Autophagy reports最新文献

Autophagy in the osteoblast lineage is essential for bone formation and skeletal homeostasis, yet the mechanisms through which it supports bone formation remain unclear. To investigate these mechanisms and evaluate the anabolic potential of autophagy stimulation, we generated a genetic mouse model in which transcription factor EB (Tfeb), a master regulator of autophagy and lysosomal biogenesis, was elevated specifically in osteoblast-lineage cells. Tfeb elevation increased the expression of autophagy and lysosomal genes and enhanced autophagic flux in osteoblasts. Stimulation of autophagy increased bone formation in both cortical and cancellous bone compartments, leading to gains in bone mass and strength. Single-cell RNA sequencing revealed reduced osteoblast apoptosis, suggesting improved cell survival as a contributor to the observed increase in osteoblast number. Our ex vivo studies also suggest that autophagy stimulation increases proliferation of osteoblats lineage cells. In addition to increasing osteoblast number, Tfeb elevation also enhanced osteoblast function, likely by increasing transcription and translation of extracellular bone matrix components. Taken together, these findings demonstrate that elevation of Tfeb in the osteoblast lineage cells stimulates autophagy, promotes bone formation, and leads to increased bone mass and strength, supporting further investigation of TFEB or autophagy activation as a potential therapeutic strategy for osteoporosis.

Acyl-CoA synthetase long-chain (ACSL) catalyzes the conversion of fatty acids into acyl-CoA, which is used for neutral lipid and phospholipid synthesis. Previous studies revealed that yeast Faa1 and mammalian ACSL4 play a crucial role in phagophore expansion by locally synthesizing phospholipids. We found that another member of ACSL protein family, ACSL3, which is involved in lipid droplet biogenesis under energy-rich conditions and is regulated by SYNTAXIN17, also participates in autophagosome formation, but in a different manner. Knockdown of ACSL3 suppressed punctum formation of early autophagosomal marker proteins such as FIP200 and WIPI2 in starved cells, generating nonfunctional multi-membrane autophagosome-like structures. In contrast, ACSL4 suppression blocked autophagosome formation without affecting punctum formation of early autophagosomal marker proteins. Mechanistic analysis revealed that ACSL3 functions independently of its enzymatic activity, while catalytic activity of ACSL4 is required for autophagosome formation as well as LC3 (known as MAP1LC3 proteins) protein lipidation. Furthermore, ACSL3 has been shown to be essential for lipid droplet biogenesis during starvation. These findings establish ACSL3 as a key player in two events in early autophagy: formation of autophagosomes and lipid droplets.

Autophagy is a cellular process to clear unwanted and dysfunctional cellular cargoes, which are sequestered in autophagosomes before their delivery to lysosomes for degradation. Autophagy cargo selection, mediated by cargo receptors, varies across cell types and conditions. Understanding the cargo features is essential for elucidating autophagy's function in specific physiological or pathological contexts. Here, we present a simple and rapid method for isolating LC3B-positive autophagosomes from the tissues of GFP-LC3 transgenic mice, a widely used autophagy reporter model, without relying on the complex ultracentrifugation steps required by traditional methods. When combined with quantitative proteomics, this approach enables efficient in vivo characterization of autophagy cargoes. We applied this method to establish autophagy cargo profiles in skeletal muscle during starvation and exercise, two physiological conditions that activate autophagy, and identified distinct cargo selection patterns, with significantly higher levels of ER-phagy and ribophagy observed during starvation. We further revealed the ER-phagy receptors TEX264 and RETREG1/FAM134B as potential mediators of the elevated ER-phagy under starvation. In summary, we report an efficient workflow for in vivo autophagy cargo characterization and provide detailed analysis and comparison of cargo profiles under starvation and exercise conditions.

Cryptochrome 1 (CRY1) promotes photomorphogenesis primarily by inhibiting Constituttive photomorphogenic 1 (COP1)/Suppressor of PHYA-105 1 (SPA1)-mediated degradation of HY5 via the 26S proteasome degradation pathway. However, it remained unknown whether autophagy, a conserved vacuolar recycling process induced by nutrient starvation, also participates in blue light signaling. Our latest study reveals that in Arabidopsis thaliana, under nutrient starvation, Autophagy-related 8 (ATG8) binds and targets Elongated hypocotyl 5 (HY5) for vacuolar degradation in darkness, thereby promoting skotomorphogenesis. Upon blue-light activation, however, CRY1 binds to ATG8 and blocks its interaction with HY5, which in turn inhibits the autophagic degradation of HY5 and promotes photomorphogenesis. Our findings thus establish a direct photoreceptor - autophagy functional connection that integrates light and nutrient cues to govern developmental transitions in plants.

Chaperone-mediated autophagy (CMA) is a selective form of lysosomal protein degradation essential for cellular proteostasis. CMA is activated during cellular stress, such as starvation, and involves the chaperone protein HSC70 (HSPA8) recognizing substrates containing KFERQ-like motifs. However, the regulatory mechanisms governing CMA activation remain poorly understood. Here, we demonstrate that the NAD⁺ -dependent deacetylase SIRT2 promotes CMA activation by deacetylating HSC70 at lysine 557 (K557). Our findings reveal that SIRT2 activity is upregulated during starvation, enhancing its interaction with HSC70 and facilitating the deacetylation of K557. Deacetylation of HSC70 at K557 increases its binding affinity to CMA substrates, thereby promoting their lysosomal degradation. Mutation of K557 to a deacetylation-mimetic arginine (K557R) enhances CMA activity under both nutrient-rich and starvation conditions, while the acetylation-mimetic glutamine mutant (K557Q) impairs substrate binding and CMA activation. Furthermore, the inhibition or knockdown of SIRT2 reduces CMA activity, which is rescued by HSC70 K557R expression. These findings identify SIRT2-mediated deacetylation of HSC70 as a regulatory mechanism for CMA activation during nutrient deprivation and highlight the role of protein lysine acetylation in proteostasis. This study provides insights into the interplay between SIRT2, HSC70, and CMA, with potential implications for diseases linked to proteostasis dysregulation, including neurodegenerative disorders and cancer.

Membrane contact sites (MCS) between organelles maintain the proximity required for controlled exchange of small molecules and ions yet preventing fusion events that would compromise organelles' identity and integrity. Here, by investigating the intracellular fate of the disease-causing Z-variant of alpha1 antitrypsin (ATZ), we report on a novel function of MCS between the endoplasmic reticulum (ER) and RAB7/LAMP1-positive endolysosomes in ER-to-lysosome-associated degradation (ERLAD). For this function, the VAPA:ORP1L:RAB7 multi-protein complex forming MCS between the ER and endolysosomes engages, in an ERLAD client-driven manner, the misfolded protein segregation complex formed by the lectin chaperone calnexin (CNX), the ER-phagy receptor FAM134B, and the ubiquitin-like protein LC3. Generation of this supramolecular complex facilitates the membrane fusion events regulated by the SNARE proteins STX17 and VAMP8 that ensure efficient delivery of ATZ polymers from their site of generation, the ER, to the site of their intracellular clearance, the degradative RAB7/LAMP1-positive endolysosomes.

Emerging evidence suggests that the propagation of α-synuclein pathology underlies the progression of Parkinson's disease and supports the hypothesis that transmission of α-synuclein aggregates contributes to dopaminergic degeneration. Autophagy, a cellular degradation process, removes protein aggregates and damaged organelles and aids in α-synuclein clearance. However, fibrillar α-synuclein aggregates may evade and even disrupt autophagy, causing toxic spread. The role of autophagy may be multifaceted in the propagation of α-synuclein: clearing α-synuclein aggregates and damaged organelles (protective) versus the release of α-synuclein aggregates (harmful). Here we review how neuronal and glial autophagy regulate α-synuclein clearance and spreading. We also discuss the need for future research to address the interplay of autophagy and α-synuclein aggregates toward therapeutic development.

The systematic dissection of molecular mechanisms through which aerobic exercise (AE) mitigates neurodegenerative pathologies remains a significant challenge. Alzheimer's disease (AD) is characterized by impaired autophagy-lysosomal flux and the accumulation of amyloid-β (Aβ) and hyperphosphorylated tau. We recently identified the β2-adrenergic receptor (β2-AR) as a key mediator of exercise-induced bene = d sought to dissect its role in regulating distinct proteostatic pathways. We revealed that AE activates β2-AR signaling to promote lysosomal acidification via upregulation of VMA21, an essential assembly factor for the vacuolar ATPase (V-ATPase) proton pump, thereby facilitating Aβ clearance. Concurrently, AE enhanced autophagosome-lysosome fusion through the β2-AR - retinoid X receptor alpha (RXRα) - charged multivesicular body protein 4B (CHMP4B) axis, promoting tau degradation. Critically, pharmacological inhibition of β2-AR fully abolished these effects. Here, we propose an integrated mechanism through which β2-AR activation by AE could coordinate dual autophagy-lysosomal recovery processes and suggest that targeting this pathway offers a promising therapeutic strategy for AD and related proteostatic disorders.

The cardiovascular system, consisting of the heart and blood vessels, ensures delivery of oxygen and nutrient-rich blood throughout the whole body. The major cell types include cardiomyocytes, endothelial cells, and vascular smooth muscle cells. Dramatic consequences, sometimes with a deadly outcome, may arise when the activity of cardiovascular cells is compromised. The cardiomyocytes are terminally differentiated cells and thus do not normally regenerate. To sustain the high energy demand of the beating heart, the cardiomyocytes contain a high amount of energy producing mitochondria. Adaptation to metabolic demands is an integral part of cellular homeostasis and involves autophagy. Autophagy is an evolutionary conserved intracellular degradation pathway of cellular constituents. Mitophagy refers to selective degradation of damaged, and thus potentially harmful, mitochondria through autophagy. Both autophagy and mitophagy are widely implicated in physiological and pathological processes within cardiovascular cells. In this review, we highlight studies applying genetic modifications in mouse models to reveal the impact of autophagy and mitophagy on cardiovascular health and disease.

Upon demonstration that basal macroautophagy plays an essential role in maintaining protein homeostasis in the mammalian CNS, there has been excitement around modulating this form of autophagy as a therapeutic strategy to combat neurodegenerative disease. Nonetheless, the initial genetic studies that spawned this excitement did little to reveal the complex physiology of autophagy regulation in neural cells, or the predicament of compartment-specific events upon which these cells rely. Pursuit of therapeutic strategies further highlighted how this intricacy extends across the different organs of the body, raising question as to how we may harness the power of macroautophagy for good while minimizing the bad. Fortunately, since these early studies, the field has made significant gains toward understanding the molecular, cellular and physiological basis of macroautophagy. Together with technological advances, they have refueled the exploration into how this powerful pathway may provide the much-needed therapeutic advances for these yet untreatable diseases. In this review, we will contextualize the insights gained over the last decade with the traditional and novel strategies that have been explored to combat disease-associated events such as abnormal protein accumulation. In addition, we will discuss key considerations and strategies that can influence how a therapeutic approach might be designed.