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1.
Int J Mol Sci ; 22(17)2021 Aug 26.
Artigo em Inglês | MEDLINE | ID: mdl-34502144

RESUMO

Impaired wound healing in people with diabetes has multifactorial causes, with insufficient neovascularization being one of the most important. Hypoxia-inducible factor-1 (HIF-1) plays a central role in the hypoxia-induced response by activating angiogenesis factors. As its activity is under precise regulatory control of prolyl-hydroxylase domain 2 (PHD-2), downregulation of PHD-2 by small interfering RNA (siRNA) could stabilize HIF-1α and, therefore, upregulate the expression of pro-angiogenic factors as well. Intracellular delivery of siRNA can be achieved with nanocarriers that must fulfill several requirements, including high stability, low toxicity, and high transfection efficiency. Here, we designed and compared the performance of layer-by-layer self-assembled siRNA-loaded gold nanoparticles with two different outer layers-Chitosan (AuNP@CS) and Poly L-arginine (AuNP@PLA). Although both formulations have exactly the same core, we find that a PLA outer layer improves the endosomal escape of siRNA, and therefore, transfection efficiency, after endocytic uptake in NIH-3T3 cells. Furthermore, we found that endosomal escape of AuNP@PLA could be improved further when cells were additionally treated with desloratadine, thus outperforming commercial reagents such as Lipofectamine® and jetPRIME®. AuNP@PLA in combination with desloratadine was proven to induce PHD-2 silencing in fibroblasts, allowing upregulation of pro-angiogenic pathways. This finding in an in vitro context constitutes a first step towards improving diabetic wound healing with siRNA therapy.


Assuntos
Indutores da Angiogênese/metabolismo , Angiopatias Diabéticas/metabolismo , Ouro , Hipóxia/metabolismo , Lisossomos , Nanopartículas , RNA Interferente Pequeno/genética , Animais , Sobrevivência Celular , Fenômenos Químicos , Angiopatias Diabéticas/etiologia , Angiopatias Diabéticas/patologia , Composição de Medicamentos , Endossomos/metabolismo , Técnicas de Transferência de Genes , Hipóxia/genética , Loratadina/análogos & derivados , Loratadina/química , Loratadina/farmacologia , Camundongos , Células NIH 3T3 , Nanopartículas/química , RNA Interferente Pequeno/administração & dosagem
2.
J Vis Exp ; (174)2021 08 19.
Artigo em Inglês | MEDLINE | ID: mdl-34487110

RESUMO

In recent years, the field of macropinocytosis has grown rapidly. Macropinocytosis has emerged as a central mechanism by which innate immune cells maintain organismal homeostasis and immunity. Simultaneously, and in contrast to its homeostatic role, it can also drive various pathologies, including cancer and viral infections. Unlike other modes of endocytosis, the tools developed for studying the maturation of macropinosomes remain underdeveloped. Here the protocol describes newly developed tools for studying the redox environment within the lumen of early and maturing macropinosomes. Methodologies for using ratiometric fluorescence microscopy in assessing the pH, production of reactive oxygen species, and the degradative capacity within the lumen of individual macropinosomes in live cells are described. Single organelle measurements offer the advantage of revealing spatiotemporal heterogeneity, which is often lost with population-based approaches. Emphasis is placed on the basic principles of dual fluorophore ratiometric microscopy, including probe selection, instrumentation, calibration, and single-cell versus population-based methods.


Assuntos
Endossomos , Pinocitose , Endossomos/metabolismo , Concentração de Íons de Hidrogênio , Microscopia de Fluorescência , Oxirredução
3.
Nat Commun ; 12(1): 5405, 2021 09 13.
Artigo em Inglês | MEDLINE | ID: mdl-34518538

RESUMO

Tumor cells evade T cell-mediated immunosurveillance via the interaction between programmed death-1 (PD-1) ligand 1 (PD-L1) on tumor cells and PD-1 on T cells. Strategies disrupting PD-1/PD-L1 have shown clinical benefits in various cancers. However, the limited response rate prompts us to investigate the molecular regulation of PD-L1. Here, we identify trafficking protein particle complex subunit 4 (TRAPPC4), a major player in vesicular trafficking, as a crucial PD-L1 regulator. TRAPPC4 interacts with PD-L1 in recycling endosomes, acting as a scaffold between PD-L1 and RAB11, and promoting RAB11-mediated recycling of PD-L1, thus replenishing its distribution on the tumor cell surface. TRAPPC4 depletion leads to a significant reduction of PD-L1 expression in vivo and in vitro. This reduction in PD-L1 facilitates T cell-mediated cytotoxicity. Overexpression of Trappc4 sensitizes tumor cells to checkpoint therapy in murine tumor models, suggesting TRAPPC4 as a therapeutic target to enhance anti-tumor immunity.


Assuntos
Antígeno B7-H1/imunologia , Neoplasias Colorretais/imunologia , Regulação Neoplásica da Expressão Gênica/imunologia , Proteínas do Tecido Nervoso/imunologia , Proteínas de Transporte Vesicular/imunologia , Animais , Antígeno B7-H1/genética , Antígeno B7-H1/metabolismo , Linhagem Celular Tumoral , Neoplasias Colorretais/genética , Neoplasias Colorretais/metabolismo , Citotoxicidade Imunológica/genética , Citotoxicidade Imunológica/imunologia , Endossomos/imunologia , Endossomos/metabolismo , Células HCT116 , Humanos , Espaço Intracelular/metabolismo , Camundongos Endogâmicos C57BL , Camundongos Knockout , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Receptor de Morte Celular Programada 1/genética , Receptor de Morte Celular Programada 1/imunologia , Receptor de Morte Celular Programada 1/metabolismo , Ligação Proteica , Transporte Proteico , Interferência de RNA , Linfócitos T/imunologia , Linfócitos T/metabolismo , Proteínas de Transporte Vesicular/genética , Proteínas de Transporte Vesicular/metabolismo
4.
Int J Mol Sci ; 22(16)2021 Aug 20.
Artigo em Inglês | MEDLINE | ID: mdl-34445706

RESUMO

Here, we present the main features of human acid sphingomyelinase (ASM), its biosynthesis, processing and intracellular trafficking, its structure, its broad substrate specificity, and the proposed mode of action at the surface of the phospholipid substrate carrying intraendolysosomal luminal vesicles. In addition, we discuss the complex regulation of its phospholipid cleaving activity by membrane lipids and lipid-binding proteins. The majority of the literature implies that ASM hydrolyses solely sphingomyelin to generate ceramide and ignores its ability to degrade further substrates. Indeed, more than twenty different phospholipids are cleaved by ASM in vitro, including some minor but functionally important phospholipids such as the growth factor ceramide-1-phosphate and the unique lysosomal lysolipid bis(monoacylglycero)phosphate. The inherited ASM deficiency, Niemann-Pick disease type A and B, impairs mainly, but not only, cellular sphingomyelin catabolism, causing a progressive sphingomyelin accumulation, which furthermore triggers a secondary accumulation of lipids (cholesterol, glucosylceramide, GM2) by inhibiting their turnover in late endosomes and lysosomes. However, ASM appears to be involved in a variety of major cellular functions with a regulatory significance for an increasing number of metabolic disorders. The biochemical characteristics of ASM, their potential effect on cellular lipid turnover, as well as a potential impact on physiological processes will be discussed.


Assuntos
Fosfolipídeos/biossíntese , Esfingomielina Fosfodiesterase/biossíntese , Esfingomielina Fosfodiesterase/metabolismo , Transporte Biológico , Ceramidas/metabolismo , Colesterol/metabolismo , Endossomos/metabolismo , Humanos , Lisossomos/metabolismo , Lipídeos de Membrana/metabolismo , Doença de Niemann-Pick Tipo A/metabolismo , Fosfolipídeos/metabolismo , Esfingomielina Fosfodiesterase/fisiologia , Esfingomielinas/metabolismo , Fosfolipases Tipo C/metabolismo , Fosfolipases Tipo C/fisiologia
5.
EMBO Rep ; 22(10): e52445, 2021 10 05.
Artigo em Inglês | MEDLINE | ID: mdl-34402186

RESUMO

In eukaryotic cells, proteins are targeted to their final subcellular locations with precise timing. A key underlying mechanism is the active transport of cognate mRNAs, which in many systems can be linked intimately to membrane trafficking. A prominent example is the long-distance endosomal transport of mRNAs and their local translation. Here, we describe current highlights of fundamental mechanisms of the underlying transport process as well as of biological functions ranging from endosperm development in plants to fungal pathogenicity and neuronal processes. Translation of endosome-associated mRNAs often occurs at the cytoplasmic surface of endosomes, a process that is needed for membrane-assisted formation of heteromeric protein complexes and for accurate subcellular targeting of proteins. Importantly, endosome-coupled translation of mRNAs encoding mitochondrial proteins, for example, seems to be particularly important for efficient organelle import and for regulating subcellular mitochondrial activity. In essence, these findings reveal a new mechanism of loading newly synthesised proteins onto endocytic membranes enabling intimate crosstalk between organelles. The novel link between endosomes and mitochondria adds an inspiring new level of complexity to trafficking and organelle biology.


Assuntos
Endossomos , Mitocôndrias , Transporte Biológico , Endossomos/metabolismo , Células Eucarióticas/metabolismo , Mitocôndrias/genética , Mitocôndrias/metabolismo , Transporte Proteico , RNA Mensageiro/genética , RNA Mensageiro/metabolismo
6.
J Virol ; 95(21): e0094421, 2021 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-34406863

RESUMO

Porcine deltacoronavirus (PDCoV) is a recently discovered coronavirus that poses a potential threat to the global swine industry. Although we know that aminopeptidase N (APN) is important for PDCoV replication, it is unclear whether it is the primary functional receptor, and the mechanism by which it promotes viral replication is not fully understood. Here, we systematically investigated the roles of porcine APN (pAPN) during PDCoV infection of nonsusceptible cells, including in viral attachment and internalization. Using a viral entry assay, we found that PDCoV can enter nonsusceptible cells but then fails to initiate efficient replication. pAPN and PDCoV virions clearly colocalized with the endocytotic markers RAB5, RAB7, and LAMP1, suggesting that pAPN mediates PDCoV entry by an endocytotic pathway. Most importantly, our study shows that regardless of which receptor PDCoV engages, only entry by an endocytotic route ultimately leads to efficient viral replication. This knowledge should contribute to the development of efficient antiviral treatments, which are especially useful in preventing cross-species transmission. IMPORTANCE PDCoV is a pathogen with the potential for transmission across diverse species, although the mechanism of such host-switching events (from swine to other species) is poorly understood. Here, we show that PDCoV enters nonsusceptible cells but without efficient replication. We also investigated the key role played by aminopeptidase N in mediating PDCoV entry via an endocytotic pathway. Our results demonstrate that viral entry via endocytosis is a major determinant of efficient PDCoV replication. This knowledge provides a basis for future studies of the cross-species transmissibility of PDCoV and the development of appropriate antiviral drugs.


Assuntos
Antígenos CD13/metabolismo , Deltacoronavirus/fisiologia , Endocitose , Internalização do Vírus , Animais , Linhagem Celular , Endossomos/metabolismo , Células HEK293 , Humanos , Concentração de Íons de Hidrogênio , Lisossomos/enzimologia , Peptídeo Hidrolases/metabolismo , Receptores de Coronavírus/metabolismo , Suínos , Vírion/fisiologia , Ligação Viral , Replicação Viral
7.
J Immunol ; 207(5): 1448-1455, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34362834

RESUMO

Identification of the receptors involved in innate immune recognition of Staphylococcus aureus, a major cause of morbidity and mortality in humans, is essential to develop alternative strategies to treat infections caused by antibiotic-resistant strains. In the current study, we examine the role of endosomal TLRs, which sense the presence of prokaryotic-type nucleic acids, in anti-staphylococcal host defenses using infection models involving genetically defective mice. Single deficiencies in TLR7, 9, or 13 resulted in mild or no decrease in host defenses. However, the simultaneous absence of TLR7, 9, and 13 resulted in markedly increased susceptibility to cutaneous and systemic S. aureus infection concomitantly with decreased production of proinflammatory chemokines and cytokines, neutrophil recruitment to infection sites, and reduced production of reactive oxygen species. This phenotype was significantly more severe than that of mice lacking TLR2, which senses the presence of staphylococcal lipoproteins. Notably, the combined absence of TLR7, 9, and 13 resulted in complete abrogation of IL-12 p70 and IFN-ß responses to staphylococcal stimulation in macrophages. Taken together, our data highlight the presence of a highly integrated endosomal detection system, whereby TLR7, 9, and 13 cooperate in sensing the presence of staphylococcal nucleic acids. We demonstrate that the combined absence of these receptors cannot be compensated for by cell surface-associated TLRs, such as TLR2, or cytosolic receptors. These data may be useful to devise strategies aimed at stimulating innate immune receptors to treat S. aureus infections.


Assuntos
Endossomos/metabolismo , Glicoproteínas de Membrana/metabolismo , Neutrófilos/imunologia , Infecções Estafilocócicas/imunologia , Staphylococcus aureus/fisiologia , Receptor 7 Toll-Like/metabolismo , Receptor Toll-Like 9/metabolismo , Receptores Toll-Like/metabolismo , Animais , Citocinas/metabolismo , Modelos Animais de Doenças , Suscetibilidade a Doenças , Feminino , Humanos , Imunidade Inata , Mediadores da Inflamação/metabolismo , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Receptor 7 Toll-Like/genética , Receptor Toll-Like 9/genética , Receptores Toll-Like/genética
8.
Int J Mol Sci ; 22(16)2021 Aug 06.
Artigo em Inglês | MEDLINE | ID: mdl-34445155

RESUMO

A main characteristic of sphingolipids is the presence of a very long chain fatty acid (VLCFA) whose function in cellular processes is not yet fully understood. VLCFAs of sphingolipids are involved in the intracellular traffic to the vacuole and the maturation of early endosomes into late endosomes is one of the major pathways for vacuolar traffic. Additionally, the anionic phospholipid phosphatidylinositol-3-phosphate (PtdIns (3)P or PI3P) is involved in protein sorting and recruitment of small GTPase effectors at late endosomes/multivesicular bodies (MVBs) during vacuolar trafficking. In contrast to animal cells, PI3P mainly localizes to late endosomes in plant cells and to a minor extent to a discrete sub-domain of the plant's early endosome (EE)/trans-Golgi network (TGN) where the endosomal maturation occurs. However, the mechanisms that control the relative levels of PI3P between TGN and MVBs are unknown. Using metazachlor, an inhibitor of VLCFA synthesis, we found that VLCFAs are involved in the TGN/MVB distribution of PI3P. This effect is independent from either synthesis of PI3P by PI3-kinase or degradation of PI(3,5)P2 into PI3P by the SUPPRESSOR OF ACTIN1 (SAC1) phosphatase. Using high-resolution live cell imaging microscopy, we detected transient associations between TGNs and MVBs but VLCFAs are not involved in those interactions. Nonetheless, our results suggest that PI3P might be transferable from TGN to MVBs and that VLCFAs act in this process.


Assuntos
Arabidopsis/metabolismo , Endossomos/metabolismo , Ácidos Graxos/metabolismo , Fosfatos de Fosfatidilinositol/metabolismo , Vias Biossintéticas , Esfingolipídeos/metabolismo , Rede trans-Golgi/metabolismo
9.
Nat Commun ; 12(1): 5131, 2021 08 26.
Artigo em Inglês | MEDLINE | ID: mdl-34446736

RESUMO

Protein delivery with cell-penetrating peptide is opening up the possibility of using targets inside cells for therapeutic or biological applications; however, cell-penetrating peptide-mediated protein delivery commonly suffers from ineffective endosomal escape and low tolerance in serum, thereby limiting in vivo efficacy. Here, we present an intracellular protein delivery system consisting of four modules in series: cell-penetrating peptide, pH-dependent membrane active peptide, endosome-specific protease sites and a leucine zipper. This system exhibits enhanced delivery efficiency and serum tolerance, depending on proteolytic cleavage-facilitated endosomal escape and leucine zipper-based dimerisation. Intravenous injection of protein phosphatase 1B fused with this system successfully suppresses the tumour necrosis factor-α-induced systemic inflammatory response and acetaminophen-induced acute liver failure in a mouse model. We believe that the strategy of using multifunctional chimaeric peptides is valuable for the development of cell-penetrating peptide-based protein delivery systems, and facilitate the development of biological macromolecular drugs for use against intracellular targets.


Assuntos
Sistemas de Liberação de Medicamentos/métodos , Falência Hepática Aguda/tratamento farmacológico , Peptídeos/química , Proteína Fosfatase 1/administração & dosagem , Animais , Peptídeos Penetradores de Células/química , Peptídeos Penetradores de Células/genética , Peptídeos Penetradores de Células/metabolismo , Endossomos/genética , Endossomos/metabolismo , Humanos , Concentração de Íons de Hidrogênio , Falência Hepática Aguda/genética , Falência Hepática Aguda/metabolismo , Camundongos Endogâmicos BALB C , Peptídeos/genética , Peptídeos/metabolismo , Proteína Fosfatase 1/química , Proteína Fosfatase 1/genética , Proteína Fosfatase 1/metabolismo , Transporte Proteico
10.
Biomolecules ; 11(7)2021 07 13.
Artigo em Inglês | MEDLINE | ID: mdl-34356645

RESUMO

Microphthalmia-associated transcription factor (MITF) is the principal transcription factor regulating pivotal processes in melanoma cell development, growth, survival, proliferation, differentiation and invasion. In recent years, convincing evidence has been provided attesting key roles of endolysosomal cation channels, specifically TPCs and TRPMLs, in cancer, including breast cancer, glioblastoma, bladder cancer, hepatocellular carcinoma and melanoma. In this review, we provide a gene expression profile of these channels in different types of cancers and decipher their roles, in particular the roles of two-pore channel 2 (TPC2) and TRPML1 in melanocytes and melanoma. We specifically discuss the signaling cascades regulating MITF and the relationship between endolysosomal cation channels, MAPK, canonical Wnt/GSK3 pathways and MITF.


Assuntos
Canais Iônicos/metabolismo , Melanócitos/metabolismo , Melanoma/patologia , Fator de Transcrição Associado à Microftalmia/metabolismo , Canais de Cálcio/genética , Canais de Cálcio/metabolismo , Endossomos/metabolismo , Expressão Gênica , Humanos , Canais Iônicos/genética , Lisossomos/metabolismo , Melanócitos/patologia , Melanoma/metabolismo , Fator de Transcrição Associado à Microftalmia/genética , Canais de Potencial de Receptor Transitório/genética , Canais de Potencial de Receptor Transitório/metabolismo
11.
Nat Commun ; 12(1): 4697, 2021 08 04.
Artigo em Inglês | MEDLINE | ID: mdl-34349123

RESUMO

Polarized epithelial cells can organize into complex structures with a characteristic central lumen. Lumen formation requires that cells coordinately orient their polarity axis so that the basolateral domain is on the outside and apical domain inside epithelial structures. Here we show that the transmembrane aminopeptidase, CD13, is a key determinant of epithelial polarity orientation. CD13 localizes to the apical membrane and associates with an apical complex with Par6. CD13-deficient cells display inverted polarity in which apical proteins are retained on the outer cell periphery and fail to accumulate at an intercellular apical initiation site. Here we show that CD13 is required to couple apical protein cargo to Rab11-endosomes and for capture of endosomes at the apical initiation site. This role in polarity utilizes the short intracellular domain but is independent of CD13 peptidase activity.


Assuntos
Antígenos CD13/metabolismo , Polaridade Celular , Células Epiteliais/citologia , Epitélio/crescimento & desenvolvimento , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Antígenos CD13/química , Antígenos CD13/genética , Células CACO-2 , Membrana Celular/metabolismo , Endocitose , Endossomos/metabolismo , Células Epiteliais/metabolismo , Humanos , Proteínas de Membrana/metabolismo , Domínios Proteicos , Proteínas rab de Ligação ao GTP/metabolismo
12.
Nat Commun ; 12(1): 4739, 2021 08 06.
Artigo em Inglês | MEDLINE | ID: mdl-34362892

RESUMO

Nicotinic acid adenine dinucleotide phosphate (NAADP) is a potent Ca2+-mobilizing second messenger which uniquely mobilizes Ca2+ from acidic endolysosomal organelles. However, the molecular identity of the NAADP receptor remains unknown. Given the necessity of the endolysosomal two-pore channel (TPC1 or TPC2) in NAADP signaling, we performed affinity purification and quantitative proteomic analysis of the interacting proteins of NAADP and TPCs. We identified a Sm-like protein Lsm12 complexed with NAADP, TPC1, and TPC2. Lsm12 directly binds to NAADP via its Lsm domain, colocalizes with TPC2, and mediates the apparent association of NAADP to isolated TPC2 or TPC2-containing membranes. Lsm12 is essential and immediately participates in NAADP-evoked TPC activation and Ca2+ mobilization from acidic stores. These findings reveal a putative RNA-binding protein to function as an NAADP receptor and a TPC regulatory protein and provides a molecular basis for understanding the mechanisms of NAADP signaling.


Assuntos
Cálcio/metabolismo , NADP/análogos & derivados , Porinas/metabolismo , Animais , Canais de Cálcio/metabolismo , Linhagem Celular , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/química , Peptídeos e Proteínas de Sinalização do Ritmo Circadiano/genética , Endossomos/metabolismo , Fibroblastos , Células HEK293 , Humanos , Lisossomos/metabolismo , Camundongos , Mutação , NADP/genética , NADP/metabolismo , Proteômica
13.
Int J Mol Sci ; 22(16)2021 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-34445480

RESUMO

Multivesicular body (MVB)-mediated endosomal sorting and macroautophagy are the main pathways mediating the transport of cellular components to the vacuole and are essential for maintaining cellular homeostasis. The interplay of these two pathways remains poorly understood in plants. In this study, we show that FYVE DOMAIN PROTEIN REQUIRED FOR ENDOSOMAL SORTING 1 (FREE1), which was previously identified as a plant-specific component of the endosomal sorting complex required for transport (ESCRT), essential for MVB biogenesis and plant growth, can be transported to the vacuole for degradation in response to iron deficiency. The vacuolar transport of ubiquitinated FREE1 protein is mediated by the autophagy pathway. As a consequence, the autophagy deficient mutants, atg5-1 and atg7-2, accumulate more endogenous FREE1 protein and display hypersensitivity to iron deficiency. Furthermore, under iron-deficient growth condition autophagy related genes are upregulated to promote the autophagic degradation of FREE1, thereby possibly relieving the repressive effect of FREE1 on iron absorption. Collectively, our findings demonstrate a unique regulatory mode of protein turnover of the ESCRT machinery through the autophagy pathway to respond to iron deficiency in plants.


Assuntos
Proteínas de Arabidopsis/química , Arabidopsis/metabolismo , Proteínas Relacionadas à Autofagia/genética , Ferro/metabolismo , Proteínas de Transporte Vesicular/química , Arabidopsis/genética , Proteínas de Arabidopsis/genética , Autofagia , Transporte Biológico , Complexos Endossomais de Distribuição Requeridos para Transporte , Endossomos/metabolismo , Mutação , Proteólise , Ubiquitinação
14.
Nat Commun ; 12(1): 4552, 2021 07 27.
Artigo em Inglês | MEDLINE | ID: mdl-34315878

RESUMO

The ability of endolysosomal organelles to move within the cytoplasm is essential for the performance of their functions. Long-range movement involves coupling of the endolysosomes to motor proteins that carry them along microtubule tracks. This movement is influenced by interactions with other organelles, but the mechanisms involved are incompletely understood. Herein we show that the sorting nexin SNX19 tethers endolysosomes to the endoplasmic reticulum (ER), decreasing their motility and contributing to their concentration in the perinuclear area of the cell. Tethering depends on two N-terminal transmembrane domains that anchor SNX19 to the ER, and a PX domain that binds to phosphatidylinositol 3-phosphate on the endolysosomal membrane. Two other domains named PXA and PXC negatively regulate the interaction of SNX19 with endolysosomes. These studies thus identify a mechanism for controlling the motility and positioning of endolysosomes that involves tethering to the ER by a sorting nexin.


Assuntos
Retículo Endoplasmático/metabolismo , Endossomos/metabolismo , Lisossomos/metabolismo , Nexinas de Classificação/metabolismo , Linhagem Celular Tumoral , Retículo Endoplasmático/ultraestrutura , Endossomos/ultraestrutura , Humanos , Lisossomos/ultraestrutura , Fosfatos de Fosfatidilinositol/metabolismo , Ligação Proteica , Domínios Proteicos , Transporte Proteico , Nexinas de Classificação/química
15.
Elife ; 102021 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-34251337

RESUMO

The endosome-associated cargo adaptor sorting nexin-27 (SNX27) is linked to various neuropathologies through sorting of integral proteins to the synaptic surface, most notably AMPA receptors. To provide a broader view of SNX27-associated pathologies, we performed proteomics in rat primary neurons to identify SNX27-dependent cargoes, and identified proteins linked to excitotoxicity, epilepsy, intellectual disabilities, and working memory deficits. Focusing on the synaptic adhesion molecule LRFN2, we established that SNX27 binds to LRFN2 and regulates its endosomal sorting. Furthermore, LRFN2 associates with AMPA receptors and knockdown of LRFN2 results in decreased surface AMPA receptor expression, reduced synaptic activity, and attenuated hippocampal long-term potentiation. Overall, our study provides an additional mechanism by which SNX27 can control AMPA receptor-mediated synaptic transmission and plasticity indirectly through the sorting of LRFN2 and offers molecular insight into the perturbed function of SNX27 and LRFN2 in a range of neurological conditions.


Assuntos
Glicoproteínas de Membrana/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Receptores de AMPA/metabolismo , Nexinas de Classificação/metabolismo , Animais , Endossomos/metabolismo , Hipocampo/metabolismo , Humanos , Potenciação de Longa Duração , Transtornos da Memória/metabolismo , Transporte Proteico , Proteômica/métodos , Ratos , Transmissão Sináptica
16.
J Vis Exp ; (172)2021 06 30.
Artigo em Inglês | MEDLINE | ID: mdl-34279508

RESUMO

Endosomal trafficking is an essential cellular process that regulates a broad range of biological events. Proteins are internalized from the plasma membrane and then transported to the early endosomes. The internalized proteins could be transited to the lysosome for degradation or recycled back to the plasma membrane. A robust endocytic recycling pathway is required to balance the removal of membrane materials from endocytosis. Various proteins are reported to regulate the pathway, including ADP-ribosylation factor 6 (ARF6). Density gradient ultracentrifugation is a classical method for cell fractionation. After the centrifugation, organelles are sedimented at their isopycnic surface. The fractions are collected and used for other downstream applications. Described here is a protocol to obtain a recycling endosome-containing fraction from transfected mammalian cells using density gradient ultracentrifugation. The isolated fractions were subjected to standard Western blotting for analyzing their protein contents. By employing this method, we identified that the plasma membrane targeting of engulfment and cell motility 1 (ELMO1), a Ras-related C3 botulinum toxin substrate 1 (Rac1) guanine nucleotide exchange factor, is through ARF6-mediated endocytic recycling.


Assuntos
Endocitose , Endossomos , Animais , Membrana Celular/metabolismo , Endossomos/metabolismo , Transporte Proteico , Ultracentrifugação
17.
J Virol ; 95(19): e0084321, 2021 09 09.
Artigo em Inglês | MEDLINE | ID: mdl-34260280

RESUMO

Adeno-associated viruses (AAVs) are small nonenveloped single-stranded DNA (ssDNA) viruses that are currently being developed as gene therapy biologics. After cell entry, AAVs traffic to the nucleus using the endo-lysosomal pathway. The subsequent decrease in pH triggers conformational changes to the capsid that enable the externalization of the capsid protein (VP) N termini, including the unique domain of the minor capsid protein VP1 (VP1u), which permits the phospholipase activity required for the capsid lysosomal egress. Here, we report the AAV9 capsid structure, determined at the endosomal pHs (7.4, 6.0, 5.5, and 4.0), and terminal galactose-bound AAV9 capsids at pHs 7.4 and 5.5 using cryo-electron microscopy and three-dimensional image reconstruction. Taken together, these studies provide insight into AAV9 capsid conformational changes at the 5-fold pore during endosomal trafficking, in both the presence and absence of its cellular glycan receptor. We visualized, for the first time, that acidification induces the externalization of the VP3 and possibly VP2 N termini, presumably in prelude to the externalization of VP1u at pH 4.0, which is essential for lysosomal membrane disruption. In addition, the structural study of AAV9-galactose interactions demonstrates that AAV9 remains attached to its glycan receptor at the late endosome pH 5.5. This interaction significantly alters the conformational stability of the variable region I of the VPs, as well as the dynamics associated with VP N terminus externalization. IMPORTANCE There are 13 distinct Adeno-associated virus (AAV) serotypes that are structurally homologous and whose capsid proteins (VP1 to -3) are similar in amino acid sequence. However, AAV9 is one of the most commonly studied and is used as a gene therapy vector. This is partly because AAV9 is capable of crossing the blood-brain barrier and readily transduces a wide array of tissues, including the central nervous system. In this study, we provide AAV9 capsid structural insight during intracellular trafficking. Although the AAV capsid has been shown to externalize the N termini of its VPs, to enzymatically disrupt the lysosome membrane at low pH, there was no structural evidence to confirm this. By utilizing AAV9 as our model, we provide the first structural evidence that the externalization process occurs at the protein interface at the icosahedral 5-fold symmetry axis and can be triggered by lowering the pH.


Assuntos
Proteínas do Capsídeo/química , Capsídeo/ultraestrutura , Dependovirus/química , Dependovirus/ultraestrutura , Endossomos/metabolismo , Galactose/metabolismo , Polissacarídeos/metabolismo , Acetilgalactosamina/metabolismo , Capsídeo/química , Microscopia Crioeletrônica , Dependovirus/metabolismo , Concentração de Íons de Hidrogênio , Processamento de Imagem Assistida por Computador , Modelos Moleculares , Conformação Proteica , Dobramento de Proteína , Receptores Virais/metabolismo
18.
Development ; 148(14)2021 07 15.
Artigo em Inglês | MEDLINE | ID: mdl-34269385

RESUMO

Fertilization triggers significant cellular remodeling through the oocyte-to-embryo transition. In this transition, the ubiquitin-proteasome system and autophagy are essential for the degradation of maternal components; however, the significance of degradation of cell surface components remains unknown. In this study, we show that multiple maternal plasma membrane proteins, such as the glycine transporter GlyT1a, are selectively internalized from the plasma membrane to endosomes in mouse embryos by the late two-cell stage and then transported to lysosomes for degradation at the later stages. During this process, large amounts of ubiquitylated proteins accumulated on endosomes. Furthermore, the degradation of GlyT1a with mutations in potential ubiquitylation sites was delayed, suggesting that ubiquitylation may be involved in GlyT1a degradation. The clathrin inhibitor blocked GlyT1a internalization. Strikingly, the protein kinase C (PKC) activator triggered the heterochronic internalization of GlyT1a; the PKC inhibitor markedly blocked GlyT1a endocytosis. Lastly, clathrin inhibition completely blocked embryogenesis at the two-cell stage and inhibited cell division after the four-cell stage. These findings demonstrate that PKC-dependent clathrin-mediated endocytosis is essential for the selective degradation of maternal membrane proteins during oocyte-to-embryo transition and early embryogenesis.


Assuntos
Clatrina/metabolismo , Desenvolvimento Embrionário/fisiologia , Endocitose/fisiologia , Proteínas de Membrana/metabolismo , Animais , Membrana Celular/metabolismo , Embrião de Mamíferos , Endossomos/metabolismo , Feminino , Fertilização , Proteínas da Membrana Plasmática de Transporte de Glicina , Masculino , Camundongos , Oócitos , Proteína Quinase C , Ubiquitina/metabolismo , Ubiquitinação
19.
Int J Mol Sci ; 22(13)2021 Jun 29.
Artigo em Inglês | MEDLINE | ID: mdl-34209489

RESUMO

The endocytosis of ligand-bound receptors and their eventual recycling to the plasma membrane (PM) are processes that have an influence on signalling activity and therefore on many cell functions, including migration and proliferation. Like other tyrosine kinase receptors (TKR), the insulin receptor (INSR) has been shown to be endocytosed by clathrin-dependent and -independent mechanisms. Once at the early endosome (EE), the sorting of the receptor, either to the late endosome (LE) for degradation or back to the PM through slow or fast recycling pathways, will determine the intensity and duration of insulin effects. Both the endocytic and the endosomic pathways are regulated by many proteins, the Arf and Rab families of small GTPases being some of the most relevant. Here, we argue for a specific role for the slow recycling route, whilst we review the main molecular mechanisms involved in INSR endocytosis, sorting and recycling, as well as their possible role in cell functions.


Assuntos
Endossomos/metabolismo , Receptor de Insulina/metabolismo , Animais , Proteínas de Transporte , Membrana Celular/metabolismo , Movimento Celular , Proliferação de Células , Clatrina/metabolismo , Endocitose , Humanos , Lisossomos , Ligação Proteica , Transporte Proteico , Receptor de Insulina/agonistas , Vesículas Transportadoras/metabolismo , Proteínas rab de Ligação ao GTP/metabolismo
20.
Nano Lett ; 21(14): 6022-6030, 2021 07 28.
Artigo em Inglês | MEDLINE | ID: mdl-34227381

RESUMO

Despite the well-recognized clinical success of therapeutic proteins, especially antibodies, their inability to penetrate the cell membrane restricts them to secretory extracellular or membrane-associated targets. Developing a direct cytosolic protein delivery system would offer unique opportunities for intracellular target-related therapeutic proteins. Here, we generated a supercharged polypeptide (SCP) with high cellular uptake efficiency, endosomal escape ability, and good biosafety and developed an SCP with an unnatural amino acid containing the phenylboronic acid (PBA) group, called PBA-SCP. PBA-SCP is capable of potently delivering proteins with various isoelectric points and molecular sizes into the cytosol of living cells without affecting their bioactivities. Importantly, cytosolically delivered antibodies remain functional and are capable of targeting, labeling, and manipulating diverse intracellular antigens. This study demonstrates an efficient and versatile intracellular protein delivery platform, especially for antibodies, and provides new possibilities for expanding protein-based therapeutics to intracellular "undruggable" targets.


Assuntos
Peptídeos , Proteínas , Transporte Biológico , Citosol/metabolismo , Endossomos/metabolismo , Peptídeos/metabolismo
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