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

Using a bioinformatic approach, we identified a TP53INP1-related gene encoding a protein with 30% identity with tumor protein 53-induced nuclear protein 1 (TP53INP1), which was named TP53INP2. TP53INP1 and TP53INP2 sequences were found in several species ranging from Homo sapiens to Drosophila melanogaster, but orthologues were found neither in earlier eukaryotes nor in prokaryotes. To gain insight into the function of the TP53INP2 protein, we carried out a yeast two-hybrid screening that showed that TP53INP2 binds to the LC3-related proteins GABARAP and GABARAP-like2, and then we demonstrated by coimmunoprecipitation that TP53INP2 interacts with these proteins, as well as with LC3 and with the autophagosome transmembrane protein VMP1. TP53INP2 translocates from the nucleus to the autophagosome structures after activation of autophagy by rapamycin or starvation. Also, we showed that TP53INP2 expression is necessary for autophagosome development because its small interfering RNA-mediated knockdown strongly decreases sensitivity of mammalian cells to autophagy. Finally, we found that interactions between TP53INP2 and LC3 or the LC3-related proteins GABARAP and GABARAP-like2 require autophagy and are modulated by wortmannin as judged by bioluminescence resonance energy transfer assays. We suggest that TP53INP2 is a scaffold protein that recruits LC3 and/or LC3-related proteins to the autophagosome membrane by interacting with the transmembrane protein VMP1. It is concluded that TP53INP2 is a novel gene involved in the autophagy of mammalian cells.
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PMID:The TP53INP2 protein is required for autophagy in mammalian cells. 1905 83

The etiologic agent of Chagas disease, Trypanosoma cruzi, infects mammalian cells activating a signal transduction cascade that leads to the formation of its parasitophorous vacuole. Previous works have demonstrated the crucial role of lysosomes in the establishment of T. cruzi infection. In this work we have studied the possible relationship between this parasite and the host cell autophagy. We show, for the first time, that the vacuole containing T. cruzi (TcPV) is decorated by the host cell autophagic protein LC3. Furthermore, live cell imaging experiments indicate that autolysosomes are recruited to parasite entry sites. Interestingly, starvation or pharmacological induction of autophagy before infection significantly increased the number of infected cells whereas inhibitors of this pathway reduced the invasion. In addition, the absence of Atg5 or the reduced expression of Beclin 1 -- two proteins required at the initial steps of autophagosome formation -- limited parasite entry and reduced the association between TcPV and the classical lysosomal marker Lamp-1. These results indicate that mammalian autophagy is a key process that favors the colonization of T. cruzi in the host cell.
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PMID:The autophagic pathway is a key component in the lysosomal dependent entry of Trypanosoma cruzi into the host cell. 1911 81

In hydra, the regulation of the balance between cell death and cell survival is essential to maintain homeostasis across the animal and promote animal survival during starvation. Moreover, this balance also appears to play a key role during regeneration of the apical head region. The recent finding that autophagy is a crucial component of this balance strengthens the value of the Hydra model system to analyze the implications of autophagy in starvation, stress response and regeneration. We describe here how we adapted to Hydra some established tools to monitor steady-state autophagy. The ATG8/LC3 marker used in biochemical and immunohistochemical analyses showed a significant increase in autophagosome formation in digestive cells after 11 days of starvation. Moreover, the maceration procedure that keeps intact the morphology of the various cell types allows the quantification of the autophagosomes and autolysosomes in any cell type, thanks to the detection of the MitoFluor or LysoTracker dyes combined with the anti-LC3, anti-LBPA, and/or anti-RSK (ribosomal S6 kinase) immunostaining. The classical activator (rapamycin) and inhibitors (wortmannin, bafilomycin A(1)) of autophagy also appear to be valuable tools to modulate autophagy in hydra, as daily-fed and starved hydra display slightly different responses. Finally, we show that the genetic circuitry underlying autophagy can be qualitatively and quantitatively tested through RNA interference in hydra repeatedly exposed to double-stranded RNAs.
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PMID:Methods to investigate autophagy during starvation and regeneration in hydra. 1918 34

Autophagy is a major intracellular catabolic pathway induced in response to amino acid starvation. Recent findings implicate it in diverse physiological/pathophysiological events, such as protein and organelle turnover, development, aging, pathogen infection, cell death, and neurodegeneration. However, experimental methods to monitor this process in mammalian cells are limited because of the deficiency of autophagic markers. Recently, MAP1-LC3 (LC3), a mammalian homolog of the yeast ubiquitin-like (UBL) protein Atg8, has been shown to selectively incorporate into the autophagosomal membrane, thus serving as a unique bona fide marker of autophagosomes in mammals. Thus, the autophagic activity can be largely determined by GFP-LC3/LC3, predominantly associated with autophagosomes (when LC3 is conjugated to phosphatidylethanolamine), both biochemically and microscopically. However, current methods to quantify autophagic activity using LC3 are time consuming, labor intensive, and require expertise in accurate interpretation. In this chapter we describe the use of flow cytometry and fluorescence-activated cell sorting (FACS) as a new assay designed to quantify autophagy in cells stably expressing GFP-LC3. Flow cytometry is a well-established technique for performing quantitative fluorescence measurements, allowing quick, accurate, and simultaneous determination of many parameters in cell subpopulations. Here flow cytometry and FACS were used to quantify the turnover of GFP-LC3 (reflecting an autophagic flux) as a reliable and simple assay to measure autophagic activity in living mammalian cells.
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PMID:Flow cytometric analysis of autophagy in living mammalian cells. 1920 Aug 80

Autophagy, a highly conserved cellular mechanism wherein various cellular components are broken down and recycled through lysosomes, occurs constitutively in the heart and may serve as a cardioprotective mechanism in some situations. It has been implicated in the development of heart failure and is up-regulated following ischemia-reperfusion injury. Autophagic flux, a measure of autophagic vesicle formation and clearance, is an important measurement in evaluating the efficacy of the pathway, however, tools to measure flux in vivo have been limited. Here, we describe the use of monodansylcadaverine (MDC) and the lysosomotropic drug chloroquine to measure autophagic flux in in vivo model systems, specifically focusing on its use in the myocardium. This method allows determination of flux as a more precise measure of autophagic activity in vivo much in the same way that Bafilomycin A(1) is used to measure flux in cell culture. MDC injected 1 h before sacrifice, colocalizes with mCherry-LC3 puncta, validating its use as a marker of autophagosomes. This chapter provides a method to measure autophagic flux in vivo in both transgenic and nontransgenic animals, using MDC and chloroquine, and in addition describes the mCherry-LC3 mouse and the advantages of this animal model in the study of cardiac autophagy. Additionally, we review several methods for inducing autophagy in the myocardium under pathological conditions such as myocardial infarction, ischemia/ reperfusion, pressure overloading, and nutrient starvation.
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PMID:Novel methods for measuring cardiac autophagy in vivo. 1921 14

Disruption of autophagy leads to accumulation of intracellular multilamellar inclusions morphologically similar to organised smooth endoplasmic reticulum (OSER) membranes. However, the relation of these membranous compartments to autophagy is unknown. The purpose of this study was to test whether OSER plays a role in the autophagic protein degradation pathway. Here, GFP-LC3 is shown to localise to the OSER membranes induced by calnexin expression both in transiently transfected HEK293 cells and in mouse embryo fibroblasts. In contrast to GFP-LC3, endogenous LC3 is excluded from these membranes under normal conditions as well as after cell starvation. Furthermore, YFP-Atg5, a protein essential for autophagy and known to reside on autophagic membranes, is excluded from the calnexin-positive inclusion structures. In cells devoid of Atg5, a protein essential for autophagy and known to reside on autophagic membranes, colocalisation of calnexin with GFP-LC3 within the multilamellar bodies is preserved. I show that calnexin, a protein enriched in the OSER, is not subject to autophagic or lysosomal degradation. Finally, GFP-LC3 targeting to these membranes is independent of its processing and insensitive to drugs modulating autophagic and lysosomal protein degradation. These observations are inconsistent with a role of autophagic/lysosomal degradation in clearance of multilamellar bodies comprising OSER. Furthermore, GFP-LC3, a fusion protein widely used as a marker for autophagic vesicles and pre-autophagic compartments, may be trapped in this compartment and this artefact must be taken into account if the construct is used to visualise autophagic membranes.
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PMID:GFP-LC3 labels organised smooth endoplasmic reticulum membranes independently of autophagy. 1925 79

Autophagy is an intracellular bulk degradation system that plays a vital role in maintaining cellular homeostasis. This degradation process involves dynamic membrane rearrangements resulting in the formation of double-membraned autophagosomes. However, the driving force for generating curvature and deformation of isolation membranes remains a mystery. Bax-interacting factor 1 (Bif-1), also known as SH3GLB1 or Endophilin B1, was originally discovered as a Bax-binding protein. Bif-1 contains an amino-terminal N-BAR (Bin-Amphiphysin-Rvs) domain and a carboxy-terminal SH3 (Src-homology 3) domain and shows membrane binding and bending activities. It has been shown that Beclin1 is involved in the nucleation of autophagosomal membranes through an unknown mechanism. It is interesting that, Bif-1 forms a complex with Beclin1 through ultraviolet irradiation resistant-associated gene (UVRAG) and promotes the activation of the class III PI3 kinase, Vps34, in mammalian cells. In response to nutrient starvation, Bif-1 accumulates in punctate foci where it co-localizes with LC3, Atg5, and Atg9. Furthermore, Bif-1-positive, crescent-shaped small vesicles expand by recruiting and fusing with Atg9-positive small membranes to complete autophagosome formation. This review highlights the role of Bif-1 in the regulation of autophagy and discusses the potential involvement of Bif-1 in the biogenesis of membranes for the formation of autophagosomes.
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PMID:Bif-1/endophilin B1: a candidate for crescent driving force in autophagy. 1926 52

Autophagy is a degradation pathway for the turnover of dysfunctional organelles or aggregated proteins in cells. Extracellular accumulation of beta-amyloid peptide has been reported to be a major cause of Alzheimer disease (AD) and large numbers of autophagic vacuoles accumulate in the brain of AD patient. However, how autophagic process is involved in Abeta-induced neurotoxicity and how Abeta peptide is transported into the neuron and metabolized is still unknown. In order to study the role of autophagic process in Abeta-induced neurotoxicity, EGFP-LC3 was overexpressed in SH-SY5Y cells (SH-SY5Y/pEGFP-LC3). It was found that treatment with Abeta(25-35), Abeta(1-42) or serum-starvation induced strong autophagy response in SH-SY5Y/pEGFP-LC3. Confocal double-staining image showed that exogenous application of Abeta(1-42) in medium caused the colocalization of Abeta(1-42) with LC3 in neuronal cells. Concomitant treatment of Abeta with a selective alpha7nAChR antagonist, alpha-bungarotoxin (alpha-BTX), enhanced Abeta-induced neurotoxicity in SH-SY5Y cells. On the other hand, nicotine (nAChR agonist) enhanced the autophagic process and also inhibited cell death following Abeta application. In addition, nicotine but not alpha-BTX increased primary hippocampal neuronal survival following Abeta treatment. Furthermore, using Atg7 siRNA to inhibit autophagosome formation in an early step or alpha7nAChR siRNA to knock down alpha7nAChR significantly enhanced Abeta-induced neurotoxicity. Confocal double-staining imaging shows that nicotine treatment in the presence of Abeta enhanced the colocalization of alpha7nAChR with autophagosomes. These results suggest that alpha7nAChR may act as a carrier to bind with eAbeta and internalize into cytoplasm and further inhibit Abeta-induced neurotoxicity via autophagic degradation pathway. Our results suggest that autophagy process plays a neuroprotective role against Abeta-induced neurotoxicity. Defect in autophagic regulation or Abeta-alpha7nAChR transport system may impair the clearance of Abeta and enhance neuronal death.
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PMID:Autophagy protects neuron from Abeta-induced cytotoxicity. 1927 May 30

Lipid droplets (LDs) are ubiquitous in eukaryotic cells, while excess free fatty acids and glucose in plasma are converted to triacylglycerol (TAG) and stored as LDs. However, the mechanism for the generation and growth of LDs in cells is largely unknown. We show here that the LC3 lipidation system essential for macroautophagy is involved in LD formation. LD formation accompanied by accumulation of TAG induced by starvation was largely suppressed in the hepatocytes that cannot execute autophagy. Under starvation conditions, LDs in addition to autophagosomes were abundantly formed in the cytoplasm of these tissue cells. Moreover, LC3 was localized on the surface of LDs and LC3-II (lipidation form) was fractionated to a perilipin (LD marker)-positive lipid fraction from the starved liver. Taken together, these results indicate that the LC3 conjugation system is critically involved in lipid metabolism via LD formation.
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PMID:The MAP1-LC3 conjugation system is involved in lipid droplet formation. 1928 58

Selective degradation of intracellular targets, such as misfolded proteins and damaged organelles, is an important homeostatic function that autophagy has acquired in addition to its more general role in restoring the nutrient balance during stress and starvation. Although the exact mechanism underlying selection of autophagic substrates is not known, ubiquitination is a candidate signal for autophagic degradation of misfolded and aggregated proteins. p62/SQSTM1 was the first protein shown to bind both target-associated ubiquitin (Ub) and LC3 conjugated to the phagophore membrane, thereby effectively acting as an autophagic receptor for ubiquitinated targets. Importantly, p62 not only mediates selective degradation but also promotes aggregation of ubiquitinated proteins that can be harmful in some cell types. Is p62 the only autophagic receptor for selective autophagy? Looking for proteins that interact with ATG8 family proteins, we identified NBR1 (neighbor of BRCA1 gene 1) as an additional LC3- and Ub-binding protein. NBR1 is degraded by autophagy depending on its LC3-interacting region (LIR) but does not strictly require p62 for this process. Like p62, NBR1 accumulates and aggregates when autophagy is inhibited and is a part of pathological inclusions. We propose that NBR1 together with p62 promotes autophagic degradation of ubiquitinated targets and simultaneously regulates their aggregation when autophagy becomes limited.
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PMID:NBR1 cooperates with p62 in selective autophagy of ubiquitinated targets. 1939 92


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