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At least 289 records · Page 16Linked to original sources
PubMed2026

KLF5 promotes proliferation, migration, and autophagy-/EMT‑associated molecular changes in lens epithelial cells via transcriptional activation of THBS1 in traumatic cataract.

PURPOSE: Traumatic cataract is a common blinding eye disease after ocular trauma, and its pathogenesis is closely related to lens epithelial cell dysfunction, while the definite molecular regulatory mechanism between upstream transcription factor and downstream target gene remains poorly clarified. This study aimed to clarify the role and molecular mechanism of the krüppel-like factor 5 (KLF5)/ thrombosponin 1 (THBS1) axis in regulating proliferation, migration, epithelial-mesenchymal transition and autophagy of lens epithelial cells in traumatic cataract, and to explore its potential clinical therapeutic value. METHODS: The GSE295383 dataset in the gene expression omnibus (GEO) database was downloaded, and the differentially expressed genes (DEGs) were screened by linear models for microarray data (limma) package of R language. Combined with Weighted gene co-expression network analysis (WGCNA), the gene co-expression network was constructed and the key modules were screened. Gene ontology (GO), kyoto encyclopedia of genes and genomes (KEGG) and gene set enrichment analysis (GSEA) combined with human transcription factor target (hTFtarget) and JASPAR databases were used to predict the upstream transcription factors of THBS1. Subsequently, SRA01/04 cells were induced with transforming growth factor-beta 2 (TGF-β2) to construct a cataract cell model. RESULTS: THBS1 and KLF5 were highly expressed in LECs exposed to TGF-β2. KLF5 could activate THBS1 transcription by binding to THBS1 promoter - 174 to -165 sites. Knockdown of THBS1 inhibited TGF-β2-induced viability, proliferation, migration, and altered the expression of epithelial-mesenchymal transition (EMT)- and autophagy-related markers in LECs. Knockdown of KLF5 downregulated THBS1 expression and produced a similar inhibitory effect, while overexpression of THBS1 reversed the effect of KLF5 knockdown. CONCLUSIONS: This study demonstrated that KLF5 promoted the proliferation, migration, and EMT‑associated molecular changes of LECs in traumatic cataract through transcriptional activation of THBS1, and regulated the expression of autophagy‑related markers in LECs, suggesting that KLF5/THBS1 axis might be a potential target for the treatment of traumatic cataract.

Cataract↗
PubMed2006

Cellular autophagy machinery is not required for vaccinia virus replication and maturation.

The origin of the primary membrane of the vaccinia virus, a double-membrane structure that surrounds the immature virions (IV), is not fully understood. Here we investigated whether the primary membrane originates from the autophagic membrane. Morphologic studies by electron microscopy (EM) showed no apparent difference in viral maturation in the autophagy-deficient cell lines, the atg5(-/-) mouse embryonic fibroblasts (MEFs) and the beclin1(-/-) embryonic stem (ES) cells, compared to their isogenic wild-type counterparts. Moreover, viral growth curves demonstrated that vaccinia viruses replicate and mature in the autophagy-deficient cell lines as efficiently as they do in their isogenic wild type counterpart cells. This study indicates that the cellular autophagy machinery is not required for the life-cycle of vaccinia virus, suggesting that the primary vaccinia viral membrane does not originate from the autophagic membrane.

Animals↗
PubMed2006

Deletion of HOG1 leads to Osmosensitivity in starvation-induced, but not rapamycin-dependent Atg8 degradation and proteolysis: further evidence for different regulatory mechanisms in yeast autophagy.

The mechanisms of regulation of autophagy are still obscure. In mammalian liver, starvation-induced autophagic proteolysis is regulated by the cellular hydration state in a microtubule- and p38(MAPK)-dependent way. Recent work shows that in yeast, loss of Hog1, the yeast orthologue of p38(MAPK), leads to osmosensitivity of starvation-induced autophagy (Prick et al., Biochem J 2006; 394:153-161), pointing to an evolutionarily conserved mechanism. In this addendum further experiments from hog1Delta yeast cells are shown, which support the hypothesis that starvation- and rapamycin-induced autophagy processes differ in their susceptibility to osmotic stress. The potential mechanisms are discussed.

Animals↗
PubMed2006

Autophagy and neurodegeneration.

The proteasome and lysosome are sophisticated apparatuses capable of shredding unnecessary proteins in eukaryotic cells. The proteasome and its partner ubiquitin (which functions as a destination signal for proteolysis) play crucial roles in selective breakdown of not only short-lived regulatory proteins but also abnormal proteins that need to be rapidly eliminated from the cells. It is generally accepted that deficits of the proteasome-ubiquitin system are associated with various neurodegenerative diseases, since ubiquitin-positive inclusions frequently appear in neurons of patients and mice models of neurodegenerative diseases. However, investigators working in the field of neuronal diseases have focused their attention in recent years on autophagy (Greek for "the eating of oneself") following the recent discovery that ablation of autophagy leads to accumulation of ubiquitin-positive inclusions, which are the pathological hallmark of neurodegenerative diseases. Here we discuss the consequences of autophagy deficiency in neurons.

Animals↗
PubMed2007

Atg26 is not involved in autophagy-related pathways in Saccharomyces cerevisiae.

Autophagy is a degradative pathway conserved among eukaryotes. It is a major route for degradation of long-lived proteins and entire organelles, such as peroxisomes. Atg26, a sterol glucosyltransferase, is specifically required for micro- and macropexophagy, but not for starvation-induced bulk autophagy in Pichia pastoris. Here we study the requirement of Saccharomyces cerevisiae Atg26 in the Cvt pathway, nonspecific autophagy and pexophagy. Our results show that the S. cerevisiae atg26Delta strain is not defective in prApe1 maturation, macroautophagy or peroxisome degradation, in contrast to the situation seen in Pichia pastoris. These studies highlight the importance of examining mutants in multiple organisms.

Autophagy↗
PubMed2007

Permeases recycle amino acids resulting from autophagy.

Autophagy is a major survival mechanism for eukaryotes to recycle cellular nutrients during stress conditions (such as nutrient limitation, or the accumulation of damaged organelles). We recently revealed a molecular mechanism by which Atg22 recycles amino acids to link the degradative and recycling functions of autophagy. Atg22 is not directly required for autophagic body breakdown, in contrast to previously reported data. Instead, we found that Atg22, Avt3 and Avt4 are partially redundant vacuolar effluxers, which mediate the efflux of leucine and other amino acids resulting from autophagy.

Amino Acid Transport Systems↗
PubMed2006

Tryptamine induces cell death with ultrastructural features of autophagy in neurons and glia: Possible relevance for neurodegenerative disorders.

Tryptamine derivatives are a family of biogenic amines that have been suggested to be modulators of brain function at physiological concentrations. However, pharmacological concentrations of these amines display amphetamine-like properties, and they seem to play a role in brain disorders. Amphetamines induce autophagy in nerve cells, and this type of cell death has also been involved in neurodegenerative diseases. In the present work, we clearly demonstrate for the very first time that high concentrations of tryptamine (0.1-1 mM) induce autophagy in HT22 and SK-N-SH nerve cell lines and in primary cultures of astrocytes, glial cells being less sensitive than neurons. Ultrastructural cell morphology shows all of the typical hallmarks of autophagy. There is no nuclear chromatin condensation, endoplasmic reticulum and mitochondria are swollen, and a great number of double-membraned autophagosomes and residual bodies can be shown in the cytoplasm. Autophagosomes and residual bodies contain mitochondria, membranes, and vesicles and remain unabridged until the cell membrane is disrupted and the cell dies. The same results have been found when cells were incubated with high concentrations of 5-methoxytryptamine (0.1-1 mM). Our results establish a possible link between the role of tryptamine derivatives in brain disorders and the presence of autophagic cell death in these kinds of disorders.

Animals↗
PubMed2001

Steroid-triggered death by autophagy.

Programmed cell death is a critical part of normal development, removing obsolete tissues or cells and sculpting body parts to assume their appropriate form and function. Most programmed cell death occurs by apoptosis of individual cells or autophagy of groups of cells. Although these pathways have distinct morphological characteristics, they also have a number of features in common, suggesting some overlap in their regulation. A recent paper by Lee and Baehrecke provides further support for this proposal.(1) These authors present, for the first time, a genetic analysis of autophagy, using the steroid-triggered metamorphosis of Drosophila as a model system. They demonstrate a remarkable degree of overlap between the control of apoptosis and autophagy as well as a key role for the steroid-inducible gene E93 in directing the autophagic death response. This paper also shows that E93 can direct cell death independently from the known death-inducer genes, defining a novel death pathway in Drosophila.

Animals↗
PubMed2004

Glycogen autophagy.

Glycogen autophagy, which includes the sequestration and degradation of cell glycogen in the autophagic vacuoles, is a selective process under conditions of demand for the massive hepatic production of glucose, as in the postnatal period. It represents a link between autophagy and glycogen metabolism. The formation of autophagic vacuoles in the hepatocytes of newborn animals is spatially and biochemically related to the degradation of cell glycogen. Many molecular elements and signaling pathways including the cyclic AMP/cyclic AMP-dependent protein kinase and the phosphoinositides/TOR pathways are implicated in the control of this process. These two pathways may converge on the same target to regulate glycogen autophagy.

Animals↗
PubMed2005

The significance of autophagy in cancer.

Autophagy, a vacuolar process of cytoplasmic degradation, is implicated in a form of programmed cell death distinct from apoptosis. The regulation of autophagy is complex and signalling pathways such as the target of rapamycin (Tor) kinase pathway, play important roles in tumourigenesis. Beclin 1, an autophagic protein, has been found to be a tumour suppressor. Conversely, cancer cells may exploit autophagy as a means to adapt to hypoxic and nutrient-limiting environments. The relative importance of autophagic cell death and apoptosis in carcinogenesis remains to be established, and the Bcl-2 family of proteins may be instrumental in coordinating the two pathways of programmed cell death.

Animals↗
PubMed1999

Autophagy is activated by apoptotic signalling in sympathetic neurons: an alternative mechanism of death execution.

Autophagy is a mechanism whereby cells digest themselves from within and so may be used in lieu of apoptosis to execute cell death. Little is known about its role in neurons. In newly isolated sympathetic neurons, two independent apoptotic stimuli, NGF-deprivation or cytosine arabinoside added in the presence of NGF, caused a 30-fold increase in autophagic particle numbers, many autophagosomes appearing before any signs of DNA-fragmentation. The anti-autophagic drug 3-methyladenine also delayed apoptosis, its neuroprotection correlating with inhibition of cytochrome c release from mitochondria and prevention of caspase activation. In contrast, autophagic activity remained elevated in neurons treated with the pan-caspase inhibitor Boc-Asp(OMe)fmk, which inhibited morphological apoptosis but did not inhibit cytochrome c release nor prevent cell death. We propose that the same apoptotic signals that cause mitochondrial dysfunction also activate autophagy. Once activated, autophagy may mediate caspase-independent neuronal death.

Adenine↗
PubMed2000

Transport of proteins to the yeast vacuole: autophagy, cytoplasm-to-vacuole targeting, and role of the vacuole in degradation.

The vacuole/lysosome performs a central role in degradation. Proteins and organelles are transported to the vacuole by selective and non-selective pathways. Transport to the vacuole by autophagy is the primary mode for degradation of cytoplasmic constituents under starvation conditions. Autophagy overlaps mechanistically and genetically with a biosynthetic pathway termed Cvt (Cytoplasm-to-vacuole targeting) that operates under vegetative conditions to transport the resident vacuolar hydrolase aminopeptidase I (API). API import has been dissected to reveal the action of a novel mechanism that transports cargo within double-membrane vesicles. Recent work has uncovered molecular components involved in autophagy and the Cvt pathway.

Aminopeptidases↗
PubMed2026

LiCl induces GSK-3β mediated autophagy, DNA damage, and cell cycle arrest in HPV driven cervical cancer cells.

High-risk HPV infections induce cervical cancer progression by disrupting cellular homeostasis and survival pathways, including autophagy. Targeting autophagy represents a promising therapeutic strategy. Lithium chloride (LiCl), extensively studied for its neuroprotective properties, can be investigated for its potential anticancer effects in HPV-driven cervical cancer cells. Treatment with 30 mM LiCl induced significant phosphorylation of glycogen synthase kinase-3β (GSK-3β) at Ser9, inducing functional inhibition and downstream signal alterations. This modulation of GSK-3β activity compromised genomic integrity, validated by increased double strand DNA breaks, increased oxidative and cellular stress, and reduced antioxidant enzyme activity. Consequently, LiCl treated cells exhibited significant G2/M phase arrest, indicating disruption in cell cycle progression. Interestingly, the observed cytotoxicity occurred independently of classical apoptotic pathways, suggesting the activation of alternative cell death mechanisms. Mechanistic studies revealed a robust autophagic flux, with GSK-3β mediated autophagy, validated through siRNA mediated knockdown experiments. These findings highlight a novel cytotoxic mechanism of LiCl and propose its potential repurposing from neurobiology to targeted cancer therapeutics.

Humans↗
PubMed2006

Apoptosome impairment during development results in activation of an autophagy program in cerebral cortex.

The deficiency of upstream regulators of the mitochondrial death pathway has been recently shown to trigger in vitro a cellular process of self-clearance with features of autophagy. We show here that, when Apaf1 (responsible for apoptosome formation) is downregulated in vivo in cortical precursors, cells express markers of neuronal differentiation, accumulate in ectopic cortical masses and show hallmarks of the beclin-1-dependent pathway of autophagy, probably activated by a depletion in growth factors in the cells' microenvironment. To visualize this process in a cell culture model system, we also used a neural precursor cell line to mimic growth factor starvation in the absence of the apoptosome and tracked autophagolysosome formation. Our findings demonstrate the existence of an interplay between the autophagy and apoptosis pathways in vivo in brain development, and possibly link the absence of apoptosis to the occurrence of pathological conditions associated with peculiar cellular morphotypes.

Animals↗
PubMed1986

Circadian rhythm in the light response of rat retinal disk-shedding and autophagy.

Under a light-dark cycle, disk-shedding and autophagy in the rat retina peak in the early and mid light phase, respectively. Under constant conditions, disk-shedding and autophagy responses after light stimulation were elicited at different time points of a 24-h cycle. The greatest magnitude of response occurred in the late dark and early light phase. Thus there is a circadian variation of the light response of important metabolic parameters in the mammalian retina. Inhibition of dopamine synthesis during the early light phase caused a significant dampening of the light responses of both disk-shedding and autophagy.

Animals↗
PubMed1981

Increased autophagy in chloroquine-treated tonic and phasic muscles: an alternative view.

Ultrastructural and cytochemical techniques were used to investigate autophagy in the tonic anterior(ALD) and phasic posterior (PLD) latissimus dorsi muscles of the chicken following chloroquine administration. Autophagic vacuoles were seen in the ALD after 1 day of chloroquine administration while no change was seen in the PLD until 3 days. In both muscles, autophagic vacuoles and myeloid bodies were found at the level of the I band. Myeloid bodies usually were found in the longitudinal rows of mitochondria in the ALD muscle. Some, but not all, of the autophagic vacuoles and myeloid bodies were cytochemically acid phosphatase positive, while the portion of the sarcoplasmic reticulum of both muscles which is normally acid phosphatase positive, while the portion of the sarcoplasmic reticulum of both muscles which is normally, acid phosphatase positive was devoid of activity following chloroquine administration. These observations are discussed in regard to accepted mechanisms of autophagy and the possible inhibition of autophagy in skeletal muscle tissue by chloroquine.

Acid Phosphatase↗
PubMed2006

Cholesterol depletion induces autophagy.

Autophagy is a mechanism to digest cells' own components, and its importance in many physiological and pathological processes is being recognized. But the molecular mechanism that regulates autophagy is not understood in detail. In the present study, we found that cholesterol depletion induces macroautophagy. The cellular cholesterol in human fibroblasts was depleted either acutely using 5mM methyl-beta-cyclodextrin or 10-20microg/ml nystatin for 1h, or metabolically by 20microM mevastatin and 200microM mevalonolactone along with 10% lipoprotein-deficient serum for 2-3 days. By any of these protocols, marked increase of LC3-II was detected by immunoblotting and by immunofluorescence microscopy, and the increase was more extensive than that caused by amino acid starvation, i.e., incubation in Hanks' solution for several hours. The induction of autophagic vacuoles by cholesterol depletion was also observed in other cell types, and the LC3-positive membranes were often seen as long tubules, >50microm in length. The increase of LC3-II by methyl-beta-cyclodextrin was suppressed by phosphatidylinositol 3-kinase inhibitors and was accompanied by dephosphorylation of mammalian target of rapamycin. By electron microscopy, autophagic vacuoles induced by cholesterol depletion were indistinguishable from those seen after amino acid starvation. These results demonstrate that a decrease in cholesterol activates autophagy by a phosphatidylinositol 3-kinase-dependent mechanism.

Animals↗
PubMed2004

Methods for monitoring autophagy.

Autophagy is an intracellular bulk degradation system that is found ubiquitously in eukaryotes. Autophagy is responsible for the degradation of most long-lived proteins and some organelles. Cytoplasmic constituents, including organelles, are sequestered into double-membraned autophagosomes, which subsequently fuse with lysosomes where their contents are degraded. This system has been implicated in various physiological processes including protein and organelle turnover, the starvation response, cellular differentiation, cell death, and pathogenesis. However, methods for monitoring autophagy have been very limited and unsatisfactory. The most standard method is conventional electron microscopy. In addition, some biochemical methods have been utilized to measure autophagic activity. Recently, the molecular basis of autophagosome formation has been extensively studied using yeast cells; these studies have provided useful marker proteins for autophagosomes. Importantly, most of these proteins are conserved in mammals. Using these probes, we can now specifically monitor autophagic activity.

Animals↗