RESUMO
Peroxisomes are organelles that play a central role in lipid metabolism and cellular redox homeostasis. The import of peroxisomal matrix proteins by peroxisomal targeting signal (PTS) receptors is an ATP-dependent mechanism. However, the energy-dependent steps do not occur early during the binding of the receptor-cargo complex to the membrane but late, because they are linked to the peroxisomal export complex for the release of the unloaded receptor. The first ATP-demanding step is the cysteine-dependent monoubiquitination of the PTS receptors, which is required for recognition by the AAA+ peroxins. They execute the second ATP-dependent step by extracting the ubiqitinated PTS receptors from the membrane for release back to the cytosol. After deubiquitination, the PTS receptors regain import competence and can facilitate further rounds of cargo import. Here, we give a general overview and discuss recent data regarding the ATP-dependent steps in peroxisome protein import.
Assuntos
Trifosfato de Adenosina , Peroxissomos , Transporte Proteico , Ubiquitinação , Peroxissomos/metabolismo , Trifosfato de Adenosina/metabolismo , Humanos , Animais , Receptor 1 de Sinal de Orientação para Peroxissomos/metabolismo , Receptor 1 de Sinal de Orientação para Peroxissomos/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Sinais de Orientação para Peroxissomos , Peroxinas/metabolismo , Peroxinas/genética , Proteínas de MembranaRESUMO
The most aggressive B cell lymphomas frequently manifest extranodal distribution and carry somatic mutations in the poorly characterized gene TBL1XR1. Here, we show that TBL1XR1 mutations skew the humoral immune response toward generating abnormal immature memory B cells (MB), while impairing plasma cell differentiation. At the molecular level, TBL1XR1 mutants co-opt SMRT/HDAC3 repressor complexes toward binding the MB cell transcription factor (TF) BACH2 at the expense of the germinal center (GC) TF BCL6, leading to pre-memory transcriptional reprogramming and cell-fate bias. Upon antigen recall, TBL1XR1 mutant MB cells fail to differentiate into plasma cells and instead preferentially reenter new GC reactions, providing evidence for a cyclic reentry lymphomagenesis mechanism. Ultimately, TBL1XR1 alterations lead to a striking extranodal immunoblastic lymphoma phenotype that mimics the human disease. Both human and murine lymphomas feature expanded MB-like cell populations, consistent with a MB-cell origin and delineating an unforeseen pathway for malignant transformation of the immune system.
Assuntos
Memória Imunológica/fisiologia , Linfoma Difuso de Grandes Células B/patologia , Proteínas Nucleares/genética , Células Precursoras de Linfócitos B/imunologia , Receptores Citoplasmáticos e Nucleares/genética , Proteínas Repressoras/genética , Animais , Fatores de Transcrição de Zíper de Leucina Básica/genética , Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Cromatina/química , Cromatina/metabolismo , Centro Germinativo/citologia , Centro Germinativo/imunologia , Centro Germinativo/metabolismo , Histona Desacetilases/metabolismo , Humanos , Linfoma Difuso de Grandes Células B/imunologia , Linfoma Difuso de Grandes Células B/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutagênese Sítio-Dirigida , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Correpressor 2 de Receptor Nuclear/química , Correpressor 2 de Receptor Nuclear/metabolismo , Células Precursoras de Linfócitos B/citologia , Células Precursoras de Linfócitos B/metabolismo , Ligação Proteica , Proteínas Proto-Oncogênicas c-bcl-6/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-bcl-6/genética , Proteínas Proto-Oncogênicas c-bcl-6/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Receptores Citoplasmáticos e Nucleares/química , Receptores Citoplasmáticos e Nucleares/metabolismo , Proteínas Repressoras/química , Proteínas Repressoras/metabolismo , Transcrição GênicaRESUMO
Efficient and regulated nucleocytoplasmic trafficking of macromolecules to the correct subcellular compartment is critical for proper functions of the eukaryotic cell. The majority of the macromolecular traffic across the nuclear pores is mediated by the Karyopherin-ß (or Kap) family of nuclear transport receptors. Work over more than two decades has shed considerable light on how the different Kap family members bring their respective cargoes into the nucleus or the cytoplasm in efficient and highly regulated manners. In this Review, we overview the main features and established functions of Kap family members, describe how Kaps recognize their cargoes and discuss the different ways in which these Kap-cargo interactions can be regulated, highlighting new findings and open questions. We also describe current knowledge of the import and export of the components of three large gene expression machines - the core replisome, RNA polymerase II and the ribosome - pointing out the questions that persist about how such large macromolecular complexes are trafficked to serve their function in a designated subcellular location.
Assuntos
Carioferinas , beta Carioferinas , Transporte Ativo do Núcleo Celular/fisiologia , Núcleo Celular/metabolismo , Carioferinas/metabolismo , Poro Nuclear/metabolismo , Receptores Citoplasmáticos e Nucleares , beta Carioferinas/metabolismoRESUMO
Transcriptional regulation of catabolic pathways is a central mechanism by which cells respond to physiological cues to generate the energy required for anabolic pathways, transport of molecules and mechanical work. Nuclear receptors are members of a superfamily of transcription factors that transduce hormonal, nutrient, metabolite and redox signals into specific metabolic gene programmes, and thus hold a major status as regulators of cellular energy generation. Nuclear receptors also regulate the expression of genes involved in cellular processes that are implicated in energy production, including mitochondrial biogenesis and autophagy. Recent advances in genome-wide approaches have considerably expanded the repertoire of both nuclear receptors and metabolic genes under their direct transcriptional control. To fine-tune the expression of their target genes, nuclear receptors must act cooperatively with other transcription factors and coregulator proteins, integrate signals from key metabolic sensory systems such as the AMP-activated protein kinase (AMPK) and mechanistic target of rapamycin (mTOR) complexes and synchronize their activities with the biological clock. Therefore, nuclear receptors must function as more than molecular switches for small lipophilic ligands - as initially ascribed - but rather must be capable of orchestrating a large ensemble of input signals. Therefore, a primary role for several nuclear receptors is to serve as the focal point of transcriptional hubs in energy metabolism: their molecular task is to receive and transduce multiple systemic and intracellular metabolic signals to maintain energy homeostasis from individual cells to the whole organism.
Assuntos
Proteínas Quinases Ativadas por AMP , Serina-Treonina Quinases TOR , Proteínas Quinases Ativadas por AMP/metabolismo , Ligantes , Serina-Treonina Quinases TOR/metabolismo , Metabolismo Energético/genética , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , SirolimoRESUMO
Approximately 30% of human lung cancers acquire mutations in either Keap1 or Nfe2l2, resulting in the stabilization of Nrf2, the Nfe2l2 gene product, which controls oxidative homeostasis. Here, we show that heme triggers the degradation of Bach1, a pro-metastatic transcription factor, by promoting its interaction with the ubiquitin ligase Fbxo22. Nrf2 accumulation in lung cancers causes the stabilization of Bach1 by inducing Ho1, the enzyme catabolizing heme. In mouse models of lung cancers, loss of Keap1 or Fbxo22 induces metastasis in a Bach1-dependent manner. Pharmacological inhibition of Ho1 suppresses metastasis in a Fbxo22-dependent manner. Human metastatic lung cancer display high levels of Ho1 and Bach1. Bach1 transcriptional signature is associated with poor survival and metastasis in lung cancer patients. We propose that Nrf2 activates a metastatic program by inhibiting the heme- and Fbxo22-mediated degradation of Bach1, and that Ho1 inhibitors represent an effective therapeutic strategy to prevent lung cancer metastasis.
Assuntos
Fatores de Transcrição de Zíper de Leucina Básica/metabolismo , Neoplasias Pulmonares/patologia , Fator 2 Relacionado a NF-E2/metabolismo , Animais , Fatores de Transcrição de Zíper de Leucina Básica/antagonistas & inibidores , Fatores de Transcrição de Zíper de Leucina Básica/genética , Linhagem Celular Tumoral , Movimento Celular , Proteínas F-Box/antagonistas & inibidores , Proteínas F-Box/genética , Proteínas F-Box/metabolismo , Feminino , Heme Oxigenase-1/antagonistas & inibidores , Heme Oxigenase-1/genética , Heme Oxigenase-1/metabolismo , Humanos , Estimativa de Kaplan-Meier , Proteína 1 Associada a ECH Semelhante a Kelch/antagonistas & inibidores , Proteína 1 Associada a ECH Semelhante a Kelch/genética , Proteína 1 Associada a ECH Semelhante a Kelch/metabolismo , Neoplasias Pulmonares/metabolismo , Neoplasias Pulmonares/mortalidade , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Fator 2 Relacionado a NF-E2/genética , Metástase Neoplásica , Interferência de RNA , RNA Interferente Pequeno/metabolismo , Receptores Citoplasmáticos e Nucleares/antagonistas & inibidores , Receptores Citoplasmáticos e Nucleares/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Ativação TranscricionalRESUMO
Increased levels of intestinal bile acids (BAs) are a risk factor for colorectal cancer (CRC). Here, we show that the convergence of dietary factors (high-fat diet) and dysregulated WNT signaling (APC mutation) alters BA profiles to drive malignant transformations in Lgr5-expressing (Lgr5+) cancer stem cells and promote an adenoma-to-adenocarcinoma progression. Mechanistically, we show that BAs that antagonize intestinal farnesoid X receptor (FXR) function, including tauro-ß-muricholic acid (T-ßMCA) and deoxycholic acid (DCA), induce proliferation and DNA damage in Lgr5+ cells. Conversely, selective activation of intestinal FXR can restrict abnormal Lgr5+ cell growth and curtail CRC progression. This unexpected role for FXR in coordinating intestinal self-renewal with BA levels implicates FXR as a potential therapeutic target for CRC.
Assuntos
Neoplasias Intestinais/metabolismo , Células-Tronco Neoplásicas/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Animais , Ácidos e Sais Biliares/metabolismo , Linhagem Celular , Proliferação de Células/genética , Neoplasias Colorretais/metabolismo , Ácido Desoxicólico/metabolismo , Regulação Neoplásica da Expressão Gênica/genética , Humanos , Neoplasias Intestinais/genética , Intestinos , Fígado , Camundongos , Camundongos Endogâmicos C57BL , Células-Tronco Neoplásicas/fisiologia , Organoides/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Fatores de Risco , Transdução de Sinais , Ácido Taurocólico/análogos & derivados , Ácido Taurocólico/metabolismo , Via de Sinalização Wnt/genética , Via de Sinalização Wnt/fisiologiaRESUMO
PIWI-interacting RNAs (piRNAs) guide transposon silencing in animals. The 22-30 nt piRNAs are processed in the cytoplasm from long non-coding RNAs that often lack RNA processing hallmarks of export-competent transcripts. By studying how these transcripts achieve nuclear export, we uncover an RNA export pathway specific for piRNA precursors in the Drosophila germline. This pathway requires Nxf3-Nxt1, a variant of the hetero-dimeric mRNA export receptor Nxf1-Nxt1. Nxf3 interacts with UAP56, a nuclear RNA helicase essential for mRNA export, and CG13741/Bootlegger, which recruits Nxf3-Nxt1 and UAP56 to heterochromatic piRNA source loci. Upon RNA cargo binding, Nxf3 achieves nuclear export via the exportin Crm1 and accumulates together with Bootlegger in peri-nuclear nuage, suggesting that after export, Nxf3-Bootlegger delivers precursor transcripts to the piRNA processing sites. These findings indicate that the piRNA pathway bypasses nuclear RNA surveillance systems to export unprocessed transcripts to the cytoplasm, a strategy also exploited by retroviruses.
Assuntos
Transporte Ativo do Núcleo Celular/fisiologia , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/metabolismo , Heterocromatina/metabolismo , Proteínas de Transporte Nucleocitoplasmático/metabolismo , RNA Interferente Pequeno/metabolismo , Proteínas de Ligação a RNA/metabolismo , Animais , Animais Geneticamente Modificados , Proteínas Argonautas/metabolismo , Linhagem Celular , Núcleo Celular/metabolismo , Citoplasma/metabolismo , RNA Helicases DEAD-box/metabolismo , Elementos de DNA Transponíveis , Inativação Gênica , Células Germinativas/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Carioferinas/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Transcrição Gênica , Proteína Exportina 1RESUMO
Receptor clustering on the cell membrane is critical in the signaling of many immunoreceptors, and this mechanism has previously been attributed to the extracellular and/or the intracellular interactions. Here, we report an unexpected finding that for death receptor 5 (DR5), a receptor in the tumor necrosis factor receptor superfamily, the transmembrane helix (TMH) alone in the receptor directly assembles a higher-order structure to drive signaling and that this structure is inhibited by the unliganded ectodomain. Nuclear magnetic resonance structure of the TMH in bicelles shows distinct trimerization and dimerization faces, allowing formation of dimer-trimer interaction networks. Single-TMH mutations that disrupt either trimerization or dimerization abolish ligand-induced receptor activation. Surprisingly, proteolytic removal of the DR5 ectodomain can fully activate downstream signaling in the absence of ligand. Our data suggest a receptor activation mechanism in which binding of ligand or antibodies to overcome the pre-ligand autoinhibition allows TMH clustering and thus signaling.
Assuntos
Receptores do Ligante Indutor de Apoptose Relacionado a TNF/metabolismo , Apoptose , Linhagem Celular Tumoral , Membrana Celular/metabolismo , Células HEK293 , Humanos , Ligantes , Modelos Moleculares , Mutagênese Sítio-Dirigida/métodos , Ligação Proteica , Proteólise , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/química , Receptores do Ligante Indutor de Apoptose Relacionado a TNF/ultraestrutura , Transdução de SinaisRESUMO
Mammals encode â¼5,000 integral membrane proteins that need to be inserted in a defined topology at the endoplasmic reticulum (ER) membrane by mechanisms that are incompletely understood. Here, we found that efficient biogenesis of ß1-adrenergic receptor (ß1AR) and other G protein-coupled receptors (GPCRs) requires the conserved ER membrane protein complex (EMC). Reconstitution studies of ß1AR biogenesis narrowed the EMC requirement to the co-translational insertion of the first transmembrane domain (TMD). Without EMC, a proportion of TMD1 inserted in an inverted orientation or failed altogether. Purified EMC and SRP receptor were sufficient for correctly oriented TMD1 insertion, while the Sec61 translocon was necessary for insertion of the next TMD. Enforcing TMD1 topology with an N-terminal signal peptide bypassed the EMC requirement for insertion in vitro and restored efficient biogenesis of multiple GPCRs in EMC-knockout cells. Thus, EMC inserts TMDs co-translationally and cooperates with the Sec61 translocon to ensure accurate topogenesis of many membrane proteins.
Assuntos
Retículo Endoplasmático/metabolismo , Membranas Intracelulares/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores de Peptídeos/metabolismo , Canais de Translocação SEC/metabolismo , Animais , Linhagem Celular Tumoral , Retículo Endoplasmático/genética , Feminino , Humanos , Domínios Proteicos , Transporte Proteico/fisiologia , Receptores Citoplasmáticos e Nucleares/genética , Receptores de Peptídeos/genética , Canais de Translocação SEC/genética , PerusRESUMO
Nuclear import receptors are central players in transporting protein cargoes into the nucleus. Moving beyond this role, four newly published articles describe a function in regulating supramolecular assemblies by fine-tuning the phase separating properties of RNA-binding proteins, which has implications for a variety of devastating neurodegenerative disorders.
Assuntos
Transporte Ativo do Núcleo Celular , Carioferinas/metabolismo , Proteína FUS de Ligação a RNA/metabolismo , Esclerose Lateral Amiotrófica/terapia , Animais , Núcleo Celular/metabolismo , Proteínas de Ligação a DNA/metabolismo , Humanos , Modelos Biológicos , Doenças Neurodegenerativas/terapia , Proteoma , RNA/metabolismo , Proteínas de Ligação a RNA/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismoRESUMO
RNA-binding proteins (RBPs) with prion-like domains (PrLDs) phase transition to functional liquids, which can mature into aberrant hydrogels composed of pathological fibrils that underpin fatal neurodegenerative disorders. Several nuclear RBPs with PrLDs, including TDP-43, FUS, hnRNPA1, and hnRNPA2, mislocalize to cytoplasmic inclusions in neurodegenerative disorders, and mutations in their PrLDs can accelerate fibrillization and cause disease. Here, we establish that nuclear-import receptors (NIRs) specifically chaperone and potently disaggregate wild-type and disease-linked RBPs bearing a NLS. Karyopherin-ß2 (also called Transportin-1) engages PY-NLSs to inhibit and reverse FUS, TAF15, EWSR1, hnRNPA1, and hnRNPA2 fibrillization, whereas Importin-α plus Karyopherin-ß1 prevent and reverse TDP-43 fibrillization. Remarkably, Karyopherin-ß2 dissolves phase-separated liquids and aberrant fibrillar hydrogels formed by FUS and hnRNPA1. In vivo, Karyopherin-ß2 prevents RBPs with PY-NLSs accumulating in stress granules, restores nuclear RBP localization and function, and rescues degeneration caused by disease-linked FUS and hnRNPA2. Thus, NIRs therapeutically restore RBP homeostasis and mitigate neurodegeneration.
Assuntos
Transporte Ativo do Núcleo Celular , Príons/química , Proteínas de Ligação a RNA/química , Receptores Citoplasmáticos e Nucleares/química , Adulto , Idoso , Animais , Citoplasma/química , Proteínas de Ligação a DNA/química , Drosophila melanogaster , Feminino , Proteínas de Fluorescência Verde/química , Células HEK293 , Células HeLa , Homeostase , Humanos , Carioferinas/química , Masculino , Pessoa de Meia-Idade , Chaperonas Moleculares/química , Mutação , Doenças Neurodegenerativas/patologia , Domínios Proteicos , Proteína EWS de Ligação a RNA/química , Fatores Associados à Proteína de Ligação a TATA/química , beta Carioferinas/químicaRESUMO
How can beneficial microorganisms be distinguished from pathogenic ones? In this issue of Immunity, Peterson et al. discovered that a specific phenazine, which is part of a family of toxic metabolites expressed by pathogenic bacteria, is detected by Caenorhabditis elegans by directly binding to a nuclear hormone receptor, promoting the expression of detoxifying enzymes and immunity-related genes, thus protecting the worm.
Assuntos
Proteínas de Caenorhabditis elegans , Animais , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Receptores Citoplasmáticos e Nucleares/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Regulação da Expressão Gênica , Transdução de SinaisRESUMO
Distinguishing infectious pathogens from harmless microorganisms is essential for animal health. The mechanisms used to identify infectious microbes are not fully understood, particularly in metazoan hosts that eat bacteria as their food source. Here, we characterized a non-canonical pattern-recognition system in Caenorhabditis elegans (C. elegans) that assesses the relative threat of virulent Pseudomonas aeruginosa (P. aeruginosa) to activate innate immunity. We discovered that the innate immune response in C. elegans was triggered by phenazine-1-carboxamide (PCN), a toxic metabolite produced by pathogenic strains of P. aeruginosa. We identified the nuclear hormone receptor NHR-86/HNF4 as the PCN sensor in C. elegans and validated that PCN bound to the ligand-binding domain of NHR-86/HNF4. Activation of NHR-86/HNF4 by PCN directly engaged a transcriptional program in intestinal epithelial cells that protected against P. aeruginosa. Thus, a bacterial metabolite is a pattern of pathogenesis surveilled by nematodes to identify a pathogen in its bacterial diet.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Animais , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Regulação da Expressão Gênica , Receptores Citoplasmáticos e Nucleares/metabolismo , Imunidade Inata , Bactérias , Pseudomonas aeruginosa/metabolismoRESUMO
The essential Mediator (MED) coactivator complex plays a well-understood role in regulation of basal transcription in all eukaryotes, but the mechanism underlying its role in activator-dependent transcription remains unknown. We investigated modulation of metazoan MED interaction with RNA polymerase II (RNA Pol II) by antagonistic effects of the MED26 subunit and the CDK8 kinase module (CKM). Biochemical analysis of CKM-MED showed that the CKM blocks binding of the RNA Pol II carboxy-terminal domain (CTD), preventing RNA Pol II interaction. This restriction is eliminated by nuclear receptor (NR) binding to CKM-MED, which enables CTD binding in a MED26-dependent manner. Cryoelectron microscopy (cryo-EM) and crosslinking-mass spectrometry (XL-MS) revealed that the structural basis for modulation of CTD interaction with MED relates to a large intrinsically disordered region (IDR) in CKM subunit MED13 that blocks MED26 and CTD interaction with MED but is repositioned upon NR binding. Hence, NRs can control transcription initiation by priming CKM-MED for MED26-dependent RNA Pol II interaction.
Assuntos
Microscopia Crioeletrônica , Quinase 8 Dependente de Ciclina , Complexo Mediador , Ligação Proteica , RNA Polimerase II , RNA Polimerase II/metabolismo , RNA Polimerase II/genética , Complexo Mediador/metabolismo , Complexo Mediador/genética , Complexo Mediador/química , Humanos , Quinase 8 Dependente de Ciclina/metabolismo , Quinase 8 Dependente de Ciclina/genética , Animais , Proteínas Intrinsicamente Desordenadas/metabolismo , Proteínas Intrinsicamente Desordenadas/genética , Proteínas Intrinsicamente Desordenadas/química , Sítios de Ligação , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Células HEK293 , Domínios e Motivos de Interação entre ProteínasRESUMO
The ability to sense and respond to proteotoxic insults declines with age, leaving cells vulnerable to chronic and acute stressors. Reproductive cues modulate this decline in cellular proteostasis to influence organismal stress resilience in Caenorhabditis elegans We previously uncovered a pathway that links the integrity of developing embryos to somatic health in reproductive adults. Here, we show that the nuclear receptor NHR-49, an ortholog of mammalian peroxisome proliferator-activated receptor α (PPARα), regulates stress resilience and proteostasis downstream from embryo integrity and other pathways that influence lipid homeostasis and upstream of HSF-1. Disruption of the vitelline layer of the embryo envelope, which activates a proteostasis-enhancing intertissue pathway in somatic cells, triggers changes in lipid catabolism gene expression that are accompanied by an increase in fat stores. NHR-49, together with its coactivator, MDT-15, contributes to this remodeling of lipid metabolism and is also important for the elevated stress resilience mediated by inhibition of the embryonic vitelline layer. Our findings indicate that NHR-49 also contributes to stress resilience in other pathways known to change lipid homeostasis, including reduced insulin-like signaling and fasting, and that increased NHR-49 activity is sufficient to improve proteostasis and stress resilience in an HSF-1-dependent manner. Together, our results establish NHR-49 as a key regulator that links lipid homeostasis and cellular resilience to proteotoxic stress.
Assuntos
Proteínas de Caenorhabditis elegans , Caenorhabditis elegans , Metabolismo dos Lipídeos , Proteostase , Receptores Citoplasmáticos e Nucleares , Reprodução , Transdução de Sinais , Estresse Fisiológico , Animais , Caenorhabditis elegans/genética , Caenorhabditis elegans/fisiologia , Proteínas de Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Metabolismo dos Lipídeos/genética , Receptores Citoplasmáticos e Nucleares/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Reprodução/genética , Reprodução/fisiologia , Complexo Mediador/genética , Complexo Mediador/metabolismoRESUMO
Four major receptor families enable cells to respond to chemical and physical signals from their proximal environment. The ligand- and voltage-gated ion channels, G-protein-coupled receptors, nuclear hormone receptors, and receptor tyrosine kinases are all allosteric proteins that carry multiple, spatially distinct, yet conformationally linked ligand-binding sites. Recent studies point to common mechanisms governing the allosteric transitions of these receptors, including the impact of oligomerization, pre-existing and functionally distinct conformational ensembles, intrinsically disordered regions, and the occurrence of allosteric modulatory sites. Importantly, synthetic allosteric modulators are being discovered for these receptors, providing an enriched, yet challenging, landscape for novel therapeutics.
Assuntos
Canais Iônicos de Abertura Ativada por Ligante/química , Receptores Proteína Tirosina Quinases/química , Receptores Citoplasmáticos e Nucleares/química , Receptores Acoplados a Proteínas G/química , Regulação Alostérica , Sítio Alostérico , Animais , Doença/genética , Desenho de Fármacos , Humanos , Canais Iônicos de Abertura Ativada por Ligante/agonistas , Ligantes , Modelos Químicos , Mutação , Conformação Proteica , Multimerização Proteica , Receptores Proteína Tirosina Quinases/agonistas , Receptores Citoplasmáticos e Nucleares/agonistas , Receptores Acoplados a Proteínas G/agonistas , Transdução de SinaisRESUMO
During development, neurons switch among growth states, such as initial axon outgrowth, axon pruning, and regrowth. By studying the stereotypic remodeling of the Drosophila mushroom body (MB), we found that the heme-binding nuclear receptor E75 is dispensable for initial axon outgrowth of MB γ neurons but is required for their developmental regrowth. Genetic experiments and pharmacological manipulations on ex-vivo-cultured brains indicate that neuronally generated nitric oxide (NO) promotes pruning but inhibits regrowth. We found that high NO levels inhibit the physical interaction between the E75 and UNF nuclear receptors, likely accounting for its repression of regrowth. Additionally, NO synthase (NOS) activity is downregulated at the onset of regrowth, at least partially, by short inhibitory NOS isoforms encoded within the NOS locus, indicating how NO production could be developmentally regulated. Taken together, these results suggest that NO signaling provides a switching mechanism between the degenerative and regenerative states of neuronal remodeling.
Assuntos
Axônios/metabolismo , Proteínas de Ligação a DNA/metabolismo , Proteínas de Drosophila/metabolismo , Drosophila melanogaster/crescimento & desenvolvimento , Drosophila melanogaster/metabolismo , Plasticidade Neuronal , Óxido Nítrico/metabolismo , Fatores de Transcrição/metabolismo , Animais , Encéfalo/metabolismo , Drosophila melanogaster/enzimologia , Corpos Pedunculados , Neurônios/metabolismo , Óxido Nítrico Sintase/metabolismo , Isoformas de Proteínas/metabolismo , Receptores Citoplasmáticos e Nucleares/metabolismoRESUMO
Nuclear hormone receptors (NRs) are ligand-binding transcription factors that are widely targeted therapeutically. Agonist binding triggers NR activation and subsequent degradation by unknown ligand-dependent ubiquitin ligase machinery. NR degradation is critical for therapeutic efficacy in malignancies that are driven by retinoic acid and estrogen receptors. Here, we demonstrate the ubiquitin ligase UBR5 drives degradation of multiple agonist-bound NRs, including the retinoic acid receptor alpha (RARA), retinoid x receptor alpha (RXRA), glucocorticoid, estrogen, liver-X, progesterone, and vitamin D receptors. We present the high-resolution cryo-EMstructure of full-length human UBR5 and a negative stain model representing its interaction with RARA/RXRA. Agonist ligands induce sequential, mutually exclusive recruitment of nuclear coactivators (NCOAs) and UBR5 to chromatin to regulate transcriptional networks. Other pharmacological ligands such as selective estrogen receptor degraders (SERDs) degrade their receptors through differential recruitment of UBR5 or RNF111. We establish the UBR5 transcriptional regulatory hub as a common mediator and regulator of NR-induced transcription.
Assuntos
Cromatina , Fatores de Transcrição , Humanos , Ligantes , Cromatina/genética , Fatores de Transcrição/metabolismo , Receptores Citoplasmáticos e Nucleares/genética , Ubiquitinas , Ubiquitina-Proteína Ligases/genéticaRESUMO
Low energy states delay aging in multiple species, yet mechanisms coordinating energetics and longevity across tissues remain poorly defined. The conserved energy sensor AMP-activated protein kinase (AMPK) and its corresponding phosphatase calcineurin modulate longevity via the CREB regulated transcriptional coactivator (CRTC)-1 in C. elegans. We show that CRTC-1 specifically uncouples AMPK/calcineurin-mediated effects on lifespan from pleiotropic side effects by reprogramming mitochondrial and metabolic function. This pro-longevity metabolic state is regulated cell nonautonomously by CRTC-1 in the nervous system. Neuronal CRTC-1/CREB regulates peripheral metabolism antagonistically with the functional PPARα ortholog, NHR-49, drives mitochondrial fragmentation in distal tissues, and suppresses the effects of AMPK on systemic mitochondrial metabolism and longevity via a cell-nonautonomous catecholamine signal. These results demonstrate that while both local and distal mechanisms combine to modulate aging, distal regulation overrides local contribution. Targeting central perception of energetic state is therefore a potential strategy to promote healthy aging.
Assuntos
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/fisiologia , Catecolaminas/metabolismo , Mitocôndrias/metabolismo , Neurônios/metabolismo , Transdução de Sinais , Transativadores/metabolismo , Proteínas Quinases Ativadas por AMP/metabolismo , Animais , Caenorhabditis elegans/citologia , Proteína de Ligação ao Elemento de Resposta ao AMP Cíclico/metabolismo , Longevidade , Receptores Citoplasmáticos e Nucleares/metabolismoRESUMO
Peroxisomes are ubiquitous organelles whose dysfunction causes fatal human diseases. Most peroxisomal enzymes are imported from the cytosol by the receptor PEX5, which interacts with a docking complex in the peroxisomal membrane and then returns to the cytosol after monoubiquitination by a membrane-embedded ubiquitin ligase. The mechanism by which PEX5 shuttles between cytosol and peroxisomes and releases cargo inside the lumen is unclear. Here, we use Xenopus egg extract to demonstrate that PEX5 accompanies cargo completely into the lumen, utilizing WxxxF/Y motifs near its N terminus that bind a lumenal domain of the docking complex. PEX5 recycling is initiated by an amphipathic helix that binds to the lumenal side of the ubiquitin ligase. The N terminus then emerges in the cytosol for monoubiquitination. Finally, PEX5 is extracted from the lumen, resulting in the unfolding of the receptor and cargo release. Our results reveal the unique mechanism by which PEX5 ferries proteins into peroxisomes.