RESUMO
BACKGROUND: Breast cancer (BC) is the most common cancer in women, with triple negative BC (TNBC) accounting for 20% of cases. While early detection and targeted therapies have improved overall life expectancy, TNBC remains resistant to current treatments. Although parity reduces the lifetime risk of developing BC, pregnancy increases the risk of developing TNBC for years after childbirth. Although numerous gene mutations have been associated with BC, no single gene alteration has been identified as a universal driver. RRAS2 is a RAS-related GTPase rarely found mutated in cancer. METHODS: Conditional knock-in mice were generated to overexpress wild type human RRAS2 in mammary epithelial cells. A human sample cohort was analyzed by RT-qPCR to measure RRAS2 transcriptional expression and to determine the frequency of both a single-nucleotide polymorphism (SNP rs8570) in the 3'UTR region of RRAS2 and of genomic DNA amplification in tumoral and non-tumoral human BC samples. RESULTS: Here we show that overexpression of wild-type RRAS2 in mice is sufficient to develop TNBC in 100% of females in a pregnancy-dependent manner. In human BC, wild-type RRAS2 is overexpressed in 68% of tumors across grade, location, and molecular type, surpassing the prevalence of any previously implicated alteration. Still, RRAS2 overexpression is notably higher and more frequent in TNBC and young parous patients. The increased prevalence of the alternate C allele at the SNP position in tumor samples, along with frequent RRAS2 gene amplification in both tumors and blood of BC patients, suggests a cause-and-effect relationship between RRAS2 overexpression and breast cancer. CONCLUSIONS: Higher than normal expression of RRAS2 not bearing activating mutations is a key driver in the majority of breast cancers, especially those of the triple-negative type and those linked to pregnancy.
Assuntos
Neoplasias de Mama Triplo Negativas , Neoplasias de Mama Triplo Negativas/genética , Neoplasias de Mama Triplo Negativas/patologia , Neoplasias de Mama Triplo Negativas/metabolismo , Feminino , Animais , Humanos , Camundongos , Gravidez , Oncogenes , Polimorfismo de Nucleotídeo Único , Período Pós-Parto/genética , Mutação , Regulação Neoplásica da Expressão Gênica , Técnicas de Introdução de Genes , Proteínas ras/genética , Proteínas ras/metabolismo , Camundongos Transgênicos , Modelos Animais de Doenças , Proteínas de Membrana , Proteínas Monoméricas de Ligação ao GTPRESUMO
AIMS: Transthyretin amyloid cardiomyopathy (ATTR-CM), a progressive and fatal cardiomyopathy, is frequently misdiagnosed or entails diagnostic delays, hindering patients from timely treatment. This study aimed to generate a systematic framework based on data from electronic health records (EHRs) to assess patients with ATTR-CM in a real-world population of heart failure (HF) patients. Predictive factors or combinations of predictive factors related to ATTR-CM in a European population were also assessed. METHODS AND RESULTS: Retrospective unstructured and semi-structured data from EHRs of patients from OLV Hospital Aalst, Belgium (2012-20), were processed using natural language processing (NLP) to generate an Observational Medical Outcomes Partnership Common Data Model database. NLP model performance was assessed on a random subset of EHRs by comparing algorithm outputs to a physician-generated standard (using precision, recall, and their harmonic mean, or F1-score). Of the 3127 HF patients, 103 potentially had ATTR-CM (age 78 ± 9 years; male 55%; ejection fraction of 48% ± 16). The mean diagnostic delay between HF and ATTR-CM diagnosis was 1.8 years. Besides HF and cardiomyopathy-related phenotypes, the strongest cardiac predictor was atrial fibrillation (AF; 72% in ATTR-CM vs. 60% in non-ATTR-CM, P = 0.02), whereas the strongest non-cardiac predictor was carpal tunnel syndrome (21% in ATTR-CM vs. 3% in non-ATTR-CM, P < 0.001). The strongest combination predictor was AF, joint disorders, and HF with preserved ejection fraction (29% in ATTR-CM vs. 18% in non-ATTR-CM: odds ratio = 2.03, 95% confidence interval = 1.28-3.22). CONCLUSIONS: Not only well-known variables associated with ATTR-CM but also unique combinations of cardiac and non-cardiac phenotypes are able to predict ATTR-CM in a real-world HF population, aiding in early identification of ATTR-CM patients.
Assuntos
Neuropatias Amiloides Familiares , Cardiomiopatias , Insuficiência Cardíaca , Idoso , Idoso de 80 Anos ou mais , Humanos , Masculino , Neuropatias Amiloides Familiares/diagnóstico , Neuropatias Amiloides Familiares/epidemiologia , Neuropatias Amiloides Familiares/complicações , Cardiomiopatias/diagnóstico , Cardiomiopatias/epidemiologia , Cardiomiopatias/complicações , Diagnóstico Tardio , Registros Eletrônicos de Saúde , Insuficiência Cardíaca/diagnóstico , Insuficiência Cardíaca/epidemiologia , Insuficiência Cardíaca/complicações , Pré-Albumina/genética , Estudos Retrospectivos , FemininoRESUMO
Successful vaccines rely on activating a functional humoral immune response through the generation of class-switched high affinity immunoglobulins (Igs). The germinal center (GC) reaction is crucial for this process, in which B cells are selected in their search for antigen and T cell help. A major hurdle to understand the mechanisms of B cell:T cell cooperation has been the lack of an antigen-specific in vitro GC system. Here we report the generation of antigen-specific, high-affinity, class-switched Igs in simple 2-cell type cultures of naive B and T cells. B cell antigen uptake by phagocytosis is key to generate these Igs. We have used the method to interrogate if T cells confer directional help to cognate B cells that present antigen and to bystander B cells. We find that bystander B cells do not generate class-switched antibodies due to a defective formation of T-B conjugates and an early conversion into memory B cells.
Assuntos
Linfócitos B , Centro Germinativo , Antígenos/metabolismo , Imunidade Humoral , RecreaçãoRESUMO
A missense change in RRAS2 (Gln72 to Leu), analogous to the Gln61-to-Leu mutation of RAS oncoproteins, has been identified as a long-tail hotspot mutation in cancer and Noonan syndrome. However, the relevance of this mutation for in vivo tumorigenesis remains understudied. Here we show, using an inducible knockin mouse model, that R-Ras2Q72L triggers rapid development of a wide spectrum of tumors when somatically expressed in adult tissues. These tumors show limited overlap with those originated by classical Ras oncogenes. R-Ras2Q72L-driven tumors can be classified into different subtypes according to therapeutic susceptibility. Importantly, the most relevant R-Ras2Q72L-driven tumors are dependent on mTORC1 but independent of phosphatidylinositol 3-kinase-, MEK-, and Ral guanosine diphosphate (GDP) dissociation stimulator. This pharmacological vulnerability is due to the extensive rewiring by R-Ras2Q72L of pathways that orthogonally stimulate mTORC1 signaling. These findings demonstrate that RRAS2Q72L is a bona fide oncogenic driver and unveil therapeutic strategies for patients with cancer and Noonan syndrome bearing RRAS2 mutations.
Assuntos
Proteínas Monoméricas de Ligação ao GTP , Síndrome de Noonan , Animais , Carcinogênese/genética , Humanos , Alvo Mecanístico do Complexo 1 de Rapamicina , Proteínas de Membrana , Camundongos , Proteínas Monoméricas de Ligação ao GTP/genética , Mutação/genética , OncogenesRESUMO
BACKGROUND: Chronic lymphocytic leukemia (CLL) is the most frequent, and still incurable, form of leukemia in the Western World. It is widely accepted that cancer results from an evolutionary process shaped by the acquisition of driver mutations which confer selective growth advantage to cells that harbor them. Clear examples are missense mutations in classic RAS genes (KRAS, HRAS and NRAS) that underlie the development of approximately 13% of human cancers. Although autonomous B cell antigen receptor (BCR) signaling is involved and mutations in many tumor suppressor genes and oncogenes have been identified, an oncogenic driver gene has not still been identified for CLL. METHODS: Conditional knock-in mice were generated to overexpress wild type RRAS2 and prove its driver role. RT-qPCR analysis of a human CLL sample cohort was carried out to measure RRAS2 transcriptional expression. Sanger DNA sequencing was used to identify a SNP in the 3'UTR region of RRAS2 in human CLL samples. RNAseq of murine CLL was carried out to identify activated pathways, molecular mechanisms and to pinpoint somatic mutations accompanying RRAS2 overexpression. Flow cytometry was used for phenotypic characterization and shRNA techniques to knockdown RRAS2 expression in human CLL. RESULTS: RRAS2 mRNA is found overexpressed in its wild type form in 82% of the human CLL samples analyzed (n = 178, mean and median = 5-fold) as well as in the explored metadata. A single nucleotide polymorphism (rs8570) in the 3'UTR of the RRAS2 mRNA has been identified in CLL patients, linking higher expression of RRAS2 with more aggressive disease. Deliberate overexpression of wild type RRAS2 in mice, but not an oncogenic Q72L mutation in the coding sequence, provokes the development of CLL. Overexpression of wild type RRAS2 in mice is accompanied by a strong convergent selection of somatic mutations in genes that have been identified in human CLL. R-RAS2 protein is physically bound to the BCR and mediates BCR signals in CLL. CONCLUSIONS: The results indicate that overexpression of wild type RRAS2 is behind the development of CLL.
Assuntos
Leucemia Linfocítica Crônica de Células B , Proteínas Monoméricas de Ligação ao GTP , Animais , Genes ras , Humanos , Leucemia Linfocítica Crônica de Células B/genética , Leucemia Linfocítica Crônica de Células B/patologia , Proteínas de Membrana/genética , Camundongos , Proteínas Monoméricas de Ligação ao GTP/genética , Mutação , Receptores de Antígenos de Linfócitos B , Transdução de SinaisRESUMO
T cells form immunological synapses with professional antigen-presenting cells (APCs) resulting in T cell activation and the acquisition of peptide antigen-MHC (pMHC) complexes from the plasma membrane of the APC. They thus become APCs themselves. We investigate the functional outcome of T-T cell antigen presentation by CD4 T cells and find that the antigen-presenting T cells (Tpres) predominantly differentiate into regulatory T cells (Treg), whereas T cells that have been stimulated by Tpres cells predominantly differentiate into Th17 pro-inflammatory cells. Using mice deficient in pMHC uptake by T cells, we show that T-T antigen presentation is important for the development of experimental autoimmune encephalitis and Th17 cell differentiation in vivo. By varying the professional APC:T cell ratio, we can modulate Treg versus Th17 differentiation in vitro and in vivo, suggesting that T-T antigen presentation underlies proinflammatory responses in conditions of antigen scarcity.
Assuntos
Apresentação de Antígeno/imunologia , Antígenos/metabolismo , Polaridade Celular/imunologia , Células Th17/imunologia , Animais , Antígenos CD28/metabolismo , Diferenciação Celular/imunologia , Membrana Celular/metabolismo , Células Dendríticas/imunologia , Modelos Animais de Doenças , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/patologia , Regulação da Expressão Gênica , Genoma , Antígenos de Histocompatibilidade Classe II/imunologia , Camundongos Endogâmicos C57BL , Linfócitos T Reguladores/imunologia , Transcrição Gênica , Trogocitose , Proteínas rho de Ligação ao GTP/deficiência , Proteínas rho de Ligação ao GTP/metabolismoRESUMO
Vimentin is an intermediate filament protein that plays key roles in integration of cytoskeletal functions, and therefore in basic cellular processes such as cell division and migration. Consequently, vimentin has complex implications in pathophysiology. Vimentin is required for a proper immune response, but it can also act as an autoantigen in autoimmune diseases or as a damage signal. Although vimentin is a predominantly cytoplasmic protein, it can also appear at extracellular locations, either in a secreted form or at the surface of numerous cell types, often in relation to cell activation, inflammation, injury or senescence. Cell surface targeting of vimentin appears to associate with the occurrence of certain posttranslational modifications, such as phosphorylation and/or oxidative damage. At the cell surface, vimentin can act as a receptor for bacterial and viral pathogens. Indeed, vimentin has been shown to play important roles in virus attachment and entry of severe acute respiratory syndrome-related coronavirus (SARS-CoV), dengue and encephalitis viruses, among others. Moreover, the presence of vimentin in specific virus-targeted cells and its induction by proinflammatory cytokines and tissue damage contribute to its implication in viral infection. Here, we recapitulate some of the pathophysiological implications of vimentin, including the involvement of cell surface vimentin in interaction with pathogens, with a special focus on its role as a cellular receptor or co-receptor for viruses. In addition, we provide a perspective on approaches to target vimentin, including antibodies or chemical agents that could modulate these interactions to potentially interfere with viral pathogenesis, which could be useful when multi-target antiviral strategies are needed.
Assuntos
Coronavírus Relacionado à Síndrome Respiratória Aguda Grave/fisiologia , Vimentina/metabolismo , Viroses/patologia , Anticorpos/imunologia , Anticorpos/metabolismo , Anticorpos/uso terapêutico , Betacoronavirus/isolamento & purificação , COVID-19 , Infecções por Coronavirus/tratamento farmacológico , Interações Hospedeiro-Patógeno , Humanos , Pandemias , Pneumonia Viral/tratamento farmacológico , SARS-CoV-2 , Bibliotecas de Moléculas Pequenas/química , Bibliotecas de Moléculas Pequenas/farmacologia , Bibliotecas de Moléculas Pequenas/uso terapêutico , Vimentina/química , Vimentina/imunologia , Viroses/tratamento farmacológico , Viroses/metabolismo , Replicação Viral/efeitos dos fármacosRESUMO
Signal strength controls the outcome of αß T cell selection in the thymus, resulting in death if the affinity of the rearranged TCR is below the threshold for positive selection, or if the affinity of the TCR is above the threshold for negative selection. Here we show that deletion of the GTPase RRAS2 results in exacerbated negative selection and above-normal expression of positive selection markers. Furthermore, Rras2-/- mice are resistant to autoimmunity both in a model of inflammatory bowel disease (IBD) and in a model of myelin oligodendrocyte glycoprotein (MOG)-induced experimental autoimmune encephalomyelitis (EAE). We show that MOG-specific T cells in Rras2-/- mice have reduced affinity for MOG/I-Ab tetramers, suggesting that enhanced negative selection leads to selection of TCRs with lower affinity for the self-MOG peptide. An analysis of the TCR repertoire shows alterations that mostly affect the TCRα variable (TRAV) locus with specific VJ combinations and CDR3α sequences that are absent in Rras2-/- mice, suggesting their involvement in autoimmunity.
Assuntos
Seleção Clonal Mediada por Antígeno , Encefalomielite Autoimune Experimental/imunologia , Rearranjo Gênico da Cadeia alfa dos Receptores de Antígenos dos Linfócitos T/imunologia , Proteínas de Membrana/imunologia , Proteínas Monoméricas de Ligação ao GTP/imunologia , Receptores de Antígenos de Linfócitos T alfa-beta/imunologia , Animais , Encefalomielite Autoimune Experimental/induzido quimicamente , Encefalomielite Autoimune Experimental/genética , Encefalomielite Autoimune Experimental/patologia , Rearranjo Gênico da Cadeia beta dos Receptores de Antígenos dos Linfócitos T/imunologia , Proteínas de Membrana/genética , Camundongos , Camundongos Knockout , Proteínas Monoméricas de Ligação ao GTP/genética , Glicoproteína Mielina-Oligodendrócito/efeitos adversos , Glicoproteína Mielina-Oligodendrócito/farmacologiaRESUMO
Successful vaccines rely on activating a functional humoral response that results from promoting a proper germinal center (GC) reaction. Key in this process is the activation of follicular B cells that need to acquire antigens and to present them to cognate CD4 T cells. Here, we report that follicular B cells can phagocytose large antigen-coated particles, a process thought to be exclusive of specialized antigen-presenting cells such as macrophages and dendritic cells. We show that antigen phagocytosis by B cells is BCR-driven and mechanistically dependent on the GTPase RhoG. Using Rhog-/- mice, we show that phagocytosis of antigen by B cells is important for the development of a strong GC response and the generation of high-affinity class-switched antibodies. Importantly, we show that the potentiation effect of alum, a common vaccine adjuvant, requires direct phagocytosis of alum-antigen complexes by B cells. These data suggest a new avenue for vaccination approaches by aiming to deliver 1-3 µm size antigen particles to follicular B cells.
Assuntos
Antígenos/imunologia , Linfócitos B/imunologia , Imunidade Humoral , Fagocitose/imunologia , Actinas/metabolismo , Adjuvantes Imunológicos , Compostos de Alúmen/metabolismo , Animais , Células Apresentadoras de Antígenos/imunologia , Linfócitos T CD4-Positivos/imunologia , GTP Fosfo-Hidrolases/genética , Centro Germinativo/citologia , Centro Germinativo/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Camundongos Transgênicos , Microesferas , Fagocitose/genética , Vacinação/métodos , Proteínas rho de Ligação ao GTPRESUMO
Upon antigen recognition within peripheral lymphoid organs, B cells interact with T cells and other immune cells to transiently form morphological structures called germinal centers (GCs), which are required for B cell clonal expansion, immunoglobulin class switching, and affinity maturation. This process, known as the GC response, is an energetically demanding process that requires the metabolic reprogramming of B cells. We showed that the Ras-related guanosine triphosphate hydrolase (GTPase) R-Ras2 (also known as TC21) plays an essential, nonredundant, and B cell-intrinsic role in the GC response. Both the conversion of B cells into GC B cells and their expansion were impaired in mice lacking R-Ras2, but not in those lacking a highly related R-Ras subfamily member or both the classic H-Ras and N-Ras GTPases. In the absence of R-Ras2, activated B cells did not exhibit increased oxidative phosphorylation or aerobic glycolysis. We showed that R-Ras2 was an effector of both the B cell receptor (BCR) and CD40 and that, in its absence, B cells exhibited impaired activation of the PI3K-Akt-mTORC1 pathway, reduced mitochondrial DNA replication, and decreased expression of genes involved in glucose metabolism. Because most human B cell lymphomas originate from GC B cells or B cells that have undergone the GC response, our data suggest that R-Ras2 may also regulate metabolism in B cell malignancies.
Assuntos
Linfócitos B/fisiologia , Metabolismo Energético , Genes ras , Centro Germinativo/fisiologia , Proteínas de Membrana/fisiologia , Mitocôndrias/metabolismo , Proteínas Monoméricas de Ligação ao GTP/fisiologia , Proteínas Proto-Oncogênicas p21(ras)/metabolismo , Animais , Linfócitos B/citologia , Antígenos CD40/genética , Antígenos CD40/metabolismo , Células Cultivadas , Feminino , Centro Germinativo/citologia , Glicólise , Ativação Linfocitária , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fosfatidilinositol 3-Quinases/genética , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/genética , Proteínas Proto-Oncogênicas c-akt/metabolismo , Proteínas Proto-Oncogênicas p21(ras)/genética , Receptores de Antígenos de Linfócitos B/genética , Receptores de Antígenos de Linfócitos B/metabolismoRESUMO
Establishing a stable interaction between a T cell and an antigen presenting cell (APC) involves the formation of an immune synapse (IS). It is through this structure that the T cell can integrate all the signals provided by the APC. The IS also serves as a mechanism for TCR downregulation through internalization. Here, we describe methods for visualizing MHC-engaged T cell receptor (TCR) internalization from the IS in human cell lines and mouse primary T cells by confocal fluorescence microscopy techniques.
Assuntos
Sinapses Imunológicas/imunologia , Receptores de Antígenos de Linfócitos T/imunologia , Linfócitos T/imunologia , Animais , Humanos , Células Jurkat , Camundongos , Microscopia Confocal/métodosRESUMO
Modulating T cell activation is critical for treating autoimmune diseases but requires avoiding concomitant opportunistic infections. Antigen binding to the T cell receptor (TCR) triggers the recruitment of the cytosolic adaptor protein Nck to a proline-rich sequence in the cytoplasmic tail of the TCR's CD3ε subunit. Through virtual screening and using combinatorial chemistry, we have generated an orally available, low-molecular weight inhibitor of the TCR-Nck interaction that selectively inhibits TCR-triggered T cell activation with an IC50 (median inhibitory concentration) ~1 nM. By modulating TCR signaling, the inhibitor prevented the development of psoriasis and asthma and, furthermore, exerted a long-lasting therapeutic effect in a model of autoimmune encephalomyelitis. However, it did not prevent the generation of a protective memory response against a mouse pathogen, suggesting that the compound might not exert its effects through immunosuppression. These results suggest that inhibiting an immediate TCR signal has promise for treating a broad spectrum of human T cell-mediated autoimmune and inflammatory diseases.
Assuntos
Doenças Autoimunes/tratamento farmacológico , Receptores de Antígenos de Linfócitos T/antagonistas & inibidores , Administração Oral , Animais , Anti-Inflamatórios/farmacologia , Doenças Autoimunes/imunologia , Proliferação de Células , Citocinas/metabolismo , Desenho de Fármacos , Feminino , Voluntários Saudáveis , Humanos , Terapia de Imunossupressão , Concentração Inibidora 50 , Ligantes , Ativação Linfocitária , Espectroscopia de Ressonância Magnética , Camundongos , Camundongos Endogâmicos C57BL , Domínios Proteicos , Receptores de Antígenos de Linfócitos T/imunologia , Transdução de Sinais , Ressonância de Plasmônio de Superfície , Linfócitos T/citologiaRESUMO
Enzymatic and non-enzymatic lipid metabolism can give rise to reactive species that may covalently modify cellular or plasma proteins through a process known as lipoxidation. Under basal conditions, protein lipoxidation can contribute to normal cell homeostasis and participate in signaling or adaptive mechanisms, as exemplified by lipoxidation of Ras proteins or of the cytoskeletal protein vimentin, both of which behave as sensors of electrophilic species. Nevertheless, increased lipoxidation under pathological conditions may lead to deleterious effects on protein structure or aggregation. This can result in impaired degradation and accumulation of abnormally folded proteins contributing to pathophysiology, as may occur in neurodegenerative diseases. Identification of the protein targets of lipoxidation and its functional consequences under pathophysiological situations can unveil the modification patterns associated with the various outcomes, as well as preventive strategies or potential therapeutic targets. Given the wide structural variability of lipid moieties involved in lipoxidation, highly sensitive and specific methods for its detection are required. Derivatization of reactive carbonyl species is instrumental in the detection of adducts retaining carbonyl groups. In addition, use of tagged derivatives of electrophilic lipids enables enrichment of lipoxidized proteins or peptides. Ultimate confirmation of lipoxidation requires high resolution mass spectrometry approaches to unequivocally identify the adduct and the targeted residue. Moreover, rigorous validation of the targets identified and assessment of the functional consequences of these modifications are essential. Here we present an update on methods to approach the complex field of lipoxidation along with validation strategies and functional assays illustrated with well-studied lipoxidation targets.
Assuntos
Lipídeos/química , Proteínas/química , Aldeídos/química , Cromatografia Líquida de Alta Pressão , Hidrazinas/química , Lipopeptídeos/análise , Proteínas/metabolismo , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por MatrizRESUMO
The vimentin filament network plays a key role in cell architecture and signalling, as well as in epithelial-mesenchymal transition. Vimentin C328 is targeted by various oxidative modifications, but its role in vimentin organization is not known. Here we show that C328 is essential for vimentin network reorganization in response to oxidants and electrophiles, and is required for optimal vimentin performance in network expansion, lysosomal distribution and aggresome formation. C328 may fulfil these roles through interaction with zinc. In vitro, micromolar zinc protects vimentin from iodoacetamide modification and elicits vimentin polymerization into optically detectable structures; in cells, zinc closely associates with vimentin and its depletion causes reversible filament disassembly. Finally, zinc transport-deficient human fibroblasts show increased vimentin solubility and susceptibility to disruption, which are restored by zinc supplementation. These results unveil a critical role of C328 in vimentin organization and open new perspectives for the regulation of intermediate filaments by zinc.
Assuntos
Acrodermatite/metabolismo , Cisteína/metabolismo , Fibroblastos/metabolismo , Estresse Oxidativo , Vimentina/metabolismo , Zinco/deficiência , Zinco/metabolismo , Acrodermatite/patologia , Fibroblastos/ultraestrutura , Imunofluorescência , Humanos , Imunoprecipitação , Técnicas In Vitro , Microscopia Confocal , Microscopia Eletrônica , Imagem Óptica , Polimerização , Ligação Proteica , Proteômica , Vimentina/ultraestruturaRESUMO
We recently reported that the isoprenylation and palmitoylation motif present at the C-terminus of human RhoB protein promotes intraluminal vesicle delivery of proteins in cells from organisms as phylogenetically apart as fungi and humans. Here we build on these observations by showing that chimeras of fluorescent proteins bearing this sequence, namely, CINCCKVL, which become isoprenylated and palmitoylated in cells, may be used to mark endolysosomes while preserving their morphology. Indeed, these chimeric proteins are devoid of the effects derived from overexpression of fluorescent constructs of full-length, active proteins widely used as endolysosomal markers, such as Lamp1 or Rab7, which cause lysosomal enlargement, or RhoB, which induces actin stress fibers. Moreover, the fact that lipidation-dependent endolysosomal localization of CINCCKVL chimeras can be ascertained in a wide variety of cells indicates that they follow a path toward endolysosomes that is conserved in diverse species. Therefore, CINCCKVL chimeras serve as robust tools to mark these late endocytic compartments.
RESUMO
The C-terminal ends of small GTPases contain hypervariable sequences which may be posttranslationally modified by defined lipid moieties. The diverse structural motifs generated direct proteins towards specific cellular membranes or organelles. However, knowledge on the factors that determine these selective associations is limited. Here we show, using advanced microscopy, that the isoprenylation and palmitoylation motif of human RhoB (-CINCCKVL) targets chimeric proteins to intraluminal vesicles of endolysosomes in human cells, displaying preferential co-localization with components of the late endocytic pathway. Moreover, this distribution is conserved in distant species, including cells from amphibians, insects and fungi. Blocking lipidic modifications results in accumulation of CINCCKVL chimeras in the cytosol, from where they can reach endolysosomes upon release of this block. Remarkably, CINCCKVL constructs are sorted to intraluminal vesicles in a cholesterol-dependent process. In the lower species, neither the C-terminal sequence of RhoB, nor the endosomal distribution of its homologs are conserved; in spite of this, CINCCKVL constructs also reach endolysosomes in Xenopus laevis and insect cells. Strikingly, this behavior is prominent in the filamentous ascomycete fungus Aspergillus nidulans, in which GFP-CINCCKVL is sorted into endosomes and vacuoles in a lipidation-dependent manner and allows monitoring endosomal movement in live fungi. In summary, the isoprenylated and palmitoylated CINCCKVL sequence constitutes a specific structure which delineates an endolysosomal sorting strategy operative in phylogenetically diverse organisms.
Assuntos
Fibroblastos/metabolismo , Processamento de Proteína Pós-Traducional , Proteínas Recombinantes de Fusão/metabolismo , Vesículas Transportadoras/metabolismo , Proteína rhoB de Ligação ao GTP/metabolismo , Motivos de Aminoácidos , Animais , Aspergillus nidulans/genética , Aspergillus nidulans/metabolismo , Transporte Biológico , Sequência Conservada , Endocitose , Endossomos/metabolismo , Feminino , Fibroblastos/citologia , Células HeLa , Humanos , Lipoilação , Lisossomos/metabolismo , Dados de Sequência Molecular , Mariposas/citologia , Mariposas/metabolismo , Ovário/citologia , Ovário/metabolismo , Prenilação , Cultura Primária de Células , Proteínas Recombinantes de Fusão/genética , Homologia de Sequência de Aminoácidos , Xenopus laevis/genética , Xenopus laevis/metabolismo , Proteína rhoB de Ligação ao GTP/genéticaRESUMO
Cyclopentenone prostaglandins (cyPG) are endogenous lipid mediators involved in the resolution of inflammation and the regulation of cell proliferation and cellular redox status. Upon exogenous administration they have shown beneficial effects in models of inflammation and tissue injury, as well as potential antitumoral actions, which have raised a considerable interest in their study for the development of therapeutic tools. Due to their electrophilic nature, the best-known mechanism of action of these mediators is the covalent modification of proteins at cysteine residues through Michael addition. Identification of cyPG targets through proteomic approaches, including MS/MS analysis to pinpoint the modified residues, is proving critical to characterize their mechanisms of action. Among the targets of cyPG are proinflammatory transcription factors, proteins involved in cell defense, such as the regulator of the antioxidant response Keap1 and detoxifying enzymes like GST, and key signaling proteins like Ras proteins. Moreover, cyPG may interact with redox-active small molecules, such as glutathione and hydrogen sulfide. Much has been learned about cyPG in the past few years and this knowledge has also contributed to clarify both pharmacological actions and signaling mechanisms of these and other electrophilic lipids. Given the fact that many cyPG targets are involved in or are targets for redox regulation, there is a complex interplay with redox-induced modifications. Here we address the modification of protein cysteine residues by cyPG elucidated by proteomic studies, paying special attention to the interplay with redox signaling.
Assuntos
Ciclopentanos/metabolismo , Cisteína/análise , Cisteína/metabolismo , Prostaglandinas/metabolismo , Proteínas/metabolismo , Proteômica/métodos , Animais , Humanos , Lipoilação , Espectrometria de Massas/métodos , Oxirredução , Proteínas/química , Transdução de Sinais , Proteínas ras/química , Proteínas ras/metabolismoRESUMO
Autophagic and endo-lysosomal degradative pathways are essential for cell homeostasis. Availability of reliable tools to interrogate these pathways is critical to unveil their involvement in physiology and pathophysiology. Although several probes have been recently developed to monitor autophagic or lysosomal compartments, their specificity has not been validated through co-localization studies with well-known markers. Here, we evaluate the selectivity and interactions between one lysosomal (Lyso-ID) and one autophagosomal (Cyto-ID) probe under conditions modulating autophagy and/or endo-lysosomal function in live cells. The probe for acidic compartments Lyso-ID was fully localized inside vesicles positive for markers of late endosome-lysosomes, including Lamp1-GFP and GFP-CINCCKVL. Induction of autophagy by amino acid deprivation in bovine aortic endothelial cells caused an early and potent increase in the fluorescence of the proposed autophagy dye Cyto-ID. Cyto-ID-positive compartments extensively co-localized with the autophagosomal fluorescent reporter RFP-LC3, although the time and/or threshold for organelle detection was different for each probe. Interestingly, use of Cyto-ID in combination with Lysotracker Red or Lyso-ID allowed the observation of structures labeled with either one or both probes, the extent of co-localization increasing upon treatment with protease inhibitors. Inhibition of the endo-lysosomal pathway with chloroquine or U18666A resulted in the formation of large Cyto-ID and Lyso-ID-positive compartments. These results constitute the first assessment of the selectivity of Cyto-ID and Lyso-ID as probes for the autophagic and lysosomal pathways, respectively. Our observations show that these probes can be used in combination with protein-based markers for monitoring the interactions of both pathways in live cells.