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1.
Nat Commun ; 11(1): 4765, 2020 09 21.
Artigo em Inglês | MEDLINE | ID: mdl-32958780

RESUMO

Fatty acids (FAs) are essential nutrients, but how they are transported into cells remains unclear. Here, we show that FAs trigger caveolae-dependent CD36 internalization, which in turn delivers FAs into adipocytes. During the process, binding of FAs to CD36 activates its downstream kinase LYN, which phosphorylates DHHC5, the palmitoyl acyltransferase of CD36, at Tyr91 and inactivates it. CD36 then gets depalmitoylated by APT1 and recruits another tyrosine kinase SYK to phosphorylate JNK and VAVs to initiate endocytic uptake of FAs. Blocking CD36 internalization by inhibiting APT1, LYN or SYK abolishes CD36-dependent FA uptake. Restricting CD36 at either palmitoylated or depalmitoylated state eliminates its FA uptake activity, indicating an essential role of dynamic palmitoylation of CD36. Furthermore, blocking endocytosis by targeting LYN or SYK inhibits CD36-dependent lipid droplet growth in adipocytes and high-fat-diet induced weight gain in mice. Our study has uncovered a dynamic palmitoylation-regulated endocytic pathway to take up FAs.


Assuntos
Antígenos CD36/metabolismo , Endocitose/fisiologia , Ácidos Graxos/metabolismo , Lipoilação , Células 3T3-L1 , Aciltransferases/metabolismo , Adipócitos/metabolismo , Animais , Antígenos CD36/deficiência , Antígenos CD36/genética , Cavéolas/metabolismo , Células Cultivadas , Dieta Hiperlipídica/efeitos adversos , Humanos , Gotículas Lipídicas/metabolismo , Masculino , Proteínas de Membrana/metabolismo , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Mutação , Obesidade/tratamento farmacológico , Fosforilação , Transdução de Sinais , Quinase Syk/antagonistas & inibidores , Quinase Syk/metabolismo , Ganho de Peso/efeitos dos fármacos , Quinases da Família src/antagonistas & inibidores , Quinases da Família src/metabolismo
2.
Proc Natl Acad Sci U S A ; 117(37): 23131-23139, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32868427

RESUMO

Lipid droplets (LDs) are intracellular organelles found in a wide range of organisms and play important roles in stress tolerance. During nitrogen (N) starvation, Chlamydomonas reinhardtii stores large amounts of triacylglycerols (TAGs) inside LDs. When N is resupplied, the LDs disappear and the TAGs are degraded, presumably providing carbon and energy for regrowth. The mechanism by which cells degrade LDs is poorly understood. Here, we isolated a mutant (dth1-1, Delayed in TAG Hydrolysis 1) in which TAG degradation during recovery from N starvation was compromised. Consequently, the dth1-1 mutant grew poorly compared to its parental line during N recovery. Two additional independent loss-of-function mutants (dth1-2 and dth1-3) also exhibited delayed TAG remobilization. DTH1 transcript levels increased sevenfold upon N resupply, and DTH1 protein was localized to LDs. DTH1 contains a putative lipid-binding domain (DTH1LBD) with alpha helices predicted to be structurally similar to those in apolipoproteins E and A-I. Recombinant DTH1LBD bound specifically to phosphatidylethanolamine (PE), a major phospholipid coating the LD surface. Overexpression of DTH1LBD in Chlamydomonas phenocopied the dth1 mutant's defective TAG degradation, suggesting that the function of DTH1 depends on its ability to bind PE. Together, our results demonstrate that the lipid-binding DTH1 plays an essential role in LD degradation and provide insight into the molecular mechanism of protein anchorage to LDs at the LD surface in photosynthetic cells.


Assuntos
Proteínas de Algas/metabolismo , Chlamydomonas reinhardtii/metabolismo , Gotículas Lipídicas/metabolismo , Proteína de Ligação a Fosfatidiletanolamina/metabolismo , Sequência de Aminoácidos , Metabolismo dos Lipídeos/fisiologia , Nitrogênio/metabolismo , Fosfolipídeos/metabolismo , Fotossíntese/fisiologia , Triglicerídeos/metabolismo
3.
Nat Commun ; 11(1): 4480, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32900992

RESUMO

Macroautophagy initiates by formation of isolation membranes, but the source of phospholipids for the membrane biogenesis remains elusive. Here, we show that autophagic membranes incorporate newly synthesized phosphatidylcholine, and that CTP:phosphocholine cytidylyltransferase ß3 (CCTß3), an isoform of the rate-limiting enzyme in the Kennedy pathway, plays an essential role. In starved mouse embryo fibroblasts, CCTß3 is initially recruited to autophagic membranes, but upon prolonged starvation, it concentrates on lipid droplets that are generated from autophagic degradation products. Omegasomes and isolation membranes emanate from around those lipid droplets. Autophagy in prolonged starvation is suppressed by knockdown of CCTß3 and is enhanced by its overexpression. This CCTß3-dependent mechanism is also present in U2OS, an osteosarcoma cell line, and autophagy and cell survival in starvation are decreased by CCTß3 depletion. The results demonstrate that phosphatidylcholine synthesis through CCTß3 activation on lipid droplets is crucial for sustaining autophagy and long-term cell survival.


Assuntos
Autofagia/fisiologia , Colina-Fosfato Citidililtransferase/metabolismo , Fibroblastos/citologia , Fibroblastos/metabolismo , Animais , Autofagossomos/metabolismo , Linhagem Celular Tumoral , Sobrevivência Celular , Colina-Fosfato Citidililtransferase/antagonistas & inibidores , Colina-Fosfato Citidililtransferase/genética , Meios de Cultura , Ativação Enzimática , Técnicas de Silenciamento de Genes , Humanos , Gotículas Lipídicas/metabolismo , Camundongos , Modelos Biológicos , Células-Tronco Embrionárias Murinas/citologia , Células-Tronco Embrionárias Murinas/metabolismo , Osteossarcoma/metabolismo , Osteossarcoma/patologia , Fosfatidilcolinas/metabolismo
4.
Arch Biochem Biophys ; 692: 108532, 2020 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-32795451

RESUMO

Fatty acid uptake and accumulation in lipid droplets are essential processes of lipid metabolism. Oocyte in vitro culture in media enriched with fatty acid is used to modify the lipid content and composition, aiming to study the consequences of obesity and enhance cell cryotolerance. We applied Raman spectroscopy and deuterium labeling approach to quantify stearic acid uptake and investigate its incorporation within oocytes. Our data suggest that deuterium labeling does not affect oocyte maturation rates. The efficiency of deuterated stearic acid (dSA) uptake was shown to decrease with the increase of its concentration in culture medium and the duration of in vitro culture. The molar ratio between dSA and bovine serum albumin has no significant effect on the dSA uptake for 200 µM but modifies concentration dependence of the lipid uptake. dSA accumulates in all the lipid droplets inside oocytes. Different lipid droplets within the same oocyte exhibit different concentrations of dSA. The scatter in the dSA concentration in lipid droplets decreases with the culture time. Using dSA as an example, we provide a comprehensive description of how fatty acid concentration, its molar ratio versus bovine serum albumin, and culture time affect the uptake of the fatty acids in oocytes. Raman microspectroscopy of deuterium-labeled fatty acids is a nondestructive tool providing information about fatty acid uptake and heterogeneity of their accumulation between lipid droplets within the single oocyte.


Assuntos
Deutério , Gotículas Lipídicas/metabolismo , Oócitos/metabolismo , Ácidos Esteáricos , Animais , Gatos , Deutério/química , Deutério/farmacocinética , Deutério/farmacologia , Feminino , Marcação por Isótopo , Oócitos/citologia , Ácidos Esteáricos/química , Ácidos Esteáricos/farmacocinética , Ácidos Esteáricos/farmacologia
5.
Proc Natl Acad Sci U S A ; 117(36): 22080-22089, 2020 09 08.
Artigo em Inglês | MEDLINE | ID: mdl-32820071

RESUMO

Nonshivering thermogenesis occurs in brown adipose tissue to generate heat in response to cold ambient temperatures. Thioesterase superfamily member 1 (Them1) is transcriptionally up-regulated in brown adipose tissue upon exposure to the cold and suppresses thermogenesis in order to conserve energy reserves. It hydrolyzes long-chain fatty acyl-CoAs that are derived from lipid droplets, preventing their use as fuel for thermogenesis. In addition to its enzymatic domains, Them1 contains a C-terminal StAR-related lipid transfer (START) domain with unknown ligand or function. By complementary biophysical approaches, we show that the START domain binds to long-chain fatty acids, products of Them1's enzymatic reaction, as well as lysophosphatidylcholine (LPC), lipids shown to activate thermogenesis in brown adipocytes. Certain fatty acids stabilize the START domain and allosterically enhance Them1 catalysis of acyl-CoA, whereas 18:1 LPC destabilizes and inhibits activity, which we verify in cell culture. Additionally, we demonstrate that the START domain functions to localize Them1 near lipid droplets. These findings define the role of the START domain as a lipid sensor that allosterically regulates Them1 activity and spatially localizes it in proximity to the lipid droplet.


Assuntos
Ácidos Graxos/metabolismo , Lisofosfatidilcolinas/metabolismo , Palmitoil-CoA Hidrolase/química , Palmitoil-CoA Hidrolase/metabolismo , Acil Coenzima A/metabolismo , Tecido Adiposo Marrom/enzimologia , Tecido Adiposo Marrom/metabolismo , Regulação Alostérica , Ácidos Graxos/química , Humanos , Cinética , Gotículas Lipídicas/enzimologia , Gotículas Lipídicas/metabolismo , Lisofosfatidilcolinas/química , Palmitoil-CoA Hidrolase/genética , Domínios Proteicos
6.
Nat Commun ; 11(1): 3944, 2020 08 07.
Artigo em Inglês | MEDLINE | ID: mdl-32769983

RESUMO

Triacylglycerols (TG) are synthesized at the endoplasmic reticulum (ER) bilayer and packaged into organelles called lipid droplets (LDs). LDs are covered by a single phospholipid monolayer contiguous with the ER bilayer. This connection is used by several monotopic integral membrane proteins, with hydrophobic membrane association domains (HDs), to diffuse between the organelles. However, how proteins partition between ER and LDs is not understood. Here, we employed synthetic model systems and found that HD-containing proteins strongly prefer monolayers and returning to the bilayer is unfavorable. This preference for monolayers is due to a higher affinity of HDs for TG over membrane phospholipids. Protein distribution is regulated by PC/PE ratio via alterations in monolayer packing and HD-TG interaction. Thus, HD-containing proteins appear to non-specifically accumulate to the LD surface. In cells, protein editing mechanisms at the ER membrane would be necessary to prevent unspecific relocation of HD-containing proteins to LDs.


Assuntos
Membrana Celular/metabolismo , Bicamadas Lipídicas/metabolismo , Gotículas Lipídicas/metabolismo , Proteínas de Membrana/metabolismo , Triglicerídeos/metabolismo , Dicroísmo Circular , Retículo Endoplasmático/metabolismo , Proteínas de Membrana/química , Simulação de Dinâmica Molecular , Domínios Proteicos , Transporte Proteico , Triglicerídeos/química
7.
PLoS Genet ; 16(8): e1008941, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32760060

RESUMO

Apolipoprotein B-containing lipoproteins (B-lps) are essential for the transport of hydrophobic dietary and endogenous lipids through the circulation in vertebrates. Zebrafish embryos produce large numbers of B-lps in the yolk syncytial layer (YSL) to move lipids from yolk to growing tissues. Disruptions in B-lp production perturb yolk morphology, readily allowing for visual identification of mutants with altered B-lp metabolism. Here we report the discovery of a missense mutation in microsomal triglyceride transfer protein (Mtp), a protein that is essential for B-lp production. This mutation of a conserved glycine residue to valine (zebrafish G863V, human G865V) reduces B-lp production and results in yolk opacity due to aberrant accumulation of cytoplasmic lipid droplets in the YSL. However, this phenotype is milder than that of the previously reported L475P stalactite (stl) mutation. MTP transfers lipids, including triglycerides and phospholipids, to apolipoprotein B in the ER for B-lp assembly. In vitro lipid transfer assays reveal that while both MTP mutations eliminate triglyceride transfer activity, the G863V mutant protein unexpectedly retains ~80% of phospholipid transfer activity. This residual phospholipid transfer activity of the G863V mttp mutant protein is sufficient to support the secretion of small B-lps, which prevents intestinal fat malabsorption and growth defects observed in the mttpstl/stl mutant zebrafish. Modeling based on the recent crystal structure of the heterodimeric human MTP complex suggests the G865V mutation may block triglyceride entry into the lipid-binding cavity. Together, these data argue that selective inhibition of MTP triglyceride transfer activity may be a feasible therapeutic approach to treat dyslipidemia and provide structural insight for drug design. These data also highlight the power of yolk transport studies to identify proteins critical for B-lp biology.


Assuntos
Proteínas de Transporte/genética , Lipídeos/genética , Lipoproteínas/genética , Triglicerídeos/genética , Animais , Fígado Gorduroso/genética , Fígado Gorduroso/patologia , Trato Gastrointestinal/metabolismo , Humanos , Imunoprecipitação , Gotículas Lipídicas/metabolismo , Lipoproteínas/metabolismo , Mutação de Sentido Incorreto/genética , Mutação Puntual/genética , Transporte Proteico/genética , Triglicerídeos/metabolismo , Peixe-Zebra/genética
9.
J Vis Exp ; (160)2020 06 08.
Artigo em Inglês | MEDLINE | ID: mdl-32568221

RESUMO

Single molecule localization microscopy (SMLM) techniques overcome the optical diffraction limit of conventional fluorescence microscopy and can resolve intracellular structures and the dynamics of biomolecules with ~20 nm precision. A prerequisite for SMLM are fluorophores that transition from a dark to a fluorescent state in order to avoid spatio-temporal overlap of their point spread functions in each of the thousands of data acquisition frames. BODIPYs are well-established dyes with numerous conjugates used in conventional microscopy. The transient formation of red-shifted BODIPY ground-state dimers (DII) results in bright single molecule emission enabling single molecule localization microscopy (SMLM). Here we present a simple but versatile protocol for SMLM with conventional BODIPY conjugates in living yeast and mammalian cells. This procedure can be used to acquire super-resolution images and to track single BODIPY-DII states to extract spatio-temporal information of BODIPY conjugates. We apply this procedure to resolve lipid droplets (LDs), fatty acids, and lysosomes in living yeast and mammalian cells at the nanoscopic length scale. Furthermore, we demonstrate the multi-color imaging capability with BODIPY dyes when used in conjunction with other fluorescent probes. Our representative results show the differential spatial distribution and mobility of BODIPY-fatty acids and neutral lipids in yeast under fed and fasted conditions. This optimized protocol for SMLM can be used with hundreds of commercially available BODIPY conjugates and is a useful resource to study biological processes at the nanoscale far beyond the applications of this work.


Assuntos
Compostos de Boro/química , Corantes Fluorescentes/química , Microscopia de Fluorescência/métodos , Imagem Individual de Molécula/métodos , Animais , Compostos de Boro/metabolismo , Sobrevivência Celular , Cor , Ácidos Graxos/metabolismo , Corantes Fluorescentes/metabolismo , Gotículas Lipídicas/metabolismo , Lisossomos/metabolismo , Leveduras/citologia
10.
Nat Commun ; 11(1): 2790, 2020 06 03.
Artigo em Inglês | MEDLINE | ID: mdl-32493904

RESUMO

Age-dependent changes in metabolism can manifest as cellular lipid accumulation, but how this accumulation is regulated or impacts longevity is poorly understood. We find that Saccharomyces cerevisiae accumulate lipid droplets (LDs) during aging. We also find that over-expressing BNA2, the first Biosynthesis of NAD+ (kynurenine) pathway gene, reduces LD accumulation during aging and extends lifespan. Mechanistically, this LD accumulation during aging is not linked to NAD+ levels, but is anti-correlated with metabolites of the shikimate and aromatic amino acid biosynthesis (SA) pathways (upstream of BNA2), which produce tryptophan (the Bna2p substrate). We provide evidence that over-expressed BNA2 skews glycolytic flux from LDs towards the SA-BNA pathways, effectively reducing LDs. Importantly, we find that accumulation of LDs does not shorten lifespan, but does protect aged cells against stress. Our findings reveal how lipid accumulation impacts longevity, and how aging cell metabolism can be rewired to modulate lipid accumulation independently from longevity.


Assuntos
Metabolismo dos Lipídeos , Saccharomyces cerevisiae/crescimento & desenvolvimento , Saccharomyces cerevisiae/metabolismo , Vias Biossintéticas , Temperatura Baixa , Gotículas Lipídicas/metabolismo , Metaboloma , NAD/metabolismo , Saccharomyces cerevisiae/citologia , Proteínas de Saccharomyces cerevisiae/metabolismo , Ácido Chiquímico/metabolismo , Estresse Fisiológico
11.
Trends Plant Sci ; 25(11): 1141-1153, 2020 11.
Artigo em Inglês | MEDLINE | ID: mdl-32565020

RESUMO

Together with sugars and proteins, lipids constitute the main carbon reserves in plants. Lipids are selectively recycled and catabolized for energy production during development and in response to environmental stresses. Autophagy is a major catabolic pathway, operating in the recycling of cellular components in eukaryotes. Although the autophagic degradation of lipids has been mainly characterized in mammals and yeast, growing evidence has highlighted the role of autophagy in several aspects of lipid metabolism in plants. Here, we summarize recent findings focusing on autophagy functions in lipid droplet (LD) metabolism. We further provide novel insights regarding the relevance of autophagy in the maintenance and clearance of mitochondria and peroxisomes and its consequences for proper lipid usage and energy homeostasis in plants.


Assuntos
Autofagia , Gotículas Lipídicas , Animais , Metabolismo Energético , Gotículas Lipídicas/metabolismo , Metabolismo dos Lipídeos , Lipídeos
12.
PLoS One ; 15(6): e0233887, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32492043

RESUMO

Increased cytoplasmic lipid droplets (LDs) and elevated AKT/mTOR signaling are characteristics of clear cell renal cell carcinoma (ccRCC). Lysophosphatidic acid (LPA), a potent lipid mitogen generated via autotaxin (elevated in ccRCC), can modulate tumor progression but its role in altering chemotherapeutic sensitivity to mTOR inhibitors is unclear and thus is the focus of the studies presented herein. Using malignant (A-498, 769-P and 786-O) and normal immortalized kidney (HK-2) cell lines, we investigated their cellular responsiveness to Temsirolimus (TEMS, mTOR inhibitor) in the absence or presence of LPA by monitoring alterations in AKT/mTOR pathway mediators (via western blotting), LDs (using LipidTOX and real-time PCR to assess transcript changes in modulators of LD biogenesis/turnover), mitochondrial networks (via immunofluorescence staining for TOM20 and TOM70), as well as cellular viability. We identified that TEMS reduced cellular viability in all renal cell lines, with increased sensitivity in the presence of an autophagy inhibitor. TEMS also altered activation of AKT/mTOR pathway mediators, abundance of LDs, and fragmentation of mitochondrial networks. We observed that these effects were antagonized by LPA. In HK-2 cells, LPA markedly increased LD size and abundance, coinciding with phospho-MAPK and phospho-S6 activation, increased diacylglycerol O-acetyltransferase 2 (DGAT2) mRNA (which produces triacylglycerides), and survival. Inhibiting MAPK partially antagonized LPA-induced LD changes. Collectively, we have identified that LPA can reverse the effects of TEMS by increasing LDs in a MAPK-dependent manner; these results suggest that LPA may contribute to the pathogenesis and chemotherapeutic resistance of ccRCC.


Assuntos
Antineoplásicos/farmacologia , Carcinoma de Células Renais/tratamento farmacológico , Neoplasias Renais/tratamento farmacológico , Lisofosfolipídeos/metabolismo , Sirolimo/análogos & derivados , Antineoplásicos/uso terapêutico , Autofagia/efeitos dos fármacos , Carcinoma de Células Renais/patologia , Linhagem Celular Tumoral , Sobrevivência Celular/efeitos dos fármacos , Resistencia a Medicamentos Antineoplásicos , Humanos , Hidroxicloroquina/farmacologia , Hidroxicloroquina/uso terapêutico , Neoplasias Renais/patologia , Gotículas Lipídicas/efeitos dos fármacos , Gotículas Lipídicas/metabolismo , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Diester Fosfórico Hidrolases/metabolismo , Transdução de Sinais/efeitos dos fármacos , Sirolimo/farmacologia , Sirolimo/uso terapêutico , Serina-Treonina Quinases TOR/antagonistas & inibidores , Serina-Treonina Quinases TOR/metabolismo
13.
PLoS Pathog ; 16(6): e1008554, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32542055

RESUMO

Lipid droplets are essential cellular organelles for storage of fatty acids and triglycerides. The hepatitis C virus (HCV) translocates several of its proteins onto their surface and uses them for production of infectious progeny. We recently reported that the lipid droplet-associated α/ß hydrolase domain-containing protein 5 (ABHD5/CGI-58) participates in HCV assembly by mobilizing lipid droplet-associated lipids. However, ABHD5 itself has no lipase activity and it remained unclear how ABHD5 mediates lipolysis critical for HCV assembly. Here, we identify adipose triglyceride lipase (ATGL) as ABHD5 effector and new host factor involved in the hepatic lipid droplet degradation as well as in HCV and lipoprotein morphogenesis. Modulation of ATGL protein expression and lipase activity controlled lipid droplet lipolysis and virus production. ABHD4 is a paralog of ABHD5 unable to activate ATGL or support HCV assembly and lipid droplet lipolysis. Grafting ABHD5 residues critical for activation of ATGL onto ABHD4 restored the interaction between lipase and co-lipase and bestowed the pro-viral and lipolytic functions onto the engineered protein. Congruently, mutation of the predicted ABHD5 protein interface to ATGL ablated ABHD5 functions in lipid droplet lipolysis and HCV assembly. Interestingly, minor alleles of ABHD5 and ATGL associated with neutral lipid storage diseases in human, are also impaired in lipid droplet lipolysis and their pro-viral functions. Collectively, these results show that ABHD5 cooperates with ATGL to mobilize triglycerides for HCV infectious virus production. Moreover, viral manipulation of lipid droplet homeostasis via the ABHD5-ATGL axis, akin to natural genetic variation in these proteins, emerges as a possible mechanism by which chronic HCV infection causes liver steatosis.


Assuntos
1-Acilglicerol-3-Fosfato O-Aciltransferase/metabolismo , Hepacivirus/fisiologia , Lipase/metabolismo , Gotículas Lipídicas/metabolismo , Lipólise , Montagem de Vírus/fisiologia , 1-Acilglicerol-3-Fosfato O-Aciltransferase/genética , Linhagem Celular Tumoral , Ativação Enzimática , Células HEK293 , Humanos , Lipase/genética , Gotículas Lipídicas/virologia , Triglicerídeos/genética , Triglicerídeos/metabolismo
14.
Am J Physiol Endocrinol Metab ; 318(6): E848-E855, 2020 06 01.
Artigo em Inglês | MEDLINE | ID: mdl-32369416

RESUMO

Disturbances in skeletal muscle lipid oxidation might induce ectopic fat deposition and lipotoxicity. Nevertheless, the cellular mechanisms that regulate skeletal muscle lipid oxidation have not been fully determined. We aimed to determine whether there was an association between relative whole body lipid oxidation and mitochondrial size or mitochondria-sarcoplasmic reticulum interactions in the skeletal muscle. Twelve healthy men were included [mean (standard deviation), 24.7 (1.5) yr old, 24.4 (2.6) kg/m2]. The respiratory quotient (RQ) was used to estimate relative lipid oxidation at rest and during exercise (50% maximal oxygen consumption, 600 kcal expended). A skeletal muscle biopsy was obtained from the vastus lateralis at rest. Transmission electron microscopy was used to determine mitochondrial size and mitochondria-sarcoplasmic reticulum interactions (≤50 nm of distance between organelles). Protein levels of fusion/fission regulators were measured in skeletal muscle by Western blot. Resting RQ and exercise RQ associated inversely with intermyofibrillar mitochondrial size (r = -0.66 and r = -0.60, respectively, P < 0.05). Resting RQ also associated inversely with the percentage of intermyofibrillar mitochondria-sarcoplasmic reticulum interactions (r = -0.62, P = 0.03). Finally, intermyofibrillar mitochondrial size associated inversely with lipid droplet density (r = -0.66, P = 0.01) but directly with mitochondria fusion-to-fission ratio (r = 0.61, P = 0.03). Our results show that whole body lipid oxidation is associated with skeletal muscle intermyofibrillar mitochondrial size, fusion phenotype, and mitochondria-sarcoplasmic-reticulum interactions in nondiabetic humans.


Assuntos
Exercício Físico/fisiologia , Metabolismo dos Lipídeos , Mitocôndrias/ultraestrutura , Dinâmica Mitocondrial , Fibras Musculares Esqueléticas/ultraestrutura , Músculo Quadríceps/ultraestrutura , Retículo Sarcoplasmático/ultraestrutura , Adolescente , Adulto , Humanos , Gotículas Lipídicas/metabolismo , Gotículas Lipídicas/ultraestrutura , Masculino , Microscopia Eletrônica de Transmissão , Mitocôndrias/metabolismo , Tamanho Mitocondrial , Fibras Musculares Esqueléticas/metabolismo , Músculo Esquelético/metabolismo , Músculo Esquelético/ultraestrutura , Oxirredução , Consumo de Oxigênio , Músculo Quadríceps/metabolismo , Adulto Jovem
15.
Life Sci ; 255: 117818, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32445757

RESUMO

Activation of hepatic stellate cells (HSCs) is a central event in the pathogenesis of liver fibrosis and is characterized by the disappearance of lipid droplets. Although the exogenous supplementation of lipid droplet content can effectively reverse the activation of HSCs, the underlying molecular mechanisms are largely unknown. In our current study, we sought to investigate the role of lncRNA-H19 in the process of lipid droplets disappearance and to further examine the underlying molecular mechanisms. We found that the lncRNA-H19 level was increased in CCl4-induced fibrotic liver, which activated HSCs. Further research showed that hypoxia inducible factor-1α (HIF-1α) significantly increased lncRNA-H19 expression by binding to the lncRNA-H19 promoter at two hypoxia response element (HRE) sites located at 492-499 and 515-522 bp. Importantly, lncRNA-H19 knockdown markedly inhibited HSC activation and alleviated liver fibrosis, indicating that lncRNA-H19 may be a potential target for anti-fibrosis therapeutic approaches. Moreover, lncRNA-H19 knockdown could reverse the lipid droplet phenotype of activated HSCs, inhibiting the phosphorylated AMPKα-mediated lipid oxidation signaling pathway. The AMPK agonist AICAR promoted AMPKα phosphorylation and abrogated lipid droplets restoration in HSCs transfected with the lncRNA-H19 knockdown plasmid. Experimental molecular analysis showed that lncRNA-H19 triggered AMPKα to interact with LKB1 and resulted in AMPKα phosphorylation, which accelerating lipid droplets degradation and lipid oxidation. Taken together, our results highlighted the role of lncRNA-H19 in the metabolism of lipid droplets in HSCs, and revealed a new molecular target for alleviating liver fibrosis.


Assuntos
Proteínas Quinases Ativadas por AMP/metabolismo , Células Estreladas do Fígado/metabolismo , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Cirrose Hepática/patologia , RNA Longo não Codificante/genética , Animais , Linhagem Celular , Técnicas de Silenciamento de Genes , Humanos , Gotículas Lipídicas/metabolismo , Cirrose Hepática/genética , Masculino , Camundongos , Camundongos Endogâmicos ICR , Elementos de Resposta/genética
16.
J Virol ; 94(15)2020 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-32461314

RESUMO

Many RNA viruses replicate in cytoplasmic compartments (virus factories or viroplasms) composed of viral and cellular proteins, but the mechanisms required for their formation remain largely unknown. Rotavirus (RV) replication in viroplasms requires interactions between virus nonstructural proteins NSP2 and NSP5, which are associated with components of lipid droplets (LDs). We previously identified two forms of NSP2 in RV-infected cells, a cytoplasmically dispersed form (dNSP2) and a viroplasm-specific form (vNSP2), which interact with hypophosphorylated and hyperphosphorylated NSP5, respectively, indicating that a coordinated phosphorylation cascade controls viroplasm assembly. The cellular kinase CK1α phosphorylates NSP2 on serine 313, triggering the localization of vNSP2 to sites of viroplasm assembly and its association with hyperphosphorylated NSP5. Using reverse genetics, we generated a rotavirus with a phosphomimetic NSP2 (S313D) mutation to directly evaluate the role of CK1α NSP2 phosphorylation in viroplasm formation. Recombinant rotavirus NSP2 S313D (rRV NSP2 S313D) is significantly delayed in viroplasm formation and in virus replication and interferes with wild-type RV replication in coinfection. Taking advantage of the delay in viroplasm formation, the NSP2 phosphomimetic mutant was used as a tool to observe very early events in viroplasm assembly. We show that (i) viroplasm assembly correlates with NSP5 hyperphosphorylation and (ii) vNSP2 S313D colocalizes with RV-induced LDs without NSP5, suggesting that vNSP2 phospho-S313 is sufficient for interacting with LDs and may be the virus factor required for RV-induced LD formation. Further studies with the rRV NSP2 S313D virus are expected to reveal new aspects of viroplasm and LD initiation and assembly.IMPORTANCE Reverse genetics was used to generate a recombinant rotavirus with a single phosphomimetic mutation in nonstructural protein 2 (NSP2 S313D) that exhibits delayed viroplasm formation, delayed replication, and an interfering phenotype during coinfection with wild-type rotavirus, indicating the importance of this amino acid during virus replication. Exploiting the delay in viroplasm assembly, we found that viroplasm-associated NSP2 colocalizes with rotavirus-induced lipid droplets prior to the accumulation of other rotavirus proteins that are required for viroplasm formation and that NSP5 hyperphosphorylation is required for viroplasm assembly. These data suggest that NSP2 phospho-S313 is sufficient for interaction with lipid droplets and may be the virus factor that induces lipid droplet biogenesis in rotavirus-infected cells. Lipid droplets are cellular organelles critical for the replication of many viral and bacterial pathogens, and thus, understanding the mechanism of NSP2-mediated viroplasm/lipid droplet initiation and interaction will lead to new insights into this important host-pathogen interaction.


Assuntos
Gotículas Lipídicas/metabolismo , Gotículas Lipídicas/virologia , Proteínas de Ligação a RNA/metabolismo , Rotavirus/fisiologia , Proteínas não Estruturais Virais/metabolismo , Replicação Viral/fisiologia , Animais , Linhagem Celular , Cricetinae , Fosforilação , Proteínas de Ligação a RNA/genética , Proteínas não Estruturais Virais/genética
17.
Pharmacol Ther ; 213: 107579, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32442437

RESUMO

Ubiquitin Proteasome System (UPS) is an adaptable and finely tuned system that sustains proteostasis network under a large variety of physiopathological conditions. Its dysregulation is often associated with the onset and progression of human diseases; hence, UPS modulation has emerged as a promising new avenue for the development of treatments of several relevant pathologies, such as cancer and neurodegeneration. The clinical interest in proteasome inhibition has considerably increased after the FDA approval in 2003 of bortezomib for relapsed/refractory multiple myeloma, which is now used in the front-line setting. Thereafter, two other proteasome inhibitors (carfilzomib and ixazomib), designed to overcome resistance to bortezomib, have been approved for treatment-experienced patients, and a variety of novel inhibitors are currently under preclinical and clinical investigation not only for haematological malignancies but also for solid tumours. However, since UPS collapse leads to toxic misfolded proteins accumulation, proteasome is attracting even more interest as a target for the care of neurodegenerative diseases, which are sustained by UPS impairment. Thus, conceptually, proteasome activation represents an innovative and largely unexplored target for drug development. According to a multidisciplinary approach, spanning from chemistry, biochemistry, molecular biology to pharmacology, this review will summarize the most recent available literature regarding different aspects of proteasome biology, focusing on structure, function and regulation of proteasome in physiological and pathological processes, mostly cancer and neurodegenerative diseases, connecting biochemical features and clinical studies of proteasome targeting drugs.


Assuntos
Neoplasias/fisiopatologia , Doenças Neurodegenerativas/fisiopatologia , Complexo de Endopeptidases do Proteassoma/metabolismo , Inibidores de Proteassoma/farmacologia , Ubiquitina/metabolismo , Quinases Ciclina-Dependentes/metabolismo , Resistência a Medicamentos/fisiologia , Fator de Transcrição E2F4/metabolismo , Holoenzimas , Humanos , Gotículas Lipídicas/metabolismo , Chaperonas Moleculares/metabolismo , Proteínas Musculares/metabolismo , NF-kappa B/metabolismo , Neoplasias/tratamento farmacológico , Doenças Neurodegenerativas/tratamento farmacológico , Complexo de Endopeptidases do Proteassoma/efeitos dos fármacos , Inibidores de Proteassoma/uso terapêutico , Proteostase/fisiologia , Proteína Supressora de Tumor p53/metabolismo
18.
Traffic ; 21(8): 545-551, 2020 08.
Artigo em Inglês | MEDLINE | ID: mdl-32424954

RESUMO

Positive sense (+) RNA viruses exploit membranes from a variety of cellular organelles to support the amplification of their genomes. This association concurs with the formation of vesicles whose main morphological feature is that of being wrapped by a double membrane. In the case of the SARS-CoV virus, the outer membrane is not discrete for each vesicle, but seems to be continuous and shared between many individual vesicles, a difference with other +RNA viruses whose nature has remained elusive. I present morphological, biochemical and pharmacological arguments defending the striking analogy of this arrangement and that of entangled, nascent Lipid Droplets whose birth has been aborted by an excess of Phosphatidic Acid. Since Phosphatidic Acid can be targeted with therapeutical purposes, considering this working hypothesis may prove important in tackling SARS-CoV infection.


Assuntos
Betacoronavirus/fisiologia , Infecções por Coronavirus/metabolismo , Infecções por Coronavirus/virologia , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/virologia , Modelos Biológicos , Ácidos Fosfatídicos/metabolismo , Pneumonia Viral/metabolismo , Pneumonia Viral/virologia , Betacoronavirus/patogenicidade , Interações entre Hospedeiro e Microrganismos/fisiologia , Humanos , Gotículas Lipídicas/metabolismo , Gotículas Lipídicas/virologia , Pandemias , Replicação Viral/fisiologia
19.
Am J Physiol Gastrointest Liver Physiol ; 319(1): G11-G22, 2020 07 01.
Artigo em Inglês | MEDLINE | ID: mdl-32463334

RESUMO

Hepatocellular carcinoma (HCC) is the fourth-leading cause of cancer death in the world. Although most cases occur in stiff, cirrhotic livers, and stiffness is a significant risk factor, HCC can also arise in noncirrhotic livers in the setting of nonalcoholic fatty liver disease (NAFLD). We hypothesized that lipid droplets in NAFLD might apply mechanical forces to the nucleus, functioning as mechanical stressors akin to stiffness. We investigated the effect of lipid droplets on cellular mechanosensing and found that primary human hepatocytes loaded with the fatty acids oleate and linoleate exhibited decreased stiffness-induced cell spreading and disrupted focal adhesions and stress fibers. The presence of large lipid droplets in hepatocytes resulted in increased nuclear localization of the mechano-sensor Yes-associated protein (YAP). In cirrhotic livers from patients with NAFLD, hepatocytes filled with large lipid droplets showed significantly higher nuclear localization of YAP as compared with cells with small lipid droplets. This work suggests that lipid droplets induce a mechanical signal that disrupts the ability of the hepatocyte to sense its underlying matrix stiffness and that the presence of lipid droplets can induce intracellular mechanical stresses.NEW & NOTEWORTHY This work examines the impact of lipid loading on mechanosensing by human hepatocytes. In cirrhotic livers, the presence of large (although not small) lipid droplets increased nuclear localization of the mechanotransducer YAP. In primary hepatocytes in culture, lipid droplets led to decreased stiffness-induced cell spreading and disrupted focal adhesions and stress fibers; the presence of large lipid droplets resulted in increased YAP nuclear localization. Collectively, the data suggest that lipid droplets induce intracellular mechanical stress.


Assuntos
Carcinoma Hepatocelular/metabolismo , Hepatócitos/metabolismo , Gotículas Lipídicas/metabolismo , Neoplasias Hepáticas/metabolismo , Carcinoma Hepatocelular/patologia , Núcleo Celular/metabolismo , Humanos , Metabolismo dos Lipídeos/fisiologia , Lipídeos , Fígado/metabolismo , Neoplasias Hepáticas/patologia , Hepatopatia Gordurosa não Alcoólica/metabolismo , Hepatopatia Gordurosa não Alcoólica/patologia
20.
Food Chem ; 327: 127061, 2020 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-32454271

RESUMO

This study mainly investigated the effect of different salt concentrations (1, 3, or 5%) on triglycerides (TG) hydrolysis in muscle during salting by analyzing moisture distribution, TG hydrolysis, TG hydrolase activity, native and phosphorylated adipose triglyceride lipase (ATGL) and hormone-sensitive lipase (HSL) protein content, lipid droplets morphology, and muscle microstructure. The results showed that increasing salt concentration could significantly decrease T21 moisture proportion and relaxation time (p < 0.05), which was more beneficial to the lipase activity. The TG hydrolase activity increased first and then decreased with the salt concentration increasing during dry-salting process, and 3% salt concentration was the point of inflection. Western blot (WB) analysis detected both ATGL, HSL and their phosphorylated proteins, which were increased with the salt content increase. The microstructure analysis showed that the lipid droplets were split into small lipid droplets with the increase of salt content, which was more conducive to the triglycerides hydrolysis.


Assuntos
Tecido Adiposo/metabolismo , Músculos Isquiossurais/metabolismo , Lipase/metabolismo , Gotículas Lipídicas/metabolismo , Cloreto de Sódio/farmacologia , Esterol Esterase/metabolismo , Triglicerídeos/metabolismo , Tecido Adiposo/efeitos dos fármacos , Animais , Músculos Isquiossurais/efeitos dos fármacos , Hidrólise , Gotículas Lipídicas/efeitos dos fármacos , Fosforilação , Suínos
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