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1.
FEBS J ; 2021 Sep 07.
Artigo em Inglês | MEDLINE | ID: mdl-34492158

RESUMO

The endoplasmic reticulum (ER) is equipped with multiple quality control systems (QCS) that are necessary for shaping the glycoproteome of eukaryotic cells. These systems facilitate the productive folding of glycoproteins, eliminate defective products, and function as effectors to evoke cellular signaling in response to various cellular stresses. These ER functions largely depend on glycans, which contain sugar-based codes that, when needed, function to recruit carbohydrate-binding proteins that determine the fate of glycoproteins. To ensure their functionality, the biosynthesis of such glycans is therefore strictly monitored by a system that selectively degrades structurally defective glycans before adding them to proteins. This system, which is referred to as the glycan QCS, serves as a mechanism to reduce the risk of abnormal glycosylation under conditions where glycan biosynthesis is genetically or metabolically stalled. On the other hand, glycan QCS increases the risk of global hypoglycosylation by limiting glycan availability, which can lead to protein misfolding and the activation of unfolded protein response to maintaining cell viability or to initiate cell death programs. This review summarizes the current state of our knowledge of the mechanisms underlying glycan QCS in mammals and its physiological and pathological roles in embryogenesis, tumor progression, and congenital disorders associated with abnormal glycosylation.

2.
Adv Exp Med Biol ; 1325: 137-149, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34495533

RESUMO

Extracellular vesicles (EVs), a generic term for any vesicles or particles that are released from cells, play an important role in modulating numerous biological and pathological events, including development, differentiation, aging, thrombus formation, immune responses, neurodegenerative diseases, and tumor progression. During the biogenesis of EVs, they encapsulate biologically active macromolecules (i.e., nucleotides and proteins) and transmit signals for delivering them to neighboring or cells that are located some distance away. In contrast, there are receptor molecules on the surface of EVs that function to mediate EV-to-cell and EV-to-matrix interactions. A growing body of evidence indicates that the EV surface is heavily modified with glycans, the function of which is to regulate the biogenesis and extracellular behaviors of EVs. In this chapter, we introduce the current status of our knowledge concerning EV glycosylation and discuss how it influences EV biology, highlighting the potential roles of EV glycans in clinical applications.


Assuntos
Exossomos , Vesículas Extracelulares , Doenças Neurodegenerativas , Exossomos/metabolismo , Vesículas Extracelulares/metabolismo , Glicosilação , Humanos , Doenças Neurodegenerativas/metabolismo
3.
Int J Mol Sci ; 22(16)2021 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-34445285

RESUMO

N-glycosylation is essential for many biological processes in mammals. A variety of N-glycan structures exist, of which, the formation of bisecting N-acetylglucosamine (GlcNAc) is catalyzed by N-acetylglucosaminyltransferase-III (GnT-III, encoded by the Mgat3 gene). We previously identified various bisecting GlcNAc-modified proteins involved in Alzheimer's disease and cancer. However, the mechanisms by which GnT-III acts on the target proteins are unknown. Here, we performed comparative glycoproteomic analyses using brain membranes of wild type (WT) and Mgat3-deficient mice. Target glycoproteins of GnT-III were enriched with E4-phytohemagglutinin (PHA) lectin, which recognizes bisecting GlcNAc, and analyzed by liquid chromatograph-mass spectrometry. We identified 32 N-glycosylation sites (Asn-Xaa-Ser/Thr, Xaa ≠ Pro) that were modified with bisecting GlcNAc. Sequence alignment of identified N-glycosylation sites that displayed bisecting GlcNAc suggested that GnT-III does not recognize a specific primary amino acid sequence. The molecular modeling of GluA1 as one of the good cell surface substrates for GnT-III in the brain, indicated that GnT-III acts on N-glycosylation sites located in a highly flexible and mobile loop of GluA1. These results suggest that the action of GnT-III is partially affected by the tertiary structure of target proteins, which can accommodate bisecting GlcNAc that generates a bulky flipped-back conformation of the modified glycans.


Assuntos
Acetilglucosamina/metabolismo , Encéfalo/metabolismo , Membrana Celular/metabolismo , Peptídeos/metabolismo , Receptores de AMPA/metabolismo , Análise de Sequência de Proteína , Acetilglucosamina/genética , Animais , Membrana Celular/genética , Glicosilação , Camundongos , Camundongos Knockout , N-Acetilglucosaminiltransferases/deficiência , N-Acetilglucosaminiltransferases/metabolismo , Mapeamento de Peptídeos , Peptídeos/genética , Receptores de AMPA/genética
4.
Mol Aspects Med ; 79: 100970, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-34053736
6.
Glycoconj J ; 38(3): 273-275, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33740223

RESUMO

This Special Issue on "Advances in Glycation: from food to human health and disease" was planned after the XXV International Symposium on Glycoconjugates (Glyco25) in Milan in order to ask special attention of importance of glycation to glycoscience community. In addition, we also celebrate the 30th anniversary of JMARS (Japan Maillard Reaction Society), and dedicated to one of the pioneers of this field, Professor Vincent Monnier, MD. He contributed enormously to studies on glycation related to aging and diseases to date and also he contributed to establish IMARS (International Maillard Reaction Society) as well as JMARS.

7.
STAR Protoc ; 2(1): 100316, 2021 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-33659899

RESUMO

N-glycosylation is a fundamental post-translational protein modification in the endoplasmic reticulum of eukaryotic cells. The biosynthetic and catabolic flux of N-glycans in eukaryotic cells has long been analyzed by metabolic labeling using radiolabeled sugars. Here, we introduce a non-radiolabeling protocol for the isolation, structural determination, and quantification of N-glycan precursors, dolichol-linked oligosaccharides, and the related metabolites, including phosphorylated oligosaccharides and nucleotide sugars. Our protocol allows for capturing of the biosynthesis and degradation of N-glycan precursors at steady state. For complete details on the use and execution of this protocol, please refer to Harada et al. (2013), Harada et al. (2020), and Nakajima et al. (2013).

8.
J Biol Chem ; 296: 100354, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33524390

RESUMO

Glycosylation, the most common posttranslational modification of proteins, is a stepwise process that relies on tight regulation of subcellular glycosyltransferase location to control the addition of each monosaccharide. Glycosyltransferases primarily reside and function in the endoplasmic reticulum (ER) and the Golgi apparatus; whether and how they traffic beyond the Golgi, how this trafficking is controlled, and how it impacts glycosylation remain unclear. Our previous work identified a connection between N-glycosylation and Rab11, a key player in the post-Golgi transport that connects recycling endosomes and other compartments. To learn more about the specific role of Rab11, we knocked down Rab11 in HeLa cells. Our findings indicate that Rab11 knockdown results in a dramatic enhancement in the sialylation of N-glycans. Structural analyses of glycans using lectins and LC-MS revealed that α2,3-sialylation is selectively enhanced, suggesting that an α2,3-sialyltransferase that catalyzes the sialyation of glycoproteins is activated or upregulated as the result of Rab11 knockdown. ST3GAL4 is the major α2,3-sialyltransferase that acts on N-glycans; we demonstrated that the localization of ST3GAL4, but not the levels of its mRNA, protein, or donor substrate, was altered by Rab11 depletion. In knockdown cells, ST3GAL4 is densely distributed in the trans-Golgi network, compared with the wider distribution in the Golgi and in other peripheral puncta in control cells, whereas the α2,6-sialyltransferase ST6GAL1 is predominantly localized to the Golgi regardless of Rab11 knockdown. This indicates that Rab11 may negatively regulate α2,3-sialylation by transporting ST3GAL4 to post-Golgi compartments (PGCs), which is a novel mechanism of glycosyltransferase regulation.


Assuntos
Sialiltransferases/metabolismo , Proteínas rab de Ligação ao GTP/metabolismo , Animais , Glicosilação , Complexo de Golgi/metabolismo , Células HeLa , Humanos , Transporte Proteico , Ratos , Rede trans-Golgi/metabolismo
9.
Biochem Soc Trans ; 49(1): 441-453, 2021 02 26.
Artigo em Inglês | MEDLINE | ID: mdl-33616615

RESUMO

Glycosylation represents one of the most abundant posttranslational modification of proteins. Glycosylation products are diverse and are regulated by the cooperative action of various glycosyltransferases, glycosidases, substrates thereof: nucleoside sugars and their transporters, and chaperons. In this article, we focus on a glycosyltransferase, α1,6-fucosyltransferase (Fut8) and its product, the core fucose structure on N-glycans, and summarize the potential protective functions of this structure against emphysema and chronic obstructive pulmonary disease (COPD). Studies of FUT8 and its enzymatic product, core fucose, are becoming an emerging area of interest in various fields of research including inflammation, cancer and therapeutics. This article discusses what we can learn from studies of Fut8 and core fucose by using knockout mice or in vitro studies that were conducted by our group as well as other groups. We also include a discussion of the potential protective functions of the keratan sulfate (KS) disaccharide, namely L4, against emphysema and COPD as a glycomimetic. Glycomimetics using glycan analogs is one of the more promising therapeutics that compensate for the usual therapeutic strategy that involves targeting the genome and the proteome. These typical glycans using KS derivatives as glycomimetics, will likely become a clue to the development of novel and effective therapeutic strategies.

10.
Mol Aspects Med ; 79: 100905, 2021 06.
Artigo em Inglês | MEDLINE | ID: mdl-33010941

RESUMO

It is well known that numerous cancer-related changes occur in glycans that are attached to glycoproteins, glycolipids and proteoglycans on the cell surface and these changes in structure and the expression of the glycans are largely regulated by glycosyl-transferases, glycosidases, nucleotide sugars and their related genes. Such structural changes in glycans on cell surface proteins may accelerate the progression, invasion and metastasis of cancer cells. Among the over 200 known glycosyltransferases and related genes, ß 1,6 N-acetylglucosaminyltransferase V (GnT-V) (the MGAT5 gene) and α 1,6 fucosyltransferase (FUT8) (the FUT8 gene) are representative enzymes in this respect because changes in glycans caused by these genes appear to be related to cancer metastasis and invasion in vitro as well as in vivo, and a number of reports on these genes in related to epithelial-mesenchymal transition (EMT) have also appeared. Another enzyme, one of the N-glycan branching enzymes, ß1,4 N-acetylglucosaminyltransferase III (GnT-III) (the MGAT3 gene) has been reported to suppress EMT. However, there are intermediate states between EMT and mesenchymal-epithelial transition (MET) and some of these genes have been implicated in both EMT and MET and are also probably in an intermediate state. Therefore, it would be difficult to clearly define which specific glycosyltransferase is involved in EMT or MET or an intermediate state. The significance of EMT and N-glycan branching glycosyltransferases needs to be reconsidered and the inhibition of their corresponding genes would also be desirable in therapeutics. This review mainly focuses on GnT-III, GnT-V and FUT8, major players as N-glycan branching enzymes in cancer in relation to EMT programs, and also discusses the catalytic mechanisms of GnT-V and FUT8 whose crystal structures have now been obtained.


Assuntos
N-Acetilglucosaminiltransferases , Neoplasias , Transição Epitelial-Mesenquimal/genética , Fucosiltransferases/genética , Humanos , N-Acetilglucosaminiltransferases/genética , Neoplasias/genética
11.
Cell Rep ; 33(2): 108261, 2020 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-33053347

RESUMO

The biogenesis of small extracellular vesicles (sEVs) is regulated by multiple molecular machineries generating considerably heterogeneous vesicle populations, including exosomes and non-exosomal vesicles, with distinct cargo molecules. However, the role of carbohydrate metabolism in generating such vesicle heterogeneity remains largely elusive. Here, we discover that 2-deoxyglucose (2-DG), a well-known glycolysis inhibitor, suppresses the secretion of non-exosomal vesicles by impairing asparagine-linked glycosylation (N-glycosylation) in mouse melanoma cells. Mechanistically, 2-DG is metabolically incorporated into N-glycan precursors, causing precursor degradation and partial hypoglycosylation. N-glycosylation blockade by Stt3a silencing is sufficient to inhibit non-exosomal vesicle secretion. In contrast, N-glycosylation blockade barely influences exosomal secretion of tetraspanin proteins. Functionally, N-glycosylation at specific sites of the hepatocyte growth factor receptor, a cargo protein of non-exosomal vesicles, facilitates its sorting into vesicles. These results uncover a link between N-glycosylation and unconventional vesicle secretion and suggest that N-glycosylation facilitates sEV biogenesis through cargo protein sorting.


Assuntos
Vesículas Extracelulares/metabolismo , Animais , Linhagem Celular Tumoral , Desoxiglucose/metabolismo , Dolicóis/metabolismo , Exossomos/metabolismo , Vesículas Extracelulares/ultraestrutura , Glicosilação , Lipídeos/química , Melanoma Experimental/metabolismo , Melanoma Experimental/patologia , Proteínas de Membrana/metabolismo , Camundongos , Metástase Neoplásica , Proteínas Proto-Oncogênicas c-met/metabolismo
13.
Biochem Biophys Res Commun ; 527(3): 682-688, 2020 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-32423823

RESUMO

Fucosylation is a type of glycosylation, a form of post-transcriptional regulation of proteins, involved in cancer and inflammation. It involves the attachment of a fucose residue to N-glycans, O-glycans, and glycolipids, which is catalyzed by a family of enzymes called fucosyltransferases (Futs). Among the many Futs, α-1,6-fucosyltransferase (Fut8) is the only enzyme that produces α-1,6-fucosylated oligosaccharides (core fucose). In the human liver, the expression and activity of Fut8 are frequently elevated during progression of chronic liver diseases. Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a well-known negative regulator of the low-density lipoprotein receptor (LDLR). Here, we found that loss of core fucose in immortalized hepatocytes led to LDLR downregulation through a dramatic induction of PCSK9. We used the immortalized hepatocytes derived from Fut8 knockout mice or a Fut8 knockdown AML12 hepatocyte cell line. Using these cells, we investigated the effects of Fut8 on hepatocyte cholesterol influx. Both cell lines had reduced LDLR protein levels, resulting from marked increases in PCSK9 expression. Intracellular cholesterol levels were significantly lower and LDL cholesterol uptake was suppressed in Fut8-KO cells. Hepatocyte nuclear factor 1α accumulated in nuclei of Fut8-KO hepatocytes, which mediated increases in PCSK9 mRNA expression. Our findings demonstrated that loss of core fucosylation promoted degradation of LDLR and impaired cholesterol uptake, which is a novel mechanism that regulates cholesterol influx, suggesting that Fut8 might be a novel causative gene for familial hypercholesterolemia.


Assuntos
Fucose/metabolismo , Hepatócitos/metabolismo , Pró-Proteína Convertase 9/metabolismo , Receptores de LDL/metabolismo , Animais , Células Cultivadas , Glicosilação , Camundongos , Camundongos Endogâmicos C57BL , Receptores de LDL/análise
14.
Biochim Biophys Acta Gen Subj ; 1864(7): 129596, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32147455

RESUMO

BACKGROUND: Previous structural analyses showed that human α1,6-fucosyltransferase, FUT8 contains a catalytic domain along with two additional domains, N-terminal α-helical domain and C-terminal Src homology 3 domain, but these domains are unique to FUT8 among glycosyltransferases. The role that these domains play in formation of the active form of FUT8 has not been investigated. This study reports on attempts to determine the involvement of these domains in the functions of FUT8. METHODS: Based on molecular modeling, the domain mutants were constructed by truncation and site-directed mutagenesis, and were heterologously expressed in Sf21 or COS-1 cells. The mutants were analyzed by SDS-PAGE and assayed for enzymatic activity. In vivo cross-linking experiments by introducing disulfide bonds were also carried out to examine the orientation of the domains in the molecular assembly. RESULTS: Mutagenesis and molecular modeling findings suggest that human FUT8 potentially forms homodimer in vivo via intermolecular hydrophobic interactions involving α-helical domains. Truncation or site-directed mutagenesis findings indicated that α-helical and SH3 domains are all required for enzymatic activity. In addition, in vivo cross-linking experiments clearly indicated that the SH3 domain located in close proximity to the α-helical domain in an intermolecular manner. CONCLUSIONS: α-Helical and SH3 domains are required for a fully active enzyme, and are also involved in homophilic dimerization, which probably results in the formation of the active form of human FUT8. GENERAL SIGNIFICANCE: α-Helical and SH3 domains, which are not commonly found in glycosyltransferases, play roles in the formation of the functional quaternary structure of human FUT8.

15.
Int J Mol Sci ; 21(2)2020 Jan 09.
Artigo em Inglês | MEDLINE | ID: mdl-31936666

RESUMO

Glycosylation is the most ubiquitous post-translational modification in eukaryotes. N-glycan is attached to nascent glycoproteins and is processed and matured by various glycosidases and glycosyltransferases during protein transport. Genetic and biochemical studies have demonstrated that alternations of the N-glycan structure play crucial roles in various physiological and pathological events including progression of cancer, diabetes, and Alzheimer's disease. In particular, the formation of N-glycan branches regulates the functions of target glycoprotein, which are catalyzed by specific N-acetylglucosaminyltransferases (GnTs) such as GnT-III, GnT-IVs, GnT-V, and GnT-IX, and a fucosyltransferase, FUT8s. Although the 3D structures of all enzymes have not been solved to date, recent progress in structural analysis of these glycosyltransferases has provided insights into substrate recognition and catalytic reaction mechanisms. In this review, we discuss the biological significance and structure-function relationships of these enzymes.


Assuntos
Glicosiltransferases/química , Glicosiltransferases/metabolismo , Modelos Moleculares , Polissacarídeos/metabolismo , Animais , Cristalografia por Raios X , Humanos , Polissacarídeos/química , Relação Estrutura-Atividade
16.
Int J Mol Sci ; 20(23)2019 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-31810196

RESUMO

Oligosaccharyltransferase (OST) is a multi-span membrane protein complex that catalyzes the addition of glycans to selected Asn residues within nascent polypeptides in the lumen of the endoplasmic reticulum. This process, termed N-glycosylation, is a fundamental post-translational protein modification that is involved in the quality control, trafficking of proteins, signal transduction, and cell-to-cell communication. Given these crucial roles, N-glycosylation is essential for homeostasis at the systemic and cellular levels, and a deficiency in genes that encode for OST subunits often results in the development of complex genetic disorders. A growing body of evidence has also demonstrated that the expression of OST subunits is cell context-dependent and is frequently altered in malignant cells, thus contributing to tumor cell survival and proliferation. Importantly, a recently developed inhibitor of OST has revealed this enzyme as a potential target for the treatment of incurable drug-resistant tumors. This review summarizes our current knowledge regarding the functions of OST in the light of health and tumor progression, and discusses perspectives on the clinical relevance of inhibiting OST as a tumor treatment.


Assuntos
Resistencia a Medicamentos Antineoplásicos/genética , Hexosiltransferases/genética , Proteínas de Membrana/genética , Neoplasias/genética , Processamento de Proteína Pós-Traducional/genética , Sequência de Aminoácidos/genética , Asparagina/genética , Progressão da Doença , Retículo Endoplasmático/genética , Glicosilação , Hexosiltransferases/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Neoplasias/tratamento farmacológico , Polissacarídeos/genética
17.
J Biol Chem ; 294(46): 17326-17338, 2019 11 15.
Artigo em Inglês | MEDLINE | ID: mdl-31594865

RESUMO

Prolonged hyperglycemia generates advanced glycation end-products (AGEs), which are believed to be involved in the pathogenesis of diabetic complications. In the present study, we developed a polyclonal antibody against fructose-modified proteins (Fru-P antibody) and identified its epitope as glucoselysine (GL) by NMR and LC-electrospray ionization (ESI)- quadrupole TOF (QTOF) analyses and evaluated its potential role in diabetes sequelae. Although the molecular weight of GL was identical to that of fructoselysine (FL), GL was distinguishable from FL because GL was resistant to acid hydrolysis, which converted all of the FLs to furosine. We also detected GL in vitro when reduced BSA was incubated with fructose for 1 day. However, when we incubated reduced BSA with glucose, galactose, or mannose for 14 days, we did not detect GL, suggesting that GL is dominantly generated from fructose. LC-ESI-MS/MS experiments with synthesized [13C6]GL indicated that the GL levels in the rat eye lens time-dependently increase after streptozotocin-induced diabetes. We observed a 31.3-fold increase in GL 8 weeks after the induction compared with nondiabetic rats, and Nϵ-(carboxymethyl)lysine and furosine increased by 1.7- and 21.5-fold, respectively, under the same condition. In contrast, sorbitol in the lens levelled off at 2 weeks after diabetes induction. We conclude that GL may be a useful biological marker to monitor and elucidate the mechanism of protein degeneration during progression of diabetes.


Assuntos
Cristalinas/metabolismo , Diabetes Mellitus Tipo 1/metabolismo , Frutose/metabolismo , Glucose/análogos & derivados , Cristalino/metabolismo , Lisina/análogos & derivados , Animais , Diabetes Mellitus Experimental/metabolismo , Glucose/metabolismo , Produtos Finais de Glicação Avançada/metabolismo , Lisina/metabolismo , Masculino , Ratos , Ratos Wistar
18.
Mol Cell Proteomics ; 18(10): 2044-2057, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31375533

RESUMO

Glycoproteins are decorated with complex glycans for protein functions. However, regulation mechanisms of complex glycan biosynthesis are largely unclear. Here we found that bisecting GlcNAc, a branching sugar residue in N-glycan, suppresses the biosynthesis of various types of terminal epitopes in N-glycans, including fucose, sialic acid and human natural killer-1. Expression of these epitopes in N-glycan was elevated in mice lacking the biosynthetic enzyme of bisecting GlcNAc, GnT-III, and was conversely suppressed by GnT-III overexpression in cells. Many glycosyltransferases for N-glycan terminals were revealed to prefer a nonbisected N-glycan as a substrate to its bisected counterpart, whereas no up-regulation of their mRNAs was found. This indicates that the elevated expression of the terminal N-glycan epitopes in GnT-III-deficient mice is attributed to the substrate specificity of the biosynthetic enzymes. Molecular dynamics simulations further confirmed that nonbisected glycans were preferentially accepted by those glycosyltransferases. These findings unveil a new regulation mechanism of protein N-glycosylation.


Assuntos
Acetilglucosamina/metabolismo , N-Acetilglucosaminiltransferases/genética , Polissacarídeos/química , Polissacarídeos/genética , Animais , Células COS , Chlorocebus aethiops , Células HEK293 , Células HeLa , Humanos , Camundongos , Simulação de Dinâmica Molecular , Mutação , N-Acetilglucosaminiltransferases/metabolismo , Especificidade por Substrato
19.
FEBS Lett ; 593(9): 942-951, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30943309

RESUMO

We investigated the correlation between metastatic behaviors of tumor cells and asparagine-linked glycosylation (N-glycosylation) of tumor-derived extracellular vesicles (EVs). Three mouse melanoma B16 variants with distinct metastatic potentials show similar gene expression levels and enzymatic activities of glycosyltransferases involved in N-glycosylation. All melanoma variants and EVs have nearly identical profiles of de-sialylated N-glycans. The major de-sialylated N-glycan structures of cells and EVs are core-fucosylated, tetra-antennary N-glycans with ß1,6-N-acetylglucosamine branches. A few N-glycans are extended by N-acetyllactosamine repeats. Sialylation of these N-glycans may generate cell-type-specific N-glycomes on EVs. Taken together, melanoma-derived EVs show high expression of tumor-associated N-glycans, and the core structure profile is inherited during multiple selection cycles of B16 melanomas and from tumor cells to EVs.


Assuntos
Vesículas Extracelulares/metabolismo , Melanoma Experimental/patologia , Nitrogênio/metabolismo , Animais , Glicosilação , Glicosiltransferases/metabolismo , Camundongos
20.
Biochim Biophys Acta Gen Subj ; 1863(4): 681-691, 2019 04.
Artigo em Inglês | MEDLINE | ID: mdl-30690120

RESUMO

BACKGROUND: Cells secrete heterogeneous populations of extracellular vesicles (EVs) via unknown mechanisms. EV biogenesis has been postulated to involve lipid-protein clusters, also known as membrane microdomains. METHODS: Membrane properties and heterogeneity of melanoma-derived EVs were analyzed by a detergent solubilization assay, sucrose density gradient ultracentrifugation and immunoprecipitation. EV secretion was modulated by RNA interference and pharmacological treatments. RESULTS: We identified two EV membranes (low-density exosomal detergent-insoluble membranes [EV-DIMs]; EV detergent-soluble membranes [EV-DSMs]) and discovered an abundant, novel type of high-density EV-DIMs. The high-density EV-DIMs accumulated the microdomain-resident protein flotillin-1, as well as a disintegrin and metalloproteinase domain containing protein 10 (Adam10), the hepatocyte growth factor receptor Met and its proteolytic fragments. Low-density EV-DIMs also contained flotillin-1. EV-DSMs were enriched with tetraspanin CD81, melanogenic enzymes and proteolytic fragments of Adam10. Intact and fragmented forms of Adam10, which resided in distinct membrane types, were secreted by different EVs. The fragmented form of Met was associated with DIMs much more efficiently than the intact form and they were secreted by distinct EVs. We identified that the endosomal sorting complexes required for transport machinery was indispensable for EV secretion of both mature and fragmented forms of Adam10 and Met. CONCLUSION: The findings of this study reveal the role of the interplay between membrane organization and sorting machineries in generating the heterogeneity of EVs. GENERAL SIGNIFICANCE: This study provides novel insights into important aspects of EV biogenesis.


Assuntos
Membrana Celular/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Proteínas de Membrana/metabolismo , Animais , Vesículas Extracelulares/metabolismo , Camundongos , Células Tumorais Cultivadas
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