Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 23
Filtrar
Mais filtros

Tipo de documento
Intervalo de ano de publicação
1.
Nat Immunol ; 15(5): 465-72, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-24705298

RESUMO

Regulatory T (Treg) cells, which maintain immune homeostasis and self-tolerance, form an immunological synapse (IS) with antigen-presenting cells (APCs). However, signaling events at the Treg cell IS remain unknown. Here we show that the kinase PKC-η associated with CTLA-4 and was recruited to the Treg cell IS. PKC-η-deficient Treg cells displayed defective suppressive activity, including suppression of tumor immunity but not of autoimmune colitis. Phosphoproteomic and biochemical analysis revealed an association between CTLA-4-PKC-η and the GIT2-αPIX-PAK complex, an IS-localized focal adhesion complex. Defective activation of this complex in PKC-η-deficient Treg cells was associated with reduced depletion of CD86 from APCs by Treg cells. These results reveal a CTLA-4-PKC-η signaling axis required for contact-dependent suppression and implicate this pathway as a potential cancer immunotherapy target.


Assuntos
Antígeno CTLA-4/metabolismo , Sinapses Imunológicas/metabolismo , Imunoterapia/tendências , Melanoma Experimental/imunologia , Melanoma Experimental/terapia , Complexos Multiproteicos/metabolismo , Proteína Quinase C/metabolismo , Linfócitos T Reguladores/imunologia , Animais , Humanos , Tolerância Imunológica/genética , Células Jurkat , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Ligação Proteica , Proteína Quinase C/genética , Proteômica , Transdução de Sinais
2.
Cell Mol Life Sci ; 79(2): 131, 2022 Feb 12.
Artigo em Inglês | MEDLINE | ID: mdl-35152348

RESUMO

Mutations in the adaptor protein PSTPIP1 cause a spectrum of autoinflammatory diseases, including PAPA and PAMI; however, the mechanism underlying these diseases remains unknown. Most of these mutations lie in PSTPIP1 F-BAR domain, which binds to LYP, a protein tyrosine phosphatase associated with arthritis and lupus. To shed light on the mechanism by which these mutations generate autoinflammatory disorders, we solved the structure of the F-BAR domain of PSTPIP1 alone and bound to the C-terminal homology segment of LYP, revealing a novel mechanism of recognition of Pro-rich motifs by proteins in which a single LYP molecule binds to the PSTPIP1 F-BAR dimer. The residues R228, D246, E250, and E257 of PSTPIP1 that are mutated in immunological diseases directly interact with LYP. These findings link the disruption of the PSTPIP1/LYP interaction to these diseases, and support a critical role for LYP phosphatase in their pathogenesis.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/química , Proteínas do Citoesqueleto/química , Diabetes Mellitus Tipo 1/etiologia , Doenças do Sistema Imunitário/etiologia , Proteína Tirosina Fosfatase não Receptora Tipo 22/química , Proteínas Adaptadoras de Transdução de Sinal/genética , Proteínas Adaptadoras de Transdução de Sinal/fisiologia , Cristalização , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/fisiologia , Células HEK293 , Humanos , Mutação , Domínios Proteicos , Multimerização Proteica , Proteína Tirosina Fosfatase não Receptora Tipo 22/genética , Proteína Tirosina Fosfatase não Receptora Tipo 22/fisiologia
3.
Proc Natl Acad Sci U S A ; 117(27): 15809-15817, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32571924

RESUMO

Src family kinase Lck plays critical roles during T cell development and activation, as it phosphorylates the TCR/CD3 complex to initiate TCR signaling. Lck is present either in coreceptor-bound or coreceptor-unbound (free) forms, and we here present evidence that the two pools of Lck have different molecular properties. We discovered that the free Lck fraction exhibited higher mobility than CD8α-bound Lck in OT-I T hybridoma cells. The free Lck pool showed more activating Y394 phosphorylation than the coreceptor-bound Lck pool. Consistent with this, free Lck also had higher kinase activity, and free Lck mediated higher T cell activation as compared to coreceptor-bound Lck. Furthermore, the coreceptor-Lck coupling was independent of TCR activation. These findings give insights into the initiation of TCR signaling, suggesting that changes in coreceptor-Lck coupling constitute a mechanism for regulation of T cell sensitivity.


Assuntos
Proteína Tirosina Quinase p56(lck) Linfócito-Específica/genética , Receptores de Antígenos de Linfócitos T alfa-beta/genética , Linfócitos T/metabolismo , Quinases da Família src/genética , Animais , Linfócitos T CD8-Positivos/imunologia , Diferenciação Celular/genética , Hibridomas/imunologia , Ativação Linfocitária/genética , Proteína Tirosina Quinase p56(lck) Linfócito-Específica/imunologia , Camundongos , Fosforilação/genética , Ligação Proteica/genética , Complexo Receptor-CD3 de Antígeno de Linfócitos T/genética , Complexo Receptor-CD3 de Antígeno de Linfócitos T/imunologia , Transdução de Sinais , Linfócitos T/imunologia
4.
Cell Mol Life Sci ; 78(24): 8243-8260, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34757442

RESUMO

Exposure to Gram-negative bacterial LPS exacerbates host immune responses and may lead to sepsis, a life-threatening condition. Despite its high mortality and morbidity, no drugs specifically directed to treating sepsis are currently available. Using human cell genetic depletion, pharmacological inhibition, live-cell microscopy and organelle-targeted molecular sensors we present evidence that the channel TRPC3 is activated intracellularly during macrophage exposure to LPS and is essential for Ca2+ release from internal stores. In this manner, TRPC3 participates in cytosolic Ca2+ elevations, activation of the transcription factor NF-κB and cytokine upregulation. We also report that TRPC3 is activated by diacylglycerol generated by the phosphatidic acid phosphatase lipin-1. In accord with this, lipin-1-deficient cells exhibit reduced Ca2+ responses to LPS challenge. Finally, pharmacological inhibition of TRPC3 reduces systemic inflammation induced by LPS in mice. Collectively, our study unveils a central component of LPS-triggered Ca2+ signaling that involves intracellular sensing of lipin-1-derived DAG by TRPC3, and opens new opportunities for the development of strategies to treat LPS-driven inflammation.


Assuntos
Citocinas/metabolismo , Diglicerídeos/efeitos adversos , Inflamação/patologia , Fosfatidato Fosfatase/metabolismo , Canais de Cátion TRPC/metabolismo , Animais , Humanos , Inflamação/induzido quimicamente , Inflamação/metabolismo , Lipopolissacarídeos/farmacologia , Masculino , Camundongos , Camundongos Endogâmicos BALB C , Canais de Cátion TRPC/genética
5.
Int J Mol Sci ; 23(19)2022 Sep 21.
Artigo em Inglês | MEDLINE | ID: mdl-36232381

RESUMO

Although the COVID-19 disease has developed into a worldwide pandemic, its pathophysiology remains to be fully understood. Insulin-degrading enzyme (IDE), a zinc-metalloprotease with a high affinity for insulin, has been found in the interactomes of multiple SARS-CoV-2 proteins. However, the relevance of IDE in the innate and adaptative immune responses elicited by circulating peripheral blood mononuclear cells is unknown. Here, we show that IDE is highly expressed on the surface of circulating monocytes, T-cells (both CD4+ and CD4-), and, to a lower extent, in B-cells from healthy controls. Notably, IDE's surface expression was upregulated on monocytes from COVID-19 patients at diagnosis, and it was increased in more severe patients. However, IDE's surface expression was downregulated (relative to healthy controls) 3 months after hospital discharge in all the studied immune subsets, with this effect being more pronounced in males than in females, and thus it was sex-dependent. Additionally, IDE levels in monocytes, CD4+ T-cells, and CD4- T-cells were inversely correlated with circulating insulin levels in COVID-19 patients (both at diagnosis and after hospital discharge). Of note, high glucose and insulin levels downregulated IDE surface expression by ~30% in the monocytes isolated from healthy donors, without affecting its expression in CD4+ T-cells and CD4- T-cells. In conclusion, our studies reveal the sex- and metabolism-dependent regulation of IDE in monocytes, suggesting that its regulation might be important for the recruitment of immune cells to the site of infection, as well as for glucometabolic control, in COVID-19 patients.


Assuntos
COVID-19 , Insulisina , Teste para COVID-19 , Feminino , Glucose , Hospitais , Humanos , Insulina/metabolismo , Insulisina/metabolismo , Leucócitos Mononucleares/metabolismo , Linfócitos/metabolismo , Masculino , Monócitos/metabolismo , SARS-CoV-2 , Zinco
6.
Molecules ; 27(7)2022 Apr 06.
Artigo em Inglês | MEDLINE | ID: mdl-35408744

RESUMO

Group IVA cytosolic phospholipase A2α (cPLA2α) is a key enzyme in physiology and pathophysiology because it constitutes a rate-limiting step in the pathway for the generation of pro- and anti-inflammatory eicosanoid lipid mediators. cPLA2α activity is tightly regulated by multiple factors, including the intracellular Ca2+ concentration, phosphorylation reactions, and cellular phosphatidylinositol (4,5) bisphosphate levels (PtdInsP2). In the present work, we demonstrate that phosphorylation of the enzyme at Ser505 is an important step for the translocation of the enzyme to PtdInsP2-enriched membranes in human cells. Constructs of eGFP-cPLA2 mutated in Ser505 to Ala (S505A) exhibit a delayed translocation in response to elevated intracellular Ca2+, and also in response to increases in intracellular PtdInsP2 levels. Conversely, translocation of a phosphorylation mimic mutant (S505E) is fully observed in response to cellular increases in PtdInsP2 levels. Collectively, these results suggest that phosphorylation of cPLA2α at Ser505 is necessary for the enzyme to translocate to internal membranes and mobilize arachidonic acid for eicosanoid synthesis.


Assuntos
Eicosanoides , Fosfatidilinositol 4,5-Difosfato , Ácido Araquidônico/metabolismo , Citosol/metabolismo , Eicosanoides/metabolismo , Fosfolipases A2 do Grupo IV/genética , Fosfolipases A2 do Grupo IV/metabolismo , Humanos , Fosfatidilinositol 4,5-Difosfato/metabolismo , Fosforilação
7.
Nature ; 504(7480): 441-5, 2013 Dec 19.
Artigo em Inglês | MEDLINE | ID: mdl-24226767

RESUMO

Development of a self-tolerant T-cell receptor (TCR) repertoire with the potential to recognize the universe of infectious agents depends on proper regulation of TCR signalling. The repertoire is whittled down during T-cell development in the thymus by the ability of quasi-randomly generated TCRs to interact with self-peptides presented by major histocompatibility complex (MHC) proteins. Low-affinity TCR interactions with self-MHC proteins generate weak signals that initiate 'positive selection', causing maturation of CD4- or CD8αß-expressing 'single-positive' thymocytes from CD4(+)CD8αß(+) 'double-positive' precursors. These develop into mature naive T cells of the secondary lymphoid organs. TCR interaction with high-affinity agonist self-ligands results in 'negative selection' by activation-induced apoptosis or 'agonist selection' of functionally differentiated self-antigen-experienced T cells. Here we show that positive selection is enabled by the ability of the T-cell-specific protein Themis to specifically attenuate TCR signal strength via SHP1 recruitment and activation in response to low- but not high-affinity TCR engagement. Themis acts as an analog-to-digital converter translating graded TCR affinity into clear-cut selection outcome. By dampening mild TCR signals Themis increases the affinity threshold for activation, enabling positive selection of T cells with a naive phenotype in response to low-affinity self-antigens.


Assuntos
Proteínas/metabolismo , Receptores de Antígenos de Linfócitos T/imunologia , Transdução de Sinais/imunologia , Linfócitos T/citologia , Linfócitos T/metabolismo , Timócitos/citologia , Timócitos/metabolismo , Animais , Apoptose , Autoantígenos/imunologia , Sinalização do Cálcio , Ativação Enzimática , MAP Quinases Reguladas por Sinal Extracelular/metabolismo , Peptídeos e Proteínas de Sinalização Intercelular , Ligantes , Camundongos , Camundongos Endogâmicos C57BL , Proteína Tirosina Fosfatase não Receptora Tipo 6/metabolismo , Proteínas/genética , Receptores de Antígenos de Linfócitos T/metabolismo , Linfócitos T/imunologia , Timócitos/imunologia
8.
J Immunol ; 183(4): 2767-74, 2009 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-19625654

RESUMO

Eicosanoids are a broad family of lipids that play a critical role in host defense against bacterial and fungal infections. The first enzyme in the metabolic pathway for the generation of eicosanoids is group IVA phospholipase A(2), also known as cytosolic phospholipase A(2)alpha (cPLA(2)alpha). During phagocytosis, cPLA(2)alpha has been found to translocate to the phagosome, although the molecular mechanism involved in such a translocation has not been elucidated. By using enhanced GFP-tagged proteins we show in this work that a nonphosphorylatable cPLA(2)alpha mutant (S505A) does not translocate to the phagosomes, but a mutant that mimics phosphorylation on Ser(505) (S505E) does it so readily. During phagocytosis, endogenous cPLA(2)alpha is phosphorylated at Ser(505), and inhibitors of JNK, but not of other related kinases such as p38 or the extracellular-regulated kinases 1 and 2, completely block such a phosphorylation. Inhibition of JNK activity also inhibits the translocation of cPLA(2)alpha to phagosomal membranes, as well as arachidonic acid release to the extracellular medium. Moreover, the S505E mutant makes the enzyme refractory to JNK inhibition, translocating normally to phagosomal membranes. Collectively, these data support a key role for JNK-mediated cPLA(2)alpha phosphorylation at Ser(505) in the sequence of events leading to translocation and activation of the enzyme to phagosomal membranes in human macrophages.


Assuntos
Fosfolipases A2 do Grupo IV/metabolismo , Proteínas Quinases JNK Ativadas por Mitógeno/fisiologia , Macrófagos/metabolismo , Fagossomos/metabolismo , Células Cultivadas , Eicosanoides/biossíntese , Ativação Enzimática/imunologia , Humanos , Macrófagos/enzimologia , Macrófagos/imunologia , Fagocitose/imunologia , Fagossomos/enzimologia , Fagossomos/imunologia , Fosforilação , Ligação Proteica/imunologia , Transporte Proteico/imunologia
9.
J Headache Pain ; 12(3): 377-80, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21308475

RESUMO

Symptomatic trigeminal neuralgia due to a brainstem infarction is said to be rare. However, facial pain is not uncommon in Wallenberg's syndrome. Facial pain related to a Wallenberg's syndrome may be either persistent of intermittent, and occasionally occurs in brief attacks. Here, we report a patient with a right lateral medullary infarction who started having first division trigeminal neuralgia 1 month after the stroke. The pain paroxysms were suppressed with gabapentin.


Assuntos
Dor Facial/etiologia , Síndrome Medular Lateral/complicações , Neuralgia do Trigêmeo/etiologia , Adulto , Dor Facial/patologia , Humanos , Síndrome Medular Lateral/patologia , Angiografia por Ressonância Magnética , Imageamento por Ressonância Magnética , Masculino , Neuralgia do Trigêmeo/patologia
10.
J Lipid Res ; 51(2): 388-99, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19717620

RESUMO

Group IVA cytosolic phospholipase A(2)alpha (cPLA(2)alpha) plays a role in the microbicidal machinery of immune cells by translocating to phagosomes to initiate the production of antimicrobial eicosanoids. In this work, we have studied the involvement of the cationic cluster of cPLA(2)alpha (Lys(488)/Lys(541)/Lys(543)/Lys(544)) in the translocation of the enzyme to the phagosomal cup in human macrophages responding to opsonized zymosan. Phagocytosis was accompanied by an increased mobilization of free arachidonic acid, which was strongly inhibited by pyrrophenone. In transfected cells, a catalytically active enhanced green fluorescent protein-cPLA(2)alpha translocated to the phagocytic cup, which was corroborated by frustrated phagocytosis experiments using immunoglobulin G-coated plates. However, a cPLA(2)alpha mutant in the polybasic cluster that cannot bind the anionic phospholipid phosphatidylinositol 4, 5-bisphosphate (PIP(2)) did not translocate to the phagocytic cup. Moreover, an enhanced yellow fluorescent protein (EYFP)-cPLA(2)alpha and an enhanced cyan fluorescent protein-pleckstrin homology (PH) domain of the phospholipase Cdelta1 (PLCdelta(1)) construct that specifically recognizes endogenous PIP(2) in the cells both localized at the same sites on the phagosome. High cellular expression of the PH domain inhibited EYFP-cPLA(2)alpha translocation. On the other hand, group V-secreted phospholipase A(2) and group VIA calcium-independent phospholipase A(2) were also studied, but the results indicated that neither of these translocated to the phagosome. Collectively, these data indicate that the polybasic cluster of cPLA(2)alpha (Lys(488)/Lys(541)/Lys(543)/Lys(544)) regulates the subcellular localization of the enzyme in intact cells under physiologically relevant conditions.


Assuntos
Fosfolipases A2 do Grupo IV/química , Fosfolipases A2 do Grupo IV/metabolismo , Lisina , Macrófagos/citologia , Macrófagos/metabolismo , Fagossomos/metabolismo , Domínio Catalítico , Ativação Enzimática/efeitos dos fármacos , Proteínas de Fluorescência Verde/metabolismo , Fosfolipases A2 do Grupo IV/genética , Humanos , Mutação , Fagocitose , Transporte Proteico , Zimosan/metabolismo , Zimosan/farmacologia
11.
Mol Biol Cell ; 17(1): 155-62, 2006 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-16221889

RESUMO

The eicosanoids are centrally involved in the onset and resolution of inflammatory processes. A key enzyme in eicosanoid biosynthesis during inflammation is group IVA phospholipase A2 (also known as cytosolic phospholipase A2alpha, cPLA2alpha). This enzyme is responsible for generating free arachidonic acid from membrane phospholipids. cPLA2alpha translocates to perinuclear membranes shortly after cell activation, in a process that is governed by the increased availability of intracellular Ca2+. However, cPLA2alpha also catalyzes membrane phospholipid hydrolysis in response to agonists that do not mobilize intracellular Ca2+. How cPLA2alpha interacts with membranes under these conditions is a major, still unresolved issue. Here, we report that phosphatidylinositol 4,5-bisphosphate [PtdIns(4,5)P2] promotes translocation of cPLA2alpha to perinuclear membranes of intact cells in a manner that is independent of rises in the intracellular Ca2+ concentration. PtdIns(4,5)P2 anchors the enzyme to perinuclear membranes and allows for a proper interaction with its phospholipid substrate to release arachidonic acid.


Assuntos
Cálcio/metabolismo , Citosol/enzimologia , Fígado/enzimologia , Membrana Nuclear/enzimologia , Fosfatidilinositol 4,5-Difosfato/farmacologia , Fosfolipases A/metabolismo , Animais , Ácido Araquidônico/metabolismo , Cálcio/farmacologia , Linhagem Celular , Sobrevivência Celular , Fosfolipases A2 do Grupo IV , Humanos , Fígado/efeitos dos fármacos , Camundongos , Mutação/genética , Membrana Nuclear/efeitos dos fármacos , Fosfatidilinositol 4,5-Difosfato/metabolismo , Fosfolipases A/genética , Fosfolipases A2 , Transporte Proteico
12.
Front Immunol ; 9: 1723, 2018.
Artigo em Inglês | MEDLINE | ID: mdl-30087680

RESUMO

Macrophages, as professional phagocytes of the immune system, possess the ability to detect and clear invading pathogens and apoptotic cells through phagocytosis. Phagocytosis involves membrane reorganization and remodeling events on the cell surface, which play an essential role in innate immunity and tissue homeostasis and the control of inflammation. In this work, we report that cells deficient in membrane ethanolamine plasmalogen demonstrate a reduced capacity to phagocytize opsonized zymosan particles. Amelioration of plasmalogen deficiency in these cells by incubation with lysoplasmalogen results in a significant augmentation of the phagocytic capacity of the cells. In parallel with these increases, restoration of plasmalogen levels in the cells also increases the number and size of lipid rafts in the membrane, reduces membrane fluidity down to levels found in cells containing normal plasmalogen levels, and improves receptor-mediated signaling. Collectively, these results suggest that membrane plasmalogen level determines characteristics of the plasma membrane such as fluidity and the formation of microdomains that are necessary for efficient signal transduction leading to optimal phagocytosis by macrophages.

13.
Nat Commun ; 5: 5624, 2014 Nov 27.
Artigo em Inglês | MEDLINE | ID: mdl-25427562

RESUMO

The earliest molecular events in T-cell recognition have not yet been fully described, and the initial T-cell receptor (TCR)-triggering mechanism remains a subject of controversy. Here, using total internal reflection/Forster resonance energy transfer microscopy, we observe a two-stage interaction between TCR, CD8 and major histocompatibility complex (MHC)-peptide. There is an early (within seconds) interaction between CD3ζ and the coreceptor CD8 that is independent of the binding of CD8 to MHC, but that requires CD8 association with Lck. Later (several minutes) CD3ζ-CD8 interactions require CD8-MHC binding. Lck can be found free or bound to the coreceptor. This work indicates that the initial TCR-triggering event is induced by free Lck.


Assuntos
Complexo CD3/metabolismo , Antígenos CD8/metabolismo , Proteína Tirosina Quinase p56(lck) Linfócito-Específica/metabolismo , Animais , Complexo CD3/genética , Antígenos CD8/genética , Feminino , Proteínas de Homeodomínio/genética , Proteínas de Homeodomínio/metabolismo , Ligantes , Proteína Tirosina Quinase p56(lck) Linfócito-Específica/genética , Complexo Principal de Histocompatibilidade , Masculino , Camundongos , Camundongos Knockout , Ligação Proteica , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/metabolismo , Sinapses/enzimologia , Sinapses/genética , Sinapses/metabolismo , Linfócitos T/metabolismo
14.
J Exp Med ; 210(9): 1807-21, 2013 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-23940257

RESUMO

Recent work has demonstrated that nonstimulatory endogenous peptides can enhance T cell recognition of antigen, but MHCI- and MHCII-restricted systems have generated very different results. MHCII-restricted TCRs need to interact with the nonstimulatory peptide-MHC (pMHC), showing peptide specificity for activation enhancers or coagonists. In contrast, the MHCI-restricted cells studied to date show no such peptide specificity for coagonists, suggesting that CD8 binding to noncognate MHCI is more important. Here we show how this dichotomy can be resolved by varying CD8 and TCR binding to agonist and coagonists coupled with computer simulations, and we identify two distinct mechanisms by which CD8 influences the peptide specificity of coagonism. Mechanism 1 identifies the requirement of CD8 binding to noncognate ligand and suggests a direct relationship between the magnitude of coagonism and CD8 affinity for coagonist pMHCI. Mechanism 2 describes how the affinity of CD8 for agonist pMHCI changes the requirement for specific coagonist peptides. MHCs that bind CD8 strongly were tolerant of all or most peptides as coagonists, but weaker CD8-binding MHCs required stronger TCR binding to coagonist, limiting the potential coagonist peptides. These findings in MHCI systems also explain peptide-specific coagonism in MHCII-restricted cells, as CD4-MHCII interaction is generally weaker than CD8-MHCI.


Assuntos
Epitopos/imunologia , Antígenos de Histocompatibilidade Classe II/metabolismo , Antígenos de Histocompatibilidade Classe I/metabolismo , Peptídeos/metabolismo , Receptores de Antígenos de Linfócitos T/agonistas , Receptores de Antígenos de Linfócitos T/metabolismo , Sequência de Aminoácidos , Animais , Linfócitos T CD8-Positivos/imunologia , Células CHO , Simulação por Computador , Cricetinae , Cricetulus , Antígenos de Histocompatibilidade Classe I/química , Antígenos de Histocompatibilidade Classe I/imunologia , Antígenos de Histocompatibilidade Classe II/química , Antígenos de Histocompatibilidade Classe II/imunologia , Humanos , Cinética , Ativação Linfocitária/imunologia , Camundongos , Modelos Moleculares , Dados de Sequência Molecular , Ovalbumina/imunologia , Peptídeos/química , Peptídeos/imunologia , Ligação Proteica/imunologia , Receptores de Antígenos de Linfócitos T/imunologia
15.
Front Immunol ; 2: 72, 2011.
Artigo em Inglês | MEDLINE | ID: mdl-22566861

RESUMO

Recent data with CD8+ T cells show that the initial phase of T cell receptor (TCR) binding to MHC-peptide (MHCp) is quickly followed by a second, stronger, binding phase representing the binding of CD8 to the MHCp. This second phase requires signaling by a Src-family kinase such as Lck. These data point out two aspects of the initial stage of TCR signaling that have not yet been clearly resolved. Firstly, how and by which Src-family kinase, is the initial phosphorylation of CD3ζ accomplished, given that the Lck associated with the co-receptors (CD4 or CD8) is not yet available. Secondly, what is the mechanism by which the co-receptor is brought close to the bound TCR before the co-receptor binds to MHCp?

16.
Sci Signal ; 4(202): ra84, 2011 Dec 06.
Artigo em Inglês | MEDLINE | ID: mdl-22155788

RESUMO

Protein kinase C η (PKCη) is abundant in T cells and is recruited to the immunological synapse that is formed between a T cell and an antigen-presenting cell; however, its function in T cells is unknown. We showed that PKCη was required for the activation of mature CD8+ T cells through the T cell receptor. Compared with wild-type T cells, PKCη-/- T cells showed poor proliferation in response to antigen stimulation, a trait shared with T cells deficient in PKCθ, which is the most abundant PKC isoform in T cells and was thought to be the only PKC isoform with a specific role in T cell activation. In contrast, only PKCη-deficient T cells showed defective homeostatic proliferation, which requires self-antigen recognition. PKCη was dispensable for thymocyte development; however, thymocytes from mice doubly deficient in PKCη and PKCθ exhibited poor development, indicating some redundancy between the PKC isoforms. Deficiency in PKCη or PKCθ had opposing effects on the relative numbers of CD4+ and CD8+ T cells. PKCη-/- mice had a higher ratio of CD4+ to CD8+ T cells compared to that of wild-type mice, whereas PKCθ-/- mice had a lower ratio. Mice deficient in both isoforms exhibited normal cell ratios. Together, these data suggest that PKCη shares some redundant roles with PKCθ in T cell biology and also performs nonredundant functions that are required for T cell homeostasis and activation.


Assuntos
Proteína Quinase C/imunologia , Linfócitos T/enzimologia , Linfócitos T/imunologia , Animais , Sequência de Bases , Relação CD4-CD8 , Linfócitos T CD4-Positivos/citologia , Linfócitos T CD4-Positivos/enzimologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD8-Positivos/citologia , Linfócitos T CD8-Positivos/enzimologia , Linfócitos T CD8-Positivos/imunologia , Sinalização do Cálcio , Proliferação de Células , Homeostase , Memória Imunológica/fisiologia , Sinapses Imunológicas/enzimologia , Isoenzimas/deficiência , Isoenzimas/genética , Isoenzimas/imunologia , Ativação Linfocitária , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , NF-kappa B/metabolismo , Fenótipo , Proteína Quinase C/deficiência , Proteína Quinase C/genética , Proteína Quinase C-theta , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Transdução de Sinais/imunologia , Linfócitos T/citologia
17.
Can J Infect Dis Med Microbiol ; 21(3): e107-8, 2010.
Artigo em Inglês | MEDLINE | ID: mdl-21886641

RESUMO

Spontaneous rupture of the spleen associated with Legionella pneumonia is a rare and life-threatening complication; only three cases have been reported to date. The authors describe a case of a 47-year-old man who presented with pneumonia and abdominal pain. He underwent a splenectomy, and was successfully treated with clarithromycin and levofloxacin.

18.
J Agric Food Chem ; 57(15): 6815-22, 2009 Aug 12.
Artigo em Inglês | MEDLINE | ID: mdl-19586031

RESUMO

Tomatoes provide an optimal mix of dietary antioxidants that may be responsible for the reported health benefits of tomato consumption. However, technological processing, packaging materials, and storage conditions have an impact on the nutritional quality of tomato products by affecting the stability of antioxidant nutrients to different extents. In this study, we evaluated the stability of the antioxidant compounds (lycopene, ascorbic acid, total phenols, and total flavonoids) present in commercially available tomato juices during storage extended for 12 months at three different temperatures (8, 22, and 37 degrees C). To further characterize the impact of storage conditions, two commonly used packaging materials (Tetra pack and glass bottles) were used to determine whether packaging materials affect antioxidant stability. Overall, the total lycopene, total phenolic compounds, and total flavonoids remained almost stable during storage for 12 months, regardless of the packaging material used, indicating that tomato juices maintain their nutritional value in terms of antioxidant composition during their shelf life. However, ascorbic acid was the most labile antioxidant and was markedly affected by storage conditions. The hydrophilic total antioxidant activity (TAA) paralleled the losses in ascorbic acid content, whereas the lipophilic TAA remained substantially stable throughout the storage trial.


Assuntos
Antioxidantes/análise , Bebidas/análise , Manipulação de Alimentos/métodos , Embalagem de Alimentos/instrumentação , Solanum lycopersicum/química , Ácido Ascórbico/análise , Carotenoides/análise , Flavonoides/análise , Manipulação de Alimentos/instrumentação , Embalagem de Alimentos/métodos , Licopeno
19.
J Biol Chem ; 284(9): 5697-708, 2009 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-19117952

RESUMO

This work investigates the metabolic origin of triacylglycerol (TAG) formed during lipid droplet (LD) biogenesis induced by stress. Cytotoxic inhibitors of fatty acid synthase induced TAG synthesis and LD biogenesis in CHO-K1 cells, in the absence of external sources of fatty acids. TAG synthesis was required for LD biogenesis and was sensitive to inhibition and down-regulation of the expression of group VIA phospholipase A(2) (iPLA(2)-VIA). Induction of stress with acidic pH, C(2)-ceramide, tunicamycin, or deprivation of glucose also stimulated TAG synthesis and LD formation in a manner dependent on iPLA(2)-VIA. Overexpression of the enzyme enhanced TAG synthesis from endogenous fatty acids and LD occurrence. During stress, LD biogenesis but not TAG synthesis required phosphorylation and activation of group IVA PLA(2) (cPLA(2)alpha). The results demonstrate that iPLA(2)-VIA provides fatty acids for TAG synthesis while cPLA(2)alpha allows LD biogenesis. LD biogenesis during stress may be a survival strategy, recycling structural phospholipids into energy-generating substrates.


Assuntos
Fosfolipases A2 do Grupo VI/metabolismo , Metabolismo dos Lipídeos/fisiologia , Estresse Oxidativo , Triglicerídeos/biossíntese , Animais , Antibacterianos/farmacologia , Células CHO , Cálcio/metabolismo , Cricetinae , Cricetulus , Inibidores Enzimáticos/farmacologia , Ácido Graxo Sintases/antagonistas & inibidores , Ácido Graxo Sintases/metabolismo , Ácidos Graxos , Citometria de Fluxo , Fluorescência , Glucose/deficiência , Fosfolipases A2 do Grupo VI/antagonistas & inibidores , Fosforilação , RNA Interferente Pequeno/farmacologia , Esfingosina/análogos & derivados , Esfingosina/farmacologia , Tunicamicina/farmacologia , Fosfolipases Tipo C/antagonistas & inibidores , Fosfolipases Tipo C/genética , Fosfolipases Tipo C/metabolismo
20.
J Biol Chem ; 283(41): 27369-27382, 2008 Oct 10.
Artigo em Inglês | MEDLINE | ID: mdl-18632668

RESUMO

Lipid droplets (LD) are organelles present in all cell types, consisting of a hydrophobic core of triacylglycerols and cholesteryl esters, surrounded by a monolayer of phospholipids and cholesterol. This work shows that LD biogenesis induced by serum, by long-chain fatty acids, or the combination of both in CHO-K1 cells was prevented by phospholipase A(2) inhibitors with a pharmacological profile consistent with the implication of group IVA cytosolic phospholipase A(2) (cPLA(2)alpha). Knocking down cPLA(2)alpha expression with short interfering RNA was similar to pharmacological inhibition in terms of enzyme activity and LD biogenesis. A Chinese hamster ovary cell clone stably expressing an enhanced green fluorescent protein-cPLA(2)alpha fusion protein (EGFP-cPLA(2)) displayed higher LD occurrence under basal conditions and upon LD induction. Induction of LD took place with concurrent phosphorylation of cPLA(2)alpha at Ser(505). Transfection of a S505A mutant cPLA(2)alpha showed that phosphorylation at Ser(505) is key for enzyme activity and LD formation. cPLA(2)alpha contribution to LD biogenesis was not because of the generation of arachidonic acid, nor was it related to neutral lipid synthesis. cPLA(2)alpha inhibition in cells induced to form LD resulted in the appearance of tubulo-vesicular profiles of the smooth endoplasmic reticulum, compatible with a role of cPLA(2)alpha in the formation of nascent LD from the endoplasmic reticulum.


Assuntos
Retículo Endoplasmático/enzimologia , Regulação Enzimológica da Expressão Gênica/fisiologia , Fosfolipases A2 do Grupo IV/metabolismo , Metabolismo dos Lipídeos/fisiologia , Animais , Células CHO , Cricetinae , Cricetulus , Inibidores Enzimáticos/farmacologia , Regulação Enzimológica da Expressão Gênica/efeitos dos fármacos , Fosfolipases A2 do Grupo IV/antagonistas & inibidores , Humanos , Metabolismo dos Lipídeos/efeitos dos fármacos , Fosforilação/efeitos dos fármacos , RNA Interferente Pequeno/farmacologia , Ratos
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA