathogenic variations in the BTK from a pool of publicly available resources, and their pathogenicity/tolerance and stability predictions were carried out. Finally, two pathogenic variations (E589G and M630K) were studied in detail and subjected to all-atom molecular dynamics simulation for 200 ns. Intramolecular hydrogen bonds (H-bonds), secondary structure, and principal component analysis revealed significant conformational changes in variants that support the structural basis of BTK dysfunction in XLA. The free energy landscape analysis revealed the presence of multiple energy minima, suggests that E589G brings a large destabilization and consequently unfolding behavior compared to M630K. Overall, our study suggests that amino acid substitutions, E589G, and M630K, significantly alter the structural conformation and stability of BTK.
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Smiljkovic D, Blatt K, Stefanzl G, Dorofeeva Y, Skrabs C, Focke‐Tejkl M, Sperr WR, Jaeger U, Valenta R, Valent P. BTK inhibition is a potent approach to block IgE-mediated histamine release in human basophils. Allergy 2017; 72:1666-1676. [PMID: 28328081 PMCID: PMC5655929 DOI: 10.1111/all.13166] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/18/2017] [Indexed: 12/29/2022]
Abstract
Background Recent data suggest that Bruton's tyrosine kinase (BTK) is an emerging therapeutic target in IgE receptor (IgER)‐cross‐linked basophils. Methods We examined the effects of four BTK inhibitors (ibrutinib, dasatinib, AVL‐292, and CNX‐774) on IgE‐dependent activation and histamine release in blood basophils obtained from allergic patients (n=11) and nonallergic donors (n=5). In addition, we examined the effects of these drugs on the growth of the human basophil cell line KU812 and the human mast cell line HMC‐1. Results All four BTK blockers were found to inhibit anti‐IgE‐induced histamine release from basophils in nonallergic subjects and allergen‐induced histamine liberation from basophils in allergic donors. Drug effects on allergen‐induced histamine release were dose dependent, with IC50 values ranging between 0.001 and 0.5 μmol/L, and the following rank order of potency: ibrutinib>AVL‐292>dasatinib>CNX‐774. The basophil‐targeting effect of ibrutinib was confirmed by demonstrating that IgE‐dependent histamine release in ex vivo blood basophils is largely suppressed in a leukemia patient treated with ibrutinib. Dasatinib and ibrutinib were also found to counteract anti‐IgE‐induced and allergen‐induced upregulation of CD13, CD63, CD164, and CD203c on basophils, whereas AVL‐292 and CNX‐774 showed no significant effects. Whereas dasatinib and CNX‐774 were found to inhibit the growth of HMC‐1 cells and KU812 cells, no substantial effects were seen with ibrutinib or AVL‐292. Conclusions BTK‐targeting drugs are potent inhibitors of IgE‐dependent histamine release in human basophils. The clinical value of BTK inhibition in the context of allergic diseases remains to be determined.
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Affiliation(s)
- D. Smiljkovic
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
| | - K. Blatt
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
- Ludwig Boltzmann Cluster Oncology Medical University of Vienna Vienna Austria
| | - G. Stefanzl
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
- Ludwig Boltzmann Cluster Oncology Medical University of Vienna Vienna Austria
| | - Y. Dorofeeva
- Division of Immunopathology Department of Pathophysiology and Allergy Research Center for Pathophysiology, Immunology and Infectiology Medical University of Vienna Vienna Austria
| | - C. Skrabs
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
| | - M. Focke‐Tejkl
- Division of Immunopathology Department of Pathophysiology and Allergy Research Center for Pathophysiology, Immunology and Infectiology Medical University of Vienna Vienna Austria
| | - W. R. Sperr
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
- Ludwig Boltzmann Cluster Oncology Medical University of Vienna Vienna Austria
| | - U. Jaeger
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
- Ludwig Boltzmann Cluster Oncology Medical University of Vienna Vienna Austria
| | - R. Valenta
- Division of Immunopathology Department of Pathophysiology and Allergy Research Center for Pathophysiology, Immunology and Infectiology Medical University of Vienna Vienna Austria
| | - P. Valent
- Department of Internal Medicine I Division of Hematology & Hemostaseology Medical University of Vienna Vienna Austria
- Ludwig Boltzmann Cluster Oncology Medical University of Vienna Vienna Austria
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Kawakami T, Blank U. From IgE to Omalizumab. JOURNAL OF IMMUNOLOGY (BALTIMORE, MD. : 1950) 2016; 197:4187-4192. [PMID: 27864548 PMCID: PMC5123831 DOI: 10.4049/jimmunol.1601476] [Citation(s) in RCA: 59] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2016] [Accepted: 10/03/2016] [Indexed: 11/19/2022]
Abstract
IgE is the least abundant Ig isotype, yet it plays a critical role in allergic reactions and host protection from helminth infection. Although IgE was discovered 50 years ago, the ultimate evidence for its role in human allergic diseases was obtained by the efficacy of anti-IgE therapy in many clinical trials on asthma and other allergic diseases. Beginning from the discovery of IgE 50 y ago, followed by studies of IgE receptors and activation mechanisms, this review provides a historic perspective of allergy research that has led to the development of anti-IgE therapy and other strategies targeting IgE and its receptors. Current IgE studies toward future precision medicine are also reviewed.
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Affiliation(s)
- Toshiaki Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, La Jolla, CA 92037;
- Department of Dermatology, University of California San Diego School of Medicine, La Jolla, CA 92093
| | - Ulrich Blank
- INSERM Unité 1149, Centre de Recherche sur I'Inflammation, 75018 Paris, France
- CNRS Equipe de Recherche Labellisée 8252, 75018 Paris, France
- Université Paris Diderot, Sorbonne Paris Cité, Faculté de Médecine, Site Xavier Bichat, 75018 Paris, France; and
- Inflamex Laboratory of Excellence, Xavier Bichat Site, 75018 Paris, France
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Rotin LE, Gronda M, MacLean N, Hurren R, Wang X, Lin FH, Wrana J, Datti A, Barber DL, Minden MD, Slassi M, Schimmer AD. Ibrutinib synergizes with poly(ADP-ribose) glycohydrolase inhibitors to induce cell death in AML cells via a BTK-independent mechanism. Oncotarget 2016; 7:2765-79. [PMID: 26624983 PMCID: PMC4823070 DOI: 10.18632/oncotarget.6409] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 11/16/2015] [Indexed: 12/15/2022] Open
Abstract
Targeting Bruton's tyrosine kinase (BTK) with the small molecule BTK inhibitor ibrutinib has significantly improved patient outcomes in several B-cell malignancies, with minimal toxicity. Given the reported expression and constitutive activation of BTK in acute myeloid leukemia (AML) cells, there has been recent interest in investigating the anti-AML activity of ibrutinib. We noted that ibrutinib had limited single-agent toxicity in a panel of AML cell lines and primary AML samples, and therefore sought to identify ibrutinib-sensitizing drugs. Using a high-throughput combination chemical screen, we identified that the poly(ADP-ribose) glycohydrolase (PARG) inhibitor ethacridine lactate synergized with ibrutinib in TEX and OCI-AML2 leukemia cell lines. The combination of ibrutinib and ethacridine induced a synergistic increase in reactive oxygen species that was functionally important to explain the observed cell death. Interestingly, synergistic cytotoxicity of ibrutinib and ethacridine was independent of the inhibitory effect of ibrutinib against BTK, as knockdown of BTK did not sensitize TEX and OCI-AML2 cells to ethacridine treatment. Thus, our findings indicate that ibrutinib may have a BTK-independent role in AML and that PARG inhibitors may have utility as part of a combination therapy for this disease.
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Affiliation(s)
- Lianne E Rotin
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | - Marcela Gronda
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Neil MacLean
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Rose Hurren
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - XiaoMing Wang
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Feng-Hsu Lin
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Jeff Wrana
- Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada
| | - Alessandro Datti
- Samuel Lunenfeld Research Institute, Toronto, Ontario, Canada.,Department of Agricultural, Food, and Environmental Sciences, University of Perugia, Perugia, Italy
| | - Dwayne L Barber
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada
| | - Mark D Minden
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
| | | | - Aaron D Schimmer
- Princess Margaret Cancer Centre, Ontario Cancer Institute, University Health Network, Toronto, Ontario, Canada.,Institute of Medical Science, University of Toronto, Toronto, Ontario, Canada
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10
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Crofford LJ, Nyhoff LE, Sheehan JH, Kendall PL. The role of Bruton's tyrosine kinase in autoimmunity and implications for therapy. Expert Rev Clin Immunol 2016; 12:763-73. [PMID: 26864273 DOI: 10.1586/1744666x.2016.1152888] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Bruton's tyrosine kinase (BTK) mediates B cell signaling and is also present in innate immune cells but not T cells. BTK propagates B cell receptor (BCR) responses to antigen-engagement as well as to stimulation via CD40, toll-like receptors (TLRs), Fc receptors (FCRs) and chemokine receptors. Importantly, BTK can modulate signaling, acting as a "rheostat" rather than an "on-off" switch; thus, overexpression leads to autoimmunity while decreased levels improve autoimmune disease outcomes. Autoreactive B cells depend upon BTK for survival to a greater degree than normal B cells, reflected as loss of autoantibodies with maintenance of total antibody levels when BTK is absent. This review describes contributions of BTK to immune tolerance, including studies testing BTK-inhibitors for treatment of autoimmune diseases.
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Affiliation(s)
- Leslie J Crofford
- a Division of Rheumatology & Immunology, Department of Medicine , Vanderbilt University , Nashville , TN , USA.,b Department of Pathology, Microbiology & Immunology , Vanderbilt University , Nashville , TN , USA
| | - Lindsay E Nyhoff
- b Department of Pathology, Microbiology & Immunology , Vanderbilt University , Nashville , TN , USA
| | - Jonathan H Sheehan
- c Center for Structural Biology, Department of Biochemistry , Vanderbilt University , Nashville , TN , USA
| | - Peggy L Kendall
- b Department of Pathology, Microbiology & Immunology , Vanderbilt University , Nashville , TN , USA.,d Division of Allergy, Pulmonary and Critical Care, Department of Medicine , Vanderbilt University , Nashville , TN , USA
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Huang W, Morales JL, Gazivoda VP, August A. Nonreceptor tyrosine kinases ITK and BTK negatively regulate mast cell proinflammatory responses to lipopolysaccharide. J Allergy Clin Immunol 2015; 137:1197-1205. [PMID: 26581914 DOI: 10.1016/j.jaci.2015.08.056] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 08/06/2015] [Accepted: 08/28/2015] [Indexed: 01/21/2023]
Abstract
BACKGROUND Mast cells are indispensable for LPS-induced septic hypothermia, in which TNF-α plays an essential role to initiate septic responses. ITK and BTK regulate mast cell responses to allergens, but their roles in mast cell responses in LPS-induced sepsis are unclear. OBJECTIVE We sought to investigate the roles of ITK and BTK in mast cell responses during LPS-induced septic inflammation. METHODS Mice (genetically modified or bone marrow-derived mast cell-reconstituted Sash) were given LPS to induce septic hypothermia in the presence or absence of indicated inhibitors. Flow cytometry was used to determine LPS-induced cell influx and TNF-α production in peritoneal cells. Microarray was used for genomewide gene expression analysis on bone marrow-derived mast cells. Quantitative PCR and multiplex were used to determine transcribed and secreted proinflammatory cytokines. Microscopy and Western blotting were used to determine activation of signal transduction pathways. RESULTS The absence of ITK and BTK leads to exacerbation of LPS-induced septic hypothermia and neutrophil influx. Itk(-/-)Btk(-/-) mast cells exhibit hyperactive preformed and LPS-induced TNF-α production, and lead to more severe LPS-induced septic hypothermia when reconstituted into mast cell-deficient Sash mice. LPS-induced nuclear factor kappa B, Akt, and p38 activation is enhanced in Itk(-/-)Btk(-/-) mast cells, and blockage of phosphatidylinositol-4,5-bisphosphate 3-kinase, Akt, or p38 downstream mitogen-activated protein kinase interacting serine/threonine kinase 1 activation significantly suppresses TNF-α hyperproduction and attenuates septic hypothermia. CONCLUSIONS ITK and BTK regulate thermal homeostasis during septic response through mast cell function in mice. They share regulatory function downstream of Toll-like receptor 4/LPS in mast cells, through regulating the activation of canonical nuclear factor kappa B, phosphatidylinositol-4,5-bisphosphate 3-kinase/Akt, and p38 signaling pathways.
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Affiliation(s)
- Weishan Huang
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY
| | - J Luis Morales
- Department of Veterinary and Biomedical Science, Center for Molecular Immunology and Infectious Disease, The Pennsylvania State University, University Park, Pa
| | - Victor P Gazivoda
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY
| | - Avery August
- Department of Microbiology and Immunology, Cornell University, Ithaca, NY.
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Schutt SD, Fu J, Nguyen H, Bastian D, Heinrichs J, Wu Y, Liu C, McDonald DG, Pidala J, Yu XZ. Inhibition of BTK and ITK with Ibrutinib Is Effective in the Prevention of Chronic Graft-versus-Host Disease in Mice. PLoS One 2015; 10:e0137641. [PMID: 26348529 PMCID: PMC4562702 DOI: 10.1371/journal.pone.0137641] [Citation(s) in RCA: 72] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 08/20/2015] [Indexed: 01/01/2023] Open
Abstract
Bruton’s Tyrosine Kinase (BTK) and IL-2 Inducible T-cell Kinase (ITK) are enzymes responsible for the phosphorylation and activation of downstream effectors in the B-cell receptor (BCR) signaling and T cell receptor (TCR) signaling pathways, respectively. Ibrutinib is an FDA-approved potent inhibitor of both BTK and ITK that impairs B-cell and T-cell function. CD4 T cells and B cells are essential for the induction of chronic graft-versus-host disease (cGVHD). We evaluated these targets by testing the ability of Ibrutinib to prevent or ameliorate cGVHD, which is one of the major complications for patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT). We found that Ibrutinib significantly alleviated cGVHD across four different mouse models, accompanied by increased long-term survival and reduced clinical score. The clinical improvements in Ibrutinib-treated recipients were associated with decreased serum-autoantibodies, costimulatory molecule activation, B-cell proliferation, and glomerulonephritis compared to vehicle controls. Ibrutinib was also able to alleviate the clinical manifestations in acute GVHD (aGVHD), where the recipients were given grafts with or without B cells, suggesting that an inhibitory effect of Ibrutinib on T cells contributes to a reduction in both aGVHD and cGVHD pathogenesis. An effective prophylactic regimen is still lacking to both reduce the incidence and severity of human cGVHD following allo-HSCT. Our study shows that Ibrutinib is an effective prophylaxis against several mouse models of cGVHD with minimal toxicity and could be a promising strategy to combat human cGVHD clinically.
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Affiliation(s)
- Steven D. Schutt
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Jianing Fu
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
- Cancer Biology PhD Program, University of South Florida and H. Lee Moffitt Cancer Center, Tampa, Florida, United States of America
| | - Hung Nguyen
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - David Bastian
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Jessica Heinrichs
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Yongxia Wu
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Chen Liu
- Pathology, Immunology and Laboratory Medicine, University of Florida, Gainesville, Florida, United States of America
| | - Daniel G. McDonald
- Department of Radiation Oncology, Medical University of South Carolina, Charleston, South Carolina, United States of America
| | - Joseph Pidala
- Blood and Bone Marrow Transplant Department, Moffitt Cancer Center, Tampa, Florida, United States of America
| | - Xue-Zhong Yu
- Department of Microbiology & Immunology, Medical University of South Carolina, Charleston, South Carolina, United States of America
- Department of Medicine, Medical University of South Carolina, Charleston, South Carolina, United States of America
- * E-mail:
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Cuajungco MP, Silva J, Habibi A, Valadez JA. The mucolipin-2 (TRPML2) ion channel: a tissue-specific protein crucial to normal cell function. Pflugers Arch 2015; 468:177-92. [PMID: 26336837 DOI: 10.1007/s00424-015-1732-2] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2015] [Revised: 08/25/2015] [Accepted: 08/27/2015] [Indexed: 12/26/2022]
Abstract
The discovery of the TRPML subfamily of ion channels has created an exciting niche in the fields of membrane trafficking, signal transduction, autophagy, and metal homeostasis. The TRPML protein subfamily consists of three members, TRPML1, TRPML2, and TRPML3, which are encoded by MCOLN1, MCOLN2, and MCOLN3 genes, respectively. They are non-selective cation channels with six predicted transmembrane domains and intracellular amino- and carboxyl-terminus regions. They localize to the plasma membrane, endosomes, and lysosomes of cells. TRPML1 is associated with the human lysosomal storage disease known as mucolipidosis type IV (MLIV), but TRPML2 and TRPML3 have not been linked with a human disease. Although TRPML1 is expressed in many tissues, TRPML3 is expressed in a varied but limited set of tissues, while TRPML2 has a more limited expression pattern where it is mostly detected in lymphoid and myeloid tissues. This review focuses on TRPML2 because it appears to play an important, yet unrecognized role in the immune system. While the evidence has been mostly indirect, we present and discuss relevant data that strengthen the connection of TRPML2 with cellular immunity. We also discuss the functional redundancy between the TRPML proteins, and how such features could be exploited as a potential therapeutic strategy for MLIV disease. We present evidence that TRPML2 expression may complement certain phenotypic alterations in MLIV cells and briefly examine the challenges of functional complementation. In conclusion, the function of TRPML2 still remains obscure, but emerging data show that it may serve a critical role in immune cell development and inflammatory responses.
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Affiliation(s)
- Math P Cuajungco
- Department of Biological Science, California State University Fullerton, 800 N. State College Blvd., Fullerton, CA, 92831, USA. .,Center for Applied Biotechnology Studies, California State University Fullerton, Fullerton, CA, 92831, USA.
| | - Joshua Silva
- Department of Biological Science, California State University Fullerton, 800 N. State College Blvd., Fullerton, CA, 92831, USA
| | - Ania Habibi
- Department of Biological Science, California State University Fullerton, 800 N. State College Blvd., Fullerton, CA, 92831, USA
| | - Jessica A Valadez
- Department of Biological Science, California State University Fullerton, 800 N. State College Blvd., Fullerton, CA, 92831, USA
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Teocchi MA, Domingues Ramalho V, Abramczuk BM, D'Souza-Li L, Santos Vilela MM. BTK mutations selectively regulate BTK expression and upregulate monocyte XBP1 mRNA in XLA patients. Immun Inflamm Dis 2015; 3:171-81. [PMID: 26417435 PMCID: PMC4578518 DOI: 10.1002/iid3.57] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 03/09/2015] [Accepted: 03/10/2015] [Indexed: 12/14/2022] Open
Abstract
Mutations in the Bruton agammaglobulinemia tyrosine kinase (BTK) gene are responsible for X-linked agammaglobulinemia (XLA). Unfolded or misfolded proteins can trigger stress pathways in the endoplasmic reticulum (ER), known as unfolded protein response (UPR). The aim was to clarify the involvement of UPR in XLA pathophysiology. By reverse transcription-quantitative PCR, we evaluated the expression of BTK and 12 UPR-related genes in eight patients. Moreover, we assessed the BTK protein expression and pattern in the patients' monocytes by flow cytometry and fluorescence immunocytochemistry. We found a reduced BTK expression in patients with stop codon mutations (P < 0.02). However, missense mutations did not affect BTK expression. Flow cytometry showed a reduction of BTK in patients which was corroborated by an absent or nonfunctional protein synthesis revealed by immunocytochemistry. In contrast with the other UPR-related genes, X-box binding protein 1 (XBP1) was markedly upregulated in the patients (P < 0.01), suggesting Toll-like receptor (TLR) activation since BTK directly interacts with TLRs as a negative regulator and XBP1 can be activated in direct response to TLR ligation. Different BTK mutations can be identified by the BTK expression. Inasmuch as UPR-related genes were downregulated or unaltered in patients, we speculate the involvement of the TLRs-XBP1 axis in the XLA pathophysiology. Such data could be the basis for further studies of this novel pathomechanism concerning XLA.
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Affiliation(s)
- Marcelo A Teocchi
- Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil
| | - Vanessa Domingues Ramalho
- Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil
| | - Beatriz M Abramczuk
- Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil
| | - Lília D'Souza-Li
- Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil ; Department of Pediatrics, Faculty of Medical Sciences, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil
| | - Maria Marluce Santos Vilela
- Center for Investigation in Pediatrics, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil ; Department of Pediatrics, Faculty of Medical Sciences, University of Campinas (UNICAMP) Campinas, São Paulo, Brazil
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15
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Wang Q, Vogan EM, Nocka LM, Rosen CE, Zorn JA, Harrison SC, Kuriyan J. Autoinhibition of Bruton's tyrosine kinase (Btk) and activation by soluble inositol hexakisphosphate. eLife 2015; 4:e06074. [PMID: 25699547 PMCID: PMC4384635 DOI: 10.7554/elife.06074] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2014] [Accepted: 02/19/2015] [Indexed: 01/07/2023] Open
Abstract
Bruton's tyrosine kinase (Btk), a Tec-family tyrosine kinase, is essential for B-cell function. We present crystallographic and biochemical analyses of Btk, which together reveal molecular details of its autoinhibition and activation. Autoinhibited Btk adopts a compact conformation like that of inactive c-Src and c-Abl. A lipid-binding PH-TH module, unique to Tec kinases, acts in conjunction with the SH2 and SH3 domains to stabilize the inactive conformation. In addition to the expected activation of Btk by membranes containing phosphatidylinositol triphosphate (PIP3), we found that inositol hexakisphosphate (IP6), a soluble signaling molecule found in both animal and plant cells, also activates Btk. This activation is a consequence of a transient PH-TH dimerization induced by IP6, which promotes transphosphorylation of the kinase domains. Sequence comparisons with other Tec-family kinases suggest that activation by IP6 is unique to Btk.
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Affiliation(s)
- Qi Wang
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States
| | - Erik M Vogan
- Beryllium Inc, Boston, United States,Laboratory of Molecular Medicine, Harvard Medical School, Howard Hughes Medical Institute, Boston, United States
| | - Laura M Nocka
- Department of Chemistry, University of California, Berkeley, Berkeley, United States
| | - Connor E Rosen
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States
| | - Julie A Zorn
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States
| | - Stephen C Harrison
- Laboratory of Molecular Medicine, Harvard Medical School, Howard Hughes Medical Institute, Boston, United States,For correspondence: (SCH)
| | - John Kuriyan
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States,California Institute for Quantitative Biosciences, University of California, Berkeley, Berkeley, United States,Department of Chemistry, University of California, Berkeley, Berkeley, United States,Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, United States, (JK)
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16
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Sibilano R, Frossi B, Pucillo CE. Mast cell activation: a complex interplay of positive and negative signaling pathways. Eur J Immunol 2014; 44:2558-66. [PMID: 25066089 DOI: 10.1002/eji.201444546] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2014] [Revised: 07/08/2014] [Accepted: 07/23/2014] [Indexed: 11/07/2022]
Abstract
Mast cells regulate the immunological responses causing allergy and autoimmunity, and contribute to the tumor microenvironment through generation and secretion of a broad array of preformed, granule-stored and de novo synthesized bioactive compounds. The release and production of mast cell mediators is the result of a coordinated signaling machinery, followed by the FcεRI and FcγR antigen ligation. In this review, we present the latest understanding of FcεRI and FcγR signaling, required for the canonical mast cell activation during allergic responses and anaphylaxis. We then describe the cooperation between the signaling of FcR and other recently characterized membrane-bound receptors (i.e., IL-33R and thymic stromal lymphopoietin receptor) and their role in the chronic settings, where mast cell activation is crucial for the development and the sustainment of chronic diseases, such as asthma or airway inflammation. Finally, we report how the FcR activation could be used as a therapeutic approach to treat allergic and atopic diseases by mast cell inactivation. Understanding the magnitude and the complexity of mast cell signaling is necessary to identify the mechanisms underlying the potential effector and regulatory roles of mast cells in the biology and pathology of those disease settings in which mast cells are activated.
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17
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Reber LL, Frossard N. Targeting mast cells in inflammatory diseases. Pharmacol Ther 2014; 142:416-35. [PMID: 24486828 DOI: 10.1016/j.pharmthera.2014.01.004] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 01/24/2014] [Indexed: 12/24/2022]
Abstract
Although mast cells have long been known to play a critical role in anaphylaxis and other allergic diseases, they also participate in some innate immune responses and may even have some protective functions. Data from the study of mast cell-deficient mice have facilitated our understanding of some of the molecular mechanisms driving mast cell functions during both innate and adaptive immune responses. This review presents an overview of the biology of mast cells and their potential involvement in various inflammatory diseases. We then discuss some of the current pharmacological approaches used to target mast cells and their products in several diseases associated with mast cell activation.
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Affiliation(s)
- Laurent L Reber
- Department of Pathology, Stanford University School of Medicine, Stanford, CA, USA.
| | - Nelly Frossard
- Laboratoire d'Innovation Thérapeutique, UMR 7200 CNRS-Université de Strasbourg, Faculté de Pharmacie, France
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18
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Park JW, Jeon YJ, Lee JC, Ahn SR, Ha SW, Bang SY, Park EK, Yi SA, Lee MG, Han JW. Destabilization of TNF-α mRNA by Rapamycin. Biomol Ther (Seoul) 2013; 20:43-9. [PMID: 24116273 PMCID: PMC3792200 DOI: 10.4062/biomolther.2012.20.1.043] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2011] [Revised: 12/22/2011] [Accepted: 12/27/2011] [Indexed: 11/24/2022] Open
Abstract
Stimulation of mast cells through the high affinity IgE receptor (FcεRI) induces degranulation, lipid mediator release, and cytokine secretion leading to allergic reactions. Although various signaling pathways have been characterized to be involved in the FcεRI-mediated responses, little is known about the precious mechanism for the expression of tumor necrosis factor-α (TNF-α) in mast cells. Here, we report that rapamycin, a specific inhibitor of mammalian target of rapamycin (mTOR), reduces the expression of TNF-α in rat basophilic leukemia (RBL-2H3) cells. IgE or specific antigen stimulation of RBL-2H3 cells increases the expression of TNF-α and activates various signaling molecules including S6K1, Akt and p38 MAPK. Rapamycin specifically inhibits antigen-induced TNF-α mRNA level, while other kinase inhibitors have no effect on TNF-α mRNA level. These data indicate that mTOR signaling pathway is the main regulation mechanism for antigen-induced TNF-α expression. TNF-α mRNA stability analysis using reporter construct containing TNF-α adenylate/uridylate-rich elements (AREs) shows that rapamycin destabilizes TNF-α mRNA via regulating the AU-rich element of TNF-α mRNA. The antigen-induced activation of S6K1 is inhibited by specific kinase inhibitors including mTOR, PI3K, PKC and Ca2+chelator inhibitor, while TNF-α mRNA level is reduced only by rapamycin treatment. These data suggest that the effects of rapamycin on the expression of TNF-α mRNA are not mediated by S6K1 but regulated by mTOR. Taken together, our results reveal that mTOR signaling pathway is a novel regulation mechanism for antigen-induced TNF-α expression in RBL-2H3 cells.
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Affiliation(s)
- Jong-Woo Park
- Research Center for Epigenome Regulation, School of Pharmacy, Sungkyunkwan University, Suwon 440-746, Republic of Korea
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19
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Block H, Zarbock A. The role of the tec kinase Bruton's tyrosine kinase (Btk) in leukocyte recruitment. Int Rev Immunol 2012; 31:104-18. [PMID: 22449072 DOI: 10.3109/08830185.2012.668982] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Recruitment of leukocytes into inflamed tissue is a key component of the immune system. The activation of integrins on leukocytes is required for their recruitment into the inflamed tissue. Btk is a cytoplasmic nonreceptor tyrosine kinase belonging to the Tec-kinase family. It plays a key role in B-cell development and function, and recently published studies revealed important roles of Btk in myeloid cells. Btk might be activated through a variety of receptors leading to activation of integrins as the pivotal element in leukocyte recruitment. This review focuses on the role of Btk in B-lymphocyte homing and in neutrophil recruitment.
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Affiliation(s)
- Helena Block
- Department of Anesthesiology and Critical Care Medicine, University of Muenster, Muenster, Germany
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21
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Hendriks RW, Bredius RG, Pike-Overzet K, Staal FJ. Biology and novel treatment options for XLA, the most common monogenetic immunodeficiency in man. Expert Opin Ther Targets 2011; 15:1003-21. [PMID: 21635151 DOI: 10.1517/14728222.2011.585971] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
INTRODUCTION X-linked agammaglobulinemia (XLA) is the most common primary immunodeficiency in man, and is caused by a single genetic defect. Inactivating mutations in the Bruton's tyrosine kinase (BTK) gene are invariably the cause of XLA,. XLA is characterized by a differentiation arrest at the pre-B cell stage, the absence of immunoglobulins and recurrent bacterial infections, making it an insidious disease that gradually disables the patient, and can result in death due to chronic lung disease. Current treatment involves prophylactic antibiotics and immunoglobulin infusions, which are non-curative. This disease is a good candidate for curative hematopoietic stem cell (HSC)-based gene therapy, which could correct the B cell and myeloid deficiencies. AREAS COVERED This paper reviews the basic biology of BTK in B cell development, the clinical features of XLA, and the possibilities of gene therapy for XLA, covering the literature from 1995 to 2010. EXPERT OPINION Work from various laboratories demonstrates the feasibility of using gene-corrected HSCs to complement the immune defects of Btk-deficiency in mice. We propose that it is timely to start clinical programs to develop stem cell based therapy for XLA, using gene-corrected autologous HSC.
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Affiliation(s)
- Rudi W Hendriks
- Department of Pulmonary Medicine, Erasmus MC, Rotterdam, The Netherlands
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22
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Ellmeier W, Abramova A, Schebesta A. Tec family kinases: regulation of FcεRI-mediated mast-cell activation. FEBS J 2011; 278:1990-2000. [PMID: 21362140 DOI: 10.1111/j.1742-4658.2011.08073.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Mast cells express the high-affinity receptor for IgE (FcεRI) and are key players in type I hypersensitivity reactions. They are critically involved in the development of allergic rhinitis, allergic asthma and systemic anaphylaxis, however, they also regulate normal physiological processes that link innate and adaptive immune responses. Thus, their activation has to be tightly controlled. One group of signaling molecules that are activated upon FcεRI stimulation is formed by Tec family kinases, and three members of this kinase family (Btk, Itk and Tec) are expressed in mast cells. Many studies have revealed important functions of Tec kinases in signaling pathways downstream of the antigen receptors in lymphocytes. This review summarizes the current knowledge about the function of Tec family kinases in FcεRI-mediated signaling pathways in mast cell.
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Affiliation(s)
- Wilfried Ellmeier
- Division of Immunobiology, Institute of Immunology, Center for Pathophysiology, Infectiology and Immunology, Medical University of Vienna, Austria.
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23
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Schmidt U, Abramova A, Boucheron N, Eckelhart E, Schebesta A, Bilic I, Kneidinger M, Unger B, Hammer M, Sibilia M, Valent P, Ellmeier W. The protein tyrosine kinase Tec regulates mast cell function. Eur J Immunol 2010; 39:3228-38. [PMID: 19688741 DOI: 10.1002/eji.200838839] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Mast cells play crucial roles in a variety of normal and pathophysiological processes and their activation has to be tightly controlled. Here, we demonstrate that the protein tyrosine kinase Tec is a crucial regulator of murine mast cell function. Tec was activated upon Fc epsilon RI stimulation of BM-derived mast cells (BMMC). The release of histamine in the absence of Tec was normal in vitro and in vivo; however, leukotriene C(4) levels were reduced in Tec(-) (/) (-) BMMC. Furthermore, the production of IL-4 was severely impaired, and GM-CSF, TNF-alpha and IL-13 levels were also diminished. Finally, a comparison of WT, Tec(-) (/) (-), Btk(-) (/) (-) and Tec(-) (/) (-)Btk(-) (/) (-) BMMC revealed a negative role for Btk in the regulation of IL-4 production, while for the efficient production of TNF-alpha, IL-13 and GM-CSF, both Tec and Btk were required. Our results demonstrate a crucial role for Tec in mast cells, which is partially different to the function of the well-characterized family member Btk.
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Affiliation(s)
- Uwe Schmidt
- Division of Immunobiology, Institute of Immunology, Center for Physiology, Pathophysiology and Immunology, Medical University of Vienna, Austria
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Akimoto M, Mishra K, Lim KT, Tani N, Hisanaga SI, Katagiri T, Elson A, Mizuno K, Yakura H. Protein Tyrosine Phosphatase ε is a Negative Regulator of FcεRI-mediated Mast Cell Responses. Scand J Immunol 2009; 69:401-11. [DOI: 10.1111/j.1365-3083.2009.02235.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Abstract
Mast cell mediator release represents a pivotal event in the initiation of inflammatory reactions associated with allergic disorders. These responses follow antigen-mediated aggregation of immunoglobulin E (IgE)-occupied high-affinity receptors for IgE (Fc epsilon RI) on the mast cell surface, a response which can be further enhanced following stem cell factor-induced ligation of the mast cell growth factor receptor KIT (CD117). Activation of tyrosine kinases is central to the ability of both Fc epsilon RI and KIT to transmit downstream signaling events required for the regulation of mast cell activation. Whereas KIT possesses inherent tyrosine kinase activity, Fc epsilon RI requires the recruitment of Src family tyrosine kinases and Syk to control the early receptor-proximal signaling events. The signaling pathways propagated by these tyrosine kinases can be further upregulated by the Tec kinase Bruton's tyrosine kinase and downregulated by the actions of the tyrosine Src homology 2 domain-containing phosphatase 1 (SHP-1) and SHP-2. In this review, we discuss the regulation and role of specific members of this tyrosine kinase network in KIT and Fc epsilon RI-mediated mast cell activation.
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Affiliation(s)
- Alasdair M Gilfillan
- Laboratory of Allergic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-1930, USA
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26
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Conley ME, Dobbs AK, Farmer DM, Kilic S, Paris K, Grigoriadou S, Coustan-Smith E, Howard V, Campana D. Primary B cell immunodeficiencies: comparisons and contrasts. Annu Rev Immunol 2009; 27:199-227. [PMID: 19302039 DOI: 10.1146/annurev.immunol.021908.132649] [Citation(s) in RCA: 281] [Impact Index Per Article: 18.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Sophisticated genetic tools have made possible the identification of the genes responsible for most well-described immunodeficiencies in the past 15 years. Mutations in Btk, components of the pre-B cell and B cell receptor (lambda5, Igalpha, Igbeta), or the scaffold protein BLNK account for approximately 90% of patients with defects in early B cell development. Hyper-IgM syndromes result from mutations in CD40 ligand, CD40, AID, or UNG in 70-80% of affected patients. Rare defects in ICOS or CD19 can result in a clinical picture that is consistent with common variable immunodeficiency, and as many as 10% of patients with this disorder have heterozygous amino acid substitutions in TACI. For all these disorders, there is considerable clinical heterogeneity in patients with the same mutation. Identifying the genetic and environmental factors that influence the clinical phenotype may enhance patient care and our understanding of normal B cell development.
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Affiliation(s)
- Mary Ellen Conley
- Department of Pediatrics, University of Tennessee College of Medicine, Memphis, Tennessee 38163, USA.
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Iyer AS, August A. The Tec family kinase, IL-2-inducible T cell kinase, differentially controls mast cell responses. THE JOURNAL OF IMMUNOLOGY 2008; 180:7869-77. [PMID: 18523250 DOI: 10.4049/jimmunol.180.12.7869] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The Tec family tyrosine kinase, IL-2-inducible T cell kinase (Itk), is expressed in T cells and mast cells. Mice lacking Itk exhibit impaired Th2 cytokine secretion; however, they have increased circulating serum IgE, but exhibit few immunological symptoms of allergic airway responses. We have examined the role of Itk in mast cell function and FcepsilonRI signaling. We report in this study that Itk null mice have reduced allergen/IgE-induced histamine release, as well as early airway hyperresponsiveness in vivo. This is due to the increased levels of IgE in the serum of these mice, because the transfer of Itk null bone marrow-derived cultured mast cells into mast cell-deficient W/W(v) animals is able to fully rescue histamine release in the W/W(v) mice. Further analysis of Itk null bone marrow-derived cultured mast cells in vitro revealed that whereas they have normal degranulation responses, they secrete elevated levels of cytokines, including IL-13 and TNF-alpha, particularly in response to unliganded IgE. Analysis of biochemical events downstream of the FcepsilonRI revealed little difference in overall tyrosine phosphorylation of specific substrates or calcium responses; however, these cells express elevated levels of NFAT, which was largely nuclear. Our results suggest that the reduced mast cell response in vivo in Itk null mice is due to elevated levels of IgE in these mice. Our results also suggest that Itk differentially modulates mast cell degranulation and cytokine production in part by regulating expression and activation of NFAT proteins in these cells.
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Affiliation(s)
- Archana S Iyer
- Center for Molecular Immunology & Infectious Disease and Department of Veterinary & Biomedical Sciences, Pennsylvania State University, University Park, PA 16802, USA
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28
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The effects of dasatinib on IgE receptor-dependent activation and histamine release in human basophils. Blood 2008; 111:3097-107. [PMID: 18180381 DOI: 10.1182/blood-2007-08-104372] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Dasatinib is a multitargeted drug that blocks several tyrosine kinases. Apart from its well-known antileukemic activity, the drug has attracted attention because of potential immunosuppressive and anti-inflammatory effects. We report that dasatinib at 1 microM completely blocks anti-IgE-induced histamine release in blood basophils in healthy donors, and allergen-induced release of histamine in sensitized individuals. In addition, dasatinib inhibited FcepsilonRI-mediated release of IL-4 and IgE-mediated up-regulation of CD13, CD63, CD164, and CD203c in basophils. The effects of dasatinib were dose-dependent (IC(50): 50-500 nM) and specific for FcepsilonRI activation in that the drug failed to inhibit C5a-induced or Ca-ionophore-induced histamine release. Interestingly, at lower concentrations, dasatinib even promoted FcepsilonRI-dependent histamine release in basophils in allergic subjects. In consecutive studies, dasatinib was found to interact with and block several FcepsilonRI downstream targets in basophils, including Btk. Correspondingly, FcepsilonRI-mediated histamine secretion in basophils was markedly reduced in Btk knockout mice and in a patient with Btk deficiency. However, the remaining "low-level" mediator secretion in Btk-deficient cells was fully blocked down again by 1 muM dasatinib. Together, these data suggest that dasatinib inhibits FcepsilonRI-mediated activation of basophils through multiple signaling molecules including Btk. Dasatinib may be an interesting agent for immunologic disorders involving Btk-dependent responses or/and FcepsilonRI activation of basophils.
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Abstract
The type I Fc epsilon receptor (Fc epsilon RI) is one of the better understood members of its class and is central to the immunological activation of mast cells and basophils, the key players in immunoglobulin E (IgE)-dependent immediate hypersensitivity. This review provides background information on several distinct regulatory mechanisms controlling this receptor's stimulus-response coupling network. First, we review the current understanding of this network's operation, and then we focus on the inhibitory regulatory mechanisms. In particular, we discuss the different known cytosolic molecules (e.g. kinases, phosphatases, and adapters) as well as cell membrane proteins involved in negatively regulating the Fc epsilon RI-induced secretory responses. Knowledge of this field is developing at a fast rate, as new proteins endowed with regulatory functions are still being discovered. Our understanding of the complex networks by which these proteins exert regulation is limited. Although the scope of this review does not include addressing several important biochemical and biophysical aspects of the regulatory mechanisms, it does provide general insights into a central field in immunology.
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Affiliation(s)
- Jakub Abramson
- Department of Immunology, The Weizmann Institute of Science, Rehovot, Israel
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30
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Abstract
Mast cells are effector cells of the innate immune system, but because they express Fc receptors (FcRs), they can be engaged in adaptive immunity by antibodies. Mast cell FcRs include immunoglobulin E (IgE) and IgG receptors and, among these, activating and inhibitory receptors. The engagement of mast cell IgG receptors by immune complexes may or may not trigger cell activation, depending on the type of mast cell. The coengagement of IgG and IgE receptors results in inhibition of mast cell activation. The Src homology-2 domain-containing inositol 5-phosphatase-1 is a major effector of negative regulation. Biological responses of mast cells depend on the balance between positive and negative signals that are generated in FcR complexes. The contribution of human mast cell IgG receptors in allergies remains to be clarified. Increasing evidence indicates that mast cells play critical roles in IgG-dependent tissue-specific autoimmune diseases. Convincing evidence was obtained in murine models of multiple sclerosis, rheumatoid arthritis, bullous pemphigoid, and glomerulonephritis. In these models, the intensity of lesions depended on the relative engagement of activating and inhibitory IgG receptors. In vitro models of mature tissue-specific murine mast cells are needed to investigate the roles of mast cells in these diseases. One such model unraveled unique differentiation/maturation-dependent biological responses of serosal-type mast cells.
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Affiliation(s)
- Odile Malbec
- Unité d'Allergologie Moléculaire et Cellulaire, Département d'Immunologie, Institut Pasteur, Paris, France
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31
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Yaghini FA, Li F, Malik KU. Expression and mechanism of spleen tyrosine kinase activation by angiotensin II and its implication in protein synthesis in rat vascular smooth muscle cells. J Biol Chem 2007; 282:16878-90. [PMID: 17442668 DOI: 10.1074/jbc.m610494200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Syk, a 72-kDa tyrosine kinase, is involved in development, differentiation, and signal transduction of hematopoietic and some non-hematopoietic cells. This study determined if Syk is expressed in vascular smooth muscle cells (VSMC) and contributes to angiotensin II (Ang II) signaling and protein synthesis. Syk was found in VSMC and was phosphorylated by Ang II through AT1 receptor. Ang II-induced Syk phosphorylation was inhibited by piceatannol and dominant negative but not wild type Syk mutant. Syk phosphorylation by Ang II was attenuated by cytosolic phospholipase A(2) (cPLA(2)) inhibitor pyrrolidine-1 and retrovirus carrying small interfering RNAs (shRNAs) of this enzyme. Arachidonic acid (AA) increased Syk phosphorylation, and AA- and Ang II-induced phosphorylation was diminished by inhibitors of AA metabolism (5,8,11,14-eicosatetraynoic acid) and lipoxygenase (LO; baicalein) but not cyclooxygenase (indomethacin). AA metabolites formed via LO, 5(S)-, 12(S)-, and 15(S)-hydroxyeicosatetraenoic acids, which activate p38 MAPK, increased Syk phosphorylation. p38 MAPK inhibitor SB202190, and dominant negative p38 MAPK mutant attenuated Ang II- and AA-induced Syk phosphorylation. Adenovirus dominant negative c-Src mutant abolished Ang II - and AA-induced Syk phosphorylation and SB202190, and dominant negative p38 MAPK mutant inhibited Ang II-induced c-Src phosphorylation. Syk dominant negative mutant but not epidermal growth factor receptor blocker AG1478 also inhibited Ang II-induced VSMC protein synthesis. These data suggest that Syk expressed in VSMC is activated by Ang II through p38 MAPK-activated c-Src subsequent to cytosolic phospholipase A(2) and generation of AA metabolites via LO, and it mediates Ang II-induced protein synthesis independent of epidermal growth factor receptor transactivation (Ang II --> cPLA(2) --> AA metabolites of LO --> p38 MAPK --> c-Src --> Syk --> protein synthesis).
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Affiliation(s)
- Fariborz A Yaghini
- Department of Pharmacology and Centers of Vascular Biology and Connective Tissue Diseases, College of Medicine, University of Tennessee Health Science Center, Memphis, Tennessee 38163, USA
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32
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Abstract
The Tec family of tyrosine kinases consists of five members (Itk, Rlk, Tec, Btk, and Bmx) that are expressed predominantly in hematopoietic cells. The exceptions, Tec and Bmx, are also found in endothelial cells. Tec kinases constitute the second largest family of cytoplasmic protein tyrosine kinases. While B cells express Btk and Tec, and T cells express Itk, Rlk, and Tec, all four of these kinases (Btk, Itk, Rlk, and Tec) can be detected in mast cells. This chapter will focus on the biochemical and cell biological data that have been accumulated regarding Itk, Rlk, Btk, and Tec. In particular, distinctions between the different Tec kinase family members will be highlighted, with a goal of providing insight into the unique functions of each kinase. The known functions of Tec kinases in T cell and mast cell signaling will then be described, with a particular focus on T cell receptor and mast cell Fc epsilon RI signaling pathways.
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Affiliation(s)
- Martin Felices
- Department of Pathology, University of Massachusetts Medical School, Massachusetts, USA
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33
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Iwaki S, Tkaczyk C, Satterthwaite AB, Halcomb K, Beaven MA, Metcalfe DD, Gilfillan AM. Btk plays a crucial role in the amplification of Fc epsilonRI-mediated mast cell activation by kit. J Biol Chem 2005; 280:40261-70. [PMID: 16176929 DOI: 10.1074/jbc.m506063200] [Citation(s) in RCA: 84] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Stem cell factor (SCF) acts in synergy with antigen to enhance the calcium signal, degranulation, activation of transcription factors, and cytokine production in human mast cells. However, the underlying mechanisms for this synergy remain unclear. Here we show, utilizing bone marrow-derived mast cells (BMMCs) from Btk and Lyn knock-out mice, that activation of Btk via Lyn plays a key role in promoting synergy. As in human mast cells, SCF enhanced degranulation and cytokine production in BMMCs. In Btk-/- BMMCs, in which there was a partial reduction in the capacity to degranulate in response to antigen, SCF was unable to enhance the residual antigen-mediated degranulation. Furthermore, as with antigen, the ability of SCF to promote cytokine production was abrogated in the Btk-/- BMMCs. The impairment of responses in Btk-/- cells correlated with an inability of SCF to augment phospholipase Cgamma1 activation and calcium mobilization, and to phosphorylate NFkappaB and NFAT for cytokine gene transcription in these cells. Similar studies with Lyn-/- and Btk-/-/Lyn-/- BMMCs indicated that Lyn was a regulator of Btk for these responses. These data demonstrate, for the first time, that Btk is a key regulator of a Kit-mediated amplification pathway that augments Fc epsilonRI-mediated mast cell activation.
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Affiliation(s)
- Shoko Iwaki
- Laboratory of Allergic Diseases, NIAID, National Institutes of Health, Bethesda, Maryland 20892-1881, USA
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34
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Abstract
The proliferation and differentiation of lymphocytes are regulated by receptors localized on the cell surface. Engagement of these receptors induces the activation of intracellular signaling proteins that transmit the receptor signals to distinct targets and control the cellular responses. The first signaling proteins to be discovered in higher organisms were the products of oncogenes. For example, the kinases Src and Abelson (Abl) were originally identified as oncogenes and were later characterized as important proteins for signal transduction in various cell types, including lymphocytes. Now, as many cellular signaling molecules have been discovered and ordered into certain pathways, we can better understand why particular signaling proteins are associated with tumorigenesis. In this review, we discuss recent progress in unraveling the molecular mechanisms of signaling pathways that control the proliferation and differentiation of early B cells. We point out the concepts of auto-inhibition and subcellular localization as crucial aspects in the regulation of B cell signaling.
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Affiliation(s)
- Hassan Jumaa
- Institute for Biology III, Albert-Ludwigs University of Freiburg and Max Planck Institute for Immunobiology, 79108 Freiburg, Germany.
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35
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Conley ME, Broides A, Hernandez-Trujillo V, Howard V, Kanegane H, Miyawaki T, Shurtleff SA. Genetic analysis of patients with defects in early B-cell development. Immunol Rev 2005; 203:216-34. [PMID: 15661032 DOI: 10.1111/j.0105-2896.2005.00233.x] [Citation(s) in RCA: 125] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
Approximately 85% of patients with defects in early B-cell development have X-linked agammaglobulinemia (XLA), a disorder caused by mutations in the cytoplasmic Bruton's tyrosine kinase (Btk). Although Btk is activated by cross-linking of a variety of cell-surface receptors, the most critical signal transduction pathway is the one initiated by the pre-B cell and B-cell antigen receptor complex. Mutations in Btk are highly diverse, and no single mutation accounts for more than 3% of patients. Although there is no strong genotype/phenotype correlation in XLA, the specific mutation in Btk is one of the factors that influences the severity of disease. Mutations in the components of the pre-B cell and B-cell antigen receptor complex account for an additional 5-7% of patients with defects in early B-cell development. Patients with defects in these proteins are clinically indistinguishable from those with XLA. However, they tend to be younger at the time of diagnosis, and whereas most patients with XLA have a small number of B cells in the peripheral circulation, these cells are not found in patients with defects in micro heavy chain or Igalpha. Polymorphic variants in the components of the pre-B cell and B-cell receptor complex, particularly micro heavy chain and lambda5, may contribute to the severity of XLA.
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Affiliation(s)
- Mary Ellen Conley
- Department of Pediatrics, University of Tennessee College of Medicine, Memphis, TN 38105, USA.
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36
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Kitaura J, Eto K, Kinoshita T, Kawakami Y, Leitges M, Lowell CA, Kawakami T. Regulation of highly cytokinergic IgE-induced mast cell adhesion by Src, Syk, Tec, and protein kinase C family kinases. THE JOURNAL OF IMMUNOLOGY 2005; 174:4495-504. [PMID: 15814670 DOI: 10.4049/jimmunol.174.8.4495] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Mast cells play a critical role in IgE-dependent immediate hypersensitivity. Recent studies have shown that, contrary to the traditional view, binding of monomeric IgE to Fc epsilon RI results in a number of biological outcomes in mast cells, including survival. However, IgE molecules display heterogeneity in inducing cytokine production; highly cytokinergic (HC) IgEs cause extensive Fc epsilon RI aggregation, which leads to potent enhancement of survival and other activation events, whereas poorly cytokinergic (PC) IgEs can do so inefficiently. The present study demonstrates that HC, but not PC, IgEs can efficiently induce adhesion and spreading of mouse mast cells on fibronectin-coated plates in slow and sustained kinetics. HC IgE-induced adhesion through beta1 and beta7 integrins promotes survival, IL-6 production, and DNA synthesis. Importantly, we have identified Lyn and Syk as requisite tyrosine kinases and Hck, Btk, and protein kinase C theta as contributory kinases in HC IgE-induced adhesion and spreading, whereas protein kinase C epsilon plays a negative role. Consistent with these results, Lyn, Syk, and Btk are activated in HC IgE-stimulated cells in a slower but more sustained manner, compared with cells stimulated with IgE and Ag. Thus, binding of HC IgEs to Fc epsilon RI induces adhesion of mast cells to fibronectin by modulating cellular activation signals in a unique fashion.
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Affiliation(s)
- Jiro Kitaura
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA
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37
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Lesourne R, Fridman WH, Daëron M. Dynamic interactions of Fc gamma receptor IIB with filamin-bound SHIP1 amplify filamentous actin-dependent negative regulation of Fc epsilon receptor I signaling. THE JOURNAL OF IMMUNOLOGY 2005; 174:1365-73. [PMID: 15661894 DOI: 10.4049/jimmunol.174.3.1365] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The engagement of high affinity receptors for IgE (FcepsilonRI) generates both positive and negative signals whose integration determines the intensity of mast cell responses. FcepsilonRI-positive signals are also negatively regulated by low affinity receptors for IgG (FcgammaRIIB). Although the constitutive negative regulation of FcepsilonRI signaling was shown to depend on the submembranous F-actin skeleton, the role of this compartment in FcgammaRIIB-dependent inhibition is unknown. We show in this study that the F-actin skeleton is essential for FcgammaRIIB-dependent negative regulation. It contains SHIP1, the phosphatase responsible for inhibition, which is constitutively associated with the actin-binding protein, filamin-1. After coaggregation, FcgammaRIIB and FcepsilonRI rapidly interact with the F-actin skeleton and engage SHIP1 and filamin-1. Later, filamin-1 and F-actin dissociate from FcR complexes, whereas SHIP1 remains associated with FcgammaRIIB. Based on these results, we propose a dynamic model in which the submembranous F-actin skeleton forms an inhibitory compartment where filamin-1 functions as a donor of SHIP1 for FcgammaRIIB, which concentrate this phosphatase in the vicinity of FcepsilonRI and thereby extinguish activation signals.
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MESH Headings
- Actins/antagonists & inhibitors
- Actins/metabolism
- Actins/physiology
- Animals
- Antigens, CD/metabolism
- Antigens, CD/physiology
- Bridged Bicyclo Compounds, Heterocyclic/pharmacology
- Cell Line, Tumor
- Contractile Proteins/metabolism
- Down-Regulation/immunology
- Filamins
- Immunoglobulin E/physiology
- Inositol Polyphosphate 5-Phosphatases
- Mast Cells/drug effects
- Mast Cells/enzymology
- Mast Cells/metabolism
- Membrane Microdomains/metabolism
- Mice
- Microfilament Proteins/metabolism
- Molecular Weight
- Phosphatidylinositol-3,4,5-Trisphosphate 5-Phosphatases
- Phosphoric Monoester Hydrolases/metabolism
- Phosphoric Monoester Hydrolases/physiology
- Protein Binding/immunology
- Protein Isoforms/metabolism
- Rats
- Receptor Aggregation/immunology
- Receptors, IgE/antagonists & inhibitors
- Receptors, IgE/metabolism
- Receptors, IgE/physiology
- Receptors, IgG/antagonists & inhibitors
- Receptors, IgG/metabolism
- Receptors, IgG/physiology
- Resting Phase, Cell Cycle/immunology
- Signal Transduction/immunology
- Thiazoles/pharmacology
- Thiazolidines
- Time Factors
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Affiliation(s)
- Renaud Lesourne
- Laboratoire d'Immunologie Cellulaire et Clinique, Institut National de la Santé et de la Recherche Médicale, Unité 255, Institut Biomédical des Cordeliers, Paris, France
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38
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Kawakami Y, Nishimoto H, Kitaura J, Maeda-Yamamoto M, Kato RM, Littman DR, Leitges M, Rawlings DJ, Kawakami T. Protein kinase C betaII regulates Akt phosphorylation on Ser-473 in a cell type- and stimulus-specific fashion. J Biol Chem 2004; 279:47720-5. [PMID: 15364915 DOI: 10.1074/jbc.m408797200] [Citation(s) in RCA: 134] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Akt (= protein kinase B), a subfamily of the AGC serine/threonine kinases, plays critical roles in survival, proliferation, glucose metabolism, and other cellular functions. Akt activation requires the recruitment of the enzyme to the plasma membrane by interacting with membrane-bound lipid products of phosphatidylinositol 3-kinase. Membrane-bound Akt is then phosphorylated at two sites for its full activation; Thr-308 in the activation loop of the kinase domain is phosphorylated by 3-phosphoinositide-dependent kinase-1 (PDK1) and Ser-473 in the C-terminal hydrophobic motif by a putative kinase PDK2. The identity of PDK2 has been elusive. Here we present evidence that conventional isoforms of protein kinase C (PKC), particularly PKCbetaII, can regulate Akt activity by directly phosphorylating Ser-473 in vitro and in IgE/antigen-stimulated mast cells. By contrast, PKCbeta is not required for Ser-473 phosphorylation in mast cells stimulated with stem cell factor or interleukin-3, in serum-stimulated fibroblasts, or in antigen receptor-stimulated T or B lymphocytes. Therefore, PKCbetaII appears to work as a cell type- and stimulus-specific PDK2.
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Affiliation(s)
- Yuko Kawakami
- Division of Cell Biology, La Jolla Institute for Allergy and Immunology, San Diego, California 92121, USA
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39
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Maeda-Yamamoto M, Inagaki N, Kitaura J, Chikumoto T, Kawahara H, Kawakami Y, Sano M, Miyase T, Tachibana H, Nagai H, Kawakami T. O-Methylated Catechins from Tea Leaves Inhibit Multiple Protein Kinases in Mast Cells. THE JOURNAL OF IMMUNOLOGY 2004; 172:4486-92. [PMID: 15034065 DOI: 10.4049/jimmunol.172.7.4486] [Citation(s) in RCA: 96] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Tea contains a variety of bioactive compounds. In this study, we show that two O-methylated catechins, (-)-epigallocatechin-3-O-(3-O-methyl) gallate and (-)-epigallocatechin-3-O-(4-O-methyl) gallate, inhibit in vivo mast cell-dependent allergic reactions more potently than their nonmethylated form, (-)-epigallocatechin-3-O-gallate. Consistent with this, these O-methylated catechins inhibit IgE/Ag-induced activation of mouse mast cells: histamine release, leukotriene release, and cytokine production and secretion were all inhibited. As a molecular basis for the catechin-mediated inhibition of mast cell activation, Lyn, Syk, and Bruton's tyrosine kinase, the protein tyrosine kinases, known to be critical for early activation events, are shown to be inhibited by the O-methylated catechins. In vitro kinase assays using purified proteins show that the O-methylated catechins can directly inhibit the above protein tyrosine kinases. These catechins inhibit IgE/Ag-induced calcium response as well as the activation of downstream serine/threonine kinases such as Akt and c-Jun N-terminal kinase. These observations for the first time have revealed the molecular mechanisms of antiallergic effects of tea-derived catechins.
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Affiliation(s)
- Mari Maeda-Yamamoto
- National Institute of Vegetable and Tea Science, National Agriculture Research Organization, and School of Pharmaceutical Sciences, University of Shizuoka, Shizuoka, Japan
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40
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Lucas JA, Miller AT, Atherly LO, Berg LJ. The role of Tec family kinases in T cell development and function. Immunol Rev 2003; 191:119-38. [PMID: 12614356 DOI: 10.1034/j.1600-065x.2003.00029.x] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Three members of the Tec family kinases, Itk, Rlk and Tec, have been implicated in signaling downstream of the T cell receptor (TCR). The activity of these kinases in T cells has been shown to be important for the full activation of phospholipase C-gamma1 (PLC-gamma1). Disruption of Tec family signaling in Itk-/- and Rlk-/-Itk-/- mice has multiple effects on T cell development, cytokine production and T-helper cell differentiation. Furthermore, mice possessing mutations in signaling molecules upstream of PLC-gamma1, such as Src homology 2 (SH2) domain-containing phosphoprotein of 76 kDa (SLP-76), linker for activation of T cells (LAT) and Vav1, or in members of the nuclear factor for activated T cells (NFAT) family of transcription factors, which are downstream of PLC-gamma1, have been found to have similar phenotypes to Tec family-deficient mice, emphasizing the importance of this pathway in regulating T cell activation, differentiation and homeostasis.
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Affiliation(s)
- Julie A Lucas
- University of Massachussets Medical School Department of Pathology, Worcester, MA 01655, USA
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41
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Abstract
AbstractHematological complications occur frequently in patients with both primary and secondary immunodeficiency disorders. Anemia, thrombocytopenia or leukopenias may bring these individuals to the attention of hematologists. Conversely, evidence suggesting a lymphoproliferative disorder may be the cause for referral. This session will provide an update on the diagnosis and treatment of immunodeficiency diseases ranging from isolated defects in antibody production to the severe combined immunodeficiencies (SCID).Immunodeficiency diseases have traditionally been defined as defects in the development and function of T and B cells, the primary effector cells of specific cellular and humoral immunity. However, it has become increasingly evident that innate immune mechanisms contribute greatly to host defense, either through acting alone or by enhancing specific T and B cell responses.In Section I, Dr. Lewis Lanier reviews the burgeoning information on the extensive families of activating and inhibitory immunoreceptors that are expressed on NK cells, dendritic cells, T and B cells, and phagocytic cells. He provides an overview on the biological functions of these receptors in host defense.In Section II, Dr. Mary Ellen Conley defines the spectrum of antibody deficiency disorders, the most frequently occurring types of primary immunodeficiencies. She covers the different defects in B-cell development and function that lead to antibody deficiencies, and includes diagnosis and therapy of these disorders.In Section III, Dr. Jennifer Puck discusses the diagnosis and treatment of the different types of SCID. She describes the genetic basis for SCID, and the benefits, pitfalls, and complications of gene therapy and bone marrow transplantation in SCID patients.
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42
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Kawakami T, Galli SJ. Regulation of mast-cell and basophil function and survival by IgE. Nat Rev Immunol 2002; 2:773-86. [PMID: 12360215 DOI: 10.1038/nri914] [Citation(s) in RCA: 434] [Impact Index Per Article: 19.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Mast cells and basophils are important effector cells in T helper 2 (T(H)2)-cell-dependent, immunoglobulin-E-associated allergic disorders and immune responses to parasites. The crosslinking of IgE that is bound to the high-affinity receptor Fc epsilon RI with multivalent antigen results in the aggregation of Fc epsilon RI and the secretion of products that can have effector, immunoregulatory or autocrine effects. This response can be enhanced markedly in cells that have been exposed to high levels of IgE, which results in the increased surface expression of Fc epsilon RI. Moreover, recent work indicates that monomeric IgE (in the absence of crosslinking) can render mast cells resistant to apoptosis induced by growth-factor deprivation in vitro and, under certain circumstances, can induce the release of cytokines. So, the binding of IgE to Fc epsilon RI might influence mast-cell and basophil survival directly or indirectly, and can also regulate cellular function.
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Affiliation(s)
- Toshiaki Kawakami
- Division of Allergy, La Jolla Institute for Allergy and Immunology, 10355 Science Center Drive, San Diego, California 92121, USA
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43
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Abstract
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 differences 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 PLCgamma1. 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.
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Affiliation(s)
- Shengli Hao
- Immunology Research Laboratories and Department of Veterinary Science, The Pennsylvania State University, 115 Henning Building, University Park, PA 16802, USA
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44
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Sharma BB, Apgar JR, Liu FT. Mast cells. Receptors, secretagogues, and signaling. Clin Rev Allergy Immunol 2002; 22:119-48. [PMID: 11975419 DOI: 10.1385/criai:22:2:119] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Bhavya B Sharma
- Division of Allergy, La Jolla Institute for Allergy and Immunology, San Diego, CA 92121, USA
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45
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Laederach A, Cradic KW, Brazin KN, Zamoon J, Fulton DB, Huang XY, Andreotti AH. Competing modes of self-association in the regulatory domains of Bruton's tyrosine kinase: intramolecular contact versus asymmetric homodimerization. Protein Sci 2002; 11:36-45. [PMID: 11742120 PMCID: PMC2368771 DOI: 10.1110/ps.26702] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2001] [Revised: 09/15/2001] [Accepted: 10/04/2001] [Indexed: 10/19/2022]
Abstract
A nuclear magnetic resonance (NMR) investigation of a fragment of the nonreceptor Tec family tyrosine kinase Btk has revealed an intricate set of coupled monomer-dimer equilibria. The Btk fragment studied contains two consecutive proline-rich motifs followed by a single Src homology 3 (SH3) domain. We provide evidence for an asymmetric homodimer in which the amino-terminal proline sequence of one monomer contacts the opposite SH3 binding pocket, whereas the carboxy-terminal proline sequence of the other monomer is engaged by the second SH3 domain across the dimer interface. We show that the asymmetric homodimer structure is mimicked by a heterodimer formed in an equimolar mixture of complimentary mutants: one carrying mutations in the amino-terminal proline stretch; the other, in the carboxy-terminal proline motif. Moreover, a monomeric species characterized by an intramolecular complex between the amino-terminal proline motif and the SH3 domain predominates at low concentration. Association constants were determined for each of the competing equilibria by NMR titration. The similarity of the determined K(a) values reveals a delicate balance between the alternative conformational states available to Btk. Thus, changes in the local concentration of Btk itself, or co-localization with exogenous signaling molecules that have high affinity for either proline sequence or the SH3 domain, can significantly alter species composition and regulate Btk kinase activity.
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Affiliation(s)
- Alain Laederach
- Department of Chemical Engineering, Iowa State University, Ames, Iowa 50010, USA
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Malaviya R, Vassilev A, Uckun FM. 2,4,6-Trihydroxy-alpha-p-methoxyphenylacetophenone (Compound D-58) is a potent inhibitor of allergic reactions. Am J Ther 2001; 8:417-24. [PMID: 11704780 DOI: 10.1097/00045391-200111000-00006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
The authors investigated the effects of 2,4,6-trihydroxy-alpha-p-methoxyphenylacetophenone (compound D-58), a potent inhibitor of protein tyrosine kinases SYK and Bruton's tyrosine kinase (BTK), on IgE receptor/FcepsilonRI-triggered mast cell-mediated acute allergic responses in vitro and in vivo. Compound D-58 abrogated IgE receptor/FcepsilonRI-mediated SYK and BTK activation as well as calcium mobilization in mast cells. Mast-cell degranulation and leukotriene (LT) C(4) release was inhibited by compound D-58 in a concentration-dependent fashion. Notably, compound D-58 prevented the mast cell mediator-induced vascular hyperpermeability in an in vivo murine model of passive cutaneous anaphylaxis as measured by the prevention of extravasation of systemically administered Evans blue dye. The results uniquely indicate that compound D-58 has potent antiallergic properties. Therefore, further development of compound D-58 may provide the basis for new and effective treatment programs for severe allergic disorders.
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Affiliation(s)
- R Malaviya
- Department of Allergy and Inflammatory Diseases, Parker Hughes Institute, 2665 Long Lake Road, St. Paul, MN 55113, USA.
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Mukhopadhyay S, Ramars AS, Ochs HD, Dash D. Bruton's tyrosine kinase is a substrate of calpain in human platelets. FEBS Lett 2001; 505:37-41. [PMID: 11557038 DOI: 10.1016/s0014-5793(01)02765-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Platelet-associated Bruton's tyrosine kinase (Btk) was completely cleaved if treated with calcium ionophore A23187 with appearance of a proteolytic product of 27 kDa size. Aggregation with thrombin also induced about 10% degradation of Btk after 30 min. Calpain inhibitors prevented Btk degradation in both. The proteolytic products of the Wiskott-Aldrich syndrome protein (WASP), a calpain and Btk substrate, and the 27 kDa degradation product of Btk did not redistribute to the Triton-insoluble cytoskeleton in thrombin-aggregated platelets, in contrast to the uncleaved proteins. The degradation of Btk and WASP was independent of their tyrosine phosphorylation status. These results indicate that Btk is an endogenous substrate for calpain, the cleavage of which may have functional consequences in long-term post-aggregation events in platelets.
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Affiliation(s)
- S Mukhopadhyay
- Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi, India
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Affiliation(s)
- S Tsukada
- Department of Molecular Medicine, Osaka University Medical School, Yamadaoka, Suita City, Osaka 565-0871, Japan
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49
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Egloff AM, Desiderio S. Identification of Phosphorylation Sites for Bruton's Tyrosine Kinase within the Transcriptional Regulator BAP/TFII-I. J Biol Chem 2001; 276:27806-15. [PMID: 11373296 DOI: 10.1074/jbc.m103692200] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Bruton's tyrosine kinase (Btk), a member of the Tec family of cytosolic kinases, is essential for B cell development and function. BAP/TFII-I, a protein implicated in transcriptional regulation, is associated with Btk in B cells and is transiently phosphorylated on tyrosine following B cell receptor engagement. BAP/TFII-I is a substrate for Btk in vitro and is hyperphosphorylated on tyrosine upon coexpression with Btk in mammalian cells. In an effort to understand the physiologic consequences of BAP/TFII-I tyrosine phosphorylation following B cell receptor stimulation, site-directed mutagenesis and phosphopeptide mapping were used to locate the predominant sites of BAP/TFII-I phosphorylation by Btk in vitro. These residues, Tyr248, Tyr357, and Tyr462, were also found to be the major sites for Btk-dependent phosphorylation of BAP/TFII-I in vivo. Residues Tyr357 and Tyr462 are contained within the loop regions of adjacent helix-loop-helix-like repeats within BAP/TFII-I. Mutation of either Tyr248, Tyr357, or Tyr462 to phenylalanine reduced transcription from a c-fos promoter relative to wild-type BAP/TFII-I in transfected COS-7 cells, consistent with the interpretation that phosphorylation at these sites contributes to transcriptional activation. Phosphorylation of BAP/TFII-I by Btk may link engagement of receptors such as surface immunoglobulin to modulation of gene expression.
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Affiliation(s)
- A M Egloff
- Department of Molecular Biology and Genetics and Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
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Mukhopadhyay S, Ramars AS, Dash D. Bruton's tyrosine kinase associates with the actin-based cytoskeleton in activated platelets. J Cell Biochem 2001; 81:659-65. [PMID: 11329620 DOI: 10.1002/jcb.1088] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Bruton's tyrosine kinase (Btk) plays a crucial role in the maturation and differentiation of B-lymphocytes and immunoglobulin synthesis. Recently Btk has been described to be present in significant amount in human platelets. To investigate the regulation of this kinase in the platelets we studied its subcellular redistribution in the resting and activated cells. In the resting platelets Btk was almost absent from the actin-based cytoskeleton. Upon challenge of the platelet thrombin receptor upto 30% of total Btk appeared in the cytoskeleton and the protein underwent phosphorylation on tyrosine. Translocation of Btk to the cytoskeleton but not aggregation was prevented by cytochalasin B, which inhibits actin polymerization. Wortmannin and genistein (inhibitors of phosphoinositide 3-kinase and protein tyrosine kinase, respectively) decreased while phenylarsine oxide (a tyrosine phosphatase inhibitor) increased the cytoskeletal content of Btk. The association of Btk with the cytoskeleton was regulated by integrin alpha(IIb)beta(3) and partly reversible. Taken together, these data suggest that Btk might be a component of a signaling complex containing specific cytoskeletal proteins in the activated platelets.
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Affiliation(s)
- S Mukhopadhyay
- Department of Biochemistry, Institute of Medical Sciences, Banaras Hindu University, Varanasi -221005, India
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