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Cells Mar 2020Autophagy is a multistep catabolic process through which misfolded, aggregated or mutated proteins and damaged organelles are internalized in membrane vesicles called... (Review)
Review
Autophagy is a multistep catabolic process through which misfolded, aggregated or mutated proteins and damaged organelles are internalized in membrane vesicles called autophagosomes and ultimately fused to lysosomes for degradation of sequestered components. The multistep nature of the process offers multiple regulation points prone to be deregulated and cause different human diseases but also offers multiple targetable points for designing therapeutic strategies. Cancer cells have evolved to use autophagy as an adaptive mechanism to survive under extremely stressful conditions within the tumor microenvironment, but also to increase invasiveness and resistance to anticancer drugs such as chemotherapy. This review collects clinical evidence of autophagy deregulation during cholangiocarcinogenesis together with preclinical reports evaluating compounds that modulate autophagy to induce cholangiocarcinoma (CCA) cell death. Altogether, experimental data suggest an impairment of autophagy during initial steps of CCA development and increased expression of autophagy markers on established tumors and in invasive phenotypes. Preclinical efficacy of autophagy modulators promoting CCA cell death, reducing invasiveness capacity and resensitizing CCA cells to chemotherapy open novel therapeutic avenues to design more specific and efficient strategies to treat this aggressive cancer.
Topics: Antineoplastic Agents; Autophagy; Cholangiocarcinoma; Humans; Lysosomes; Signal Transduction; Tumor Microenvironment
PubMed: 32143356
DOI: 10.3390/cells9030614 -
Autophagy May 2024MCOLN1 and MCOLN3 are two Ca release channels residing in the endolysosomal membrane. They are activated by phosphatidylinositol (PtdIns)-3-phosphate (PtdIns3P) and/or... (Review)
Review
MCOLN1 and MCOLN3 are two Ca release channels residing in the endolysosomal membrane. They are activated by phosphatidylinositol (PtdIns)-3-phosphate (PtdIns3P) and/or PtdIns(3,5)P. Their activities are also regulated by lumenal pH, with low pH enhancing that of MCOLN1 and high pH increasing that of MCOLN3. Recent studies further suggest that upon starvation, both MCOLN1 and MCOLN3 are activated by a reduction in MTORC1 activity; their activation in turn regulates MTORC1 activity to facilitate macroautophagic/autophagic flux. On the one hand, MCOLN3 appears to be recruited to phagophores where it is activated by PtdIns3P and high pH to inhibit MTORC1 activity using a positive feedback mechanism, thereby increasing autophagy induction. On the other hand, MCOLN1 is activated by PtdIns(3,5)P and low pH in (auto)lysosomes to increase MTORC1 activity using a negative feedback mechanism, promoting autophagic lysosome reformation. The cell uses the two feedback mechanisms to ensure efficient autophagic flux to survive adverse conditions such as nutrient deprivation and bacterial infection.
Topics: Mechanistic Target of Rapamycin Complex 1; Autophagy; Humans; Animals; Transient Receptor Potential Channels; Lysosomes; Models, Biological
PubMed: 38180017
DOI: 10.1080/15548627.2023.2300922 -
The Journal of Biological Chemistry Aug 2017Cell-to-cell transmission of intracellular protein aggregates is considered a central event in many neurodegenerative diseases, but little is known about the underlying...
Cell-to-cell transmission of intracellular protein aggregates is considered a central event in many neurodegenerative diseases, but little is known about the underlying molecular mechanisms. A new study employs fluorescence quenching to examine the fate of α-synuclein, a key molecule in the pathology of Parkinson's disease and related disorders, in primary cultured neurons, finding that endocytosis and lysosomal processing of exogenous fibrils may explain the transmission of α-synuclein pathology.
Topics: Animals; Endocytosis; Humans; Lysosomes; Models, Biological; Neurons; Protein Aggregation, Pathological; alpha-Synuclein
PubMed: 28801354
DOI: 10.1074/jbc.H117.780296 -
Methods in Molecular Biology (Clifton,... 2015Autophagy (self-eating) is a highly conserved, vesicular pathway that cells use to eat pieces of themselves, including damaged organelles, protein aggregates or invading...
Autophagy (self-eating) is a highly conserved, vesicular pathway that cells use to eat pieces of themselves, including damaged organelles, protein aggregates or invading pathogens, for self-preservation and survival (Choi et al., N Engl J Med 368:651-662, 2013; Lamb et al., Nat Rev Mol Cell Biol 14:759-774, 2013). Autophagy can be delineated into three major vesicular compartments (the phagophore, autophagosome, autolysosome, see Fig. 1). The initial stages of the pathway involve the formation of phagophores (also called isolation membranes), which are open, cup-shaped membranes that expand and sequester the cytosolic components, including organelles and aggregated proteins or intracellular pathogens. Closure of the phagophore creates an autophagosome, which is a double-membrane vesicle. Fusion of the autophagosome with the lysosome, to form an autolysosome, delivers the content of the autophagosome into the lysosomal lumen and allows degradation to occur.Autophagy is a dynamic process that is initiated within 15 min of amino acid starvation in cell culture systems (Köchl et al., Traffic 7:129-145, 2006) and is likely to occur as rapidly in vivo (Mizushima et al., J Cell Biol 152:657-668, 2001). To initiate studies on the formation of the autophagosomes, and trafficking to and from the autophagic pathway, an ideal starting approach is to do a morphological analysis in fixed cells. Additional validation of the morphological data can be obtained using simple Western blot analysis. Here we describe the most commonly used morphological technique to study autophagy, in particular, using the most reliable marker, microtubule-associated protein 1A/1B-light chain 3 (LC3). In addition, we describe a second immunofluorescence assay to determine if autophagy is being induced, using an antibody to WD repeat domain, phosphoinositide interacting 2 (WIPI2), an effector of the phosphatidylinositol (3)-phosphate (PI3P) produced during autophagosome formation.
Topics: Animals; Autophagy; Blotting, Western; Humans; Lysosomes; Microscopy, Fluorescence; Microtubule-Associated Proteins; Phagosomes
PubMed: 25702116
DOI: 10.1007/978-1-4939-2309-0_12 -
Trends in Biochemical Sciences Feb 2019Lysosomes, the degradation center of the cell, are filled with acidic hydrolases. Lysosomes generate nutrient-sensitive signals to regulate the import of H, hydrolases,... (Review)
Review
Lysosomes, the degradation center of the cell, are filled with acidic hydrolases. Lysosomes generate nutrient-sensitive signals to regulate the import of H, hydrolases, and endocytic and autophagic cargos, as well as the export of their degradation products (catabolites). In response to environmental and cellular signals, lysosomes change their positioning, number, morphology, size, composition, and activity within minutes to hours to meet the changing cellular needs. Ion channels in the lysosome are essential transducers that mediate signal-initiated Ca/Fe/Zn release and H/Na/K-dependent changes of membrane potential across the perimeter membrane. Dysregulation of lysosomal ion flux impairs lysosome movement, membrane trafficking, nutrient sensing, membrane repair, organelle membrane contact, and lysosome biogenesis and adaptation. Hence, activation and inhibition of lysosomal channels by synthetic modulators may tune lysosome function to maintain cellular health and promote cellular clearance in lysosome storage disorders.
Topics: Animals; Cell Line; Humans; Ion Channels; Lysosomes; Models, Molecular; Particle Size; Signal Transduction
PubMed: 30424907
DOI: 10.1016/j.tibs.2018.10.006 -
Cellular and Molecular Life Sciences :... Mar 2018Autophagy is a highly regulated process in eukaryotes to maintain homeostasis and manage stress responses. Understanding the regulatory mechanisms and key players... (Review)
Review
Autophagy is a highly regulated process in eukaryotes to maintain homeostasis and manage stress responses. Understanding the regulatory mechanisms and key players involved in autophagy will provide critical insights into disease-related pathogenesis and potential clinical treatments. In this review, we describe the hallmark events involved in autophagy, from its initiation, to the final destruction of engulfed targets. Furthermore, based on structural and biochemical data, we evaluate the roles of key players in these processes and provide rationale as to how they control autophagic events in a highly ordered manner.
Topics: Animals; Autophagy; Humans; Lysosomes; Membrane Fusion; Models, Biological; Phagosomes; Protein Binding
PubMed: 28939950
DOI: 10.1007/s00018-017-2657-z -
Molecular Neurobiology Mar 2018Prion diseases are transmissible, familial or sporadic. The prion protein (PrP), a normal cell surface glycoprotein, is ubiquitously expressed throughout the body. While... (Review)
Review
Prion diseases are transmissible, familial or sporadic. The prion protein (PrP), a normal cell surface glycoprotein, is ubiquitously expressed throughout the body. While loss of function of PrP does not elicit apparent phenotypes, generation of misfolded forms of the protein or its aberrant metabolic isoforms has been implicated in a number of neurodegenerative disorders such as scrapie, kuru, Creutzfeldt-Jakob disease, fatal familial insomnia, Gerstmann-Sträussler-Scheinker and bovine spongiform encephalopathy. These diseases are all phenotypically characterised by spongiform vacuolation of the adult brain, hence collectively termed as late-onset spongiform neurodegeneration. Misfolded form of PrP (PrP) and one of its abnormal metabolic isoforms (the transmembrane PrP) are known to be disease-causing agents that lead to progressive loss of structure or function of neurons culminating in neuronal death. The aberrant forms of PrP utilise and manipulate the various intracellular quality control mechanisms during pathogenesis of these diseases. Amongst these, the lysosomal quality control machinery emerges as one of the primary targets exploited by the disease-causing isoforms of PrP. The autophagosomal-lysosomal degradation pathway is adversely affected in multiple ways in prion diseases and may hence be regarded as an important modulator of neurodegeneration. Some of the ESCRT pathway proteins have also been shown to be involved in the manifestation of disease phenotype. This review discusses the significance of the lysosomal quality control pathway in affecting transmissible and familial types of prion diseases.
Topics: Animals; Brain; Humans; Lysosomes; Prion Diseases; Prions; Quality Control; Signal Transduction
PubMed: 28421536
DOI: 10.1007/s12035-017-0512-8 -
Autophagy Apr 2024Autophagy, an important cellular stress response mechanism, is often exploited by a variety of cancer cells to sustain rapid growth under stresses such as nutrient...
Autophagy, an important cellular stress response mechanism, is often exploited by a variety of cancer cells to sustain rapid growth under stresses such as nutrient deprivation and hypoxia. Autophagy also plays a key role in tumor resistance to chemotherapy, radiotherapy or targeted therapy. Inhibition of autophagy is therefore a promising tumor treatment strategy. However, there is still a lack of effective autophagy inhibitors suitable for clinical use. Most drug development has focused on enzymes like the VPS34 and ULK1 kinases, or the cysteine protease ATG4B, which plays different roles in autophagy. We discovered a drug molecule Eltrombopag that inhibits the expression of autophagic lysosomal genes at the stage of transcriptional level, where the synthesis of these proteins has not really begun, by directly inhibiting the TFEB (transcription factor EB). This drug can improve the therapeutic effect of Temozolomide on glioblastoma treatment, further confirming the value of inhibiting autophagy in the treatment of cancer. VPS34: vacuolar protein sorting 34; ULK1: unc-51 like autophagy activating kinase 1; TFEB: transcription factor EB; MITF: microphthalmia-associated transcription factor; TFE3: transcription factor E3; EO: Eltrombopag; ITC: isothermal titration calorimetry; bHLH-LZ: basic helix-loop-helix leucine zipper; LAMP1: lysosomal-associated membrane protein 1; CTSF: cathepsin F; HEXA: hexosaminidase subunit alpha.
Topics: Autophagy; Humans; Animals; Lysosomes; Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; Neoplasms
PubMed: 37036151
DOI: 10.1080/15548627.2023.2197364 -
BMB Reports May 2020As an intracellular degradation system, autophagy is an essential and defensive cellular program required for cell survival and cellular metabolic homeostasis in... (Review)
Review
As an intracellular degradation system, autophagy is an essential and defensive cellular program required for cell survival and cellular metabolic homeostasis in response to various stresses, such as nutrient deprivation and the accumulation of damaged organelles. In general, autophagy flux consists of four steps: (1) initiation (formation of phagophore), (2) maturation and completion of autophagosome, (3) fusion of autophagosomes with lysosomes (formation of autolysosome), and (4) degradation of intravesicular components within autolysosomes. The number of genes and reagents that modulate autophagy is increasing. Investigation of their effect on autophagy flux is critical to understanding the roles of autophagy in many physiological and pathological processes. In this review, we summarize and discuss ways to analyze autophagy flux quantitatively and qualitatively with the use of imaging tools. The suggested imaging method can help estimate whether each modulator is an inhibitor or a promoter of autophagy and elucidate the mode of action of specific genes and reagents on autophagy processes. [BMB Reports 2020; 53(5): 241-247].
Topics: Animals; Autophagosomes; Autophagy; Humans; Lysosomes; Optical Imaging
PubMed: 32317089
DOI: 10.5483/BMBRep.2020.53.5.046 -
Nature Cell Biology Mar 2018
Topics: Animals; Autophagosomes; Autophagy; Autophagy-Related Proteins; Humans; Lysosomes; Signal Transduction
PubMed: 29476159
DOI: 10.1038/s41556-018-0061-z