RESUMO
T cell acute lymphoblastic leukemia (T-ALL) and T cell lymphoblastic lymphoma (T-LBL) are rare aggressive hematological malignancies. Current treatment consists of intensive chemotherapy, leading to 80% overall survival but are associated with severe toxic side effects. Furthermore, 10-20% of patients still die from relapsed or refractory disease providing a strong rationale for more specific, targeted therapeutic strategies with less toxicities. Here, we report a novel MYH9::PDGFRB fusion in a T-LBL patient and demonstrate that this fusion product is constitutively active and sufficient to drive oncogenic transformation in vitro and in vivo. Expanding our analysis more broadly across T-ALL, we found a T-ALL cell line and multiple patient derived xenograft models with PDGFRB hyperactivation in the absence of a fusion, with high PDGFRB expression in TLX3 and HOXA T-ALL molecular subtypes. To target this PDGFRB hyperactivation, we evaluated the therapeutic effects of a selective PDGFRB inhibitor, CP-673451, both in vitro and in vivo and demonstrated sensitivity if the receptor is hyperactivated. Altogether, our work reveals that hyperactivation of PDGFRB is an oncogenic driver in T-ALL/T-LBL and that screening T-ALL/TLBL patients for phosphorylated PDGFRB levels can serve as a biomarker for PDGFRB inhibition as a novel targeted therapeutic strategy in their treatment regimen.
RESUMO
T-cell acute lymphoblastic leukemia (T-ALL) and T-cell acute lymphoblastic lymphoma (T-LBL) are aggressive hematological malignancies that are currently treated with high-dose chemotherapy. Over the last several years, the search toward novel and less-toxic therapeutic strategies for T-ALL/T-LBL patients has largely focused on the identification of cell-intrinsic properties of the tumor cell. However, non-cell-autonomous activation of specific oncogenic pathways might also offer opportunities that could be exploited at the therapeutic level. In line with this, we here show that endogenous interleukin 7 (IL7) can increase the expression of the oncogenic kinase proviral integration site for Moloney-murine leukemia 1 (PIM1) in CD127+ T-ALL/T-LBL, thereby rendering these tumor cells sensitive to in vivo PIM inhibition. In addition, using different CD127+ T-ALL/T-LBL xenograft models, we also reveal that residual tumor cells, which remain present after short-term in vivo chemotherapy, display consistent upregulation of PIM1 as compared with bulk nontreated tumor cells. Notably, this effect was transient as increased PIM1 levels were not observed in reestablished disease after abrogation of the initial chemotherapy. Furthermore, we uncover that this phenomenon is, at least in part, mediated by the ability of glucocorticoids to cause transcriptional upregulation of IL7RA in T-ALL/T-LBL patient-derived xenograft (PDX) cells, ultimately resulting in non-cell-autonomous PIM1 upregulation by endogenous IL7. Finally, we confirm in vivo that chemotherapy in combination with a pan-PIM inhibitor can improve leukemia survival in a PDX model of CD127+ T-ALL. Altogether, our work reveals that IL7 and glucocorticoids coordinately drive aberrant activation of PIM1 and suggests that IL7-responsive CD127+ T-ALL and T-LBL patients could benefit from PIM inhibition during induction chemotherapy.
Assuntos
Protocolos de Quimioterapia Combinada Antineoplásica/farmacologia , Citocinas/farmacologia , Regulação Neoplásica da Expressão Gênica/efeitos dos fármacos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/tratamento farmacológico , Proteínas Proto-Oncogênicas c-pim-1/metabolismo , Linfócitos T/imunologia , Animais , Apoptose , Proliferação de Células , Quimioterapia Combinada , Humanos , Camundongos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/imunologia , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Linfócitos T/efeitos dos fármacos , Células Tumorais Cultivadas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Modulators of epithelial-to-mesenchymal transition (EMT) have recently emerged as novel players in the field of leukemia biology. The mechanisms by which EMT modulators contribute to leukemia pathogenesis, however, remain to be elucidated. Here we show that overexpression of SNAI1, a key modulator of EMT, is a pathologically relevant event in human acute myeloid leukemia (AML) that contributes to impaired differentiation, enhanced self-renewal, and proliferation of immature myeloid cells. We demonstrate that ectopic expression of Snai1 in hematopoietic cells predisposes mice to AML development. This effect is mediated by interaction with the histone demethylase KDM1A/LSD1. Our data shed new light on the role of SNAI1 in leukemia development and identify a novel mechanism of LSD1 corruption in cancer. This is particularly pertinent given the current interest surrounding the use of LSD1 inhibitors in the treatment of multiple different malignancies, including AML.
Assuntos
Transformação Celular Neoplásica , Transição Epitelial-Mesenquimal/genética , Histona Desmetilases/metabolismo , Leucemia Mieloide Aguda/patologia , Fatores de Transcrição da Família Snail/fisiologia , Animais , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Transformação Celular Neoplásica/metabolismo , Células HEK293 , Células HL-60 , Histona Desmetilases/genética , Humanos , Leucemia Mieloide Aguda/genética , Leucemia Mieloide Aguda/metabolismo , Camundongos , Camundongos Transgênicos , Ligação Proteica , Fatores de Transcrição da Família Snail/genética , Fatores de Transcrição da Família Snail/metabolismoAssuntos
Rearranjo Gênico , Genes myc , Predisposição Genética para Doença , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Animais , Biomarcadores Tumorais , Variações do Número de Cópias de DNA , Modelos Animais de Doenças , Estudos de Associação Genética , Humanos , Camundongos , Terapia de Alvo Molecular , Leucemia-Linfoma Linfoblástico de Células T Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Translocação Genética , Ensaios Antitumorais Modelo de XenoenxertoAssuntos
Leucemia-Linfoma Linfoblástico de Células T Precursoras , Inibidores de Proteínas Quinases/farmacologia , Proteínas Proto-Oncogênicas c-pim-1 , Linhagem Celular Tumoral , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células T Precursoras/enzimologia , Proteínas Proto-Oncogênicas c-pim-1/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-pim-1/metabolismoRESUMO
T cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy. Current intensified therapeutic protocols coincide with severe side effects, and no salvage therapy is available for primary therapy-resistant or relapsed patients. This highlights the need to identify new therapeutic targets in T-ALL. PSIP1, dispensable for normal hematopoiesis, is a dependency factor in KMT2A-rearranged myeloid leukemia. Nonetheless, loss-of-function mutations suggest a tumor suppressor role for PSIP1 in T-ALL. Here, we demonstrate that the loss of Psip1 accelerates T-ALL initiation in mice which we correlated with reduced H3K27me3 binding. Contrastingly, loss of PSIP1 impaired cell proliferation in several T-ALL cell lines. In cell lines, PSIP1 down-regulation leads to a reduction of COX20, an assembly factor of the cytochrome c oxidase in the mitochondria, and to a reduction in mitochondrial respiration. This indicates that PSIP1 can exert a dual role in the context of T-ALL, either as a tumor suppressor gene during tumor initiation or as a dependency factor in tumor maintenance.
Assuntos
Leucemia-Linfoma Linfoblástico de Células T Precursoras , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Animais , Camundongos , Humanos , Linhagem Celular Tumoral , Proliferação de Células , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/genética , Mitocôndrias/metabolismo , Regulação Leucêmica da Expressão Gênica , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/genéticaRESUMO
T-lineage acute lymphoblastic leukemia (T-ALL) is an aggressive hematological malignancy that accounts for 10%-15% of pediatric and 25% of adult ALL cases. Although the prognosis of T-ALL has improved over time, the outcome of T-ALL patients with primary resistant or relapsed leukemia remains poor. Therefore, further progress in the treatment of T-ALL requires a better understanding of its biology and the development of more effective precision oncologic therapies. The proto-oncogene MYB is highly expressed in diverse hematologic malignancies, including T-ALLs with genomic aberrations that further potentiate its expression and activity. Previous studies have associated MYB with a malignant role in the pathogenesis of several cancers. However, its role in the induction and maintenance of T-ALL remains relatively poorly understood. In this study, we found that an increased copy number of MYB is associated with higher MYB expression levels, and might be associated with inferior event-free survival of pediatric T-ALL patients. Using our previously described conditional Myb overexpression mice, we generated two distinct MYB-driven T-ALL mouse models. We demonstrated that the overexpression of Myb synergizes with Pten deletion but not with the overexpression of Lmo2 to accelerate the development of T-cell lymphoblastic leukemias. We also showed that MYB is a dependency factor in T-ALL since RNA interference of Myb blocked cell cycle progression and induced apoptosis in both human and murine T-ALL cell lines. Finally, we provide preclinical evidence that targeting the transcriptional activity of MYB can be a useful therapeutic strategy for the treatment of T-ALL.
RESUMO
T-cell lymphoblastic lymphoma (T-LBL) is a rare and aggressive lymphatic cancer, often diagnosed at a young age. Patients are treated with intensive chemotherapy, potentially followed by a hematopoietic stem cell transplantation. Although prognosis of T-LBL has improved with intensified treatment protocols, they are associated with side effects and 10-20% of patients still die from relapsed or refractory disease. Given this, the search toward less toxic anti-lymphoma therapies is ongoing. Here, we targeted the recently described DNA hypermethylated profile in T-LBL with the DNA hypomethylating agent decitabine. We evaluated the anti-lymphoma properties and downstream effects of decitabine, using patient derived xenograft (PDX) models. Decitabine treatment resulted in prolonged lymphoma-free survival in all T-LBL PDX models, which was associated with downregulation of the oncogenic MYC pathway. However, some PDX models showed more benefit of decitabine treatment compared to others. In more sensitive models, differentially methylated CpG regions resulted in more differentially expressed genes in open chromatin regions. This resulted in stronger downregulation of cell cycle genes and upregulation of immune response activating transcripts. Finally, we suggest a gene signature for high decitabine sensitivity in T-LBL. Altogether, we here delivered pre-clinical proof of the potential use of decitabine as a new therapeutic agent in T-LBL.
RESUMO
The holistic nature of omics studies makes them ideally suited to generate hypotheses on health and disease. Sequencing-based genomics and mass spectrometry (MS)-based proteomics are linked through epigenetic regulation mechanisms. However, epigenomics is currently mainly focused on DNA methylation status using sequencing technologies, while studying histone posttranslational modifications (hPTMs) using MS is lagging, partly because reuse of raw data is impractical. Yet, targeting hPTMs using epidrugs is an established promising research avenue in cancer treatment. Therefore, we here present the most comprehensive MS-based preprocessed hPTM atlas to date, including 21 T-cell acute lymphoblastic leukemia (T-ALL) cell lines. We present the data in an intuitive and browsable single licensed Progenesis QIP project and provide all essential quality metrics, allowing users to assess the quality of the data, edit individual peptides, try novel annotation algorithms and export both peptide and protein data for downstream analyses, exemplified by the PeptidoformViz tool. This data resource sets the stage for generalizing MS-based histone analysis and provides the first reusable histone dataset for epidrug development.
Assuntos
Histonas , Leucemia , Humanos , Epigênese Genética , Histonas/metabolismo , Espectrometria de Massas/métodos , Peptídeos/química , Processamento de Proteína Pós-Traducional , Linfócitos T/química , Leucemia-Linfoma Linfoblástico de Células T PrecursorasRESUMO
The extracellular complex between the haematopoietic receptor Flt3 and its cytokine ligand (FL) is the cornerstone of signalling cascades that are central to early haematopoiesis and the immune system. Here, efficient protocols for the production of two ectodomain variants of human Flt3 receptor, Flt3D1-D5 and Flt3D1-D4, for structural studies are reported based on tetracycline-inducible stable cell lines in HEK293S cells deficient in N-acetylglycosaminyltransferase I (GnTI-/-) that can secrete the target proteins with limited and homogeneous N-linked glycosylation to milligram amounts. The ensuing preparative purification of Flt3 receptor-ligand complexes yielded monodisperse complex preparations that were amenable to crystallization. Crystals of the Flt3D1-D4-FL and Flt3D1-D5-FL complexes diffracted to 4.3 and 7.8â Å resolution, respectively, and exhibited variable diffraction quality even within the same crystal. The resulting data led to the successful structure determination of Flt3D1-D4-FL via a combination of molecular-replacement and density-modification protocols exploiting the noncrystallographic symmetry and high solvent content of the crystals.
Assuntos
Proteínas de Membrana/química , Proteínas de Membrana/metabolismo , Proteínas Recombinantes/química , Proteínas Recombinantes/metabolismo , Tirosina Quinase 3 Semelhante a fms/química , Tirosina Quinase 3 Semelhante a fms/metabolismo , Animais , Cristalografia por Raios X , Células HEK293 , Humanos , Proteínas de Membrana/genética , Modelos Moleculares , Dados de Sequência Molecular , N-Acetilglucosaminiltransferases/genética , N-Acetilglucosaminiltransferases/metabolismo , Conformação Proteica , Proteínas Recombinantes/genética , Tirosina Quinase 3 Semelhante a fms/genéticaRESUMO
B-cell lymphoma 2 (BCL-2) has recently emerged as a therapeutic target for early T-cell progenitor acute lymphoblastic leukemia (ETP-ALL), a high-risk subtype of human T-cell ALL. The major clinical challenge with targeted therapeutics, such as the BCL-2 inhibitor ABT-199, is the development of acquired resistance. We assessed the in vivo response of luciferase-positive LOUCY cells to ABT-199 monotherapy and observed specific residual disease in the splenic microenvironment. Of note, these results were confirmed by using a primary ETP-ALL patient-derived xenograft. Splenomegaly has previously been associated with poor prognosis in diverse types of leukemia. However, the exact mechanism by which the splenic microenvironment alters responses to specific targeted therapies remains largely unexplored. We show that residual LOUCY cells isolated from the spleen microenvironment displayed reduced BCL-2 dependence, which was accompanied by decreased BCL-2 expression levels. Notably, this phenotype of reduced BCL-2 dependence could be recapitulated by using human splenic fibroblast coculture experiments and was confirmed in an in vitro chronic ABT-199 resistance model of LOUCY. Finally, single-cell RNA-sequencing was used to show that ABT-199 triggers transcriptional changes in T-cell differentiation genes in leukemic cells obtained from the spleen microenvironment. Of note, increased expression of CD1a and sCD3 was also observed in ABT199-resistant LOUCY clones, further reinforcing the idea that a more differentiated leukemic population might display decreased sensitivity toward BCL-2 inhibition. Overall, our data reveal the spleen as a site of residual disease for ABT-199 treatment in ETP-ALL and provide evidence for plasticity in T-cell differentiation as a mechanism of therapy resistance.
Assuntos
Proteínas Proto-Oncogênicas c-bcl-2 , Baço , Compostos Bicíclicos Heterocíclicos com Pontes , Humanos , Proteínas Proto-Oncogênicas c-bcl-2/genética , Sulfonamidas , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Mantle cell lymphoma (MCL) is an aggressive B cell lymphoma with poor long-term overall survival. Currently, MCL research and development of potential cures is hampered by the lack of good in vivo models. MCL is characterized by recurrent translocations of CCND1 or CCND2, resulting in overexpression of the cell cycle regulators cyclin D1 or D2, respectively. Here, we show, for the first time, that hematopoiesis-specific activation of cyclin D2 is sufficient to drive murine MCL-like lymphoma development. Furthermore, we demonstrate that cyclin D2 overexpression can synergize with loss of p53 to form aggressive and transplantable MCL-like lymphomas. Strikingly, cyclin D2-driven lymphomas display transcriptional, immunophenotypic, and functional similarities with B1a B cells. These MCL-like lymphomas have B1a-specific B cell receptors (BCRs), show elevated BCR and NF-κB pathway activation, and display increased MALT1 protease activity. Finally, we provide preclinical evidence that inhibition of MALT1 protease activity, which is essential for the development of early life-derived B1a cells, can be an effective therapeutic strategy to treat MCL.
Assuntos
Ciclina D2/genética , Linfoma de Célula do Manto/genética , Linfoma de Célula do Manto/patologia , Proteína de Translocação 1 do Linfoma de Tecido Linfoide Associado à Mucosa/antagonistas & inibidores , Aloenxertos , Animais , Linfócitos B/metabolismo , Linfócitos B/patologia , Ciclina D2/metabolismo , Regulação Neoplásica da Expressão Gênica , Linfoma de Célula do Manto/tratamento farmacológico , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Proteína de Translocação 1 do Linfoma de Tecido Linfoide Associado à Mucosa/metabolismo , Neoplasias Experimentais/tratamento farmacológico , Neoplasias Experimentais/genética , Neoplasias Experimentais/patologia , Células Neoplásicas Circulantes , Proteína Supressora de Tumor p53/genética , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
T cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic malignancy with inferior outcome compared with that of B cell ALL. Here, we show that Runt-related transcription factor 2 (RUNX2) was upregulated in high-risk T-ALL with KMT2A rearrangements (KMT2A-R) or an immature immunophenotype. In KMT2A-R cells, we identified RUNX2 as a direct target of the KMT2A chimeras, where it reciprocally bound the KMT2A promoter, establishing a regulatory feed-forward mechanism. Notably, RUNX2 was required for survival of immature and KMT2A-R T-ALL cells in vitro and in vivo. We report direct transcriptional regulation of CXCR4 signaling by RUNX2, thereby promoting chemotaxis, adhesion, and homing to medullary and extramedullary sites. RUNX2 enabled these energy-demanding processes by increasing metabolic activity in T-ALL cells through positive regulation of both glycolysis and oxidative phosphorylation. Concurrently, RUNX2 upregulation increased mitochondrial dynamics and biogenesis in T-ALL cells. Finally, as a proof of concept, we demonstrate that immature and KMT2A-R T-ALL cells were vulnerable to pharmacological targeting of the interaction between RUNX2 and its cofactor CBFß. In conclusion, we show that RUNX2 acts as a dependency factor in high-risk subtypes of human T-ALL through concomitant regulation of tumor metabolism and leukemic cell migration.
Assuntos
Subunidade alfa 1 de Fator de Ligação ao Core/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Animais , Linhagem Celular Tumoral , Quimiotaxia de Leucócito , Criança , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Subunidade beta de Fator de Ligação ao Core/metabolismo , Progressão da Doença , Regulação da Expressão Gênica no Desenvolvimento , Regulação Neoplásica da Expressão Gênica , Rearranjo Gênico , Hematopoese , Histona-Lisina N-Metiltransferase/genética , Histona-Lisina N-Metiltransferase/metabolismo , Humanos , Técnicas In Vitro , Camundongos , Proteína de Leucina Linfoide-Mieloide/genética , Proteína de Leucina Linfoide-Mieloide/metabolismo , Biogênese de Organelas , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Receptores CXCR4/metabolismo , Transdução de SinaisAssuntos
Proteínas de Ligação a DNA , Dioxigenases , Leucemia-Linfoma Linfoblástico de Células T Precursoras , Proteínas Proto-Oncogênicas , Humanos , Leucemia-Linfoma Linfoblástico de Células T Precursoras/metabolismo , Leucemia-Linfoma Linfoblástico de Células T Precursoras/genética , Leucemia-Linfoma Linfoblástico de Células T Precursoras/patologia , Proteínas Proto-Oncogênicas/metabolismo , Proteínas Proto-Oncogênicas/genética , Proteínas de Ligação a DNA/metabolismo , Proteínas de Ligação a DNA/genética , Genes Supressores de TumorRESUMO
In cancer research, it remains challenging to functionally validate putative novel oncogenic drivers and to establish relevant preclinical models for evaluation of novel therapeutic strategies. Here, we describe an optimized and efficient pipeline for the generation of novel conditional overexpression mouse models in which putative oncogenes, along with an eGFP/Luciferase dual reporter, are expressed from the endogenous ROSA26 (R26) promoter. The efficiency of this approach was demonstrated by the generation and validation of novel R26 knock-in (KI) mice that allow conditional overexpression of Jarid2, Runx2, MN1 and a dominant negative allele of ETV6. As proof of concept, we confirm that MN1 overexpression in the hematopoietic lineage is sufficient to drive myeloid leukemia. In addition, we show that T-cell specific activation of MN1 in combination with loss of Pten increases tumour penetrance and stimulates the formation of Lyl1+ murine T-cell lymphoblastic leukemias or lymphomas (T-ALL/T-LBL). Finally, we demonstrate that these luciferase-positive murine AML and T-ALL/T-LBL cells are transplantable into immunocompromised mice allowing preclinical evaluation of novel anti-leukemic drugs in vivo.
Assuntos
Neoplasias Hematológicas/genética , Oncogenes/genética , Animais , Subunidade alfa 1 de Fator de Ligação ao Core/genética , Feminino , Técnicas de Introdução de Genes , Genes Reporter , Neoplasias Hematológicas/etiologia , Humanos , Leucemia/etiologia , Leucemia/genética , Leucemia Mieloide/genética , Masculino , Camundongos , Camundongos Transgênicos , Transplante de Neoplasias , Complexo Repressor Polycomb 2/genética , Transativadores/genética , Proteínas Supressoras de Tumor/genéticaRESUMO
The serotonin (5-HT) 5-HT(7) receptors are expressed in both the central nervous system and in peripheral tissues. Receptor distribution studies and pharmacological studies have established that 5-HT(7) receptors play an important role in the control of circadian rhythms and thermoregulation. Selective 5-HT(7) receptor ligands have potential therapeutic applications for the treatment of pain and migraine, schizophrenia, anxiety, cognitive disturbances and inflammation. We have cloned two novel C-terminal splice variants of the 5-HT(7) receptor from mouse brain. These two new splice variants have almost identical sequences as the rat 5-HT(7(b)) and 5-HT(7(c)) splice variants and so were given the same name. Ligand binding assays ([(3)H]5-CT), membrane localization and functional studies in transiently transfected cells indicated that all three splice variants are well expressed on the membrane and no major differences in their respective pharmacology and their ability to activate adenylyl cyclase were observed. This is in analogy with previous reports comparing either the rat or the human variants.
Assuntos
Processamento Alternativo , Camundongos/genética , Ratos/genética , Receptores de Serotonina/genética , Adenilil Ciclases/genética , Adenilil Ciclases/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Animais , Encéfalo/metabolismo , Células CHO , Linhagem Celular , Clonagem Molecular , Cricetinae , Cricetulus , Humanos , Rim/citologia , Dados de Sequência Molecular , Estrutura Terciária de Proteína , Ensaio Radioligante , Receptores de Serotonina/metabolismo , Homologia de Sequência de Aminoácidos , TransfecçãoRESUMO
Three 5-HT(7) receptor isoforms are expressed in rat and man, which differ in the amino acid sequence of their C-terminus. Thus far, no changes have been observed in the pharmacological profile of all three isoforms. To further elucidate the signal transduction pathway specific for these receptor variants, we screened for possible interacting proteins of the C-terminus of the h5-HT(7(a)) variant in a human foetal brain cDNA library. Using a yeast two-hybrid assay, we isolated PLAC-24/eIF3k as a possible interacting candidate. The association of PLAC-24 with all three receptor variants was observed and further reconfirmed in vivo by co-immunoprecipitation of PLAC-24 with the full-length receptor isoforms in transfected COS-7 cells. Studies with different deletion mutants of the receptor showed that the interaction between PLAC-24 and the receptor is not restricted to the C-terminus of the receptor. PLAC-24/eIF3k consists of 3 domains: an N-terminal HAM domain, a central WH domain and a C-terminal tail. We generated different domain constructs of PLAC-24, which indicated that the HAM and WH domain both interact with the 5-HT(7(a)) receptor. Overexpression of PLAC-24 in HEK293 cells, stably expressing the h5-HT(7(a)) receptor, caused a threefold augmentation in the expression levels of the receptor. Co-localisation studies in COS-7 cells showed that PLAC-24 relocates from the nucleus and perinuclear sites towards the plasma membrane upon co-expression with the receptor. On the other hand, the expression of domain variants of PLAC-24 seems to block the translocation of the receptor towards the membrane. These observations suggest that PLAC-24 may play a role in the transport and the stabilisation of newly synthesised 5-HT(7) receptor towards the plasma membrane.
Assuntos
Proteínas Associadas aos Microtúbulos/metabolismo , Receptores de Serotonina/metabolismo , Sequência de Aminoácidos , Animais , Sítios de Ligação , Células COS , Chlorocebus aethiops , Humanos , Proteínas Associadas aos Microtúbulos/fisiologia , Dados de Sequência Molecular , Isoformas de Proteínas , Estrutura Terciária de Proteína , Transporte Proteico , Receptores Acoplados a Proteínas G/metabolismo , Receptores de Serotonina/genética , Homologia de Sequência de Aminoácidos , Transfecção , Técnicas do Sistema de Duplo-HíbridoRESUMO
The dopamine D4 receptor is a G protein-coupled receptor that binds with high affinity various antipsychotics. The receptor may be involved in attention/cognition, and in genetic studies a polymorphic repeat sequence in its coding sequence has been associated with attention deficit/hyperactivity disorder. We developed an inducible episomal expression system based on the reverse tetracycline transactivator and Epstein-Barr viral sequences. In HEK293rtTA cells expressing the dopamine D4 receptor from this episomal expression vector, addition of doxycycline in combination with sodium butyrate and trichostatin A induces high levels of receptor expression, resulting in 1970 +/- 20 fmol/mg membrane protein. Addition of the dopamine D4 receptor and serotonin 5-HT2A receptor antagonist pipamperone to these cells further increased the expression of the dopamine receptor, reaching 3800 +/- 60 fmol/mg membrane protein. This up-regulation was not restricted to the dopamine D4 receptor but was also found for the serotonin 5-HT2A receptor. We further provide evidence that the increase in receptor expression is not due to increased mRNA synthesis. As pipamperone could rescue the expression of a folding mutant of the dopamine D4 receptor (M345), we propose that pipamperone acts as a pharmacological chaperone for correct receptor folding thereby resulting in an increased dopamine D4 receptor expression. This study describes a strong and inducible expression system for proteins, difficult to express in other heterologous expression systems. This study also demonstrates that pipamperone, an antipsychotic, acts as a pharmacological chaperone and by doing so, increases the expression level of the dopamine D4 receptor. The fact that ligands can also act as pharmacological chaperones is a fairly new additional element in the regulation of receptor expression levels with potential great impact in drug treatment.
Assuntos
Antipsicóticos/farmacologia , Butirofenonas/farmacologia , Receptores de Dopamina D2/efeitos dos fármacos , Animais , Células CHO , Células Cultivadas , Cricetinae , Humanos , Camundongos , Chaperonas Moleculares/farmacologia , RNA Mensageiro/análise , Receptor 5-HT2A de Serotonina/análise , Receptor 5-HT2A de Serotonina/efeitos dos fármacos , Receptor 5-HT2A de Serotonina/genética , Receptores de Dopamina D2/análise , Receptores de Dopamina D2/genéticaRESUMO
Dopamine receptors are G protein-coupled receptors involved in regulation of cognition, learning, movement and endocrine signaling. The action of G protein-coupled receptors is highly regulated by multifunctional proteins, such as ß-arrestins which can control receptor desensitization, ubiquitination and signaling. Previously, we have reported that ß-arrestin 2 interacts with KLHL12, a BTB-Kelch protein which functions as an adaptor in a Cullin3-based E3 ligase complex and promotes ubiquitination of the dopamine D4 receptor. Here, we have investigated the molecular basis of the interaction between KLHL12 and ß-arrestins and questioned its functional relevance. Our data demonstrate that ß-arrestin 1 and ß-arrestin 2 bind constitutively to the most common dopamine D4 receptor polymorphic variants and to KLHL12 and that all three proteins can interact within a single macromolecular complex. Surprisingly, stimulation of the receptor has no influence on the association between these proteins or their cellular distribution. We found that Cullin3 also interacts with both ß-arrestins but has no influence on their ubiquitination. Knockout of one of the two ß-arrestins hampers neither interaction between the dopamine D4 receptor and KLHL12, nor ubiquitination of the receptor. Finally, our results indicate that p44/42 MAPK phosphorylation, the signaling pathway which is often regulated by ß-arrestins is not influenced by KLHL12, but seems to be exclusively mediated by Gαi protein upon dopamine D4 receptor stimulation.
Assuntos
Proteínas dos Microfilamentos/metabolismo , Receptores de Dopamina D4/metabolismo , beta-Arrestinas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Animais , Proteínas Culina/metabolismo , Dopamina/farmacologia , Proteínas de Ligação ao GTP/metabolismo , Células HEK293 , Humanos , Repetição Kelch , Camundongos , Camundongos Knockout , Proteínas dos Microfilamentos/química , Proteína Quinase 1 Ativada por Mitógeno/metabolismo , Proteína Quinase 3 Ativada por Mitógeno/metabolismo , Modelos Biológicos , Proteínas Mutantes/metabolismo , Toxina Pertussis/farmacologia , Fosforilação/efeitos dos fármacos , Ligação Proteica/efeitos dos fármacos , Domínios Proteicos , Multimerização Proteica/efeitos dos fármacos , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitinação/efeitos dos fármacosRESUMO
DOPAMINE D4 RECEPTOR POLYMORPHISM: The dopamine D4 receptor has an important polymorphism in its third intracellular loop that is intensively studied and has been associated with several abnormal conditions, among others, attention deficit hyperactivity disorder. KLHL12 PROMOTES UBIQUITINATION OF THE DOPAMINE D4 RECEPTOR ON NON-LYSINE RESIDUES: In previous studies we have shown that KLHL12, a BTB-Kelch protein, specifically interacts with the polymorphic repeats of the dopamine D4 receptor and enhances its ubiquitination, which, however, has no influence on receptor degradation. In this study we provide evidence that KLHL12 promotes ubiquitination of the dopamine D4 receptor on non-lysine residues. By using lysine-deficient receptor mutants and chemical approaches we concluded that ubiquitination on cysteine, serine and/or threonine is possible. DIFFERENTIAL UBIQUITINATION OF THE DOPAMINE D4 RECEPTOR POLYMORPHIC VARIANTS: Additionally, we show that the dopamine D4.7 receptor variant, which is associated with a predisposition to develop attention deficient hyperactivity disorder, is differentially ubiquitinated compared to the other common receptor variants D4.2 and D4.4. Together, our study suggests that GPCR ubiquitination is a complex and variable process.