RESUMO
Dolichol is a lipid critical for N-glycosylation as a carrier for activated sugars and nascent oligosaccharides. It is commonly thought to be directly produced from polyprenol by the enzyme SRD5A3. Instead, we found that dolichol synthesis requires a three-step detour involving additional metabolites, where SRD5A3 catalyzes only the second reaction. The first and third steps are performed by DHRSX, whose gene resides on the pseudoautosomal regions of the X and Y chromosomes. Accordingly, we report a pseudoautosomal-recessive disease presenting as a congenital disorder of glycosylation in patients with missense variants in DHRSX (DHRSX-CDG). Of note, DHRSX has a unique dual substrate and cofactor specificity, allowing it to act as a NAD+-dependent dehydrogenase and as a NADPH-dependent reductase in two non-consecutive steps. Thus, our work reveals unexpected complexity in the terminal steps of dolichol biosynthesis. Furthermore, we provide insights into the mechanism by which dolichol metabolism defects contribute to disease.
Assuntos
Dolicóis , Dolicóis/metabolismo , Dolicóis/biossíntese , Humanos , Glicosilação , 3-Oxo-5-alfa-Esteroide 4-Desidrogenase/metabolismo , 3-Oxo-5-alfa-Esteroide 4-Desidrogenase/genética , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Defeitos Congênitos da Glicosilação/metabolismo , Defeitos Congênitos da Glicosilação/genética , Masculino , Mutação de Sentido Incorreto , FemininoRESUMO
Living organisms are constantly exposed to DNA damage, and optimal repair is therefore crucial. A characteristic hallmark of the response is the formation of sub-compartments around the site of damage, known as foci. Following multiple DNA breaks, the transcription factor p53 exhibits oscillations in its nuclear concentration, but how this dynamics can affect the repair remains unknown. Here, we formulate a theory for foci formation through droplet condensation and discover how oscillations in p53, with its specific periodicity and amplitude, optimize the repair process by preventing Ostwald ripening and distributing protein material in space and time. Based on the theory predictions, we reveal experimentally that the oscillatory dynamics of p53 does enhance the repair efficiency. These results connect the dynamical signaling of p53 with the microscopic repair process and create a new paradigm for the interplay of complex dynamics and phase transitions in biology.
Assuntos
Proteínas Proto-Oncogênicas c-mdm2 , Proteína Supressora de Tumor p53 , Proteína Supressora de Tumor p53/metabolismo , Proteínas Proto-Oncogênicas c-mdm2/genética , Proteínas Proto-Oncogênicas c-mdm2/metabolismo , Reparo do DNA , Dano ao DNA , Transdução de Sinais/fisiologiaRESUMO
In this review, we describe speculative ideas and early stage research concerning the flow of genetic information from the nuclear residence of genes to the disparate, cytoplasmic sites of protein synthesis. We propose that this process of information transfer is meticulously guided by transient structures formed from protein segments of low sequence complexity/intrinsic disorder. These low complexity domains are ubiquitously associated with regulatory proteins that control gene expression and RNA biogenesis, but they are also found in the central channel of nuclear pores, the nexus points of intermediate filament assembly, and the locations of action of other well-studied cellular proteins and pathways. Upon being organized into localized cellular positions via mechanisms utilizing properly folded protein domains, thereby facilitating elevated local concentration, certain low complexity domains adopt cross-ß interactions that are both structurally specific and labile to disassembly. These weakly tethered assemblies, we propose, are built to relay the passage of genetic information from one site to another within a cell, ensuring that the process is of extreme fidelity.
Assuntos
Proteínas Intrinsicamente Desordenadas/genética , Proteínas Intrinsicamente Desordenadas/metabolismo , Modelos Biológicos , Animais , Grânulos Citoplasmáticos/genética , Grânulos Citoplasmáticos/metabolismo , Expressão Gênica , Transtornos Heredodegenerativos do Sistema Nervoso/genética , Transtornos Heredodegenerativos do Sistema Nervoso/metabolismo , Humanos , Hidrogéis , Proteínas Intrinsicamente Desordenadas/química , Modelos Moleculares , Mutação , Domínios e Motivos de Interação entre Proteínas , RNA Mensageiro/genética , RNA Mensageiro/metabolismo , Proteína FUS de Ligação a RNA/química , Proteína FUS de Ligação a RNA/genética , Proteína FUS de Ligação a RNA/metabolismoRESUMO
The inner nuclear membrane (INM) encases the genome and is fused with the outer nuclear membrane (ONM) to form the nuclear envelope. The ONM is contiguous with the endoplasmic reticulum (ER), the main site of phospholipid synthesis. In contrast to the ER and ONM, evidence for a metabolic activity of the INM has been lacking. Here, we show that the INM is an adaptable membrane territory capable of lipid metabolism. S. cerevisiae cells target enzymes to the INM that can promote lipid storage. Lipid storage involves the synthesis of nuclear lipid droplets from the INM and is characterized by lipid exchange through Seipin-dependent membrane bridges. We identify the genetic circuit for nuclear lipid droplet synthesis and a role of these organelles in regulating this circuit by sequestration of a transcription factor. Our findings suggest a link between INM metabolism and genome regulation and have potential relevance for human lipodystrophy.
Assuntos
Gotículas Lipídicas/metabolismo , Lipídeos de Membrana/metabolismo , Membrana Nuclear/metabolismo , Núcleo Celular , Diglicerídeos/metabolismo , Retículo Endoplasmático , Gotículas Lipídicas/fisiologia , Metabolismo dos Lipídeos/fisiologia , Lipídeos , Proteínas de Membrana , Ácidos Fosfatídicos/metabolismo , Saccharomyces cerevisiae/metabolismoRESUMO
Lipid droplets (LDs) are ubiquitous organelles that store neutral lipids for energy or membrane synthesis and act as hubs for metabolic processes. Cells generate LDs de novo, converting cells to emulsions with LDs constituting the dispersed oil phase in the aqueous cytoplasm. Here we review our current view of LD biogenesis. We present a model of LD formation from the ER in distinct steps and highlight the biology of proteins that govern this biophysical process. Areas of incomplete knowledge are identified, as are connections with physiology and diseases linked to alterations in LD biology.
Assuntos
Gotículas Lipídicas/metabolismo , Animais , Fenômenos Biofísicos , Humanos , Modelos Biológicos , Proteínas/metabolismo , Triglicerídeos/metabolismoRESUMO
Innate lymphoid cells (ILCs) play an important role in the control and maintenance of barrier immunity. However, chronic activation of ILCs results in immune-mediated pathology. Here, we show that tissue-resident type 2 ILCs (ILC2s) display a distinct metabolic signature upon chronic activation. In the context of allergen-driven airway inflammation, ILC2s increase their uptake of both external lipids and glucose. Externally acquired fatty acids are transiently stored in lipid droplets and converted into phospholipids to promote the proliferation of ILC2s. This metabolic program is imprinted by interleukin-33 (IL-33) and regulated by the genes Pparg and Dgat1, which are both controlled by glucose availability and mTOR signaling. Restricting dietary glucose by feeding mice a ketogenic diet largely ablated ILC2-mediated airway inflammation by impairing fatty acid metabolism and the formation of lipid droplets. Together, these results reveal that pathogenic ILC2 responses require lipid metabolism and identify ketogenic diet as a potent intervention strategy to treat airway inflammation.
Assuntos
Alérgenos/administração & dosagem , Asma/dietoterapia , Diacilglicerol O-Aciltransferase/imunologia , Dieta Cetogênica/métodos , Interleucina-33/imunologia , Gotículas Lipídicas/metabolismo , Subpopulações de Linfócitos T/imunologia , Alternaria/química , Animais , Asma/induzido quimicamente , Asma/imunologia , Asma/patologia , Linhagem da Célula/efeitos dos fármacos , Linhagem da Célula/genética , Linhagem da Célula/imunologia , Citocinas/administração & dosagem , Diacilglicerol O-Aciltransferase/genética , Modelos Animais de Doenças , Ácidos Graxos/imunologia , Ácidos Graxos/metabolismo , Regulação da Expressão Gênica , Glucose/imunologia , Glucose/metabolismo , Imunidade Inata , Interleucina-33/administração & dosagem , Interleucina-33/genética , Interleucinas/administração & dosagem , Gotículas Lipídicas/imunologia , Pulmão/efeitos dos fármacos , Pulmão/imunologia , Pulmão/patologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , PPAR gama/genética , PPAR gama/imunologia , Papaína/administração & dosagem , Fosfolipídeos/imunologia , Fosfolipídeos/metabolismo , Cultura Primária de Células , Subpopulações de Linfócitos T/classificação , Subpopulações de Linfócitos T/efeitos dos fármacos , Serina-Treonina Quinases TOR/genética , Serina-Treonina Quinases TOR/imunologia , Linfopoietina do Estroma do TimoRESUMO
Lipid droplets (LDs) store lipids for energy and are central to cellular lipid homeostasis. The mechanisms coordinating lipid storage in LDs with cellular metabolism are unclear but relevant to obesity-related diseases. Here we utilized genome-wide screening to identify genes that modulate lipid storage in macrophages, a cell type involved in metabolic diseases. Among â¼550 identified screen hits is MLX, a basic helix-loop-helix leucine-zipper transcription factor that regulates metabolic processes. We show that MLX and glucose-sensing family members MLXIP/MondoA and MLXIPL/ChREBP bind LDs via C-terminal amphipathic helices. When LDs accumulate in cells, these transcription factors bind to LDs, reducing their availability for transcriptional activity and attenuating the response to glucose. Conversely, the absence of LDs results in hyperactivation of MLX target genes. Our findings uncover a paradigm for a lipid storage response in which binding of MLX transcription factors to LD surfaces adjusts the expression of metabolic genes to lipid storage levels.
Assuntos
Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/metabolismo , Regulação da Expressão Gênica , Glucose/metabolismo , Gotículas Lipídicas/metabolismo , Proteoma/metabolismo , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/antagonistas & inibidores , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos/genética , Células Cultivadas , Testes Genéticos , Humanos , Macrófagos/citologia , Macrófagos/metabolismo , Ligação Proteica , Proteoma/análise , RNA Interferente Pequeno , Transcrição GênicaRESUMO
Liquid-liquid phase-separated (LLPS) states are key to compartmentalizing components in the absence of membranes; however, it is unclear whether LLPS condensates are actively and specifically organized in the subcellular space and by which mechanisms. Here, we address this question by focusing on the ParABS DNA segregation system, composed of a centromeric-like sequence (parS), a DNA-binding protein (ParB), and a motor (ParA). We show that parS and ParB associate to form nanometer-sized, round condensates. ParB molecules diffuse rapidly within the nucleoid volume but display confined motions when trapped inside ParB condensates. Single ParB molecules are able to rapidly diffuse between different condensates, and nucleation is strongly favored by parS. Notably, the ParA motor is required to prevent the fusion of ParB condensates. These results describe a novel active mechanism that splits, segregates, and localizes non-canonical LLPS condensates in the subcellular space.
Assuntos
Trifosfato de Adenosina/fisiologia , Fenômenos Fisiológicos Bacterianos , Proteínas de Escherichia coli/fisiologia , Transição de Fase , DNA Primase/fisiologia , DNA Bacteriano , Microscopia/métodos , Nanopartículas , Imagem Individual de Molécula/métodosRESUMO
Lipid droplets (LDs) provide a reservoir for triacylglycerol storage and are a central hub for fatty acid trafficking and signaling in cells. Lipolysis promotes mitochondrial biogenesis and oxidative metabolism via a SIRT1/PGC-1α/PPARα-dependent pathway through an unknown mechanism. Herein, we identify that monounsaturated fatty acids (MUFAs) allosterically activate SIRT1 toward select peptide-substrates such as PGC-1α. MUFAs enhance PGC-1α/PPARα signaling and promote oxidative metabolism in cells and animal models in a SIRT1-dependent manner. Moreover, we characterize the LD protein perilipin 5 (PLIN5), which is known to enhance mitochondrial biogenesis and function, to be a fatty-acid-binding protein that preferentially binds LD-derived monounsaturated fatty acids and traffics them to the nucleus following cAMP/PKA-mediated lipolytic stimulation. Thus, these studies identify the first-known endogenous allosteric modulators of SIRT1 and characterize a LD-nuclear signaling axis that underlies the known metabolic benefits of MUFAs and PLIN5.
Assuntos
Ácidos Graxos Monoinsaturados/metabolismo , Gotículas Lipídicas/química , Perilipina-5/metabolismo , Sirtuína 1/metabolismo , Regulação Alostérica , Animais , Transporte Biológico , Linhagem Celular , Células Cultivadas , Dieta , Ácidos Graxos/metabolismo , Lipase/metabolismo , Masculino , Camundongos Endogâmicos C57BL , Azeite de Oliva , Perilipina-5/fisiologia , Coativador 1-alfa do Receptor gama Ativado por Proliferador de Peroxissomo/metabolismo , Transcrição GênicaRESUMO
In eukaryotes, gene expression is performed by three RNA polymerases that are targeted to promoters by molecular complexes. A unique common factor, the TATA-box binding protein (TBP), is thought to serve as a platform to assemble pre-initiation complexes competent for transcription. Here, we describe a novel molecular mechanism of nutrient regulation of gene transcription by dynamic O-GlcNAcylation of TBP. We show that O-GlcNAcylation at T114 of TBP blocks its interaction with BTAF1, hence the formation of the B-TFIID complex, and its dynamic cycling on and off of DNA. Transcriptomic and metabolomic analyses of TBPT114A CRISPR/Cas9-edited cells showed that loss of O-GlcNAcylation at T114 increases TBP binding to BTAF1 and directly impacts expression of 408 genes. Lack of O-GlcNAcylation at T114 is associated with a striking reprogramming of cellular metabolism induced by a profound modification of the transcriptome, leading to gross alterations in lipid storage.
Assuntos
Glucose/metabolismo , Gotículas Lipídicas/metabolismo , Metabolismo dos Lipídeos , Fatores Associados à Proteína de Ligação a TATA/metabolismo , Proteína de Ligação a TATA-Box/metabolismo , Fator de Transcrição TFIID/metabolismo , Animais , Cromatina/genética , Cromatina/metabolismo , Diabetes Mellitus Experimental/genética , Diabetes Mellitus Experimental/metabolismo , Regulação da Expressão Gênica , Glicosilação , Células HEK293 , Células HeLa , Humanos , Metabolismo dos Lipídeos/genética , Masculino , Complexos Multiproteicos , Ratos Sprague-Dawley , Transdução de Sinais , Fatores Associados à Proteína de Ligação a TATA/genética , Proteína de Ligação a TATA-Box/genética , Fatores de Tempo , Fator de Transcrição TFIID/genética , Transcrição Gênica , TranscriptomaRESUMO
Lipid droplets (LDs) form inter-organelle contacts with the endoplasmic reticulum (ER) that promote their biogenesis, while LD contacts with mitochondria enhance ß-oxidation of contained fatty acids. Viruses have been shown to take advantage of lipid droplets to promote viral production, but it remains unclear whether they also modulate the interactions between LDs and other organelles. Here, we showed that coronavirus ORF6 protein targets LDs and is localized to the mitochondria-LD and ER-LD contact sites, where it regulates LD biogenesis and lipolysis. At the molecular level, we find that ORF6 inserts into the LD lipid monolayer via its two amphipathic helices. ORF6 further interacts with ER membrane proteins BAP31 and USE1 to mediate ER-LDs contact formation. Additionally, ORF6 interacts with the SAM complex in the mitochondrial outer membrane to link mitochondria to LDs. In doing so, ORF6 promotes cellular lipolysis and LD biogenesis to reprogram host cell lipid flux and facilitate viral production.
Assuntos
Coronavirus , Coronavirus/metabolismo , Retículo Endoplasmático/metabolismo , Gotículas Lipídicas/metabolismo , Lipólise , Ácidos Graxos/metabolismoRESUMO
Upon DNA damage, cells activate the DNA damage response (DDR) to coordinate proliferation and DNA repair. Dietary, metabolic, and environmental inputs are emerging as modulators of how DNA surveillance and repair take place. Lipids hold potential to convey these cues, although little is known about how. We observed that lipid droplet (LD) number specifically increased in response to DNA breaks. Using Saccharomyces cerevisiae and cultured human cells, we show that the selective storage of sterols into these LD concomitantly stabilizes phosphatidylinositol-4-phosphate (PI(4)P) at the Golgi, where it binds the DDR kinase ATM. In turn, this titration attenuates the initial nuclear ATM-driven response to DNA breaks, thus allowing processive repair. Furthermore, manipulating this loop impacts the kinetics of DNA damage signaling and repair in a predictable manner. Thus, our findings have major implications for tackling genetic instability pathologies through dietary and pharmacological interventions.
Assuntos
Proteínas Serina-Treonina Quinases , Proteínas de Saccharomyces cerevisiae , Humanos , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Proteínas de Saccharomyces cerevisiae/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Esteróis/metabolismo , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Dano ao DNA , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismoRESUMO
In Parkinson's disease (PD), α-synuclein (αS) pathologically impacts the brain, a highly lipid-rich organ. We investigated how alterations in αS or lipid/fatty acid homeostasis affect each other. Lipidomic profiling of human αS-expressing yeast revealed increases in oleic acid (OA, 18:1), diglycerides, and triglycerides. These findings were recapitulated in rodent and human neuronal models of αS dyshomeostasis (overexpression; patient-derived triplication or E46K mutation; E46K mice). Preventing lipid droplet formation or augmenting OA increased αS yeast toxicity; suppressing the OA-generating enzyme stearoyl-CoA-desaturase (SCD) was protective. Genetic or pharmacological SCD inhibition ameliorated toxicity in αS-overexpressing rat neurons. In a C. elegans model, SCD knockout prevented αS-induced dopaminergic degeneration. Conversely, we observed detrimental effects of OA on αS homeostasis: in human neural cells, excess OA caused αS inclusion formation, which was reversed by SCD inhibition. Thus, monounsaturated fatty acid metabolism is pivotal for αS-induced neurotoxicity, and inhibiting SCD represents a novel PD therapeutic approach.
Assuntos
Antiparkinsonianos/farmacologia , Descoberta de Drogas/métodos , Inibidores Enzimáticos/farmacologia , Metabolismo dos Lipídeos/efeitos dos fármacos , Metabolômica/métodos , Neurônios/efeitos dos fármacos , Doença de Parkinson/tratamento farmacológico , Estearoil-CoA Dessaturase/antagonistas & inibidores , alfa-Sinucleína/toxicidade , Animais , Caenorhabditis elegans/efeitos dos fármacos , Caenorhabditis elegans/enzimologia , Caenorhabditis elegans/genética , Linhagem Celular , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/enzimologia , Córtex Cerebral/patologia , Diglicerídeos/metabolismo , Modelos Animais de Doenças , Neurônios Dopaminérgicos/efeitos dos fármacos , Neurônios Dopaminérgicos/enzimologia , Neurônios Dopaminérgicos/patologia , Humanos , Células-Tronco Pluripotentes Induzidas/efeitos dos fármacos , Células-Tronco Pluripotentes Induzidas/enzimologia , Células-Tronco Pluripotentes Induzidas/patologia , Gotículas Lipídicas/efeitos dos fármacos , Gotículas Lipídicas/enzimologia , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Terapia de Alvo Molecular , Degeneração Neural , Células-Tronco Neurais/efeitos dos fármacos , Células-Tronco Neurais/enzimologia , Células-Tronco Neurais/patologia , Neurônios/enzimologia , Neurônios/patologia , Ácido Oleico/metabolismo , Doença de Parkinson/enzimologia , Doença de Parkinson/genética , Doença de Parkinson/patologia , Ratos Sprague-Dawley , Saccharomyces cerevisiae/efeitos dos fármacos , Saccharomyces cerevisiae/enzimologia , Saccharomyces cerevisiae/genética , Estearoil-CoA Dessaturase/metabolismo , Triglicerídeos/metabolismo , alfa-Sinucleína/genéticaRESUMO
The Wnt/Wingless signaling pathway plays critical roles in metazoan development and energy metabolism, but its role in regulating lipid homeostasis remains not fully understood. Here, we report that the activation of canonical Wnt/Wg signaling promotes lipolysis while concurrently inhibiting lipogenesis and fatty acid ß-oxidation in both larval and adult adipocytes, as well as cultured S2R+ cells, in Drosophila. Using RNA-sequencing and CUT&RUN (Cleavage Under Targets & Release Using Nuclease) assays, we identified a set of Wnt target genes responsible for intracellular lipid homeostasis. Notably, active Wnt signaling directly represses the transcription of these genes, resulting in decreased de novo lipogenesis and fatty acid ß-oxidation, but increased lipolysis. These changes lead to elevated free fatty acids and reduced triglyceride (TG) accumulation in adipocytes with active Wnt signaling. Conversely, downregulation of Wnt signaling in the fat body promotes TG accumulation in both larval and adult adipocytes. The attenuation of Wnt signaling also increases the expression of specific lipid metabolism-related genes in larval adipocytes, wing discs, and adult intestines. Taken together, these findings suggest that Wnt signaling-induced transcriptional repression plays an important role in regulating lipid homeostasis by enhancing lipolysis while simultaneously suppressing lipogenesis and fatty acid ß-oxidation.
Assuntos
Proteínas de Drosophila , Via de Sinalização Wnt , Animais , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Adipócitos/metabolismo , Mobilização Lipídica , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Proteína Wnt1/metabolismo , Proteína Wnt1/genética , Lipólise , Lipogênese/genética , Triglicerídeos/metabolismo , Metabolismo dos Lipídeos/genética , Larva/metabolismo , Larva/genética , Transcrição Gênica , HomeostaseRESUMO
A missense variant in patatin-like phospholipase domain-containing protein 3 [PNPLA3(I148M)] is the most impactful genetic risk factor for fatty liver disease (FLD). We previously showed that PNPLA3 is ubiquitylated and subsequently degraded by proteasomes and autophagosomes and that the PNPLA3(148M) variant interferes with this process. To define the machinery responsible for PNPLA3 turnover, we used small interfering (si)RNAs to inactivate components of the ubiquitin proteasome system. Inactivation of bifunctional apoptosis regulator (BFAR), a membrane-bound E3 ubiquitin ligase, reproducibly increased PNPLA3 levels in two lines of cultured hepatocytes. Conversely, overexpression of BFAR decreased levels of endogenous PNPLA3 in HuH7 cells. BFAR and PNPLA3 co-immunoprecipitated when co-expressed in cells. BFAR promoted ubiquitylation of PNPLA3 in vitro in a reconstitution assay using purified, epitope-tagged recombinant proteins. To confirm that BFAR targets PNPLA3, we inactivated Bfar in mice. Levels of PNPLA3 protein were increased twofold in hepatic lipid droplets of Bfar-/- mice with no associated increase in PNPLA3 mRNA levels. Taken together these data are consistent with a model in which BFAR plays a role in the post-translational degradation of PNPLA3. The identification of BFAR provides a potential target to enhance PNPLA3 turnover and prevent FLD.
Assuntos
Proteínas Adaptadoras de Transdução de Sinal , Proteínas Reguladoras de Apoptose , Proteínas de Membrana , Hepatopatia Gordurosa não Alcoólica , Animais , Camundongos , Aciltransferases , Hepatócitos/metabolismo , Hepatopatia Gordurosa não Alcoólica/metabolismo , Fosfolipases A2 Independentes de Cálcio/genética , Ubiquitina , Ubiquitina-Proteína Ligases/genética , Proteínas de Membrana/metabolismo , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas Reguladoras de Apoptose/metabolismo , Humanos , Linhagem Celular TumoralRESUMO
Omega-3 polyunsaturated fatty acids (PUFA) found primarily in fish oil have been a popular supplement for cardiovascular health because they can substantially reduce circulating triglyceride levels in the bloodstream to prevent atherosclerosis. Beyond this established extracellular activity, here, we report a mode of action of PUFA, regulating intracellular triglyceride metabolism and lipid droplet (LD) dynamics. Real-time imaging of the subtle and highly dynamic changes of intracellular lipid metabolism was enabled by a fluorescence lifetime probe that addressed the limitations of intensity-based fluorescence quantifications. Surprisingly, we found that among omega-3 PUFA, only docosahexaenoic acid (DHA) promoted the lipolysis in LDs and reduced the overall fat content by approximately 50%, and consequently helped suppress macrophage differentiation into foam cells, one of the early steps responsible for atherosclerosis. Eicosapentaenoic acid, another omega-3 FA in fish oil, however, counteracted the beneficial effects of DHA on lipolysis promotion and cell foaming prevention. These in vitro findings warrant future validation in vivo.
Assuntos
Aterosclerose , Ácidos Graxos Ômega-3 , Humanos , Lipólise , Fluorescência , Ácidos Graxos Ômega-3/metabolismo , Óleos de Peixe/farmacologia , Ácidos Docosa-Hexaenoicos/metabolismo , Macrófagos/metabolismo , TriglicerídeosRESUMO
Genomic information must be faithfully transmitted into two daughter cells during mitosis. To ensure the transmission process, interphase chromatin is further condensed into mitotic chromosomes. Although protein factors like condensins and topoisomerase IIα are involved in the assembly of mitotic chromosomes, the physical bases of the condensation process remain unclear. Depletion attraction/macromolecular crowding, an effective attractive force that arises between large structures in crowded environments around chromosomes, may contribute to the condensation process. To approach this issue, we investigated the "chromosome milieu" during mitosis of living human cells using an orientation-independent-differential interference contrast module combined with a confocal laser scanning microscope, which is capable of precisely mapping optical path differences and estimating molecular densities. We found that the molecular density surrounding chromosomes increased with the progression from prophase to anaphase, concurring with chromosome condensation. However, the molecular density went down in telophase, when chromosome decondensation began. Changes in the molecular density around chromosomes by hypotonic or hypertonic treatment consistently altered the condensation levels of chromosomes. In vitro, native chromatin was converted into liquid droplets of chromatin in the presence of cations and a macromolecular crowder. Additional crowder made the chromatin droplets stiffer and more solid-like. These results suggest that a transient rise in depletion attraction, likely triggered by the relocation of macromolecules (proteins, RNAs, and others) via nuclear envelope breakdown and by a subsequent decrease in cell volumes, contributes to mitotic chromosome condensation, shedding light on a different aspect of the condensation mechanism in living human cells.
Assuntos
Cromatina , Cromossomos Humanos , Mitose , Humanos , Células HeLa , Cromatina/metabolismo , Cromossomos Humanos/metabolismo , Cromossomos Humanos/genética , Microscopia Confocal , Complexos Multiproteicos/metabolismo , Adenosina Trifosfatases , Proteínas de Ligação a DNARESUMO
Metabolic reprogramming is critical during clear cell renal cell carcinoma (ccRCC) tumorigenesis, manifested by accumulation of lipid droplets (LDs), organelles that have emerged as new hallmarks of cancer. Yet, regulation of their biogenesis is still poorly understood. Here, we demonstrate that MYC inhibition in ccRCC cells lacking the von Hippel Lindau (VHL) gene leads to increased triglyceride content potentiating LD formation in a glutamine-dependent manner. Importantly, the concurrent inhibition of MYC signaling and glutamine metabolism prevented LD accumulation and reduced tumor burden in vivo. Furthermore, we identified the hypoxia-inducible lipid droplet-associated protein (HILPDA) as the key driver for induction of MYC-driven LD accumulation and demonstrated that conversely, proliferation, LD formation, and tumor growth are impaired upon its downregulation. Finally, analysis of ccRCC tissue as well as healthy renal control samples postulated HILPDA as a specific ccRCC biomarker. Together, these results provide an attractive approach for development of alternative therapeutic interventions for the treatment of this type of renal cancer.
Assuntos
Carcinoma de Células Renais , Neoplasias Renais , Gotículas Lipídicas , Proteínas Proto-Oncogênicas c-myc , Humanos , Carcinoma de Células Renais/patologia , Linhagem Celular Tumoral , Regulação Neoplásica da Expressão Gênica , Glutamina/metabolismo , Neoplasias Renais/patologia , Gotículas Lipídicas/efeitos dos fármacos , Gotículas Lipídicas/metabolismo , Proteínas Proto-Oncogênicas c-myc/antagonistas & inibidores , Proteínas Proto-Oncogênicas c-myc/metabolismo , Transdução de Sinais , Regulação para Cima , Proteína Supressora de Tumor Von Hippel-Lindau/genética , Proteína Supressora de Tumor Von Hippel-Lindau/metabolismo , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismoRESUMO
Microbes have developed many strategies to subvert host organisms, which, in turn, evolved several innate immune responses. As major lipid storage organelles of eukaryotes, lipid droplets (LDs) are an attractive source of nutrients for invaders. Intracellular viruses, bacteria, and protozoan parasites induce and physically interact with LDs, and the current view is that they "hijack" LDs to draw on substrates for host colonization. This dogma has been challenged by the recent demonstration that LDs are endowed with a protein-mediated antibiotic activity, which is upregulated in response to danger signals and sepsis. Dependence on host nutrients could be a generic "Achilles' heel" of intracellular pathogens and LDs a suitable chokepoint harnessed by innate immunity to organize a front-line defense. Here, we will provide a brief overview of the state of the conflict and discuss potential mechanisms driving the formation of the 'defensive-LDs' functioning as hubs of innate immunity.
Assuntos
Anti-Infecciosos , Gotículas Lipídicas , Humanos , Gotículas Lipídicas/metabolismo , Organelas , Bactérias , Imunidade Inata , Anti-Infecciosos/metabolismo , Metabolismo dos LipídeosRESUMO
Lipid droplets (LDs) are the main organelles for lipid storage, and their surfaces contain unique proteins with diverse functions, including those that facilitate the deposition and mobilization of LD lipids. Among organelles, LDs have an unusual structure with an organic, hydrophobic oil phase covered by a phospholipid monolayer. The unique properties of LD monolayer surfaces require proteins to localize to LDs by distinct mechanisms. Here we review the two pathways known to mediate direct LD protein localization: the CYTOLD pathway mediates protein targeting from the cytosol toLDs, and the ERTOLD pathway functions in protein targeting from the endoplasmic reticulum toLDs. We describe the emerging principles for each targeting pathway in animal cells and highlight open questions in the field.