Autophagy reports最新文献

Disrupted intestinal homeostasis and barrier function contribute to the development of diseases such as inflammatory bowel disease. BECLIN-1, a core component of two class III phosphatidylinositol 3 kinase complexes, has a dual role in autophagy and endocytic trafficking. Emerging evidence suggests that its endocytic trafficking function is essential for intestinal integrity. To investigate the fatal gastrointestinal phenotype observed in BECLIN-1 knockout mice, we used organoids derived from these animals to show that BECLIN-1 deletion disrupts the localization of CADHERIN1/ECADHERIN to adherens junctions and OCCLUDIN to tight junctions. Impaired cargo trafficking to the lysosome was also observed. Filamentous actin cytoskeleton also became disorganized though there were no changes in its spatial interaction with CATENIN BETA1/BETA-CATENIN nor in BETA-CATENIN localization. The trafficking defects were all less pronounced or absent in organoids lacking an autophagy-only regulator, ATG7, emphasizing BECLIN-1's trafficking role in maintaining gut homeostasis and barrier function. These findings advance our understanding of epithelial dysfunction and the mechanisms underlying intestinal diseases.

Ischemic brain injury occurs in many clinical settings, including stroke, cardiac arrest, hypovolemic shock, cardiac surgery, cerebral edema, and cerebral vasospasm. Decades of work have revealed many important mechanisms related to ischemic brain injury. However, there remain significant gaps in the scientific knowledge to reconcile many ischemic brain injury events. Brain ischemia leads to protein misfolding and aggregation, and damages almost all types of subcellular organelles including mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes, etc. Irreparably damaged organelles and insoluble protein aggregates are normally removed by autophagy. The build-up of common autophagic components, such as LC3, p62, and ubiquitinated proteins, are generally observed in brain tissue samples in animal models of both global and focal brain ischemia, but the interpretation of the role of these autophagy-related changes in ischemic brain injury in the literature has been controversial. Many pathological events or mechanisms underlying dysfunctional autophagy after brain ischemia remain unknown. This review aims to provide an update of the current knowledge and future research directions regarding the critical role of dysfunctional autophagy in ischemic brain injury.

Amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD) represent two extremes of a neurodegenerative disease spectrum characterised by overlapping genetic, clinical, and neuropathological features. This review covers the intricate relationship between both ALS and FTD and defects in the autophagy and endolysosomal pathway as recent evidence has pointed towards alterations in these pathways as being a root cause of disease pathogenesis. Here, we review the current knowledge on the interplay between ALS/FTD and lysosomebased proteostasis pathways and carefully asses the steps of the autophagy and endolysosomal pathways that are impaired by ALS or FTDcausing variants. Finally, we present a comprehensive overview of therapeutic strategies aimed at restoring autophagic and lysosomal function as potential avenues for mitigating the impact of these devastating diseases. Through this review, we aim to enhance the understanding of the pathophysiological mechanisms involving autophagy and/or the endolysosomal system that underlie the ALS-FTD spectrum and underscore the necessity for specific therapeutic approaches that target these shared vulnerabilities.

Tropheryma whipplei, the agent of Whipple's disease, is an intracellular pathogen that replicates in macrophages. The phagocytic and cellular processes leading to the formation of T. whipplei replicative vacuole remain poorly understood. Macrophage microbicidal activity is largely related to macro/autophagy which is also essential for cell homeostasis. Here, we show that T. whipplei uptake by macrophages involved LC3-associated phagocytosis (LAP). Bacteria then escaped into the cytosol from where they were recaptured by xenophagy. We also demonstrate that T. whipplei blocked the autophagic flux to build its replicative compartment. Inhibition of LAP resulted in the decrease of interleukin (IL)-10 secretion and the restoration of the autophagy flux, suggesting that modulation of autophagy during infection alters immune response and promote persistence. Our results provide new insight in the intracellular fate of the bacteria during macrophage infection and suggest the possible involvement of previously unknown virulence factors in T. whipplei infection.

In plants, a large part of the nutrients used to generate seed lipid and protein reserves is derived from both the degradation of macromolecules in source leaves and the transfer of small catabolic molecules like amino acids from the senescing leaves to the seeds. Studies of autophagy mutants in Arabidopsis showed that autophagy is a master player controlling 60% of the remobilization of nitrogen from senescing leaf tissues to developing seeds, and strongly impacting reserve deposition, especially in the protein to lipid ratio. Since autophagy is largely enhanced in leaves during senescence and in the seeds during maturation, we investigated the roles of autophagy in these sources and sink tissues, to identify checkpoints controlling seed filling and quality. Through gene complementation using tissue-specific promoters, we demonstrated that while autophagy regulates nitrogen flux to the seeds in source leaves, the autophagy taking place in seeds during their maturation is essential to reach the appropriate seed quality in terms of C and N storage. Overall, these results highlight the multiple roles of autophagy in the optimal development of the plant throughout its entire lifespan.

Pavarotti (Pav) and its binding partner Tumbleweed (Tum) are well known for their evolutionarily conserved roles in microtubule-dependent movements during cytokinesis. In post-mitotic pav RNAi muscles, we unexpectedly observed the accumulation of puncta marked by ubiquitin, p62, and Atg8a without an obvious disorganization of the microtubule network. Some of these autophagosomal structures clustered together and colocalized with mitochondria. The Pav-Tum complex was enriched in muscle nuclei, consistent with roles for Pav and Tum in nuclear envelope (NE) budding, an alternative pathway for the export of large ribonucleoproteins. One of the established cargoes of the Drosophila NE budding pathway, Marf mRNA, was indeed reduced in the myoplasm of pav RNAi muscles. Moreover, RNAi knockdown of Marf or the NE budding components Wash or Torsin also caused the clustering of p62-marked mitochondria. These data together define a model whereby blocking NE budding reduces mitochondrial activity and in turn recruits p62 and autophagic structures for a lysosomal fate.

RAB11FIP4 (RAB11 family interacting protein 4), a RAB11A (Ras-related protein Rab-11) effector protein downregulated in cystinosis, plays a crucial role in cellular trafficking. Reconstitution of RAB11FIP4 in cystinotic cells restores multiple cellular functions, including lysosomal trafficking, autophagy, and the endoplasmic reticulum stress response. These findings identify RAB11FIP4 as both a key player in cystinosis pathogenesis and a promising therapeutic target. The purpose of this punctum is to highlight how restoring RAB11FIP4 expression rescues cellular homeostasis in cystinosis through the regulation of trafficking pathways.

FABP3 and FABP7 are members of the fatty acid-binding protein (FABP) family that transport fatty acids to intracellular organelles, which are elevated in patients with Alzheimer disease (AD). However, their role in the disease pathogenesis remain poorly understood. In a Drosophila model of AD, neuronal fabp knockdown inhibited autophagic flux and increased amyloid-beta (Aβ) aggregation, exacerbating neurodegeneration. Conversely, fabp overexpression had the opposite effect and improved memory. The modulation of Ecdysone-induced protein 75B (Eip75B) levels, the Drosophila homolog of peroxisome proliferator-activated receptor, a lipid-activated nuclear receptor that functions as a transcription factor, affected the expression of autophagy-related genes and the role of fabp in Aβ pathology. These results suggest that fabp regulates Aβ pathology through autophagy by modulating Eip75B and highlight the importance of proper fatty acid transport in neurons for autophagy regulation and Aβ pathogenesis.

Glycogen is a primary cellular energy store in numerous eukaryotes. Its biosynthesis is a main strategy to cope with forthcoming starvation. During starvation, glycogen is processed in the cytosol or delivered for degradation to animal lysosomes or yeast vacuoles by macroautophagy (hereafter autophagy). However, the mechanism of glycogen autophagy is poorly understood, especially in the heart and skeletal muscles that suffer from the lysosomal glycogen accumulation in Pompe disease. We recently developed the Komagataella phaffii yeast as a simple model to study glycogen autophagy and found that this pathway proceeds non-selectively. However, studies in Saccharomyces cerevisiae proposed glycogen as a non-preferred cargo of bulk autophagy. In our latest study with new fluorescent reporters for glycogen, we clarified cargo properties of K. phaffii glycogen. Both homologous and heterologous markers of glycogen are delivered to the vacuole and degraded with efficiencies that are independent of glycogen, suggesting that glycogen is a neutral cargo of bulk autophagy. This work provides insights into the evolutionary diversity of glycogen autophagy in yeasts with implications for understanding this process in complex eukaryotes.

Macrophages act to defend against infection, but can fail to completely prevent bacterial replication and dissemination in an immunocompetent host. Recent studies have shown that activation of a host transcription factor, TFEB, a regulator of lysosomal biogenesis, could restrict intramacrophage replication of the human pathogen Mycobacterium tuberculosis and synergize with suboptimal levels of the antibiotic rifampin to reduce bacterial loads. Currently available small molecule TFEB activators lack selectivity and potency, but could be potentially useful in a variety of pathological conditions with suboptimal lysosomal activity. TFEB nuclear translocation and activation depend on its phosphorylation status which is controlled by multiple cellular pathways. We devised a whole cell, high throughput screening assay to identify small molecules that activate TFEB by establishing a stably transfected HEK293T reporter cell line for ATF4, a basic leucine zipper transcription factor induced by stress response and activated in parallel to TFEB. We optimized its use in vitro using compounds that target endoplasmic reticulum stress and intracellular calcium signaling. We report results from screening the commercially available LOPAC library and the Selleck Chemicals library modified to include only FDA-approved drugs and clinical research compounds. We identified twenty-one compounds across six clinical use categories that activate ATF4, and confirmed that two proteasome inhibitors promote TFEB activation. The results of this study provide an assay that could be used to screen for small molecules that activate ATF4 and TFEB and a potential list of compounds identified as activators of the ATF4 transcription factor in response to cellular stress.