Autophagy最新文献

Apoptotic bodies (ABs) are a type of extracellular vesicles (EVs) that could contribute to the paracrine effect of stem cells. However, their potential in treating cardiovascular diseases is largely unexplored. This study investigated the therapeutic effects of ABs derived from human umbilical cord mesenchymal stem cells (MSCs) on cardiac recovery in a porcine model of myocardial infarction (MI). In vitro, ABs reduced apoptosis and cytotoxicity in cardiomyocytes under oxygen and glucose deprivation (OGD) conditions and enhanced the capacity of migration and tube formation in endothelial cells. In vivo, akin to MSCs, administration of ABs improved contractile function, reduced infarct size, and mitigated adverse remodeling in pig hearts with MI, concomitantly with increased cardiomyocyte survival and angiogenesis. These cardioprotective effects were mediated through the regulation of autophagy by activating the adenosine monophosphate - activated protein kinase (AMPK) and transcription factor EB (TFEB) signaling pathways. microRNAs contained in ABs were sequenced, revealing that let-7f-5p was the most abundant. let-7f-5p promoted AMPK phosphorylation by targeting protein phosphatase 2 regulatory subunit B alpha (PPP2R2A) and decreased TFEB phosphorylation by targeting MAP4K3 to regulate autophagy, thereby contributing to the effects of ABs. Overall, these findings indicate that MSC-derived ABs have the potential to be a promising and effective acellular therapeutic option for treating MI.

Cells maintain organelle integrity and metabolic balance through tightly coordinated quality control systems. Autophagy plays a central role by recycling damaged and unnecessary cellular components, with selective pathways providing specificity through dedicated receptors. Although OPTN is well-established as a receptor for mitophagy, aggrephagy, and xenophagy, its role in pexophagy, the selective autophagic degradation of peroxisomes, has only recently been recognized. Our recent work identifies the peroxisomal membrane protein PEX14 as a critical docking platform for OPTN, enabling recruitment of autophagic machinery and initiation of pexophagy. How PEX14 engages OPTN, what triggers this interaction, and how it drives the autophagic engulfment of peroxisomes remain unclear. In this punctum, we contextualize our findings and highlight unresolved questions that must be addressed to understand the physiological and pathological relevance of this process.

Reticulophagy, a selective macroautophagy/autophagy process targeting endoplasmic reticulum fragments via receptors, plays a critical role in cellular homeostasis. This study reveals that CCPG1, a reticulophagy receptor, drives bladder cancer (BLCA) tumorigenesis and confers cisplatin resistance. We observed elevated reticulophagy activity in BLCA cells compared to normal counterparts, particularly under conditions of nutrient stress. CCPG1 expression was significantly upregulated in BLCA patient samples and correlated with poor prognosis. Functional studies demonstrated that CCPG1 knockdown suppressed reticulophagy, leading to decreased cell proliferation and increased apoptosis. Conversely, overexpression of the wild-type CCPG1, but not a MAP1LC3/LC3-binding-deficient variant, rescued reticulophagy and promoted tumor growth. Notably, we found that cisplatin treatment inhibited reticulophagy by downregulating CCPG1 expression through the ATM-CHEK2/Chk2 signaling pathway. CCPG1 knockdown synergistically enhanced cisplatin cytotoxicity to BLCA cells, while CCPG1 overexpression conferred resistance. These findings highlight CCPG1-mediated reticulophagy as a driver of BLCA progression and as a potential prognostic biomarker and therapeutic target.

Mitophagy is essential for eliminating dysfunctional mitochondria and is closely implicated in the immune evasion of several pathogens, including S. typhimurium. However, the specific mechanisms regarding the interaction between S. typhimurium and host cells in relation to mitophagy and xenophagy and their contribution to pathogen survival are unclear. Herein, using both in vitro and in vivo systems, we found that S. typhimurium escaped host innate immunity by repressing mitophagy and xenophagy to facilitate its intracellular replication. Moreover, we identified a novel xenophagy modulator, fisetin that could activate mitophagy to restrict intracellular S. typhimurium replication in RAW264.7 and bone marrow-derived macrophages, which was abolished by mitophagy inhibitor Mdivi-1. RNA-Seq transcriptome and metabolomics analysis demonstrated the effectiveness of fisetin in alleviating S. typhimurium infection. Confocal microscopy analysis revealed that fisetin-induced mitophagy promoted xenophagy, whereas inhibiting mitophagy repressed xenophagy and facilitated the survival of S. typhimurium. Our study further demonstrates that fisetin-induced mitophagy requires the recruitment of phosphorylation of TBK1 to mitochondria, which is a protein implicated in mitophagy and xenophagy. Additionally, fisetin improved the body weight loss, relative spleen, kidney, and liver weights, hepatic damage, and S. typhimurium load, all of which were abrogated by Mdivi-1 or Pink1 siRNA treatment in S. typhimurium-infected mice. Collectively, our results suggest that S. typhimurium induces mitochondrial damage whilst inhibiting mitophagy, while fisetin promotes xenophagy and restrains S. typhimurium survival by facilitating PINK1-PRKN-mediated mitophagy and p-TBK1 mitochondrial recruitment. Fisetin proves effective as a xenophagy enhancer in reducing intracellular Salmonella burden.Abbreviations: BafA1: bafilomycin A₁; BMDM: mouse bone marrow-derived macrophage; CFU: colony-forming units; LAMP2: lysosomal-associated membrane protein 2; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; LDH: lactate dehydrogenase; Mdivi-1: mitochondrial division inhibitor 1; OPTN: optineurin; PBS, phosphate-buffered saline; PINK1: PTEN induced putative kinase 1; siRNA: interfering RNA; SQSTM1/p62: sequestosome 1; S. typhimurium: Salmonella enterica serovar typhimurium; T3SS: type III secretion system 1; TBK1: TANK-binding kinase 1.

The conjugation of mammalian Atg8 (ATG8)-family proteins to membrane components is a fundamental process in membrane ATG8ylation (lipidation). While membrane ATG8ylation is well-characterized, protein ATG8ylation, the direct conjugation of ATG8 to cellular proteins, remains enigmatic. In this study, we demonstrate that protein ATG8ylation depends exclusively on ATG4, ATG3, and ATG7. We discovered that the core macroautophagy/autophagy E1 enzyme ATG7 serves a dual role: it is not only the essential E1 enzyme for protein ATG8ylation but also a key substrate. We determined that ATG7 K140 is the modification site and show that protein ATG8ylation of ATG7 forms a mono-LC3B conjugate. We demonstrated that this self-modification creates a negative-feedback loop by hindering the ATG7-ATG3 interaction, thereby attenuating autophagic flux. Our findings redefine ATG7 as a central player and regulator in the protein ATG8ylation cascade, revealing a new mechanism of autophagy regulation.Abbreviation: ATG: autophagy related; GABARAP: GABA type A receptor-associated protein; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; PE: phosphatidylethanolamine; ULK1: unc-51 like autophagy activating kinase 1.

Endoplasmic reticulum (ER) exit sites (ERES) serve as essential hubs for the packaging and export of secretory proteins into the COPII vesicular pathway. Previous studies have shown that ERES are dynamic and capable of adapting to stress, but the molecular details controlling their degradation under nutrient-stress conditions were largely unknown. A recent study by Liao et al. introduces a new mechanism in which ERES are degraded through lysosome-dependent microautophagy in response to nutrient stress. This process is uniquely facilitated by COPII components, the calcium-binding adaptor ALG2, and the ESCRT machinery. The authors demonstrate that inhibiting MTOR triggers calcium release from lysosomes, which then recruits ALG2, leading to SEC31 ubiquitination and subsequently promoting PDCD6IP/ALIX-ESCRT-dependent lysosomal engulfment of ERES. This research reveals an unexplored pathway for the quality control and recycling of secretory machinery, thereby improving our understanding of ER turnover and establishing a mechanistic link between nutrient sensing, autophagy, and remodeling of the secretory pathway.

Autophagosome formation is catalyzed by multiple branches of Atg protein machineries, calling for the existence of a master regulator to coordinate their distinct activities. A prime candidate of such a regulator is Atg8. This protein has a well-established role in controlling phagophore expansion. But the signaling mechanism has been unclear. Our recent work demonstrates that Atg8 recruits activated Atg1 to the phagophore, together forming such a master switch. Our data indicate that different branches of Atg proteins localize to spatially separated zones. The physical distances among the zones, at times exceeding 250 nm, would limit signal transduction efficiency if a signaling molecule were exclusively localized to a single zone. By covering the phagophore surface, Atg8 maintains physical proximity to different Atg machineries, and transmits a permissive signal by recruiting activated Atg1. Compromising Atg8-mediated Atg1 recruitment leads to confinement of Atg1 to the initiation protein condensate and failure of phagophore expansion. Conversely, the Atg8-Atg1 switch can be manually augmented to substantially increase autophagosome size and autophagic flux. Our work thus reveals a critical regulatory circuit of macroautophagy/autophagy that is built on the spatial organization of Atg protein machineries.

Ferritinophagy is a selective form of macroautophagy/autophagy that mediates the degradation of ferritin complexes, releasing stored iron, and maintaining intracellular iron homeostasis. Proper regulation of ferritinophagy is essential for cellular adaptation to metabolic stress, whereas dysregulation disrupts iron balance and contributes to pathological processes. Excessive ferritinophagy leads to iron overload and reactive oxygen species accumulation, driving oxidative stress, ferroptosis, and inflammation, which are key contributors to cellular injury and progressive organ dysfunction. Despite advances in our understanding of autophagy and ferroptosis, the specific role of ferritinophagy in organ-specific injury remains unclear. In this review, we provide a comprehensive overview of the molecular mechanisms of ferritinophagy and critically examine its emerging roles in the pathogenesis of injuries to the heart, liver, lungs, and kidneys. We further highlight the therapeutic potential of targeting ferritinophagy and propose future research directions aimed at harnessing this pathway for the treatment of organ injuries.Abbreviations: 3-MA: 3-methyladenine; ACO1/IRP1: aconitase 1; AKI: acute kidney injury; ARDS: acute respiratory distress syndrome; ATG: autophagy related; BECN1: beclin 1; CARM1/PRMT4: coactivator associated arginine methyltransferase 1; CIRBP: cold inducible RNA binding protein; CKD: chronic kidney disease; COPD: chronic obstructive pulmonary disease; ELAVL1: ELAV like RNA binding protein 1; Fer-1: ferrostatin-1; FTH1: ferritin heavy chain 1; GABARAP: GABA type A receptor-associated protein; GPX4: glutathione peroxidase 4; HAMP/hepcidin: hepcidin antimicrobial peptide; HCC: hepatocellular carcinoma; HERC2: HECT and RLD domain containing E3 ubiquitin protein ligase 2; HSCs: hepatic stellate cells; IL13: interleukin 13; IL6: interleukin 6; I/R: ischemia-reperfusion; IRE: iron-responsive element; IREB2/IRP2: iron responsive element binding protein 2; LPS: lipopolysaccharide; MAP1LC3/LC3: microtubule associated protein 1 light chain 3; MDA: malondialdehyde; MIOX: myo-inositol oxygenase; NCOA4: nuclear receptor coactivator 4; NFE2L2/Nrf2: NFE2 like bZIP transcription factor 2; ROS: reactive oxygen species; SIRT1: sirtuin 1; SLC40A1/ferroportin: solute carrier family 40 member 1; STAT3: signal transducer and activator of transcription 3; STEAP3: STEAP3 metalloreductase; TFRC/TfR1: transferrin receptor; USP11: ubiquitin specific peptidase 11; YAP1: Yes1 associated transcriptional regulator.

Rheumatoid arthritis (RA) is characterized by synovitis and joint destruction, with macrophages playing a crucial role in pathogenesis. Macroautophagy/autophagy is essential for cellular homeostasis and has been implicated in RA, but its role in macrophage polarization remains unclear. This study aimed to investigate the expression of autophagy-related molecules and macrophage phenotypes in RA synovium. Synovial tissues from patients with RA were analyzed and compared with samples of osteoarthritis (OA) and less-inflammatory synovium (LIS) obtained at immediate surgery for hip fracture. Synovitis severity was histologically assessed, and cellular ultrastructure was examined via electron microscopy. Immunohistochemistry, western blot, and flow cytometry were used to analyze autophagy-related molecules and macrophage phenotypes. RA synovium exhibited significant inflammation, with macrophage-like synovial cells and intimal macrophages showing abundant autophagy-related structures in comparison to those of OA and LIS. Autophagy markers, BECN1 (beclin 1), WIPI2, ATG5, ATG16L1, LC3B, ATG3, SQSTM1, and LAMP1, were highly expressed in CD68⁺ macrophages but less in CD248/TEM-1⁺ fibroblasts. Western blot confirmed higher levels of autophagy-related proteins in RA synovial tissue compared with OA and LIS. Macrophage polarization analysis identified M1-like (NOS2⁺/iNOS⁺, CD86⁺), M2-like (CD163⁺, MRC1/CD206⁺, MERTK⁺), and M1/M2-like (CD86⁺ MRC1⁺ NOS2⁺ CD163⁺) populations. M1/M2-like macrophages showed the highest autophagy-related molecule expression. Autophagy is strongly associated with macrophage polarization in RA synovium. M1/M2-like macrophages, highly enriched in autophagy markers, may play an anti-inflammatory role in modulating inflammation and tissue repair. These findings suggest a potential autophagy-mediated regulatory mechanism in RA macrophage function.Abbreviations: ATG: autophagy related; BECN1: beclin 1; IL: interleukin; LAMP1: lysosomal associated membrane protein 1; LIS: less-inflammatory synovium; MAP1LC3/LC3: microtubule sssociated protein 1 light chain 3; MFI: mean fluorescence intensity; OA: osteoarthritis; PG: phagophore; RA: rheumatoid arthritis. SQSTM1: sequestosome 1; TNF: tumor necrosis factor; WIPI2: WD repeat domain, phosphoinositide interacting 2.