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Salmond RJ, Emery J, Okkenhaug K, Zamoyska R. MAPK, Phosphatidylinositol 3-Kinase, and Mammalian Target of Rapamycin Pathways Converge at the Level of Ribosomal Protein S6 Phosphorylation to Control Metabolic Signaling in CD8 T Cells. THE JOURNAL OF IMMUNOLOGY 2009; 183:7388-97. [DOI: 10.4049/jimmunol.0902294] [Citation(s) in RCA: 95] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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North CM, Crawford RB, Lu H, Kaminski NE. Simultaneous in vivo time course and dose response evaluation for TCDD-induced impairment of the LPS-stimulated primary IgM response. Toxicol Sci 2009; 112:123-32. [PMID: 19675145 PMCID: PMC2769062 DOI: 10.1093/toxsci/kfp187] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2009] [Accepted: 07/28/2009] [Indexed: 11/14/2022] Open
Abstract
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a potent suppressor of humoral immunity but the specific molecular mechanisms responsible for immunosuppression by TCDD are poorly understood. In vivo and in vitro studies of the primary humoral IgM response demonstrated that the B cell is a sensitive cell type to modulation by TCDD. We hypothesized that in vivo administration of TCDD disrupts expression of transcription factors controlling B cell to plasma cell differentiation. Female C57BL6 mice were treated with a single dose of TCDD (3, 10, or 30 microg/kg) and/or vehicle (sesame oil). On day 4 post-TCDD administration mice were sensitized with 25 microg lipopolysacchride (LPS) by intraperitioneal injection to stimulate an immune response. Splenocytes were isolated on subsequent days following LPS, up to 3 days post-LPS, and the expression of IgM, XBP-1, PAX5, BCL-6, and Blimp-1 was assessed. TCDD treatment dose-dependently suppressed LPS-induced IgM antibody-forming cell number, which was correlated with decreased frequency of CD19+ CD138+ cells. Gene expression analysis revealed that TCDD caused a dose-dependent suppression of Igmicro chain, Igkappa chain, IgJ chain, XBP-1, and Blimp-1. TCDD also dose-dependently suppressed LPS-stimulated increases in Blimp-1 protein expression in CD19+ B cells. The deregulation of Blimp-1 expression by TCDD provides a partial explanation for the concomitant suppression of the IgM response and confirms previous observations established in vitro.
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Affiliation(s)
- Colin M. North
- Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Robert B. Crawford
- Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Haitian Lu
- Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan 48824
| | - Norbert E. Kaminski
- Center for Integrative Toxicology, Michigan State University, East Lansing, Michigan 48824
- Department of Pharmacology & Toxicology, Michigan State University, East Lansing, Michigan 48824
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Oak JS, Chen J, Peralta RQ, Deane JA, Fruman DA. The p85β regulatory subunit of phosphoinositide 3-kinase has unique and redundant functions in B cells. Autoimmunity 2009; 42:447-58. [DOI: 10.1080/08916930902911746] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Shor B, Cavender D, Harris C. A kinase-dead knock-in mutation in mTOR leads to early embryonic lethality and is dispensable for the immune system in heterozygous mice. BMC Immunol 2009; 10:28. [PMID: 19457267 PMCID: PMC2698930 DOI: 10.1186/1471-2172-10-28] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2009] [Accepted: 05/20/2009] [Indexed: 01/21/2023] Open
Abstract
Background The mammalian target of rapamycin protein (mTOR) is an evolutionarily conserved kinase that regulates protein synthesis, cell cycle progression and proliferation in response to various environmental cues. As a critical downstream mediator of PI3K signaling, mTOR is important for lymphocyte development and function of mature T and B-cells. Most studies of mTOR in immune responses have relied on the use of pharmacological inhibitors, such as rapamycin. Rapamycin-FKBP12 complex exerts its immunosuppressive and anti-proliferative effect by binding outside the kinase domain of mTOR, and subsequently inhibiting downstream mTOR signaling. Results To determine the requirement for mTOR kinase activity in the immune system function, we generated knock-in mice carrying a mutation (D2338) in the catalytic domain of mTOR. While homozygous mTOR kd/kd embryos died before embryonic day 6.5, heterozygous mTOR+/kd mice appeared entirely normal and are fertile. mTOR +/kd mice exhibited normal T and B cell development and unaltered proliferative responses of splenocytes to IL-2 and TCR/CD28. In addition, heterozygousity for the mTOR kinase-dead allele did not sensitize T cells to rapamycin in a CD3-mediated proliferation assay. Unexpectedly, mTOR kinase activity towards its substrate 4E-BP1 was not decreased in hearts and livers from heterozygous animals. Conclusion Altogether, our findings indicate that mTOR kinase activity is indispensable for the early development of mouse embryos. Moreover, a single wild type mTOR allele is sufficient to maintain normal postnatal growth and lymphocyte development and proliferation.
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Affiliation(s)
- Boris Shor
- Inflammation Research Team, Drug Discovery, Johnson and Johnson Pharmaceutical Research and Development, LLC, Raritan, NJ, USA.
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Abstract
The potent immunosuppressive action of rapamycin is commonly ascribed to inhibition of growth factor-induced T cell proliferation. However, it is now evident that the serine/threonine protein kinase mammalian target of rapamycin (mTOR) has an important role in the modulation of both innate and adaptive immune responses. mTOR regulates diverse functions of professional antigen-presenting cells, such as dendritic cells (DCs), and has important roles in the activation of effector T cells and the function and proliferation of regulatory T cells. In this Review, we discuss our current understanding of the mTOR pathway and the consequences of mTOR inhibition, both in DCs and T cells, including new data on the regulation of forkhead box P3 expression.
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Abstract
The phosphoinositide 3-kinase (PI3K) family of lipid kinases regulates diverse aspects of lymphocyte behavior. This review discusses how genetic and pharmacological tools have yielded an increasingly detailed understanding of how PI3K enzymes function at different stages of lymphocyte development and activation. Following antigen receptor engagement, activated PI3K generates 3-phosphorylated inositol lipid products that serve as membrane targeting signals for numerous proteins involved in the assembly of multiprotein complexes, termed signalosomes, and immune synapse formation. In B cells, class IA PI3K is the dominant subgroup whose loss causes profound defects in development and antigen responsiveness. In T cells, both class IA and IB PI3K contribute to development and immune function. PI3K also regulates both chemokine responsiveness and antigen-driven changes in lymphocyte trafficking. PI3K modulates the function not only of effector T cells, but also regulatory T cells; these disparate functions culminate in unexpected autoimmune phenotypes in mice with PI3K-deficient T cells. Thus, PI3K signaling is not a simple switch to promote cellular activation, but rather an intricate web of interactions that must be properly balanced to ensure appropriate cellular responses and maintain immune homeostasis. Defining these complexities remains a challenge for pharmaceutical development of PI3K inhibitors to combat inflammation and autoimmunity.
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Affiliation(s)
- David A Fruman
- Department of Molecular Biology and Biochemistry, and Center for Immunology, University of California at Irvine, Irvine, CA, USA.
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Meyer-Bahlburg A, Bandaranayake AD, Andrews SF, Rawlings DJ. Reduced c-myc expression levels limit follicular mature B cell cycling in response to TLR signals. THE JOURNAL OF IMMUNOLOGY 2009; 182:4065-75. [PMID: 19299704 DOI: 10.4049/jimmunol.0802961] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The splenic B cell compartment is comprised of two major, functionally distinct, mature B cell subsets, i.e., follicular mature (FM) and marginal zone (MZ) B cells. Whereas MZ B cells exhibit a robust proliferative response following stimulation with the TLR4 ligand LPS, FM B cells display markedly delayed and reduced levels of proliferation to the identical stimulus. The current study was designed to identify a potential mechanism(s) accounting for this differential responsiveness. In contrast to the delay in cell cycle entry, FM and MZ B cells exhibited nearly identical LPS-driven alterations in the expression level of cell surface activation markers. Furthermore, both the NF-kappaB and mTOR signaling cascades were similarly activated by LPS stimulation in FM vs MZ B cells, while inducible activation of ERK and AKT were nearly absent in both subsets. MZ B cells, however, exhibited higher basal levels of phospho-AKT and pS6, consistent with a preactivated status. Importantly, both basal and LPS activation-induced c-myc expression was markedly reduced in FM vs MZ B cells and enforced c-myc expression fully restored the defective proliferative response in FM B cells. These data support a model wherein TLR responses in FM B cells are tightly regulated by limiting c-myc levels, thereby providing an important checkpoint to control nonspecific FM B cell activation in the absence of cognate Ag.
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Weichhart T, Säemann MD. The multiple facets of mTOR in immunity. Trends Immunol 2009; 30:218-26. [PMID: 19362054 DOI: 10.1016/j.it.2009.02.002] [Citation(s) in RCA: 191] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2008] [Revised: 02/10/2009] [Accepted: 02/13/2009] [Indexed: 12/27/2022]
Abstract
The mammalian target of rapamycin (mTOR) is an evolutionarily conserved serine-threonine kinase that is known to sense the environmental and cellular nutrition status to control cell growth. In immunity, mTOR is essential for both the proper activation and subsequent proliferation of effector T cells, yet also restrains the development of regulatory T cells. However, in monocytes/macrophages and peripheral myeloid dendritic cells, mTOR restricts proinflammatory and promotes anti-inflammatory responses, whereas, in plasmacytoid dendritic cells, mTOR fosters type I interferon production. These results place mTOR in a novel immunoregulatory context that highlights the potential of mTOR inhibitors as both immunosuppressant and anti-cancer agents.
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Affiliation(s)
- Thomas Weichhart
- Department of Internal Medicine III, Clinical Division of Nephrology and Dialysis, Medical University Vienna, Währinger Gürtel 18 - 20, A-1090 Vienna, Austria.
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Mendes SDS, Candi A, Vansteenbrugge M, Pignon MR, Bult H, Boudjeltia KZ, Munaut C, Raes M. Microarray analyses of the effects of NF-kappaB or PI3K pathway inhibitors on the LPS-induced gene expression profile in RAW264.7 cells: synergistic effects of rapamycin on LPS-induced MMP9-overexpression. Cell Signal 2009; 21:1109-22. [PMID: 19285553 DOI: 10.1016/j.cellsig.2009.02.025] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2008] [Revised: 02/09/2009] [Accepted: 02/13/2009] [Indexed: 12/25/2022]
Abstract
Lipopolysaccharide (LPS) activates a broad range of signalling pathways including mainly NF-kappaB and the MAPK cascade, but recent evidence suggests that LPS stimulation also activates the PI3K pathway. To unravel the specific roles of both pathways in LPS signalling and gene expression profiling, we investigated the effects of different inhibitors of NF-kappaB (BAY 11-7082), PI3K (wortmannin and LY294002) but also of mTOR (rapamycin), a kinase acting downstream of PI3K/Akt, in LPS-stimulated RAW264.7 macrophages, analyzing their effects on the LPS-induced gene expression profile using a low density DNA microarray designed to monitor the expression of pro-inflammatory genes. After statistical and hierarchical cluster analyses, we determined five clusters of genes differentially affected by the four inhibitors used. In the fifth cluster corresponding to genes upregulated by LPS and mainly affected by BAY 11-7082, the gene encoding MMP9 displayed a particular expression profile, since rapamycin drastically enhanced the LPS-induced upregulation at both the mRNA and protein levels. Rapamycin also enhanced the LPS-induced NF-kappaB transactivation as determined by a reporter assay, phosphorylation of the p38 and Erk1/2 MAPKs, and counteracted PPAR activity. These results suggest that mTOR could negatively regulate the effects of LPS on the NF-kappaB and MAPK pathways. We also performed real-time RT-PCR assays on mmp9 expression using rosiglitazone (agonist of PPARgamma), PD98059 (inhibitor of Erk 1/2) and SB203580 (inhibitor of p38(MAPK)), that were able to counteract the rapamycin mediated overexpression of mmp9 in response to LPS. Our results suggest a new pathway involving mTOR for regulating specifically mmp9 in LPS-stimulated RAW264.7 cells.
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Affiliation(s)
- Sofia Dos Santos Mendes
- University of Namur-FUNDP, Research Unit in Cellular Biology, Rue de Bruxelles 61, Namur, Belgium
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Raghu R, Sharma D, Ramakrishnan R, Khanam S, Chintalwar GJ, Sainis KB. Molecular events in the activation of B cells and macrophages by a non-microbial TLR4 agonist, G1-4A from Tinospora cordifolia. Immunol Lett 2009; 123:60-71. [DOI: 10.1016/j.imlet.2009.02.005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2008] [Revised: 02/10/2009] [Accepted: 02/10/2009] [Indexed: 11/25/2022]
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Zhang TT, Okkenhaug K, Nashed BF, Puri KD, Knight ZA, Shokat KM, Vanhaesebroeck B, Marshall AJ. Genetic or pharmaceutical blockade of p110delta phosphoinositide 3-kinase enhances IgE production. J Allergy Clin Immunol 2008; 122:811-819.e2. [PMID: 19014771 DOI: 10.1016/j.jaci.2008.08.008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 07/02/2008] [Accepted: 08/11/2008] [Indexed: 12/20/2022]
Abstract
BACKGROUND Recent studies indicate that pharmaceutical blockade of phosphoinositide 3-kinase (PI3K) signaling enzymes might be effective in reducing allergic airway inflammation. Signals generated by the p110delta PI3K isoform play critical roles in signaling through antigen and cytokine receptors and were shown to be required for induction of type 2, but not type 1, cytokine responses. OBJECTIVE We sought to determine the effect of genetic or pharmaceutical inactivation of p110delta PI3K on induction of IgE responses. METHODS We determined the effect of p110delta inactivation on induction of systemic IgE responses and on the ability of purified B lymphocytes to undergo IgE isotype switch in vitro. IgG and IgE germline transcription, postswitch transcription, protein expression, and secretion were measured, as well as cell division and expression of activation-induced cytidine deaminase, an enzyme required for isotype switch. RESULTS Paradoxically, inactivation of p110delta PI3K led to markedly increased IgE responses, despite reduced production of other antibody isotypes. This result was seen by using genetic inactivation of p110delta inhibition with IC87114 compound or blockade with the broad-spectrum PI3K inhibitors PIK-90 and PI-103. Significant increases in IgG1/IgE double-positive cells were observed, indicating that inactivation of PI3K leads to uncontrolled sequential switching from IgG1 to IgE. Disruption of p110delta signaling results in increased germline transcription at the epsilon locus and increased activation-induced cytidine deaminase expression, suggesting deregulation at the level of the isotype switch process. CONCLUSION Blockade of PI3K signaling leads to markedly enhanced B-cell switch to IgE and increased IgE levels in vivo, despite reduced type 2 cytokine production.
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Affiliation(s)
- Ting-Ting Zhang
- CIHR National Training Program in Allergy and Asthma Research, University of Manitoba, Winnipeg, Manitoba, Canada; Department of Immunology, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Klaus Okkenhaug
- Laboratory of Lymphocyte Signalling and Development, the Babraham Institute, Cambridge, United Kingdom
| | - Baher F Nashed
- CIHR National Training Program in Allergy and Asthma Research, University of Manitoba, Winnipeg, Manitoba, Canada; Department of Immunology, University of Manitoba, Winnipeg, Manitoba, Canada
| | | | - Zachary A Knight
- Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, Calif
| | - Kevan M Shokat
- Howard Hughes Medical Institute, Department of Cellular and Molecular Pharmacology, University of California, San Francisco, Calif
| | - Bart Vanhaesebroeck
- Institute of Cancer, Queen Mary's School of Medicine and Dentistry, University of London, London, United Kingdom
| | - Aaron J Marshall
- CIHR National Training Program in Allergy and Asthma Research, University of Manitoba, Winnipeg, Manitoba, Canada; Department of Immunology, University of Manitoba, Winnipeg, Manitoba, Canada.
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Wiskott-Aldrich syndrome protein deficiency in B cells results in impaired peripheral homeostasis. Blood 2008; 112:4158-69. [PMID: 18687984 PMCID: PMC2582000 DOI: 10.1182/blood-2008-02-140814] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
To more precisely identify the B-cell phenotype in Wiskott-Aldrich syndrome (WAS), we used 3 distinct murine in vivo models to define the cell intrinsic requirements for WAS protein (WASp) in central versus peripheral B-cell development. Whereas WASp is dispensable for early bone marrow B-cell development, WASp deficiency results in a marked reduction in each of the major mature peripheral B-cell subsets, exerting the greatest impact on marginal zone and B1a B cells. Using in vivo bromodeoxyuridine labeling and in vitro functional assays, we show that these deficits reflect altered peripheral homeostasis, partially resulting from an impairment in integrin function, rather than a developmental defect. Consistent with these observations, we also show that: (1) WASp expression levels increase with cell maturity, peaking in those subsets exhibiting the greatest sensitivity to WASp deficiency; (2) WASp(+) murine B cells exhibit a marked selective advantage beginning at the late transitional B-cell stage; and (3) a similar in vivo selective advantage is manifest by mature WASp(+) human B cells. Together, our data provide a better understanding of the clinical phenotype of WAS and suggest that gene therapy might be a useful approach to rescue altered B-cell homeostasis in this disease.
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Krauß S, Foerster J, Schneider R, Schweiger S. Protein Phosphatase 2A and Rapamycin Regulate the Nuclear Localization and Activity of the Transcription Factor GLI3. Cancer Res 2008; 68:4658-65. [DOI: 10.1158/0008-5472.can-07-6174] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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