Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Despite recent advances in understanding the functions of autophagy in developmental and pathological conditions, the underlying mechanism of where and how autophagosomal structures acquire membrane remains enigmatic. Here, we provide evidence that post-Golgi membrane traffic plays a crucial role in autophagosome formation. Increased secretion of constitutive cargo from the trans-Golgi network (TGN) to the plasma membrane induced the formation of microtubule-associated protein light chain 3 (LC3)-positive structures. At the early phase of autophagy, LC3 associated with and then budded off from a distinct TGN domain without constitutive TGN-to-plasma cargo and TGN-to-endosome proteins. The clathrin adaptor protein AP1 and clathrin localized to starvation- and rapamycin-induced autophagosomes. Dysfunction of the AP1-dependent clathrin coating at the TGN but not at the plasma membrane prevented autophagosome formation. Our results thus suggest an essential role of the TGN in autophagosome biogenesis, providing membrane to autophagosomes through an AP1-dependent pathway.
 ...
PMID:AP1 is essential for generation of autophagosomes from the trans-Golgi network. 2232 8

Selective autophagy is a process whereby specific targeted cargo proteins, aggregates, or organelles are sequestered into double-membrane-bound phagophores before fusion with the lysosome for protein degradation. It has been demonstrated that the microtubule network is important for the formation and movement of autophagosomes. Nbr1 is a selective cargo receptor that through its interaction with LC3 recruits ubiquitinated proteins for autophagic degradation. This study demonstrates an interaction between the evolutionarily conserved FW domain of Nbr1 with the microtubule-associated protein MAP1B. Upon autophagy induction, MAP1B localisation is focused into discrete vesicles with Nbr1. This colocalisation is dependent upon an intact microtubule network as depolymerisation by nocodazole treatment abolishes starvation-induced MAP1B recruitment to these vesicles. MAP1B is not recruited to autophagosomes for protein degradation as blockage of lysosomal acidification does not result in significant increased MAP1B protein levels. However, the protein levels of phosphorylated MAP1B are significantly increased upon blockage of autophagic degradation. This is the first evidence that links the ubiquitin receptor Nbr1, which shuttles ubiquitinated proteins to be degraded by autophagy, to the microtubule network.
 ...
PMID:MAP1B Interaction with the FW Domain of the Autophagic Receptor Nbr1 Facilitates Its Association to the Microtubule Network. 2265 11

As the function of autophagy becomes evident in a number of diseases, including cancer and infection, it is crucial to construct macrophage cell lines with stable expression of the microtubule-associated protein light chain 3 (GFP-LC3). In this study, a mouse LC3 open-reading frame was amplified by RT-PCR, and cloned into the pEGFP-C1 plasmid for expression of the GFP-LC3 fusion protein. The recombinant plasmid was transfected into RAW264.7 cells using Lipofectamine 2000 reagent and stably transfected clones were selected by G418 screening. Autophagic puncta formation was observed by fluorescense microscopy. Additionally, we found that starvation treatment induced a significant increase in the number of autophagosomes, while wortmannin treatment significantly repressed the formation of autophagosomes. This study indicated that the RAW264.7 cell line stably expressing GFP-LC3 is available for use in a GFP-LC3 puncta formation assay, and may contribute to basic investigations of autophagic function or drug screening targeted at autophagy.
 ...
PMID:A method for the establishment of a cell line with stable expression of the GFP-LC3 reporter protein. 2282 56

Autophagy is a natural process of 'self-eating' that occurs within cells and can be either pro-survival or can cause cell death. As a pro-survival mechanism, autophagy obtains energy by recycling cellular components such as macromolecules or organelles. In response to nutrient deprivation, e.g. depletion of amino acids or serum, autophagy is induced and most of these signals converge on the kinase mTOR (mammalian target of rapamycin). It is commonly accepted that glucose inhibits autophagy, since its deprivation from cells cultured in full medium induces autophagy by a mechanism involving AMPK (AMP-activated protein kinase), mTOR and Ulk1. However, we show in the present study that under starvation conditions addition of glucose produces the opposite effect. Specifically, the results of the present study demonstrate that the presence of glucose induces an increase in the levels of LC3 (microtubule-associated protein 1 light chain)-II, in the number and volume density of autophagic vacuoles and in protein degradation by autophagy. Addition of glucose also increases intracellular ATP, which is in turn necessary for the induction of autophagy because the glycolysis inhibitor oxamate inhibits it, and there is also a good correlation between LC3-II and ATP levels. Moreover, we also show that, surprisingly, the induction of autophagy by glucose is independent of AMPK and mTOR and mainly relies on p38 MAPK (mitogen-activated protein kinase).
 ...
PMID:Glucose induces autophagy under starvation conditions by a p38 MAPK-dependent pathway. 2311 32

Upon starvation, cells undergo autophagy, an intracellular bulk-degradation process, to provide the required nutrients. Here, we observed that phospholipase C-related catalytically inactive protein (PRIP) binds to microtubule-associated protein 1 light chain 3 (LC3), a mammalian autophagy-related initiator that regulates the autophagy pathway. Then, we examined the involvement of PRIP in the nutrient depletion-induced autophagy pathway. Enhanced colocalization of PRIP with LC3 was clearly seen in nutrient-starved mouse embryonic fibroblasts under a fluorescent microscope, and interaction of the proteins was revealed by immunoprecipitation experiments with an anti-LC3 antibody. Under starvation conditions, there were more green fluorescent protein fused-LC3 dots in mouse embryonic fibroblasts from PRIP-deficient mice than in fibroblasts from wild type cells. The formation of new dots in a single cell increased, as assessed by time-lapse microscopy. Furthermore, the increase in autophagosome formation in PRIP-deficient cells was notably inhibited by exogenously overexpressed PRIP. Taken together, PRIP is a novel LC3-binding protein that acts as a negative modulator of autophagosome formation.
 ...
PMID:Phospholipase C-related catalytically inactive protein, a novel microtubule-associated protein 1 light chain 3-binding protein, negatively regulates autophagosome formation. 2339 61

CD133/Prominin-1 is a pentaspan transmembrane protein that has been frequently used as a biomarker for cancer stem cells, although its biological function is unclear. The aim of our study was to explore the intrinsic functions of CD133 membrane protein in hepatoma cells during autophagy, apoptosis, tumorigenesis and cell survival through expression or downregulation of CD133. In this study, CD133 was found to be dynamically released from plasma membrane into cytoplasm in both of complete medium(CM) and low glucose medium (LGM), and LGM promoted this translocation. Expression of CD133 enhanced autophagic activity in LGM, while silencing CD133 attenuated this activity in HCC LM3 and Huh-7 cells, suggesting that CD133 is associated with autophagy. Immunofluorescence and time-lapsed confocal techniques confirmed that CD133 was associated with autophagy marker, microtubule-associated protein light chain3 (LC3) and lysosome marker during the glucose starvation. We further found that Huh-7 cells with stable expression of shCD133 (Huh-7sh133) impaired the ability of cell proliferation and formation of xenograft tumors in the NOD/SCID mice. Although loss of CD133 did not affect the rates of glucose uptake in Huh-7con and Huh-7sh133 cells under the CM, Huh-7sh133 cells obviously died fast than Huh-7con cells in the LGM and decreased the rate of glucose uptake and ATP production. Furthermore, targeting CD133 by CD133mAb resulted in cell death in HepG2 cells, especially in the LGM, via inhibition of autophagic activity and increase of apoptosis. The results demonstrated that CD133 is involved in cell survival through regulation of autophagy and glucose uptake, which may be necessary for cancer stem cells to survive in tumor microenvironment.
 ...
PMID:CD133/prominin-1-mediated autophagy and glucose uptake beneficial for hepatoma cell survival. 2343 59

Autophagy is a complex, multi-step and biologically important pathway mediated by autophagosomes and autolysosomes. Accurately dissecting and detecting different stages of autophagy is important to elucidate its molecular mechanism and thereby facilitate the discovery of pharmaceutical molecules. We herein reported a small-molecule synthetic probe, Zn-G 4, which is only fluorescent upon starvation- or chemical agent-induced autophagy within the autolysosome or possible the late endosome/lysosome networks. The probe can be detected by one-photon microscopy, which gives a high signal-to-noise ratio readout of autophagic activity. The pH gradient-independent fluorescence can be detected both in live and prestained fixed cells. Moreover, the fluorescent recording can be used to quantify autophagic activity at a single point without transfection or false positive signals due to protein aggregation. Furthermore, autophagy-induced fluorescence in autolysosomes can also be detected by two-photon microscopy, suggesting potential applications in deep tissue and in vivo. In conclusion, we have developed a sensitive and specific autolysosomal probe that can be used for monitoring autophagy during later stages along with quantitative assays together with widely used early markers or microtubule-associated protein 1 light chain 3 (LC3)-based probes.
 ...
PMID:A sensitive and quantitative autolysosome probe for detecting autophagic activity in live and prestained fixed cells. 2357 40

The flow cytometric use of LysoTracker dyes was employed to investigate the autophagic process and to compare this with the upregulation of autophagy marker, the microtubule-associated protein LC3B. Although the mechanism of action of LysoTracker dyes is not fully understood, they have been used in microscopy to image acidic spherical organelles, and their use in flow cytometry has not been thoroughly investigated in the study of autophagy. This investigation uses numerous autophagy-inducing agents including chloroquine (CQ), rapamycin, low serum (<1%) RPMI, and nutrient starvation to induce autophagy in Jurkat T-cell leukemia and K562 erythromyeloid cell lines. LC3B showed an increase with CQ treatment although this was different to LysoTracker signals in terms of dose and time. Rapamycin, low serum (<1%) RPMI, and nutrient starvation induction of autophagy also induced an increase in LysoTracker and LC3B signals. CQ also induced apoptosis in cell lines, which was blocked by pan-caspase inhibitor z-VAD resulting in a reduction in cells undergoing apoptosis and a subsequent upregulation of autophagic markers LC3B and lysosomal dye signals. Given that LC3B and LysoTracker are measuring different biological events in the autophagic process, they surprisingly both upregulated during autophagic process. This study, however, shows that although LysoTracker dyes do not specifically label lysosomes or autophagosomes within the cell, they allow the simultaneous measurement of an autophagy-related process and other live-cell functions, which are not possible with the standard LC3B antibody-labeling technique. This method has the advantage of other live-cell LCB-GFP-tagged experiments in that be used to analyze patient cells as well as easier to use and significantly less costly.
 ...
PMID:Use of LysoTracker dyes: a flow cytometric study of autophagy. 2384 75

Yeast Atg8 and mammalian microtubule-associated protein light chain 3 (LC3) are landmark proteins essential for autophagy. Here the lepidopteran Atg8, a homolog of LC3, is characterized. Sequence analysis reveals that Atg8 proteins are highly conserved in lepidopteran species. The abundance of endogeous Atg8 and the ratios of Atg8 conjugation to phosphatidylethanolamine (Atg8-PE)/Atg8 are different among several lepidopteran cell lines and different tissues of Helicoverpa armigera larvae. Both the density of fluorescent pre-autophagosomal structures with GFP-Ha Atg8 and the abundance of Atg6 are positively correlated with levels of Atg8-PE in different cell lines. The mutant GFP-Atg8(G116A) has lost the function in punctual formation, suggesting that G116 is important for autophagy. Exogenous factors have significant influences on the conversion of Atg8 in lepidopteran cells. Bacillus thuringiensis enhances the degradation of Atg8 in Spodoptera litura Sl-HP cells. Atg8-PE degrades gradually with extension of amino acid starvation, and bafilomycin A1 can block the decrease through the inhibition of autophagosome fusion with lysosome. Interestingly, high pH is more effective than amino acid starvation in Bombyx mori Bme cells to induce the conversion of BmAtg8 to BmAgt8-PE. Change of the quality of fetal bovine serum in the culture medium results in alteration of the ratio of Atg8-PE/Atg8 in some lepidopteran cell lines.
...
PMID:Characterization of Atg8 in lepidopteran insect cells. 2395 53

Autophagy is a conserved mechanism for controlling the degradation of misfolded proteins and damaged organelles in eukaryotes and can be induced by nutrient withdrawal, including serum starvation. Although differential acetylation of autophagy-related proteins has been reported to be involved in autophagic flux, the regulation of acetylated microtubule-associated protein 1 light chain 3 (LC3) is incompletely understood. In this study, we found that the acetylation levels of phosphotidylethanolamine (PE)-conjugated LC3B (LC3B-II), which is a critical component of double-membrane autophagosome, were profoundly decreased in HeLa cells upon autophagy induction by serum starvation. Pretreatment with lysosomal inhibitor chloroquine did not attenuate such deacetylation. Under normal culture medium, we observed increased levels of acetylated LC3B-II in cells treated with tubacin, a specific inhibitor of histone deacetylase 6 (HDAC6). However, tubacin only partially suppressed serum-starvation-induced LC3B-II deacetylation, suggesting that HDAC6 is not the only deacetylase acting on LC3B-II during serum-starvation-induced autophagy. Interestingly, tubacin-induced increase in LC3B-II acetylation was associated with p62/SQSTM1 accumulation upon serum starvation. HDAC6 knockdown did not influence autophagosome formation but resulted in impaired degradation of p62/SQSTM1 during serum starvation. Collectively, our data indicated that LC3B-II deacetylation, which was partly mediated by HDAC6, is involved in autophagic degradation during serum starvation.
...
PMID:LC3B-II deacetylation by histone deacetylase 6 is involved in serum-starvation-induced autophagic degradation. 2422 Mar 35


<< Previous 1 2 3 4 5 6 7 Next >>