RESUMO
OBJECTIVES: To assess the safety and immunogenicity of a fourth vaccination (second booster) in individuals aged ≥75 years. METHODS: Participants were randomized to BNT162b2 (Comirnaty, 30 µg) or messenger RNA (mRNA)-1273 (Spikevax, 100 µg). The primary end point was the rate of two-fold antibody titer increase 14 days after vaccination, targeting the receptor binding domain (RBD) region of wild-type SARS-CoV-2. The secondary end points included changes in neutralizing activity against wild-type and 25 variants. Safety was assessed by monitoring solicited adverse events (AEs) for 7 days. RESULTS: A total of 269 participants (mean age 81 years, mRNA-1273 n = 135/BNT162b2 n = 134) were included. Two-fold anti-RBD immunoglobulin (Ig) G titer increase was achieved by 101 of 129 (78%) and 116 of 133 (87%) subjects in the BNT162b2 and the mRNA-1273 group, respectively (P = 0.054). A second booster of mRNA-1273 provided higher anti-RBD IgG geometric mean titer: 21.326 IU/mL (95% confidence interval: 18.235-24.940) vs BNT162b2: 15.181 IU/mL (95% confidence interval: 13.172-17.497). A higher neutralizing activity was noted for the mRNA-1273 group. The most frequent AE was pain at the injection site (51% in mRNA-1273 and 48% in BNT162b2). Participants in the mRNA-1273 group had less vaccine-related AEs (30% vs 39%). CONCLUSIONS: A second booster of either BNT162b2 or mRNA-1273 provided substantial IgG increase. Full-dose mRNA-1273 provided higher IgG levels and neutralizing capacity against SARS-CoV-2, with similar safety profile for subjects of advanced age.
Assuntos
Vacina de mRNA-1273 contra 2019-nCoV , Anticorpos Neutralizantes , Anticorpos Antivirais , Vacina BNT162 , COVID-19 , Imunização Secundária , Imunogenicidade da Vacina , SARS-CoV-2 , Humanos , Vacina BNT162/imunologia , Masculino , Feminino , Idoso , COVID-19/prevenção & controle , COVID-19/imunologia , SARS-CoV-2/imunologia , Anticorpos Antivirais/sangue , Idoso de 80 Anos ou mais , Vacina de mRNA-1273 contra 2019-nCoV/imunologia , Anticorpos Neutralizantes/sangue , Vacinas contra COVID-19/imunologia , Vacinas contra COVID-19/efeitos adversos , Vacinas contra COVID-19/administração & dosagem , Imunoglobulina G/sangue , Glicoproteína da Espícula de Coronavírus/imunologiaRESUMO
BACKGROUND: Vaccination remains crucial for protection against severe SARS-CoV-2 infection, especially for people of advanced age, however, optimal dosing regimens are as yet lacking. METHODS: EU-COVAT-1-AGED Part A is a randomised controlled, adaptive, multicentre phase II trial evaluating safety and immunogenicity of a 3rd vaccination (1st booster) in individuals ≥75 years. Fifty-three participants were randomised to full-doses of either mRNA-1273 (Spikevax®, 100 µg) or BNT162b2 (Comirnaty®, 30 µg). The primary endpoint was the rate of 2-fold circulating antibody titre increase 14 days post-vaccination measured by quantitative electrochemiluminescence (ECL) immunoassay, targeting RBD region of Wuhan wild-type SARS-CoV-2. Secondary endpoints included the changes in neutralising capacity against wild-type and 25 variants of concern at 14 days and up to 12 months. Safety was assessed by monitoring of solicited adverse events (AEs) for seven days after on-study vaccination. Unsolicited AEs were collected until the end of follow-up at 12 months, SAEs were pursued for a further 30 days. RESULTS: Between 08th of November 2021 and 04th of January 2022, 53 participants ≥75 years received a COVID-19 vaccine as 1st booster. Fifty subjects (BNT162b2 n = 25/mRNA-1273 n = 25) were included in the analyses for immunogenicity at day 14. The primary endpoint of a 2-fold anti-RBD IgG titre increase 14 days after vaccination was reached for all subjects. A 3rd vaccination of full-dose mRNA-1273 provided higher anti-RBD IgG titres (Geometric mean titre) D14 mRNA-127310711 IU/mL (95 %-CI: 8003;14336) vs. BNT162b2: 7090 IU/mL (95 %-CI: 5688;8837). We detected a pattern showing higher neutralising capacity of full-dose mRNA-1273 against wild-type as well as for 23 out of 25 tested variants. INTERPRETATION: Third doses of either BNT162b2 or mRNA-1273 provide substantial circulating antibody increase 14 days after vaccination. Full-dose mRNA-1273 provides higher antibody levels with an overall similar safety profile for people ≥75 years. FUNDING: This trial was funded by the European Commission (Framework Program HORIZON 2020).
Assuntos
Vacina de mRNA-1273 contra 2019-nCoV , Vacina BNT162 , Humanos , Adulto , Idoso , Vacinas contra COVID-19/efeitos adversos , RNA Mensageiro , Imunoglobulina G , Imunogenicidade da Vacina , Anticorpos Antivirais , Anticorpos NeutralizantesRESUMO
BACKGROUND: In the ongoing COVID-19 pandemic, advanced age is a risk factor for a severe clinical course of SARS-CoV-2 infection. Thus, older people may benefit in particular from booster doses with potent vaccines and research should focus on optimal vaccination schedules. In addition to each individual's medical history, immunosenescence warrants further research in this population. This study investigates vaccine-induced immune response over 1 year. METHODS/DESIGN: EU-COVAT-1-AGED is a randomised controlled, adaptive, multicentre phase II protocol evaluating different booster strategies in individuals aged ≥75 years (n=600) already vaccinated against SARS-CoV-2. The initial protocol foresaw a 3rd vaccination (1st booster) as study intervention. The present modified Part B of this trial foresees testing of mRNA-1273 (Spikevax®) vs. BNT162b2 (Comirnaty®) as 4th vaccination dose (2nd booster) for comparative assessment of their immunogenicity and safety against SARS-CoV-2 wild-type and variants. The primary endpoint of the trial is to assess the rate of 2-fold antibody titre increase 14 days after vaccination measured by quantitative enzyme-linked immunosorbent assay (Anti-RBD-ELISA) against wild-type virus. Secondary endpoints include the changes in neutralising antibody titres (Virus Neutralisation Assay) against wild-type as well as against Variants of Concern (VOC) at 14 days and up to 12 months. T cell response measured by qPCR will be performed in subgroups at 14 days as exploratory endpoint. Biobanking samples are being collected for neutralising antibody titres against potential future VOC. Furthermore, potential correlates between humoral immune response, T cell response and neutralising capacity will be assessed. The primary endpoint analysis will be triggered as soon as for all patients the primary endpoint (14 days after the 4th vaccination dose) has been observed. DISCUSSION: The EU-COVAT-1-AGED trial Part B compares immunogenicity and safety of mRNA-1273 (Spikevax®) and BNT162b2 (Comirnaty®) as 4th SARS-CoV-2 vaccine dose in adults ≥75 years of age. The findings of this trial have the potential to optimise the COVID-19 vaccination strategy for this at-risk population. TRIAL REGISTRATION: ClinicalTrials.gov NCT05160766 . Registered on 16 December 2021. PROTOCOL VERSION: V06_0: 27 July 2022.
Assuntos
COVID-19 , Vacinas , Adulto , Idoso , Anticorpos Neutralizantes , Anticorpos Antivirais , Vacina BNT162 , Bancos de Espécimes Biológicos , COVID-19/prevenção & controle , Vacinas contra COVID-19/efeitos adversos , Ensaios Clínicos Fase II como Assunto , Humanos , Pandemias/prevenção & controle , Ensaios Clínicos Controlados Aleatórios como Assunto , SARS-CoV-2RESUMO
BACKGROUND: Lipedema is a chronic disorder of the adipose tissue that affects mainly women, characterised by symmetrical, excessive fatty tissue on the legs and pain. Standard conservative treatment is long-term comprehensive decongestive therapy (CDT) to alleviate lipedema-related pain and to improve psychosocial well-being, mobility and physical activity. Patients may benefit from surgical removal of abnormally propagated adipose tissue by liposuction. The LIPLEG trial evaluates the efficacy and safety of liposuction compared to standard CDT. METHODS/DESIGN: LIPLEG is a randomised controlled multicentre investigator-blinded trial. Women with lipedema (n=405) without previous liposuction will be allocated 2:1 to liposuction or CDT. The primary outcome of the trial is leg pain reduction by ≥2 points on a visual analogue scale ranging 0-10 at 12 months on CDT or post-completion of liposuction. Secondary outcomes include changes in leg pain severity, health-related quality of life, depression tendency, haematoma tendency, prevalence of oedema, modification physical therapy scope, body fat percentage, leg circumference and movement restriction. The primary analysis bases on intention-to-treat. Success proportions are compared using the Mantel-Haenszel test stratified by lipedema stage at a 5% two-sided significance level. If this test is statistically significant, the equality of the response proportions in the separate strata is evaluated by Fisher's exact test in a hierarchical test strategy. DISCUSSION: LIPLEG assesses whether surgical treatment of lipedema is safe and effective to reduce pain and other lipedema-related health issues. The findings of this trial have the potential to change the standard of care in lipedema. TRIAL REGISTRATION: ClinicalTrials.gov NCT04272827. Registered on February 14, 2020. TRIAL STATUS: Protocol version is 02_0, December 17, 2019.
Assuntos
Lipectomia , Lipedema , Edema , Exercício Físico , Feminino , Humanos , Lipectomia/efeitos adversos , Lipedema/diagnóstico , Lipedema/terapia , Qualidade de Vida , Resultado do TratamentoRESUMO
BACKGROUND: Regional differences in the underlying causes, manifestations and treatment of mucormycosis have been noted in studies covering Europe, Asia and South America. OBJECTIVES: To review cases of mucormycosis across the Middle East and North Africa (MENA) region in order to identify epidemiological, treatment and outcome trends in this region. PATIENTS/METHODS: Cases of proven or probable invasive mucormycosis from the region were identified from the FungiScope® database and the medical literature. For each case, information on underlying condition, site of infection, pathogenic species, therapeutic intervention, type of antifungal therapy and outcome were analysed. RESULTS: We identified 310 cases of mucormycosis in the MENA region. The number of reported cases increased by decade from 23 before 1990 to 127 in the 2010s. In this region, the most common underlying conditions associated with mucormycosis were diabetes mellitus (49.7%) and conditions associated with immunosuppression (46.5%). The majority of patients received treatment with antifungals (93.5%), with a large proportion treated with both antifungals and surgery (70.6%). Overall mortality rates decreased from 47.8% before 1990 to 32.3% in the 2010s. CONCLUSIONS: The number of reported cases of mucormycosis in the MENA region has risen over the past few decades, in line with increases in the number of patients with underlying conditions associated with this infection. Although the majority of patients received treatment with antifungal therapies and/or surgery, the associated mortality rate remains high and there is a clear need for more effective prevention and treatment strategies in the MENA region.
Assuntos
Mucormicose , África do Norte/epidemiologia , Antifúngicos/uso terapêutico , Complicações do Diabetes , Humanos , Terapia de Imunossupressão , Oriente Médio/epidemiologia , Mortalidade , Mucormicose/tratamento farmacológico , Mucormicose/epidemiologia , Mucormicose/patologia , Mucormicose/cirurgia , Sistema de Registros , Fatores de RiscoRESUMO
BACKGROUND: The new Rasamsonia spp. complex can develop invasive infection in immunosuppression or chronic pulmonary disease. It has potential to be misidentified as other genera due to morphological similarities. Nowadays, there is a gap of knowledge on this fungi. OBJECTIVES: To provide knowledge base of risk factors and therapeutic decisions in invasive Rasamsonia spp. complex infection. PATIENTS/METHODS: Cases of invasive infection due to Rasamsonia spp. (formerly Geosmithia/Penicillium spp.) from FungiScope® registry and all reported cases from a literature were included. RESULTS: We identified 23 invasive infections due to Rasamsonia spp., six (26.1%) in the FungiScope® registry. Main risk factors were chronic granulomatous disease (n = 12, 52.2%), immunosuppressive treatment (n = 10, 43.5%), haematopoietic stem cell transplantation (n = 7, 30.4%), graft-versus-host disease and major surgery (n = 4, 17.4%, each). Predominantly affected organs were the lungs (n = 21, 91.3%), disease disseminated in seven cases (30.4%). Fungal misidentification occurred in 47.8% (n = 11), and sequencing was used in 69.6% of the patients (n = 16) to diagnose. Breakthrough infection occurred in 13 patients (56.5%). All patients received antifungal treatment, mostly posaconazole (n = 11), caspofungin (n = 10) or voriconazole (n = 9). Combination therapy was administered in 13 patients (56.5%). Susceptibility testing showed high minimum inhibitory concentrations for azoles and amphotericin B, but not for echinocandins. No preferable treatment influencing favourable outcome was identified. Overall mortality was 39% (n = 9). CONCLUSION: Rasamsonia spp. are emerging fungi causing life-threatening infections, especially in immunocompromised and critically ill patients. Mortality is high. Treatment is challenging and clinicians dealing with this patient population should become aware of this infection constituting a medical emergency.
Assuntos
Antifúngicos/uso terapêutico , Doenças Transmissíveis Emergentes/epidemiologia , Eurotiales/patogenicidade , Infecções Fúngicas Invasivas/epidemiologia , Micoses/epidemiologia , Adolescente , Adulto , Antifúngicos/farmacologia , Canadá/epidemiologia , Doenças Transmissíveis Emergentes/tratamento farmacológico , Doenças Transmissíveis Emergentes/microbiologia , Doenças Transmissíveis Emergentes/mortalidade , Tosse , Dispneia , Europa (Continente)/epidemiologia , Eurotiales/efeitos dos fármacos , Feminino , Doenças Hematológicas/complicações , Humanos , Hospedeiro Imunocomprometido , Infecções Fúngicas Invasivas/tratamento farmacológico , Infecções Fúngicas Invasivas/microbiologia , Infecções Fúngicas Invasivas/mortalidade , Japão/epidemiologia , Pneumopatias Fúngicas/tratamento farmacológico , Pneumopatias Fúngicas/epidemiologia , Pneumopatias Fúngicas/microbiologia , Pneumopatias Fúngicas/mortalidade , Masculino , Testes de Sensibilidade Microbiana , Pessoa de Meia-Idade , Micoses/tratamento farmacológico , Micoses/microbiologia , Micoses/mortalidade , Sistema de Registros , Fatores de Risco , Estados Unidos/epidemiologia , Adulto JovemRESUMO
BACKGROUND: Proliferative vitreoretinopathy (PVR) is the major cause for postoperative failure after vitreo-retinal surgery for primary rhegmatogenous retinal detachment (RRD). Adjunct pharmaceutical therapy was found to be ineffective once PVR is established. Preliminary data suggest that prevention of PVR yields better functional outcome. So far, there is no standard therapy to prevent PVR. METHODS/DESIGN: This is a randomized, double-blind, controlled, multicenter, interventional trial with one interim analysis. High-risk patients for PVR with primary RRD will be allocated equally to the following treatment arms: (a) verum: intraoperative adjuvant application of 5-fluorouracil (5-FU) and low-molecular-weight heparin (LMWH) via intraocular infusion during routine pars plana vitrectomy (PPV) and (b) placebo: routinely used intraocular infusion with balanced salt solution during routine PPV. PVR risk is assessed by non-invasive aqueous flare measurement by using laser flare photometry. The primary endpoint of the trial is the occurrence of PVR grade CP (C: full-thickness retinal folds or subretinal strands in clock hours; P: located posterior to equator) 1 or higher within 12 weeks after treatment. Secondary endpoints include PVR grade CA (A: located anterior to equator), best corrected visual acuity, number and extent of surgical procedures to achieve retinal re-attachment, and occurrence of drug-related adverse events within 12 weeks. It is assumed, on the basis of previously published results, that the incidence of PVR grade CP 1 is 35% in the control group and that a reduction by one third would be clinically relevant. Given the sequential design and adjustment for a dropout rate of 5%, a total sample size of 560 patients (280 per group) was calculated to ensure a power of 80% for the confirmatory analysis. DISCUSSION: The present trial uses intraoperative intravitreal 5-FU and LMWH as a prophylactic therapy in high-risk patients with primary RRD, aiming to reduce the incidence of PVR in the group that receives the trial drug. Using laser flare photometry to identify high-risk patients for PVR, this trial will test the effectiveness of a simple treatment to prevent PVR. TRIAL REGISTRATION: EudraCT no.: 2015-004731-12, registered October 21, 2015; ClinicalTrials.gov Identifier: NCT02834559 , registered July 12, 2016. Protocol version: Version 02. Date: September 18, 2016.
Assuntos
Fluoruracila/administração & dosagem , Heparina de Baixo Peso Molecular/administração & dosagem , Complicações Pós-Operatórias/prevenção & controle , Ensaios Clínicos Controlados Aleatórios como Assunto , Descolamento Retiniano/cirurgia , Vitreorretinopatia Proliferativa/prevenção & controle , Interpretação Estatística de Dados , Método Duplo-Cego , Determinação de Ponto Final , Humanos , Injeções Intravítreas , Estudos Multicêntricos como Assunto , Avaliação de Resultados em Cuidados de Saúde , Projetos de Pesquisa , Tamanho da AmostraRESUMO
Inflammation is a complex process involving the contribution of leukocytes and blood vessels, which collectively aim to restore homeostasis following injury to the body. Leukocytes are essential front-line responders to infectious or noninfectious injury and can be deployed within minutes of sensing damage. A typical inflammatory response leads to the exit of circulating leukocytes into the surrounding extravascular space, which follows a series of increasingly adhesive events - collectively termed the "multistep adhesion cascade." The Ras homology (Rho) family of small GTPases (RhoGTPases) are intracellular proteins involved in translating extracellular signals into cellular behavior, such as adhesion and migration. This chapter focuses on how to prepare, perform, and monitor RhoGTPase activation assays using classic pull-down assays. Although this chapter focuses on RhoGTPase signaling downstream of L-selectin clustering, the methods outlined here can be applied to analyzing RhoGTPase activity in response to stimulating other surface receptors.
Assuntos
Leucócitos/metabolismo , Proteínas rho de Ligação ao GTP/metabolismo , Animais , Bioensaio/métodos , Adesão Celular/fisiologia , Linhagem Celular , Movimento Celular/fisiologia , Inflamação/metabolismo , Selectina L/metabolismo , Camundongos , Transdução de Sinais/fisiologiaRESUMO
The anti-diabetic drug metformin regulates T-cell responses to immune activation and is proposed to function by regulating the energy-stress-sensing adenosine-monophosphate-activated protein kinase (AMPK). However, the molecular details of how metformin controls T cell immune responses have not been studied nor is there any direct evidence that metformin acts on T cells via AMPK. Here, we report that metformin regulates cell growth and proliferation of antigen-activated T cells by modulating the metabolic reprogramming that is required for effector T cell differentiation. Metformin thus inhibits the mammalian target of rapamycin complex I signalling pathway and prevents the expression of the transcription factors c-Myc and hypoxia-inducible factor 1 alpha. However, the inhibitory effects of metformin on T cells did not depend on the expression of AMPK in T cells. Accordingly, experiments with metformin inform about the importance of metabolic reprogramming for T cell immune responses but do not inform about the importance of AMPK.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Metformina/farmacologia , Linfócitos T/efeitos dos fármacos , Animais , Transporte Biológico/efeitos dos fármacos , Linfócitos T CD8-Positivos/efeitos dos fármacos , Linfócitos T CD8-Positivos/metabolismo , Linhagem Celular , Glucose/metabolismo , Alvo Mecanístico do Complexo 1 de Rapamicina , Camundongos , Complexos Multiproteicos/metabolismo , Linfócitos T/metabolismo , Serina-Treonina Quinases TOR/metabolismoRESUMO
The present study has examined the role of the serine/threonine kinase LKB1 in the survival and differentiation of CD4/8 double positive thymocytes. LKB1-null DPs can respond to signals from the mature α/ß T-cell-antigen receptor and initiate positive selection. However, in the absence of LKB1, thymocytes fail to mature to conventional single positive cells causing severe lymphopenia in the peripheral lymphoid tissues. LKB1 thus appears to be dispensable for positive selection but important for the maturation of positively selected thymocytes. LKB1 also strikingly prevented the development of invariant Vα14 NKT cells and innate TCR αß gut lymphocytes. Previous studies with gain of function mutants have suggested that the role of LKB1 in T cell development is mediated by its substrate the AMP-activated protein kinase (AMPK). The present study now analyses the impact of AMPK deletion in DP thymocytes and shows that the role of LKB1 during the development of both conventional and innate T cells is mediated by AMPK-independent pathways.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas Quinases Ativadas por AMP/genética , Animais , Células Cultivadas , Citometria de Fluxo , Immunoblotting , Camundongos , Camundongos Mutantes , Proteínas Serina-Treonina Quinases/genética , Receptores de Antígenos de Linfócitos T/genética , Receptores de Antígenos de Linfócitos T/metabolismo , Transdução de Sinais/genética , Transdução de Sinais/fisiologiaRESUMO
The adenosine monophosphate-activated protein kinase (AMPK) is activated by antigen receptor signals and energy stress in T cells. In many cell types, AMPK can maintain energy homeostasis and can enforce quiescence to limit energy demands. We consequently evaluated the importance of AMPK for controlling the transition of metabolically active effector CD8 T lymphocytes to the metabolically quiescent catabolic memory T cells during the contraction phase of the immune response. We show that AMPKα1 activates rapidly in response to the metabolic stress caused by glucose deprivation of CD8 cytotoxic T lymphocytes (CTLs). Moreover, AMPKα1 restrains mammalian target of rapamycin complex 1 activity under conditions of glucose stress. AMPKα1 activity is dispensable for proliferation and differentiation of CTLs. However, AMPKα1 is required for in vivo survival of CTLs following withdrawal of immune stimulation. AMPKα1(null) T cells also show a striking defect in their ability to generate memory CD8 T-cell responses during Listeria monocytogenes infection. These results show that AMPKα1 monitors energy stress in CTLs and controls CD8 T-cell memory.
Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Linfócitos T CD8-Positivos/imunologia , Linfócitos T CD8-Positivos/metabolismo , Glucose/metabolismo , Memória Imunológica , Proteínas Quinases Ativadas por AMP/genética , Animais , Células Cultivadas , Memória Imunológica/genética , Camundongos , Linfócitos T Citotóxicos/imunologia , Linfócitos T Citotóxicos/metabolismoRESUMO
Leukocyte function-associated antigen-1 (LFA-1) and very late antigen-4 (VLA-4) integrins are essential for lymphocyte adhesion, trafficking and effector functions. Protein kinase D (PKD) has previously been implicated in lymphocyte integrin regulation through regulation of Rap1 activity. However, the true role of PKD in integrin regulation in primary lymphocytes has not previously been investigated. The major PKD isoform in lymphocytes is PKD2. Here we employed PKD2-deficient mice, a specific PKD kinase inhibitor, as well as PKD-null DT40 B cells to investigate the role of PKD in integrin regulation in lymphocytes. We report that PKD2-deficient lymphocytes bound normally to integrin ligands in static and shear flow adhesion assays. They also homed normally to lymphoid organs after adoptive transfer into wild-type mice. DT40 B cells devoid of any PKD isoforms and primary lymphocytes pretreated with a specific PKD inhibitor bound normally to integrin ligands, indicating that multiple PKD isoforms do not redundantly regulate lymphocyte integrins. In addition, PKD2-deficient lymphocytes, as well as DT40 cells devoid of any PKD isoforms, could activate Rap1 in response to B-cell receptor ligation or phorbol ester treatment. Together, these results show that the PKD family does not play a critical role in lymphocyte integrin-mediated cell adhesion or lymphocyte trafficking in vivo.
Assuntos
Linfócitos/imunologia , Tecido Linfoide/imunologia , Proteínas Quinases/metabolismo , Animais , Linfócitos B/enzimologia , Linfócitos B/imunologia , Adesão Celular , Células Cultivadas , Proteínas Ativadoras de GTPase/metabolismo , Integrinas/química , Integrinas/metabolismo , Isoenzimas/genética , Isoenzimas/metabolismo , Linfócitos/enzimologia , Camundongos , Ésteres de Forbol/metabolismo , Proteína Quinase D2 , Proteínas Quinases/genética , Receptores de Antígenos de Linfócitos B/metabolismoRESUMO
L-selectin is a cell adhesion molecule (CAM) that is essential for the tethering and subsequent rolling of naïve lymphocytes along the luminal wall of postcapillary venules entering lymph nodes. As with many CAMs, L-selectin has the capacity to transduce intracellular signals in response to ligand binding. This implicates CAMs involved in tethering and rolling as contributors to intracellular signals that lead to the transition from rolling to arrest. In addition, studies in L: -selectin-null mice have also revealed a role for L: -selectin in chemokine-directed cell migration of leucocytes in tissues. The Ras homology (Rho) family of small GTPases are intracellular proteins that respond to signals received from the surrounding environment. The RhoGTPases typically activate downstream targets involved in the remodelling of the actin cytoskeleton, which is essential for continued progression through the multi-step adhesion cascade. This chapter will focus on how to prepare, perform and monitor RhoGTPase activation assays in response to L: -selectin stimulation. Although this section focuses on L: -selectin stimulation, the methods outlined here can be applied to analysing RhoGTPase activity in response to stimulating other receptors involved in tethering/rolling such as CD44, P-selectin glycoprotein ligand-1 and E-selectin ligand-1.
Assuntos
Ensaios Enzimáticos/métodos , Linfócitos/enzimologia , Proteínas rho de Ligação ao GTP/metabolismo , Animais , Western Blotting , Células Cultivadas , Eletroforese em Gel de Poliacrilamida , Selectina L/metabolismo , Camundongos , Proteínas Recombinantes de Fusão/metabolismo , Proteína cdc42 de Ligação ao GTP/metabolismoRESUMO
L-selectin is a cell adhesion molecule that tethers leukocytes to the luminal walls of venules during inflammation and enables them to roll under the force of blood flow. Clustering of L-selectin during rolling is thought to promote outside-in signals that lead to integrin activation and chemokine receptor expression, ultimately contributing to leukocyte arrest. Several studies have underscored the importance of the L-selectin cytoplasmic tail in functionally regulating adhesion and signaling. Interestingly, the L-selectin tail comprises only 17 amino acids, and yet it is thought to bind simultaneously to several proteins. For example, constitutive association of calmodulin (CaM) and ezrin/radixin/moesin (ERM) to L-selectin confers resistance to proteolysis and microvillar positioning, respectively. In this report we found that recombinant purified CaM and ERM bound non-competitively to the same tail of L-selectin. Furthermore, molecular modeling supported the possibility that CaM, L-selectin, and moesin could form a heterotrimeric complex. Finally, using fluorescence lifetime imaging microscopy to measure fluorescence resonance energy transfer, it was shown that CaM, L-selectin, and ERM could interact simultaneously in vivo. Moreover, L-selectin clustering promoted CaM/ERM interaction in cis (i.e. derived from neighboring L-selectin tails). These results highlight a novel intracellular event that occurs as a consequence of L-selectin clustering, which could participate in transducing signals that promote the transition from rolling to arrest.