RESUMO
Neutral sphingomyelinase-2 (nSMase2), gene name sphingomyelin phosphodiesterase-3 (Smpd3), is a key regulatory enzyme responsible for generating the sphingolipid ceramide. The function of nSMase2 in the brain is still controversial. To better understand the functional roles of nSMase2 in the aging mouse brain, we applied RNA-seq analysis, which identified a total of 1462 differentially abundant mRNAs between +/fro and fro/fro, of which 891 were increased and 571 were decreased in nSMase2-deficient mouse brains. The most strongly enriched GO and KEGG annotation terms among transcripts increased in fro/fro mice included synaptogenesis, synapse development, synaptic signaling, axon development, and axonogenesis. Among decreased transcripts, enriched annotations included ribosome assembly and mitochondrial protein complex functions. KEGG analysis of decreased transcripts also revealed overrepresentation of annotations for Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington disease (HD). Ingenuity Pathway Analysis (IPA) tools predicted lower susceptibility to these neurodegenerative disorders, as well as predictions agreeing with stronger synaptic function, learning, and memory in fro/fro mice. The IPA tools identified signaling proteins, epigenetic regulators, and microRNAs as likely upstream regulators of the broader set of genes encoding the affected transcripts. It also revealed 16 gene networks, each linked to biological processes identified as overrepresented annotations among the affected transcripts by multiple analysis methods. Therefore, the analysis of these RNA-seq data indicates that nSMase2 impacts synaptic function and neural development, and may contribute to the onset and development of neurodegenerative diseases in middle-aged mice.
Assuntos
Encéfalo , Esfingomielina Fosfodiesterase , Animais , Esfingomielina Fosfodiesterase/genética , Esfingomielina Fosfodiesterase/metabolismo , Camundongos , Encéfalo/metabolismo , Encéfalo/crescimento & desenvolvimento , Transcriptoma , Envelhecimento/genética , Envelhecimento/metabolismo , Camundongos Endogâmicos C57BL , MasculinoRESUMO
Extracellular vesicles (EVs) are shed from the plasma membrane, but the regulation and function of these EVs remain unclear. We found that oxidative stress induced by H2O2 in Hela cells stimulated filopodia formation and the secretion of EVs. EVs were small (150 nm) and labeled for CD44, indicating that they were derived from filopodia. Filopodia-derived small EVs (sEVs) were enriched with the sphingolipid ceramide, consistent with increased ceramide in the plasma membrane of filopodia. Ceramide was colocalized with neutral sphingomyelinase 2 (nSMase2) and acid sphingomyelinase (ASM), two sphingomyelinases generating ceramide at the plasma membrane. Inhibition of nSMase2 and ASM prevented oxidative stress-induced sEV shedding but only nSMase2 inhibition prevented filopodia formation. nSMase2 was S-palmitoylated and interacted with ASM in filopodia to generate ceramide for sEV shedding. sEVs contained nSMase2 and ASM and decreased the level of these two enzymes in oxidatively stressed Hela cells. A novel metabolic labeling technique for EVs showed that oxidative stress induced secretion of fluorescent sEVs labeled with NBD-ceramide. NBD-ceramide-labeled sEVs transported ceramide to mitochondria, ultimately inducing cell death in a proportion of neuronal (N2a) cells. In conclusion, using Hela cells we provide evidence that oxidative stress induces interaction of nSMase2 and ASM at filopodia, which leads to shedding of ceramide-rich sEVs that target mitochondria and propagate cell death.
Assuntos
Ceramidas , Vesículas Extracelulares , Estresse Oxidativo , Pseudópodes , Esfingomielina Fosfodiesterase , Humanos , Vesículas Extracelulares/metabolismo , Ceramidas/metabolismo , Pseudópodes/metabolismo , Pseudópodes/efeitos dos fármacos , Células HeLa , Esfingomielina Fosfodiesterase/metabolismo , Peróxido de Hidrogênio/metabolismo , Membrana Celular/metabolismoRESUMO
In Alzheimer's disease (AD), reactive astrocytes produce extracellular vesicles (EVs) that affect mitochondria in neurons. Here, we show that Aß-induced generation of the sphingolipid ceramide by acid sphingomyelinase (A-SMase) triggered proinflammatory cytokine (C1q, TNF-α, IL-1α) release by microglia, which induced the reactive astrocytes phenotype and secretion of EVs enriched with ceramide. These EVs impeded the capacity of neurons to respond to energy demand. Inhibition of A-SMase with Arc39 and Imipramine reduced the secretion of cytokines from microglia, prompting us to test the effect of Imipramine on EV secretion and AD pathology in the 5xFAD mouse model. Brain derived-EVs from 5xFAD mice treated with Imipramine contained reduced levels of the astrocytic marker GFAP, ceramide, and Aß and did not impair mitochondrial respiration when compared to EVs derived from untreated 5xFAD brain. Consistently, Imipramine-treated 5xFAD mice showed reduced AD pathology. Our study identifies A-SMase inhibitors as potential AD therapy by preventing cyotokine-elicited secretion of mitotoxic EVs from astrocytes.
Assuntos
Doença de Alzheimer , Vesículas Extracelulares , Animais , Camundongos , Doença de Alzheimer/tratamento farmacológico , Astrócitos , Esfingomielina Fosfodiesterase , Imipramina/farmacologia , CeramidasRESUMO
BACKGROUND: Previously, we showed that the sphingosine-1-phosphate (S1P) transporter spinster 2 (Spns2) mediates activation of microglia in response to amyloid ß peptide (Aß). Here, we investigated if Ponesimod, a functional S1P receptor 1 (S1PR1) antagonist, prevents Aß-induced activation of glial cells and Alzheimer's disease (AD) pathology. METHODS: We used primary cultures of glial cells and the 5XFAD mouse model to determine the effect of Aß and Ponesimod on glial activation, Aß phagocytosis, cytokine levels and pro-inflammatory signaling pathways, AD pathology, and cognitive performance. FINDINGS: Aß42 increased the levels of TLR4 and S1PR1, leading to their complex formation. Ponesimod prevented the increase in TLR4 and S1PR1 levels, as well as the formation of their complex. It also reduced the activation of the pro-inflammatory Stat1 and p38 MAPK signaling pathways, while activating the anti-inflammatory Stat6 pathway. This was consistent with increased phagocytosis of Aß42 in primary cultured microglia. In 5XFAD mice, Ponesimod decreased the levels of TNF-α and CXCL10, which activate TLR4 and Stat1. It also increased the level of IL-33, an anti-inflammatory cytokine that promotes Aß42 phagocytosis by microglia. As a result of these changes, Ponesimod decreased the number of Iba-1+ microglia and GFAP+ astrocytes, and the size and number of amyloid plaques, while improving spatial memory as measured in a Y-maze test. INTERPRETATION: Ponesimod targeting S1PR1 is a promising therapeutic approach to reprogram microglia, reduce neuroinflammation, and increase Aß clearance in AD. FUNDING: NIHR01AG064234, RF1AG078338, R21AG078601, VAI01BX003643.
Assuntos
Doença de Alzheimer , Peptídeos beta-Amiloides , Camundongos , Animais , Peptídeos beta-Amiloides/metabolismo , Receptor 4 Toll-Like/metabolismo , Doenças Neuroinflamatórias , Receptores de Esfingosina-1-Fosfato/metabolismo , Doença de Alzheimer/metabolismo , Microglia/metabolismo , Citocinas/metabolismo , Anti-Inflamatórios/farmacologia , Camundongos Transgênicos , Modelos Animais de DoençasRESUMO
Female biased pathology and cognitive decline in Alzheimer's disease (AD) have been consistently observed with unclear underlying mechanisms. Although brain sphingolipid ceramide is elevated in AD patients, whether and how ceramide may contribute to sex-specific differences in amyloid pathology is unknown. Here we investigated the sex-specific impact of chronic pharmacological inhibition of neutral sphingomyelinase (nSMase), a key enzyme responsible for ceramide metabolism, on in vivo neuron-derived exosome dynamics, Aß plaque load, and cognitive function in the APPNL-F/NL-F knock-in (APP NL-F) AD mouse model. Our results found sex-specific increase of cortical C20:0 ceramide and brain exosome levels only in APP NL-F but not in age-matched WT mice. Although nSMase inhibition similarly blocks exosome spreading in male and female mice, significantly reduced amyloid pathology was mostly observed in cortex and hippocampus of female APP NL-F mice with only modest effect found on male APP NL-F mice. Consistently, T maze test to examine spatial working memory revealed a female-specific reduction in spontaneous alternation rate in APP NL-F mice, which was fully reversed with chronic nSMase inhibition. Together, our results suggest that disease induced changes in ceramide and exosome pathways contribute to the progression of female-specific amyloid pathology in APP NL-F AD models.
Assuntos
Doença de Alzheimer , Exossomos , Camundongos , Masculino , Feminino , Animais , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Exossomos/metabolismo , Camundongos Transgênicos , Placa Amiloide/metabolismo , Proteínas Amiloidogênicas , Neurônios/metabolismo , Modelos Animais de DoençasRESUMO
We developed a new method to isolate small extracellular vesicles (sEVs) from male and female wild-type and 5xFAD mouse brains to investigate the sex-specific functions of sEVs in Alzheimer's disease (AD). A mass spectrometric analysis revealed that sEVs contained proteins critical for EV formation and Aß. ExoView analysis showed that female mice contained more GFAP and Aß-labeled sEVs, suggesting that a larger proportion of sEVs from the female brain is derived from astrocytes and/or more likely to bind to Aß. Moreover, sEVs from female brains had more acid sphingomyelinase (ASM) and ceramide, an enzyme and its sphingolipid product important for EV formation and Aß binding to EVs, respectively. We confirmed the function of ASM in EV formation and Aß binding using co-labeling and proximity ligation assays, showing that ASM inhibitors prevented complex formation between Aß and ceramide in primary cultured astrocytes. Finally, our study demonstrated that sEVs from female 5xFAD mice were more neurotoxic than those from males, as determined by impaired mitochondrial function (Seahorse assays) and LDH cytotoxicity assays. Our study suggests that sex-specific sEVs are functionally distinct markers for AD and that ASM is a potential target for AD therapy.
Assuntos
Doença de Alzheimer , Vesículas Extracelulares , Camundongos , Masculino , Feminino , Animais , Doença de Alzheimer/metabolismo , Peptídeos beta-Amiloides/metabolismo , Encéfalo/metabolismo , Vesículas Extracelulares/metabolismo , Ceramidas/metabolismoRESUMO
Globally, most cases of gastroenteritis are caused by pandemic GII.4 human norovirus (HuNoV) strains with no approved therapies or vaccines available. The cellular pathways that these strains exploit for cell entry and internalization are unknown. Here, using nontransformed human jejunal enteroids (HIEs) that recapitulate the physiology of the gastrointestinal tract, we show that infectious GII.4 virions and virus-like particles are endocytosed using a unique combination of endosomal acidification-dependent clathrin-independent carriers (CLIC), acid sphingomyelinase (ASM)-mediated lysosomal exocytosis, and membrane wound repair pathways. We found that besides the known interaction of the viral capsid Protruding (P) domain with host glycans, the Shell (S) domain interacts with both galectin-3 (gal-3) and apoptosis-linked gene 2-interacting protein X (ALIX), to orchestrate GII.4 cell entry. Recognition of the viral and cellular determinants regulating HuNoV entry provides insight into the infection process of a non-enveloped virus highlighting unique pathways and targets for developing effective therapeutics.
Assuntos
Membrana Celular , Norovirus , Internalização do Vírus , Humanos , Clatrina , Norovirus/fisiologia , Transdução de Sinais , Membrana Celular/virologiaRESUMO
Many membrane-resident and secreted proteins, including growth factors and their receptors are N-glycosylated. The initial N-glycan structure is synthesized in the endoplasmic reticulum (ER) as a branched structure on a lipid anchor (dolicholpyrophosphate) and then co-translationally, "en bloc" transferred and linked via N-acetylglucosamine to asparagine within a specific N-glycosylation acceptor sequence of the nascent recipient protein. In the ER and then the Golgi apparatus, the N-linked glycan structure is modified by hydrolytic removal of sugar residues ("trimming") followed by re-glycosylation with additional sugar residues ("processing") such as galactose, fucose or sialic acid to form complex N-glycoproteins. While the sequence of the reactions leading to biosynthesis, "en bloc" transfer and processing of N-glycans is well investigated, it is still not completely understood how N-glycans affect the biological fate and function of N-glycoproteins. This review will discuss the biology of N-glycoprotein synthesis, processing and function with specific reference to the physiology and pathophysiology of the immune and nervous system, as well as infectious diseases such as Covid-19.
Assuntos
Asparagina , COVID-19 , Humanos , Asparagina/química , Asparagina/metabolismo , Fucose , Ácido N-Acetilneuramínico , Galactose , Acetilglucosamina , Glicoproteínas/química , Glicoproteínas/metabolismo , Polissacarídeos/química , Polissacarídeos/metabolismo , LipídeosRESUMO
Membrane contact sites (MCS), close membrane apposition between organelles, are platforms for interorganellar transfer of lipids including cholesterol, regulation of lipid homeostasis, and co-ordination of endocytic trafficking. Sphingosine kinases (SphKs), two isoenzymes that phosphorylate sphingosine to the bioactive sphingosine-1-phosphate (S1P), have been implicated in endocytic trafficking. However, the physiological functions of SphKs in regulation of membrane dynamics, lipid trafficking and MCS are not known. Here, we report that deletion of SphKs decreased S1P with concomitant increases in its precursors sphingosine and ceramide, and markedly reduced endoplasmic reticulum (ER) contacts with late endocytic organelles. Expression of enzymatically active SphK1, but not catalytically inactive, rescued the deficit of these MCS. Although free cholesterol accumulated in late endocytic organelles in SphK null cells, surprisingly however, cholesterol transport to the ER was not reduced. Importantly, deletion of SphKs promoted recruitment of the ER-resident cholesterol transfer protein Aster-B (also called GRAMD1B) to the plasma membrane (PM), consistent with higher accessible cholesterol and ceramide at the PM, to facilitate cholesterol transfer from the PM to the ER. In addition, ceramide enhanced in vitro binding of the Aster-B GRAM domain to phosphatidylserine and cholesterol liposomes. Our study revealed a previously unknown role for SphKs and sphingolipid metabolites in governing diverse MCS between the ER network and late endocytic organelles versus the PM to control the movement of cholesterol between distinct cell membranes.
Assuntos
Fosfatidilserinas , Esfingosina , Ceramidas/metabolismo , Colesterol/metabolismo , Retículo Endoplasmático/metabolismo , Isoenzimas/metabolismo , Lipossomos/metabolismo , Lisofosfolipídeos , Fosfatidilserinas/metabolismo , Esfingolipídeos/metabolismo , Esfingosina/análogos & derivados , Esfingosina/metabolismoRESUMO
The formation of extracellular vesicles (EVs) is induced by the sphingolipid ceramide. How this pathway is regulated is not entirely understood. Here, we report that the ceramide transport protein (CERT) mediates a non-vesicular transport of ceramide between the endoplasmic reticulum (ER) and the multivesicular endosome at contact sites. The process depends on the interaction of CERT's PH domain with PI4P generated by PI4KIIα at endosomes. Furthermore, a complex is formed between the START domain of CERT, which carries ceramide, and the Tsg101 protein, which is part of the endosomal sorting complex required for transport (ESCRT-I). Inhibition of ceramide biosynthesis reduces CERT-Tsg101 complex formation. Overexpression of CERT increases EV secretion while its inhibition reduces EV formation and the concentration of ceramides and sphingomyelins in EVs. In conclusion, we discovered a function of CERT in regulating the sphingolipid composition and biogenesis of EVs, which links ceramide to the ESCRT-dependent pathway.
Assuntos
Vesículas Extracelulares , Esfingolipídeos , Proteínas de Transporte , Ceramidas , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Vesículas Extracelulares/metabolismo , Proteínas Serina-Treonina QuinasesRESUMO
The protection mediated by the bioactive sphingolipid sphingosine-1-phosphate (S1P) declines during Alzheimer's disease (AD) progression, especially in patients carrying the apolipoprotein E ε4 (APOE4) isoform. The drug FTY720 mimics S1P bioactivity, but its efficacy in treating AD is unclear. Two doses of FTY720 (0.1 mg / kg and 0.5 mg / kg daily) were given by oral gavage for 15 weeks to transgenic mouse models of familial AD carrying human apolipoprotein E (APOE) APOE3 (E3FAD) or APOE4 (E4FAD). After 12 weeks of treatment, animals were subjected to behavioral tests for memory, locomotion, and anxiety. Blood was withdrawn at different time points and brains were collected for sphingolipids analysis by mass spectrometry, gene expression by RT-PCR and Aß quantification by ELISA. We discovered that low levels of S1P in the plasma is associated with a higher probability of failing the memory test and that FTY720 prevents memory impairments in E4FAD. The beneficial effect of FTY720 was induced by a shift of the sphingolipid metabolism in the brain towards a lower production of toxic metabolites, like ceramide d18:1/16:0 and d18:1/22:0, and reduction of amyloid-ß burden and inflammation. In conclusion, we provide further evidence of the druggability of the sphingolipid system in AD.
Assuntos
Doença de Alzheimer , Apolipoproteína E4 , Doença de Alzheimer/tratamento farmacológico , Doença de Alzheimer/genética , Doença de Alzheimer/prevenção & controle , Animais , Apolipoproteína E4/genética , Apolipoproteína E4/metabolismo , Apolipoproteína E4/uso terapêutico , Encéfalo/metabolismo , Ceramidas/metabolismo , Modelos Animais de Doenças , Cloridrato de Fingolimode/metabolismo , Cloridrato de Fingolimode/farmacologia , Cloridrato de Fingolimode/uso terapêutico , Humanos , Transtornos da Memória/tratamento farmacológico , Transtornos da Memória/metabolismo , Transtornos da Memória/prevenção & controle , Camundongos , Esfingolipídeos/metabolismoRESUMO
We have shown that deficiency of neutral sphingomyelinase 2 (nSMase2), an enzyme generating the sphingolipid ceramide, improves memory in adult mice. Here, we performed sphingolipid and RNA-seq analyses on the cortex from 10-month-old nSMase2-deficient (fro/fro) and heterozygous (+ /fro) mice. fro/fro cortex showed reduced levels of ceramide, particularly in astrocytes. Differentially abundant transcripts included several functionally related groups, with decreases in mitochondrial oxidative phosphorylation and astrocyte activation transcripts, while axon guidance and synaptic transmission and plasticity transcripts were increased, indicating a role of nSMase2 in oxidative stress, astrocyte activation, and cognition. Experimentally induced oxidative stress decreased the level of glutathione (GSH), an endogenous inhibitor of nSMase2, and increased immunolabeling for ceramide in primary + /fro astrocytes, but not in fro/fro astrocytes. ß-galactosidase activity was lower in 5-week-old fro/fro astrocytes, indicating delayed senescence due to nSMase2 deficiency. In fro/fro cortex, levels of the senescence markers C3b and p27 and the proinflammatory cytokines interleukin 1ß, interleukin 6, and tumor necrosis factor α were reduced, concurrent with twofold decreased phosphorylation of their downstream target, protein kinase Stat3. RNA and protein levels of the ionotropic glutamate receptor subunit 2B (Grin2b/NR2B) were increased by twofold, which was previously shown to enhance cognition. This was consistent with threefold reduced levels of exosomes carrying miR-223-3p, a micro-RNA downregulating NR2B. In summary, our data show that nSMase2 deficiency prevents oxidative stress-induced elevation of ceramide and secretion of exosomes by astrocytes that suppress neuronal function, indicating a role of nSMase2 in the regulation of neuroinflammation and cognition.
Assuntos
Astrócitos , Esfingomielina Fosfodiesterase , Animais , Astrócitos/metabolismo , Ceramidas/metabolismo , Camundongos , Plasticidade Neuronal , Estresse Oxidativo , RNA/metabolismo , Esfingolipídeos/metabolismo , Esfingomielina Fosfodiesterase/genética , Esfingomielina Fosfodiesterase/metabolismoRESUMO
Adiponectin receptor 1 (ADIPOR1) is a lipid and glucose metabolism regulator that possesses intrinsic ceramidase activity. Mutations of the ADIPOR1 gene have been associated with nonsyndromic and syndromic retinitis pigmentosa. Here, we show that the absence of AdipoR1 in mice leads to progressive photoreceptor degeneration, significant reduction of electroretinogram amplitudes, decreased retinoid content in the retina, and reduced cone opsin expression. Single-cell RNA-Seq results indicate that ADIPOR1 encoded the most abundantly expressed ceramidase in mice and one of the 2 most highly expressed ceramidases in the human retina, next to acid ceramidase ASAH1. We discovered an accumulation of ceramides in the AdipoR1-/- retina, likely due to insufficient ceramidase activity for healthy retina function, resulting in photoreceptor death. Combined treatment with desipramine/L-cycloserine (DC) lowered ceramide levels and exerted a protective effect on photoreceptors in AdipoR1-/- mice. Moreover, we observed improvement in cone-mediated retinal function in the DC-treated animals. Lastly, we found that prolonged DC treatment corrected the electrical responses of the primary visual cortex to visual stimuli, approaching near-normal levels for some parameters. These results highlight the importance of ADIPOR1 ceramidase in the retina and show that pharmacological inhibition of ceramide generation can provide a therapeutic strategy for ADIPOR1-related retinopathy.
Assuntos
Ceramidases/antagonistas & inibidores , DNA/genética , Mutação , Receptores de Adiponectina/genética , Células Fotorreceptoras Retinianas Cones/metabolismo , Doenças Retinianas/genética , Animais , Análise Mutacional de DNA , Modelos Animais de Doenças , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Mutantes , Receptores de Adiponectina/metabolismo , Células Fotorreceptoras Retinianas Cones/patologia , Doenças Retinianas/metabolismo , Doenças Retinianas/patologiaRESUMO
Exosomes are nano-sized lipid vesicles that are produced by all eukaryotic cells, and they typically range in size from 30 to 150 nm. Exosomes were discovered almost 40 years ago; however, the last two decades have attracted considerable attention due to exosomes' inherent abilities to shuttle nucleic acids, lipids and proteins between cells, along with their natural affinity to exosome target cells. From a pharmaceutical perspective, exosomes are regarded as naturally produced nanoparticle drug delivery vehicles. The application of exosomes as a means of drug delivery offers critical advantages compared to other nanoparticulate drug delivery systems, such as liposomes and polymeric nanoparticles. These advantages are due to the exosomes' intrinsic features, such as low immunogenicity, biocompatibility, stability, and their ability to overcome biological barriers. Herein, we outline the structure and origin of exosomes, as well as their biological functions. We also touch upon recent advances in exosome labeling, imaging and drug loading. Finally, we discuss exosomes in targeted drug delivery and clinical trial development.
Assuntos
Vesículas Extracelulares , Animais , Técnicas e Procedimentos Diagnósticos , Sistemas de Liberação de Medicamentos , Tratamento Farmacológico , Vesículas Extracelulares/metabolismo , Humanos , Distribuição TecidualRESUMO
The blood-brain barrier (BBB) prevents the transfer of many therapeutic drugs across the brain. Therefore, the leading treatment strategies of Alzheimer's disease (AD) are often unsuccessful. Another challenge is to achieve specific targetability across BBB and diagnosis. Herein, theranostic-based strategies are emerging in order to combine therapeutic, targeting, and diagnostic capabilities. Recent nanotechnological advancements enable a common platform for the formulation and development of efficient theranostics. This can be attained by engineering some of the properties of nanomaterials, thus enabling them to become efficient and suitable theranostics. In this review, we discuss the various novel approaches of theranostic nanomaterials owing to multimodal functionality across the brain as an effective and probable treatment as well as early (timely) diagnosis of Alzheimer's disease. In this respect, we conducted a PubMed search to review the latest development in theranostic nanomaterials, especially for Alzheimer's (major type of dementia) therapy that led us to discuss the present theranostic nanomaterials utilizing drug carriers that include cargo, targeting ligands, and imaging agents for delivery to particular tissues, cells, or subcellular components. Our focus is on strategies for syntheses, but we will also consider the challenges and prospects associated with this evolving technology. The current review includes knowledge of the history, overview of AD, and therapeutics with a future approach of using theranostic nanomaterials as personalized medicines.
Assuntos
Doença de Alzheimer , Nanopartículas , Nanoestruturas , Doença de Alzheimer/diagnóstico , Doença de Alzheimer/tratamento farmacológico , Portadores de Fármacos , Humanos , Nanopartículas/uso terapêutico , Nanoestruturas/uso terapêutico , Medicina de Precisão , Nanomedicina Teranóstica/métodosRESUMO
BACKGROUND: Dysregulation of ceramide and sphingomyelin levels have been suggested to contribute to the pathogenesis of Alzheimer's disease (AD). Ceramide transfer proteins (CERTs) are ceramide carriers which are crucial for ceramide and sphingomyelin balance in cells. Extracellular forms of CERTs co-localize with amyloid-ß (Aß) plaques in AD brains. To date, the significance of these observations for the pathophysiology of AD remains uncertain. METHODS: A plasmid expressing CERTL, the long isoform of CERTs, was used to study the interaction of CERTL with amyloid precursor protein (APP) by co-immunoprecipitation and immunofluorescence in HEK cells. The recombinant CERTL protein was employed to study interaction of CERTL with amyloid-ß (Aß), Aß aggregation process in presence of CERTL, and the resulting changes in Aß toxicity in neuroblastoma cells. CERTL was overexpressed in neurons by adeno-associated virus (AAV) in a mouse model of familial AD (5xFAD). Ten weeks after transduction, animals were challenged with behavior tests for memory, anxiety, and locomotion. At week 12, brains were investigated for sphingolipid levels by mass spectrometry, plaques, and neuroinflammation by immunohistochemistry, gene expression, and/or immunoassay. RESULTS: Here, we report that CERTL binds to APP, modifies Aß aggregation, and reduces Aß neurotoxicity in vitro. Furthermore, we show that intracortical injection of AAV, mediating the expression of CERTL, decreases levels of ceramide d18:1/16:0 and increases sphingomyelin levels in the brain of male 5xFAD mice. CERTL in vivo over-expression has a mild effect on animal locomotion, decreases Aß formation, and modulates microglia by decreasing their pro-inflammatory phenotype. CONCLUSION: Our results demonstrate a crucial role of CERTL in regulating ceramide levels in the brain, in amyloid plaque formation and neuroinflammation, thereby opening research avenues for therapeutic targets of AD and other neurodegenerative diseases.
Assuntos
Doença de Alzheimer , Doença de Alzheimer/genética , Peptídeos beta-Amiloides/metabolismo , Precursor de Proteína beta-Amiloide/genética , Precursor de Proteína beta-Amiloide/metabolismo , Animais , Encéfalo/metabolismo , Ceramidas , Modelos Animais de Doenças , Inflamação , Masculino , Camundongos , Camundongos Transgênicos , Placa AmiloideRESUMO
Microtubules are polymers composed of αß-tubulin subunits that provide structure to cells and play a crucial role in in the development and function of neuronal processes and cilia, microtubule-driven extensions of the plasma membrane that have sensory (primary cilia) or motor (motile cilia) functions. To stabilize microtubules in neuronal processes and cilia, α tubulin is modified by the posttranslational addition of an acetyl group, or acetylation. We discovered that acetylated tubulin in microtubules interacts with the membrane sphingolipid, ceramide. However, the molecular mechanism and function of this interaction are not understood. Here, we show that in human induced pluripotent stem cell-derived neurons, ceramide stabilizes microtubules, which indicates a similar function in cilia. Using proximity ligation assays, we detected complex formation of ceramide with acetylated tubulin in Chlamydomonas reinhardtii flagella and cilia of human embryonic kidney (HEK293T) cells, primary cultured mouse astrocytes, and ependymal cells. Using incorporation of palmitic azide and click chemistry-mediated addition of fluorophores, we show that a portion of acetylated tubulin is S-palmitoylated. S-palmitoylated acetylated tubulin is colocalized with ceramide-rich platforms in the ciliary membrane, and it is coimmunoprecipitated with Arl13b, a GTPase that mediates transport of proteins into cilia. Inhibition of S-palmitoylation with 2-bromo palmitic acid or inhibition of ceramide biosynthesis with fumonisin B1 reduces formation of the Arl13b-acetylated tubulin complex and its transport into cilia, concurrent with impairment of ciliogenesis. Together, these data show, for the first time, that ceramide-rich platforms mediate membrane anchoring and interaction of S-palmitoylated proteins that are critical for cilium formation, stabilization, and function.
Assuntos
Tubulina (Proteína)RESUMO
Extracellular vesicles (EVs) are secreted by eukaryotic cells and serve as carriers for a variety of cell signaling factors, including RNAs, proteins, and lipids. We described a unique population of EVs, the membrane of which is highly enriched with the sphingolipid ceramide. We suggested that ceramide in the EV membrane is organized in ceramide-rich platforms (CRPs), a type of lipid raft that mediates interaction of ceramide with ceramide-associated proteins (CAPs). Here, we describe methods using anti-ceramide antibody to isolate ceramide-enriched EVs and detect exosomes after uptake into recipient cells. In addition, we discuss methods for EV analysis using nanoparticle tracking and mass spectrometry. The methods can be extended to the isolation of other types of EVs and "mobile rafts" transported by EVs from donor to recipient cells using antibodies against lipids specific for these EVs.
Assuntos
Ceramidas/metabolismo , Vesículas Extracelulares/metabolismo , Animais , Anticorpos/metabolismo , Linhagem Celular , Exossomos/metabolismo , Humanos , Espectrometria de Massas/métodos , Lipídeos de Membrana/metabolismo , Microdomínios da Membrana/metabolismo , Camundongos , Nanopartículas/metabolismo , Transdução de Sinais/fisiologia , Esfingolipídeos/metabolismoRESUMO
The detection of protein complexes by coimmunoprecipitation or two-hybrid analysis is often limited to cytosolic and soluble proteins, while interaction between membrane proteins or proteins and lipids is hampered by solubilization artefacts or absence of appropriate antibodies to detect a complex. More recently, the proximity ligation assay (PLA) using antibodies for in situ detection of protein complexes in cells and cross-linkable lipid analogs that can be endowed with molecular tags for pull-down assyas were techniques utilized to identify and monitor interaction between proteins and lipids. We have developed a novel technique termed "cross-link/PLA" combining a cross-linkable ceramide analog with PLA and anti-ceramide antibody to visualize lipid-protein complexes in ceramide-rich platforms (CRPs), a particular type of lipid raft. This chapter will discuss experimental protocols and data analysis to use cross-link/PLA for detection and visualization of lipid-protein complexes in CRPs and other types of lipid rafts.