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1.
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
2.
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
3.
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
4.
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
5.
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
6.
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
7.
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
8.
Physiol Rev ; 104(3): 1335-1385, 2024 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-38451235

RESUMO

The endomembrane system consists of organellar membranes in the biosynthetic pathway [endoplasmic reticulum (ER), Golgi apparatus, and secretory vesicles] as well as those in the degradative pathway (early endosomes, macropinosomes, phagosomes, autophagosomes, late endosomes, and lysosomes). These endomembrane organelles/vesicles work together to synthesize, modify, package, transport, and degrade proteins, carbohydrates, and lipids, regulating the balance between cellular anabolism and catabolism. Large ion concentration gradients exist across endomembranes: Ca2+ gradients for most endomembrane organelles and H+ gradients for the acidic compartments. Ion (Na+, K+, H+, Ca2+, and Cl-) channels on the organellar membranes control ion flux in response to cellular cues, allowing rapid informational exchange between the cytosol and organelle lumen. Recent advances in organelle proteomics, organellar electrophysiology, and luminal and juxtaorganellar ion imaging have led to molecular identification and functional characterization of about two dozen endomembrane ion channels. For example, whereas IP3R1-3 channels mediate Ca2+ release from the ER in response to neurotransmitter and hormone stimulation, TRPML1-3 and TMEM175 channels mediate lysosomal Ca2+ and H+ release, respectively, in response to nutritional and trafficking cues. This review aims to summarize the current understanding of these endomembrane channels, with a focus on their subcellular localizations, ion permeation properties, gating mechanisms, cell biological functions, and disease relevance.


Assuntos
Canais Iônicos , Humanos , Animais , Canais Iônicos/metabolismo , Membranas Intracelulares/metabolismo , Organelas/metabolismo , Organelas/fisiologia
9.
Commun Biol ; 7(1): 334, 2024 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-38491121

RESUMO

VPS37A, an ESCRT-I complex component, is required for recruiting a subset of ESCRT proteins to the phagophore for autophagosome closure. However, the mechanism by which VPS37A is targeted to the phagophore remains obscure. Here, we demonstrate that the VPS37A N-terminal domain exhibits selective interactions with highly curved membranes, mediated by two membrane-interacting motifs within the disordered regions surrounding its Ubiquitin E2 variant-like (UEVL) domain. Site-directed mutations of residues in these motifs disrupt ESCRT-I localization to the phagophore and result in defective phagophore closure and compromised autophagic flux in vivo, highlighting their essential role during autophagy. In conjunction with the UEVL domain, we postulate that these motifs guide a functional assembly of the ESCRT machinery at the highly curved tip of the phagophore for autophagosome closure. These results advance the notion that the distinctive membrane architecture of the cup-shaped phagophore spatially regulates autophagosome biogenesis.


Assuntos
Autofagossomos , Autofagia , Autofagossomos/metabolismo , Autofagia/fisiologia , Membranas Intracelulares/metabolismo , Endossomos/metabolismo , Complexos Endossomais de Distribuição Requeridos para Transporte/genética , Complexos Endossomais de Distribuição Requeridos para Transporte/metabolismo
10.
Mol Biol Cell ; 35(5): ar70, 2024 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-38536415

RESUMO

Lysosome turnover and biogenesis are induced in response to treatment of cells with agents that cause membrane rupture, but whether other stress conditions engage similar homeostatic mechanisms is not well understood. Recently we described a form of selective turnover of lysosomes that is induced by metabolic stress or by treatment of cells with ionophores or lysosomotropic agents, involving the formation of intraluminal vesicles within intact organelles through microautophagy. Selective turnover involves noncanonical autophagy and the lipidation of LC3 onto lysosomal membranes, as well as the autophagy gene-dependent formation of intraluminal vesicles. Here, we find a form of microautophagy induction that requires activity of the lipid kinase PIKfyve and is associated with the nuclear translocation of TFEB, a known mediator of lysosome biogenesis. We show that LC3 undergoes turnover during this process, and that PIKfyve is required for the formation of intraluminal vesicles and LC3 turnover, but not for LC3 lipidation onto lysosomal membranes, demonstrating that microautophagy is regulated by PIKfyve downstream of noncanonical autophagy. We further show that TFEB activation requires noncanonical autophagy but not PIKfyve, distinguishing the regulation of biogenesis from microautophagy occurring in response to agents that induce lysosomal stress.


Assuntos
Lisossomos , Microautofagia , Autofagia , Fatores de Transcrição de Zíper de Leucina e Hélice-Alça-Hélix Básicos , Membranas Intracelulares/metabolismo , Ionóforos , Lisossomos/metabolismo , Humanos , Linhagem Celular Tumoral
11.
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
12.
Cells ; 13(5)2024 Mar 05.
Artigo em Inglês | MEDLINE | ID: mdl-38474423

RESUMO

Although it has been known for decades that lysosomes are central for degradation and recycling in the cell, their pivotal role as nutrient sensing signaling hubs has recently become of central interest. Since lysosomes are highly dynamic and in constant change regarding content and intracellular position, fusion/fission events allow communication between organelles in the cell, as well as cell-to-cell communication via exocytosis of lysosomal content and release of extracellular vesicles. Lysosomes also mediate different forms of regulated cell death by permeabilization of the lysosomal membrane and release of their content to the cytosol. In cancer cells, lysosomal biogenesis and autophagy are increased to support the increased metabolism and allow growth even under nutrient- and oxygen-poor conditions. Tumor cells also induce exocytosis of lysosomal content to the extracellular space to promote invasion and metastasis. However, due to the enhanced lysosomal function, cancer cells are often more susceptible to lysosomal membrane permeabilization, providing an alternative strategy to induce cell death. This review summarizes the current knowledge of cancer-associated alterations in lysosomal structure and function and illustrates how lysosomal exocytosis and release of extracellular vesicles affect disease progression. We focus on functional differences depending on lysosomal localization and the regulation of intracellular transport, and lastly provide insight how new therapeutic strategies can exploit the power of the lysosome and improve cancer treatment.


Assuntos
Membranas Intracelulares , Neoplasias , Humanos , Membranas Intracelulares/metabolismo , Morte Celular , Neoplasias/metabolismo , Transdução de Sinais , Lisossomos/metabolismo
13.
PLoS Pathog ; 20(3): e1012085, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38484009

RESUMO

Elaborate viral replication organelles (VROs) are formed to support positive-strand RNA virus replication in infected cells. VRO formation requires subversion of intracellular membranes by viral replication proteins. Here, we showed that the key ATG8f autophagy protein and NBR1 selective autophagy receptor were co-opted by Tomato bushy stunt virus (TBSV) and the closely-related carnation Italian ringspot virus. Knockdown of ATG8f or NBR1 in plants led to reduced tombusvirus replication, suggesting pro-viral function for selective autophagy. BiFC and proximity-labeling experiments showed that the TBSV p33 replication protein interacted with ATG8f and NBR1 to recruit them to VROs. In addition, we observed that several core autophagy proteins, such as ATG1a, ATG4, ATG5, ATG101 and the plant-specific SH3P2 autophagy adaptor proteins were also re-localized to TBSV VROs, suggesting that TBSV hijacks the autophagy machinery in plant cells. We demonstrated that subversion of autophagy components facilitated the recruitment of VPS34 PI3 kinase and enrichment of phospholipids, such as phosphatidylethanolamine and PI3P phosphoinositide in the VRO membranes. Hijacking of autophagy components into TBSV VROs led to inhibition of autophagic flux. We also found that a fraction of the subverted ATG8f and NBR1 was sequestered in biomolecular condensates associated with VROs. We propose that the VRO-associated condensates trap those autophagy proteins, taking them away from the autophagy pathway. Overall, tombusviruses hijack selective autophagy to provide phospholipid-rich membranes for replication and to regulate the antiviral autophagic flux.


Assuntos
Tombusvirus , Tombusvirus/fisiologia , Saccharomyces cerevisiae/genética , Membranas Intracelulares/metabolismo , Replicação Viral/fisiologia , Fosfolipídeos/metabolismo , Proteínas Virais/genética , Proteínas Virais/metabolismo , Autofagia , Organelas/metabolismo , RNA Viral/genética
14.
Methods Mol Biol ; 2776: 151-159, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38502502

RESUMO

The outer and the inner membranes of the chloroplast envelope, also called OEM and IEM, have distinct lipid and protein compositions. They host molecular systems involved in the biogenesis of the organelle, its cellular function, and its communication with other compartments. Here we describe a method for the isolation of these two membranes starting from intact chloroplast preparations, with two alternative procedures based on the starting material. One was developed from spinach leaves, the other from pea leaves. The two procedures differ in the method used to isolate and rupture chloroplasts and separate each membrane.


Assuntos
Membranas Intracelulares , Magnoliopsida , Membranas Intracelulares/metabolismo , Magnoliopsida/metabolismo , Cloroplastos/metabolismo , Proteínas de Membrana/metabolismo
15.
Mol Cell ; 84(8): 1556-1569.e10, 2024 Apr 18.
Artigo em Inglês | MEDLINE | ID: mdl-38503285

RESUMO

Cells respond to lysosomal membrane permeabilization by membrane repair or selective macroautophagy of damaged lysosomes, termed lysophagy, but it is not fully understood how this decision is made. Here, we uncover a pathway in human cells that detects lipid bilayer perturbations in the limiting membrane of compromised lysosomes, which fail to be repaired, and then initiates ubiquitin-triggered lysophagy. We find that SPG20 binds the repair factor IST1 on damaged lysosomes and, importantly, integrates that with the detection of damage-associated lipid-packing defects of the lysosomal membrane. Detection occurs via sensory amphipathic helices in SPG20 before rupture of the membrane. If lipid-packing defects are extensive, such as during lipid peroxidation, SPG20 recruits and activates ITCH, which marks the damaged lysosome with lysine-63-linked ubiquitin chains to initiate lysophagy and thus triages the lysosome for destruction. With SPG20 being linked to neurodegeneration, these findings highlight the relevance of a coordinated lysosomal damage response for cellular homeostasis.


Assuntos
Lisossomos , Macroautofagia , Humanos , Autofagia/fisiologia , Membranas Intracelulares/metabolismo , Lipídeos , Lisossomos/metabolismo , Ubiquitina/genética , Ubiquitina/metabolismo
16.
Proc Natl Acad Sci U S A ; 121(9): e2318046121, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38386713

RESUMO

Apoptosis linked Gene-2 (ALG-2) is a multifunctional intracellular Ca2+ sensor and the archetypal member of the penta-EF hand protein family. ALG-2 functions in the repair of damage to both the plasma and lysosome membranes and in COPII-dependent budding at endoplasmic reticulum exit sites (ERES). In the presence of Ca2+, ALG-2 binds to ESCRT-I and ALIX in membrane repair and to SEC31A at ERES. ALG-2 also binds directly to acidic membranes in the presence of Ca2+ by a combination of electrostatic and hydrophobic interactions. By combining giant unilamellar vesicle-based experiments and molecular dynamics simulations, we show that charge-reversed mutants of ALG-2 at these locations disrupt membrane recruitment. ALG-2 membrane binding mutants have reduced or abrogated ERES localization in response to Thapsigargin-induced Ca2+ release but still localize to lysosomes following lysosomal Ca2+ release. In vitro reconstitution shows that the ALG-2 membrane-binding defect can be rescued by binding to ESCRT-I. These data thus reveal the nature of direct Ca2+-dependent membrane binding and its interplay with Ca2+-dependent protein binding in the cellular functions of ALG-2.


Assuntos
Fenômenos Fisiológicos Celulares , Membranas Intracelulares , Membranas , Divisão Celular , Complexos Endossomais de Distribuição Requeridos para Transporte/genética
17.
ACS Nano ; 18(8): 6186-6201, 2024 Feb 27.
Artigo em Inglês | MEDLINE | ID: mdl-38346399

RESUMO

Endocytosis is a major bottleneck toward cytosolic delivery of nucleic acids, as the vast majority of nucleic acid drugs remain trapped within endosomes. Current trends to overcome endosomal entrapment and subsequent degradation provide varied success; however, active delivery agents such as cell-penetrating peptides have emerged as a prominent strategy to improve cytosolic delivery. Yet, these membrane-active agents have poor selectivity for endosomal membranes, leading to toxicity. A hallmark of endosomes is their acidic environment, which aids in degradation of foreign materials. Here, we develop a pH-triggered spherical nucleic acid that provides smart antisense oligonucleotide (ASO) release upon endosomal acidification and selective membrane disruption, termed DNA EndosomaL Escape Vehicle Response (DELVR). We anchor i-Motif DNA to a nanoparticle (AuNP), where the complement strand contains both an ASO sequence and a functionalized endosomal escape peptide (EEP). By orienting the EEP toward the AuNP core, the EEP is inactive until it is released through acidification-induced i-Motif folding. In this study, we characterize a small library of i-Motif duplexes to develop a structure-switching nucleic acid sequence triggered by endosomal acidification. We evaluate antisense efficacy using HIF1a, a hypoxic indicator upregulated in many cancers, and demonstrate dose-dependent activity through RT-qPCR. We show that DELVR significantly improves ASO efficacy in vitro. Finally, we use fluorescence lifetime imaging and activity measurement to show that DELVR benefits synergistically from nuclease- and pH-driven release strategies with increased ASO endosomal escape efficiency. Overall, this study develops a modular platform that improves the cytosolic delivery of nucleic acid therapeutics and offers key insights for overcoming intracellular barriers.


Assuntos
Ácidos Nucleicos , Ácidos Nucleicos/metabolismo , Endossomos/química , Endocitose/fisiologia , Membranas Intracelulares , DNA/metabolismo
18.
Nature ; 627(8003): 445-452, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38383785

RESUMO

Reversible modification of target proteins by ubiquitin and ubiquitin-like proteins (UBLs) is widely used by eukaryotic cells to control protein fate and cell behaviour1. UFM1 is a UBL that predominantly modifies a single lysine residue on a single ribosomal protein, uL24 (also called RPL26), on ribosomes at the cytoplasmic surface of the endoplasmic reticulum (ER)2,3. UFM1 conjugation (UFMylation) facilitates the rescue of 60S ribosomal subunits (60S) that are released after ribosome-associated quality-control-mediated splitting of ribosomes that stall during co-translational translocation of secretory proteins into the ER3,4. Neither the molecular mechanism by which the UFMylation machinery achieves such precise target selection nor how this ribosomal modification promotes 60S rescue is known. Here we show that ribosome UFMylation in vivo occurs on free 60S and we present sequential cryo-electron microscopy snapshots of the heterotrimeric UFM1 E3 ligase (E3(UFM1)) engaging its substrate uL24. E3(UFM1) binds the L1 stalk, empty transfer RNA-binding sites and the peptidyl transferase centre through carboxy-terminal domains of UFL1, which results in uL24 modification more than 150 Å away. After catalysing UFM1 transfer, E3(UFM1) remains stably bound to its product, UFMylated 60S, forming a C-shaped clamp that extends all the way around the 60S from the transfer RNA-binding sites to the polypeptide tunnel exit. Our structural and biochemical analyses suggest a role for E3(UFM1) in post-termination release and recycling of the large ribosomal subunit from the ER membrane.


Assuntos
Retículo Endoplasmático , Processamento de Proteína Pós-Traducional , Subunidades Ribossômicas Maiores de Eucariotos , Ubiquitina-Proteína Ligases , Sítios de Ligação , Biocatálise , Microscopia Crioeletrônica , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Membranas Intracelulares/química , Membranas Intracelulares/metabolismo , Membranas Intracelulares/ultraestrutura , Peptidil Transferases/química , Peptidil Transferases/metabolismo , Peptidil Transferases/ultraestrutura , Ligação Proteica , Proteínas Ribossômicas/química , Proteínas Ribossômicas/metabolismo , Proteínas Ribossômicas/ultraestrutura , Subunidades Ribossômicas Maiores de Eucariotos/química , Subunidades Ribossômicas Maiores de Eucariotos/metabolismo , Subunidades Ribossômicas Maiores de Eucariotos/ultraestrutura , RNA de Transferência/metabolismo , Especificidade por Substrato , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/ultraestrutura
19.
Nature ; 627(8003): 437-444, 2024 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-38383789

RESUMO

Stalled ribosomes at the endoplasmic reticulum (ER) are covalently modified with the ubiquitin-like protein UFM1 on the 60S ribosomal subunit protein RPL26 (also known as uL24)1,2. This modification, which is known as UFMylation, is orchestrated by the UFM1 ribosome E3 ligase (UREL) complex, comprising UFL1, UFBP1 and CDK5RAP3 (ref. 3). However, the catalytic mechanism of UREL and the functional consequences of UFMylation are unclear. Here we present cryo-electron microscopy structures of UREL bound to 60S ribosomes, revealing the basis of its substrate specificity. UREL wraps around the 60S subunit to form a C-shaped clamp architecture that blocks the tRNA-binding sites at one end, and the peptide exit tunnel at the other. A UFL1 loop inserts into and remodels the peptidyl transferase centre. These features of UREL suggest a crucial function for UFMylation in the release and recycling of stalled or terminated ribosomes from the ER membrane. In the absence of functional UREL, 60S-SEC61 translocon complexes accumulate at the ER membrane, demonstrating that UFMylation is necessary for releasing SEC61 from 60S subunits. Notably, this release is facilitated by a functional switch of UREL from a 'writer' to a 'reader' module that recognizes its product-UFMylated 60S ribosomes. Collectively, we identify a fundamental role for UREL in dissociating 60S subunits from the SEC61 translocon and the basis for UFMylation in regulating protein homeostasis at the ER.


Assuntos
Retículo Endoplasmático , Processamento de Proteína Pós-Traducional , Subunidades Ribossômicas Maiores de Eucariotos , Ubiquitina-Proteína Ligases , Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Sítios de Ligação , Proteínas de Ciclo Celular/química , Proteínas de Ciclo Celular/metabolismo , Proteínas de Ciclo Celular/ultraestrutura , Microscopia Crioeletrônica , Retículo Endoplasmático/metabolismo , Retículo Endoplasmático/ultraestrutura , Homeostase , Membranas Intracelulares/metabolismo , Peptidil Transferases/química , Peptidil Transferases/metabolismo , Peptidil Transferases/ultraestrutura , Proteínas Ribossômicas/química , Proteínas Ribossômicas/metabolismo , Proteínas Ribossômicas/ultraestrutura , RNA de Transferência/metabolismo , Canais de Translocação SEC/química , Canais de Translocação SEC/metabolismo , Canais de Translocação SEC/ultraestrutura , Proteínas Supressoras de Tumor/química , Proteínas Supressoras de Tumor/metabolismo , Proteínas Supressoras de Tumor/ultraestrutura , Ubiquitina-Proteína Ligases/química , Ubiquitina-Proteína Ligases/metabolismo , Ubiquitina-Proteína Ligases/ultraestrutura , Subunidades Ribossômicas Maiores de Eucariotos/química , Subunidades Ribossômicas Maiores de Eucariotos/metabolismo , Subunidades Ribossômicas Maiores de Eucariotos/ultraestrutura
20.
Elife ; 132024 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-38240316

RESUMO

Lysosomes are active sites to integrate cellular metabolism and signal transduction. A collection of proteins associated with the lysosome mediate these metabolic and signaling functions. Both lysosomal metabolism and lysosomal signaling have been linked to longevity regulation; however, how lysosomes adjust their protein composition to accommodate this regulation remains unclear. Using deep proteomic profiling, we systemically profiled lysosome-associated proteins linked with four different longevity mechanisms. We discovered the lysosomal recruitment of AMP-activated protein kinase and nucleoporin proteins and their requirements for longevity in response to increased lysosomal lipolysis. Through comparative proteomic analyses of lysosomes from different tissues and labeled with different markers, we further elucidated lysosomal heterogeneity across tissues as well as the increased enrichment of the Ragulator complex on Cystinosin-positive lysosomes. Together, this work uncovers lysosomal proteome heterogeneity across multiple scales and provides resources for understanding the contribution of lysosomal protein dynamics to signal transduction, organelle crosstalk, and organism longevity.


Assuntos
Lisossomos , Proteômica , Lisossomos/metabolismo , Membranas Intracelulares/metabolismo , Proteoma/metabolismo , Transdução de Sinais
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