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1.
Nat Commun ; 15(1): 6993, 2024 Aug 14.
Artigo em Inglês | MEDLINE | ID: mdl-39143098

RESUMO

RNA interference (RNAi) is a gene-silencing mechanism triggered by the cytosolic entry of double-stranded RNAs (dsRNAs). Many animal cells internalize extracellular dsRNAs via endocytosis for RNAi induction. However, it is not clear how the endocytosed dsRNAs are translocated into the cytosol across the endo/lysosomal membrane. Herein, we show that in Drosophila S2 cells, endocytosed dsRNAs induce lysosomal membrane permeabilization (LMP) that allows cytosolic dsRNA translocation. LMP mediated by dsRNAs requires the lysosomal Cl-/H+ antiporter ClC-b/DmOstm1. In clc-b or dmostm1 knockout S2 cells, extracellular dsRNAs are endocytosed and reach the lysosomes normally but fail to enter the cytosol. Pharmacological induction of LMP restores extracellular dsRNA-directed RNAi in clc-b or dmostm1-knockout cells. Furthermore, clc-b or dmostm1 mutant flies are defective in extracellular dsRNA-directed RNAi and its associated antiviral immunity. Therefore, endocytosed dsRNAs have an intrinsic ability to induce ClC-b/DmOstm1-dependent LMP that allows cytosolic dsRNA translocation for RNAi responses in Drosophila cells.


Assuntos
Citosol , Proteínas de Drosophila , Endocitose , Lisossomos , Interferência de RNA , RNA de Cadeia Dupla , Animais , RNA de Cadeia Dupla/metabolismo , Lisossomos/metabolismo , Citosol/metabolismo , Proteínas de Drosophila/metabolismo , Proteínas de Drosophila/genética , Drosophila melanogaster/metabolismo , Drosophila melanogaster/genética , Canais de Cloreto/metabolismo , Canais de Cloreto/genética , Linhagem Celular , Membranas Intracelulares/metabolismo , Permeabilidade , Drosophila/metabolismo , Drosophila/genética
2.
Methods Mol Biol ; 2841: 165-170, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39115775

RESUMO

Vesicle trafficking is an essential cellular process conserved in eukaryotes to precisely transport proteins to their destinations. The plant endomembrane system plays a pivotal role in orchestrating this vesicle-mediated protein transport process, making its study essential for a comprehensive understanding of plant growth and development. Pharmaceutical analysis proves highly useful in investigating the plant endomembrane system. To facilitate further studies in this area, we present a summary of several commonly used chemical inhibitors in this chapter, providing a practical resource for researchers interested in the plant endomembrane system.


Assuntos
Transporte Proteico , Plantas/metabolismo , Membranas Intracelulares/metabolismo , Membranas Intracelulares/efeitos dos fármacos , Proteínas de Plantas/metabolismo , Membrana Celular/metabolismo
3.
Curr Top Membr ; 93: 85-116, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-39181579

RESUMO

Lysosomes are more than just cellular recycling bins; they play a crucial role in regulating key cellular functions. Proper lysosomal function is essential for growth pathway regulation, cell proliferation, and metabolic homeostasis. Impaired lysosomal function is associated with lipid storage disorders and neurodegenerative diseases. Lysosomes form extensive and dynamic close contacts with the membranes of other organelles, including the endoplasmic reticulum, mitochondria, peroxisomes, and lipid droplets. These membrane contacts sites (MCSs) are vital for many lysosomal functions. In this chapter, we will explore lysosomal MCSs focusing on the machinery that mediates these contacts, how they are regulated, and their functional implications on physiology and pathology.


Assuntos
Comunicação Celular , Homeostase , Lisossomos , Lisossomos/metabolismo , Humanos , Animais , Membranas Intracelulares/metabolismo
4.
Plant Physiol Biochem ; 214: 108961, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39067102

RESUMO

Winter crops acquire frost tolerance during the process of cold acclimation when plants are exposed to low but non-freezing temperatures that is connected to specific metabolic adjustments. Warm breaks during/after cold acclimation disturb the natural process of acclimation, thereby decreasing frost tolerance and can even result in a resumption of growth. This phenomenon is called deacclimation. In the last few years, studies that are devoted to deacclimation have become more important (due to climate changes) and necessary to be able to understand the mechanisms that occur during this phenomenon. In the acclimation of plants to low temperatures, the importance of plant membranes is indisputable; that is why the main aim of our studies was to answer the question of whether (and to what extent) deacclimation alters the physicochemical properties of the plant membranes. The studies were focused on chloroplast membranes from non-acclimated, cold-acclimated and deacclimated cultivars of winter oilseed rape. The analysis of the membranes (formed from chloroplast lipid fractions) using the Langmuir technique revealed that cold acclimation increased membrane fluidity (expressed as the Alim values), while deacclimation generally decreased the values that were induced by cold. Moreover, because the chloroplast membranes were penetrated by lipophilic molecules such as carotenoids or tocopherols, the relationships between the structure of the lipids and the content of these antioxidants in the chloroplast membranes during the process of the cold acclimation and deacclimation of oilseed rape are discussed.


Assuntos
Aclimatação , Cloroplastos , Temperatura Baixa , Aclimatação/fisiologia , Cloroplastos/metabolismo , Brassica napus/metabolismo , Brassica napus/fisiologia , Carotenoides/metabolismo , Fluidez de Membrana/fisiologia , Membranas Intracelulares/metabolismo
5.
Nat Cell Biol ; 26(7): 1139-1153, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38992139

RESUMO

The mammalian Golgi is composed of stacks that are laterally connected into a continuous ribbon-like structure. The integrity and function of the ribbon is disrupted under stress conditions, but the molecular mechanisms remain unclear. Here we show that the ribbon is maintained by biomolecular condensates of RNA and the Golgi matrix protein GM130 (GOLGA2). We identify GM130 as a membrane-bound RNA-binding protein, which directly recruits RNA and associated RNA-binding proteins to the Golgi membrane. Acute degradation of RNA or GM130 in cells disrupts the ribbon. Under stress conditions, RNA dissociates from GM130 and the ribbon is disjointed, but after the cells recover from stress the ribbon is restored. When overexpressed in cells, GM130 forms RNA-dependent liquid-like condensates. GM130 contains an intrinsically disordered domain at its amino terminus, which binds RNA to induce liquid-liquid phase separation. These co-condensates are sufficient to link purified Golgi membranes, reconstructing lateral linking of stacks into a ribbon-like structure. Together, these studies show that RNA acts as a structural biopolymer that together with GM130 maintains the integrity of the Golgi ribbon.


Assuntos
Autoantígenos , Complexo de Golgi , Proteínas de Membrana , RNA , Complexo de Golgi/metabolismo , Humanos , Autoantígenos/metabolismo , Autoantígenos/genética , Autoantígenos/química , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/química , RNA/metabolismo , RNA/genética , Proteínas de Ligação a RNA/metabolismo , Proteínas de Ligação a RNA/genética , Proteínas de Ligação a RNA/química , Células HeLa , Condensados Biomoleculares/metabolismo , Ligação Proteica , Membranas Intracelulares/metabolismo , Animais , Células HEK293
6.
PLoS Pathog ; 20(7): e1011959, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-39008516

RESUMO

An essential aspect of positive-sense RNA virus replication is anchoring the replication complex (RC) to cellular membranes. Positive-sense RNA viruses employ diverse strategies, including co-translational membrane targeting through signal peptides and co-opting cellular membrane trafficking components. Often, N-terminal nonstructural proteins play a crucial role in linking the RC to membranes, facilitating the early association of the replication machinery. Astroviruses utilize a polyprotein strategy to synthesize nonstructural proteins, relying on subsequent processing to form replication-competent complexes. This study provides evidence for the perinuclear ER membrane association of RCs in five distinct human astrovirus strains. Using tagged recombinant classical human astrovirus 1 and neurotropic MLB2 strains, we establish that the N-terminal domain guides the ER membrane association. We identified di-arginine motifs responsible for the perinuclear ER retention and formation of functional RCs through mutational analysis of the N-terminal domain in replicon and reverse genetics systems. In addition, we demonstrate the association of key components of the astrovirus replication complex: double-stranded RNA, RNA-dependent RNA polymerase, protease, and N-terminal protein. Our findings highlight the intricate virus-ER interaction mechanism employed by astroviruses, potentially leading to the development of novel antiviral intervention strategies.


Assuntos
Retículo Endoplasmático , Mamastrovirus , Proteínas não Estruturais Virais , Replicação Viral , Proteínas não Estruturais Virais/metabolismo , Proteínas não Estruturais Virais/genética , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/virologia , Replicação Viral/fisiologia , Humanos , Mamastrovirus/metabolismo , Mamastrovirus/genética , Infecções por Astroviridae/virologia , Infecções por Astroviridae/metabolismo , Membranas Intracelulares/metabolismo , Membranas Intracelulares/virologia
7.
Life Sci Alliance ; 7(10)2024 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-39079741

RESUMO

Protein glycosylation plays a vital role in various cellular functions, many of which occur within the Golgi apparatus. The Golgi pH regulator (GPHR) is essential for the proper functioning of the Golgi apparatus. The lysosomal membrane contains highly glycosylated membrane proteins in abundance. This study investigated the role of the Golgi luminal pH in N-glycosylation of lysosomal membrane proteins and the effect of this protein modification on membrane stability using Gphr-deficient MEFs. We showed that Gphr deficiency causes an imbalance in the Golgi luminal pH, resulting in abnormal protein N-glycosylation, indicated by a reduction in sialylated glycans and markedly reduced molecular weight of glycoproteins. Further experiments using FRAP and PLA revealed that Gphr deficiency prevented the trafficking dynamics and proximity condition of glycosyltransferases in the Golgi apparatus. In addition, incomplete N-glycosylation of lysosomal membrane proteins affected lysosomal membrane stability, as demonstrated by the increased susceptibility to lysosomal damage. Thus, this study highlights the critical role of Golgi pH regulation in controlling protein glycosylation and the impact of Golgi dysfunction on lysosomal membrane stability.


Assuntos
Complexo de Golgi , Homeostase , Membranas Intracelulares , Lisossomos , Proteínas de Membrana , Glicosilação , Complexo de Golgi/metabolismo , Lisossomos/metabolismo , Concentração de Íons de Hidrogênio , Animais , Proteínas de Membrana/metabolismo , Camundongos , Membranas Intracelulares/metabolismo , Transporte Proteico , Humanos , Glicosiltransferases/metabolismo , Proteínas de Membrana Lisossomal/metabolismo , Glicoproteínas/metabolismo
8.
Biochem Pharmacol ; 227: 116438, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-39025409

RESUMO

Valproic acid (VPA) has broad efficacy against several seizures but causes liver injury limiting its prolonged clinical use. Some studies have demonstrated that VPA-induced hepatotoxicity is characterized by microvesicular hepatic steatosis. However, novel detailed mechanisms to explain VPA-induced hepatic steatosis and experimentally rigorously validated protective agents are still lacking. In this study, 8-week-old C57BL/6J mice were gavaged with VPA (500 mg/kg/d) for 4 weeks to establish an in vivo model of VPA-induced chronic liver injury. Quantitative proteomic and non-targeted lipidomic analyses were performed to explore the underlying mechanisms of VPA-induced hepatotoxicity. As a result, VPA-induced hepatotoxicity is associated with impaired autophagic flux, which is attributed to lysosomal dysfunction. Further studies revealed that VPA-induced lysosomal membrane permeabilization (LMP), allows soluble lysosomal enzymes to leak into the cytosol, which subsequently led to impaired lysosomal acidification. A lower abundance of glycerophospholipids and an increased abundance of lysophospholipids in liver tissues of mice in the VPA group strongly indicated that VPA-induced LMP may be mediated by the activation of phospholipase PLA2G4A. Metformin (Met) acted as a potential protective agent attenuating VPA-induced liver dysfunction and excessive lipid accumulation. Molecular docking and cellular thermal shift assays demonstrated that Met inhibited the activity of PLA2G4A by directly binding to it, thereby ameliorating VPA-induced LMP and autophagic flux impairment. In conclusion, this study highlights the therapeutic potential of targeting PLA2G4A-mediated lysosomal dysfunction in VPA-induced hepatotoxicity.


Assuntos
Autofagia , Fosfolipases A2 do Grupo IV , Lisossomos , Camundongos Endogâmicos C57BL , Ácido Valproico , Animais , Ácido Valproico/toxicidade , Autofagia/efeitos dos fármacos , Camundongos , Lisossomos/efeitos dos fármacos , Lisossomos/metabolismo , Masculino , Fosfolipases A2 do Grupo IV/metabolismo , Fosfolipases A2 do Grupo IV/antagonistas & inibidores , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Doença Hepática Induzida por Substâncias e Drogas/prevenção & controle , Doença Hepática Induzida por Substâncias e Drogas/patologia , Humanos , Simulação de Acoplamento Molecular , Anticonvulsivantes/farmacologia , Anticonvulsivantes/toxicidade , Membranas Intracelulares/efeitos dos fármacos , Membranas Intracelulares/metabolismo , Permeabilidade/efeitos dos fármacos , Metformina/farmacologia
9.
ACS Chem Biol ; 19(8): 1773-1785, 2024 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-39069657

RESUMO

Organelles feature characteristic lipid compositions that lead to differences in membrane properties. In cells, membrane ordering and fluidity are commonly measured using the solvatochromic dye Laurdan, whose fluorescence is sensitive to lipid packing. As a general lipophilic dye, Laurdan stains all hydrophobic environments in cells; therefore, it is challenging to characterize membrane properties in specific organelles or assess their responses to pharmacological treatments in intact cells. Here, we describe the synthesis and application of Laurdan-derived probes that read out the membrane packing of individual cellular organelles. The set of organelle-targeted Laurdans (OTL) localizes to the ER, mitochondria, lysosomes, and Golgi compartments with high specificity while retaining the spectral resolution needed to detect biological changes in membrane ordering. We show that ratiometric imaging with OTLs can resolve membrane heterogeneity within organelles as well as changes in lipid packing resulting from inhibition of trafficking or bioenergetic processes. We apply these probes to characterize organelle-specific responses to saturated lipid stress. While the ER and lysosomal membrane fluidity is sensitive to exogenous saturated fatty acids, that of mitochondrial membranes is protected. We then use differences in ER membrane fluidity to sort populations of cells based on their fatty acid diet, highlighting the ability of organelle-localized solvatochromic probes to distinguish between cells based on their metabolic state. These results expand the repertoire of targeted membrane probes and demonstrate their application in interrogating lipid dysregulation.


Assuntos
2-Naftilamina , Lauratos , Fluidez de Membrana , Organelas , Humanos , Lauratos/química , Lauratos/farmacologia , 2-Naftilamina/análogos & derivados , 2-Naftilamina/química , Fluidez de Membrana/efeitos dos fármacos , Organelas/metabolismo , Organelas/efeitos dos fármacos , Corantes Fluorescentes/química , Ácidos Graxos/metabolismo , Lisossomos/metabolismo , Lisossomos/efeitos dos fármacos , Membranas Intracelulares/metabolismo , Membranas Intracelulares/efeitos dos fármacos , Mitocôndrias/metabolismo , Mitocôndrias/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/efeitos dos fármacos
10.
Nat Commun ; 15(1): 5388, 2024 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-38918376

RESUMO

Heparan sulfate (HS) is degraded in lysosome by a series of glycosidases. Before the glycosidases can act, the terminal glucosamine of HS must be acetylated by the integral lysosomal membrane enzyme heparan-α-glucosaminide N-acetyltransferase (HGSNAT). Mutations of HGSNAT cause HS accumulation and consequently mucopolysaccharidosis IIIC, a devastating lysosomal storage disease characterized by progressive neurological deterioration and early death where no treatment is available. HGSNAT catalyzes a unique transmembrane acetylation reaction where the acetyl group of cytosolic acetyl-CoA is transported across the lysosomal membrane and attached to HS in one reaction. However, the reaction mechanism remains elusive. Here we report six cryo-EM structures of HGSNAT along the reaction pathway. These structures reveal a dimer arrangement and a unique structural fold, which enables the elucidation of the reaction mechanism. We find that a central pore within each monomer traverses the membrane and controls access of cytosolic acetyl-CoA to the active site at its luminal mouth where glucosamine binds. A histidine-aspartic acid catalytic dyad catalyzes the transfer reaction via a ternary complex mechanism. Furthermore, the structures allow the mapping of disease-causing variants and reveal their potential impact on the function, thus creating a framework to guide structure-based drug discovery efforts.


Assuntos
Acetiltransferases , Microscopia Crioeletrônica , Lisossomos , Mucopolissacaridose III , Mucopolissacaridose III/genética , Mucopolissacaridose III/metabolismo , Mucopolissacaridose III/enzimologia , Humanos , Lisossomos/metabolismo , Lisossomos/enzimologia , Acetiltransferases/metabolismo , Acetiltransferases/química , Acetiltransferases/genética , Domínio Catalítico , Mutação , Heparitina Sulfato/metabolismo , Acetilcoenzima A/metabolismo , Acetilcoenzima A/química , Modelos Moleculares , Glucosamina/metabolismo , Glucosamina/química , Acetilação , Membranas Intracelulares/metabolismo
11.
Nat Commun ; 15(1): 5157, 2024 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-38886340

RESUMO

The eukaryotic asparagine (N)-linked glycan is pre-assembled as a fourteen-sugar oligosaccharide on a lipid carrier in the endoplasmic reticulum (ER). Seven sugars are first added to dolichol pyrophosphate (PP-Dol) on the cytoplasmic face of the ER, generating Man5GlcNAc2-PP-Dol (M5GN2-PP-Dol). M5GN2-PP-Dol is then flipped across the bilayer into the lumen by an ER translocator. Genetic studies identified Rft1 as the M5GN2-PP-Dol flippase in vivo but are at odds with biochemical data suggesting Rft1 is dispensable for flipping in vitro. Thus, the question of whether Rft1 plays a direct or an indirect role during M5GN2-PP-Dol translocation has been controversial for over two decades. We describe a completely reconstituted in vitro assay for M5GN2-PP-Dol translocation and demonstrate that purified Rft1 catalyzes the translocation of M5GN2-PP-Dol across the lipid bilayer. These data, combined with in vitro results demonstrating substrate selectivity and rft1∆ phenotypes, confirm the molecular identity of Rft1 as the M5GN2-PP-Dol ER flippase.


Assuntos
Retículo Endoplasmático , Retículo Endoplasmático/metabolismo , Proteínas de Saccharomyces cerevisiae/metabolismo , Proteínas de Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Saccharomyces cerevisiae/genética , Transporte Biológico , Oligossacarídeos/metabolismo , Fosfatos de Dolicol/metabolismo , Fosfatos de Dolicol/genética , Bicamadas Lipídicas/metabolismo , Proteínas de Transferência de Fosfolipídeos/metabolismo , Proteínas de Transferência de Fosfolipídeos/genética , Membranas Intracelulares/metabolismo , Lipopolissacarídeos
12.
Proc Natl Acad Sci U S A ; 121(22): e2321167121, 2024 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-38776370

RESUMO

C-terminal Domain Nuclear Envelope Phosphatase 1 (CTDNEP1) is a noncanonical protein serine/threonine phosphatase that has a conserved role in regulating ER membrane biogenesis. Inactivating mutations in CTDNEP1 correlate with the development of medulloblastoma, an aggressive childhood cancer. The transmembrane protein Nuclear Envelope Phosphatase 1 Regulatory Subunit 1 (NEP1R1) binds CTDNEP1, but the molecular details by which NEP1R1 regulates CTDNEP1 function are unclear. Here, we find that knockdown of NEP1R1 generates identical phenotypes to reported loss of CTDNEP1 in mammalian cells, establishing CTDNEP1-NEP1R1 as an evolutionarily conserved membrane protein phosphatase complex that restricts ER expansion. Mechanistically, NEP1R1 acts as an activating regulatory subunit that directly binds and increases the phosphatase activity of CTDNEP1. By defining a minimal NEP1R1 domain sufficient to activate CTDNEP1, we determine high-resolution crystal structures of the CTDNEP1-NEP1R1 complex bound to a peptide sequence acting as a pseudosubstrate. Structurally, NEP1R1 engages CTDNEP1 at a site distant from the active site to stabilize and allosterically activate CTDNEP1. Substrate recognition is facilitated by a conserved Arg residue in CTDNEP1 that binds and orients the substrate peptide in the active site. Together, this reveals mechanisms for how NEP1R1 regulates CTDNEP1 and explains how cancer-associated mutations inactivate CTDNEP1.


Assuntos
Retículo Endoplasmático , Humanos , Cristalografia por Raios X , Retículo Endoplasmático/metabolismo , Membranas Intracelulares/metabolismo , Proteínas de Membrana/metabolismo , Proteínas de Membrana/genética , Proteínas de Membrana/química , Fosfoproteínas Fosfatases/metabolismo , Fosfoproteínas Fosfatases/genética , Fosfoproteínas Fosfatases/química , Ligação Proteica
13.
Proc Natl Acad Sci U S A ; 121(22): e2315690121, 2024 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-38781206

RESUMO

The prion-like spread of protein aggregates is a leading hypothesis for the propagation of neurofibrillary lesions in the brain, including the spread of tau inclusions associated with Alzheimer's disease. The mechanisms of cellular uptake of tau seeds and subsequent nucleated polymerization of cytosolic tau are major questions in the field, and the potential for coupling between the entry and nucleation mechanisms has been little explored. We found that in primary astrocytes and neurons, endocytosis of tau seeds leads to their accumulation in lysosomes. This in turn leads to lysosomal swelling, deacidification, and recruitment of ESCRT proteins, but not Galectin-3, to the lysosomal membrane. These observations are consistent with nanoscale damage of the lysosomal membrane. Live cell imaging and STORM superresolution microscopy further show that the nucleation of cytosolic tau occurs primarily at the lysosome membrane under these conditions. These data suggest that tau seeds escape from lysosomes via nanoscale damage rather than wholesale rupture and that nucleation of cytosolic tau commences as soon as tau fibril ends emerge from the lysosomal membrane.


Assuntos
Citosol , Lisossomos , Proteínas tau , Proteínas tau/metabolismo , Lisossomos/metabolismo , Citosol/metabolismo , Animais , Astrócitos/metabolismo , Astrócitos/patologia , Neurônios/metabolismo , Neurônios/patologia , Humanos , Membranas Intracelulares/metabolismo , Endocitose , Camundongos , Células Cultivadas
14.
Proc Natl Acad Sci U S A ; 121(22): e2318412121, 2024 May 28.
Artigo em Inglês | MEDLINE | ID: mdl-38781205

RESUMO

Lysosomes are central players in cellular catabolism, signaling, and metabolic regulation. Cellular and environmental stresses that damage lysosomal membranes can compromise their function and release toxic content into the cytoplasm. Here, we examine how cells respond to osmotic stress within lysosomes. Using sensitive assays of lysosomal leakage and rupture, we examine acute effects of the osmotic disruptant glycyl-L-phenylalanine 2-naphthylamide (GPN). Our findings reveal that low concentrations of GPN rupture a small fraction of lysosomes, but surprisingly trigger Ca2+ release from nearly all. Chelating cytoplasmic Ca2+ makes lysosomes more sensitive to GPN-induced rupture, suggesting a role for Ca2+ in lysosomal membrane resilience. GPN-elicited Ca2+ release causes the Ca2+-sensor Apoptosis Linked Gene-2 (ALG-2), along with Endosomal Sorting Complex Required for Transport (ESCRT) proteins it interacts with, to redistribute onto lysosomes. Functionally, ALG-2, but not its ESCRT binding-disabled ΔGF122 splice variant, increases lysosomal resilience to osmotic stress. Importantly, elevating juxta-lysosomal Ca2+ without membrane damage by activating TRPML1 also recruits ALG-2 and ESCRTs, protecting lysosomes from subsequent osmotic rupture. These findings reveal that Ca2+, through ALG-2, helps bring ESCRTs to lysosomes to enhance their resilience and maintain organelle integrity in the face of osmotic stress.


Assuntos
Cálcio , Complexos Endossomais de Distribuição Requeridos para Transporte , Lisossomos , Pressão Osmótica , Lisossomos/metabolismo , Humanos , Cálcio/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte/genética , Membranas Intracelulares/metabolismo , Células HeLa , Canais de Potencial de Receptor Transitório/metabolismo , Canais de Potencial de Receptor Transitório/genética , Proteínas de Ligação ao Cálcio , Proteínas Reguladoras de Apoptose
15.
Biochem Soc Trans ; 52(3): 1233-1241, 2024 Jun 26.
Artigo em Inglês | MEDLINE | ID: mdl-38747700

RESUMO

PROPPINs constitute a conserved protein family with multiple members being expressed in many eukaryotes. PROPPINs have mainly been investigated for their role in autophagy, where they co-operate with several core factors for autophagosome formation. Recently, novel functions of these proteins on endo-lysosomal compartments have emerged. PROPPINs support the division of these organelles and the formation of tubulo-vesicular cargo carriers that mediate protein exit from them, such as those generated by the Retromer coat. In both cases, PROPPINs provide membrane fission activity. Integrating information from yeast and human cells this review summarizes the most important molecular features that allow these proteins to facilitate membrane fission and thus provide a critical element to endo-lysosomal protein traffic.


Assuntos
Autofagia , Endossomos , Lisossomos , Humanos , Lisossomos/metabolismo , Autofagia/fisiologia , Endossomos/metabolismo , Animais , Transporte Proteico , Membranas Intracelulares/metabolismo
16.
Exp Neurol ; 377: 114807, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38704082

RESUMO

Repeated sevoflurane exposure in neonatal mice can leads to neuronal apoptosis and mitochondrial dysfunction. The mitochondria are responsible for energy production to maintain homeostasis in the central nervous system. The mitochondria-associated endoplasmic reticulum membrane (MAM) is located between the mitochondria and endoplasmic reticulum (ER), and it is critical for mitochondrial function and cell survival. MAM malfunction contributes to neurodegeneration, however, whether it is involved in sevoflurane-induced neurotoxicity remains unknown. Our study demonstrated that repeated sevoflurane exposure induced mitochondrial dysfunction and dampened the MAM structure. The upregulated ER-mitochondria tethering enhanced Ca2+ transition from the cytosol to the mitochondria. Overload of mitochondrial Ca2+ contributed to opening of the mitochondrial permeability transition pore (mPTP), which caused neuronal apoptosis. Mitofusin 2(Mfn2), a key regulator of ER-mitochondria contacts, was found to be suppressed after repeated sevoflurane exposure, while restoration of Mfn2 expression alleviated cognitive dysfunction due to repeated sevoflurane exposure in the adult mice. These evidences suggest that sevoflurane-induced MAM malfunction is vulnerable to Mfn2 suppression, and the enhanced ER-mitochondria contacts promotes mitochondrial Ca2+ overload, contributing to mPTP opening and neuronal apoptosis. This paper sheds light on a novel mechanism of sevoflurane-induced neurotoxicity. Furthermore, targeting Mfn2-mediated regulation of the MAM structure and mitochondrial function may provide a therapeutic advantage in sevoflurane-induced neurodegeneration.


Assuntos
Retículo Endoplasmático , GTP Fosfo-Hidrolases , Mitocôndrias , Sevoflurano , Animais , Sevoflurano/toxicidade , Sevoflurano/farmacologia , GTP Fosfo-Hidrolases/metabolismo , Camundongos , Retículo Endoplasmático/efeitos dos fármacos , Retículo Endoplasmático/metabolismo , Mitocôndrias/efeitos dos fármacos , Mitocôndrias/metabolismo , Camundongos Endogâmicos C57BL , Apoptose/efeitos dos fármacos , Anestésicos Inalatórios/toxicidade , Anestésicos Inalatórios/farmacologia , Masculino , Cálcio/metabolismo , Membranas Intracelulares/efeitos dos fármacos , Membranas Intracelulares/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/metabolismo , Proteínas de Transporte da Membrana Mitocondrial/efeitos dos fármacos
17.
Nat Commun ; 15(1): 3767, 2024 May 04.
Artigo em Inglês | MEDLINE | ID: mdl-38704407

RESUMO

Tools for accessing and studying organelles remain underdeveloped. Here, we present a method by which giant organelle vesicles (GOVs) are generated by submitting cells to a hypotonic medium followed by plasma membrane breakage. By this means, GOVs ranging from 3 to over 10 µm become available for micromanipulation. GOVs are made from organelles such as the endoplasmic reticulum, endosomes, lysosomes and mitochondria, or in contact with one another such as giant mitochondria-associated ER membrane vesicles. We measure the mechanical properties of each organelle-derived GOV and find that they have distinct properties. In GOVs procured from Cos7 cells, for example, bending rigidities tend to increase from the endoplasmic reticulum to the plasma membrane. We also found that the mechanical properties of giant endoplasmic reticulum vesicles (GERVs) vary depending on their interactions with other organelles or the metabolic state of the cell. Lastly, we demonstrate GERVs' biochemical activity through their capacity to synthesize triglycerides and assemble lipid droplets. These findings underscore the potential of GOVs as valuable tools for studying the biophysics and biology of organelles.


Assuntos
Retículo Endoplasmático , Membranas Intracelulares , Animais , Chlorocebus aethiops , Células COS , Retículo Endoplasmático/metabolismo , Membranas Intracelulares/metabolismo , Membrana Celular/metabolismo , Mitocôndrias/metabolismo , Organelas/metabolismo , Gotículas Lipídicas/metabolismo , Triglicerídeos/metabolismo , Humanos , Lisossomos/metabolismo
18.
Autophagy ; 20(9): 2000-2016, 2024 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-38762757

RESUMO

Bleomycin exhibits effective chemotherapeutic activity against multiple types of tumors, and also induces various side effects, such as pulmonary fibrosis and neuronal defects, which limit the clinical application of this drug. Macroautophagy/autophagy has been recently reported to be involved in the functions of bleomycin, and yet the mechanisms of their crosstalk remain insufficiently understood. Here, we demonstrated that reactive oxygen species (ROS) produced during bleomycin activation hampered autophagy flux by inducing lysosomal membrane permeabilization (LMP) and obstructing lysosomal degradation. Exhaustion of ROS with N-acetylcysteine relieved LMP and autophagy defects. Notably, we observed that LMP and autophagy blockage preceded the emergence of cellular senescence during bleomycin treatment. In addition, promoting or inhibiting autophagy-lysosome degradation alleviated or exacerbated the phenotypes of senescence, respectively. This suggests the alternation of autophagy activity is more a regulatory mechanism than a consequence of bleomycin-induced cellular senescence. Taken together, we reveal a specific role of bleomycin-induced ROS in mediating defects of autophagic degradation and further regulating cellular senescence in vitro and in vivo. Our findings, conversely, indicate the autophagy-lysosome degradation pathway as a target for modulating the functions of bleomycin. These provide a new perspective for optimizing bleomycin as a clinically applicable chemotherapeutics devoid of severe side-effects.Abbreviations: AT2 cells: type II alveolar epithelial cells; ATG7: autophagy related 7; bEnd.3: mouse brain microvascular endothelial cells; BNIP3L: BCL2/adenovirus E1B interacting protein 3-like; CCL2: C-C motif chemokine ligand 2; CDKN1A: cyclin dependent kinase inhibitor 1A; CDKN2A: cyclin dependent kinase inhibitor 2A; FTH1: ferritin heavy polypeptide 1; γ-H2AX: phosphorylated H2A.X variant histone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HUVEC: human umbilical vein endothelial cells; HT22: hippocampal neuronal cell lines; Il: interleukin; LAMP: lysosomal-associated membrane protein; LMP: lysosome membrane permeabilization; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NCOA4: nuclear receptor coactivator 4; PI3K: phosphoinositide 3-kinase; ROS: reactive oxygen species; RPS6KB/S6K: ribosomal protein S6 kinase; SA-GLB1/ß-gal: senescence-associated galactosidase, beta 1; SAHF: senescence-associated heterochromatic foci; SASP: senescence-associated secretory phenotype; SEC62: SEC62 homolog, preprotein translocation; SEP: superecliptic pHluorin; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB.


Assuntos
Autofagia , Bleomicina , Senescência Celular , Lisossomos , Espécies Reativas de Oxigênio , Bleomicina/farmacologia , Senescência Celular/efeitos dos fármacos , Espécies Reativas de Oxigênio/metabolismo , Lisossomos/metabolismo , Lisossomos/efeitos dos fármacos , Autofagia/efeitos dos fármacos , Autofagia/fisiologia , Animais , Humanos , Camundongos , Membranas Intracelulares/metabolismo , Membranas Intracelulares/efeitos dos fármacos , Permeabilidade/efeitos dos fármacos , Camundongos Endogâmicos C57BL
19.
Nat Commun ; 15(1): 4025, 2024 May 13.
Artigo em Inglês | MEDLINE | ID: mdl-38740804

RESUMO

Intracellular membranes composing organelles of eukaryotes include membrane proteins playing crucial roles in physiological functions. However, a comprehensive understanding of the cellular responses triggered by intracellular membrane-focused oxidative stress remains elusive. Herein, we report an amphiphilic photocatalyst localised in intracellular membranes to damage membrane proteins oxidatively, resulting in non-canonical pyroptosis. Our developed photocatalysis generates hydroxyl radicals and hydrogen peroxides via water oxidation, which is accelerated under hypoxia. Single-molecule magnetic tweezers reveal that photocatalysis-induced oxidation markedly destabilised membrane protein folding. In cell environment, label-free quantification reveals that oxidative damage occurs primarily in membrane proteins related to protein quality control, thereby aggravating mitochondrial and endoplasmic reticulum stress and inducing lytic cell death. Notably, the photocatalysis activates non-canonical inflammasome caspases, resulting in gasdermin D cleavage to its pore-forming fragment and subsequent pyroptosis. These findings suggest that the oxidation of intracellular membrane proteins triggers non-canonical pyroptosis.


Assuntos
Inflamassomos , Proteínas de Membrana , Oxirredução , Piroptose , Humanos , Inflamassomos/metabolismo , Proteínas de Membrana/metabolismo , Estresse Oxidativo , Catálise , Estresse do Retículo Endoplasmático , Peróxido de Hidrogênio/metabolismo , Proteínas de Ligação a Fosfato/metabolismo , Radical Hidroxila/metabolismo , Mitocôndrias/metabolismo , Membranas Intracelulares/metabolismo , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Camundongos , Animais , Processos Fotoquímicos , Dobramento de Proteína , Caspases/metabolismo , Gasderminas
20.
Artigo em Inglês | MEDLINE | ID: mdl-38488191

RESUMO

Lysosomes play a central role in biochemical signal transduction and oxidative stress in cells. Inducing lysosome membrane penetration (LMP) to cause lysosomal-dependent cell death (LCD) in tumor cells is an effective strategy for cancer therapy. Chemical drugs can destroy the stability of lysosomes by neutralizing protons within the lysosomes or enhancing the fragility of the lysosomal membranes. However, there remain several unsolved problems of traditional drugs in LMP induction due to insufficient lysosomal targeting, fast metabolism, and toxicity in normal cells. With the development of nanotechnology, magnetic nanoparticles have been demonstrated to target lysosomes naturally, providing a versatile tool for lysosomal modulation. Combined with excellent tissue penetration and spatiotemporal manipulability of magnetic fields, magnetic modulation of lysosomes progresses rapidly in inducing LMP and LCD for cancer therapy. This review comprehensively discussed the strategies of magnetic modulation of lysosomes for cancer therapy. The intrinsic mechanisms of LMP-induced LCD were first introduced. Then, the modulation of lysosomes by diverse physical outputs of magnetic fields was emphatically discussed. Looking forward, this review will shed the light on the prospect of magnetic modulation of lysosomes, inspiring future research of magnetic modulation strategy in cancer therapy. This article is categorized under: Therapeutic Approaches and Drug Discovery > Emerging Technologies Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.


Assuntos
Membranas Intracelulares , Neoplasias , Humanos , Morte Celular/fisiologia , Membranas Intracelulares/metabolismo , Lisossomos/metabolismo , Neoplasias/tratamento farmacológico , Neoplasias/metabolismo , Fenômenos Magnéticos
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