1,721,001 research outputs found
Glutamine contributes to maintenance of mouse embryonic stem cell self-renewal through PKC-dependent downregulation of HDAC1 and DNMT1/3a
No full textAlthough glutamine (Gln) is not an essential amino acid, it is considered a critical substrate in many key metabolic processes that control a variety of physiological functions and are involved in regulating early embryonic development. Thus, we investigated the effect of Gln on regulation of mouse embryonic stem cell (mESC) self-renewal and related signaling pathways. Gln deprivation decreased Oct4 expression as well as expression of cell cycle regulatory proteins. However, Gln treatment retained the expression of cell cycle regulatory proteins and the Oct4 in mESCs, which were blocked by compound 968 (a glutaminase inhibitor). In addition, Gln stimulated PI3K/Akt pathway, which subsequently elicited PKCE translocation to membrane without an influx of intracellular Ca2+. Inhibition of Akt and PKC blocked Gln-induced Oct4 expression and proliferation. Gln also stimulated mTOR phosphorylation in a time-dependent manner, which abolished by PKC inhibition. Furthermore, Gln increased the cellular population of both Oct4 and bromodeoxyuridine positive cells, suggesting that Gln regulates self-renewal ability of mESCs. Gln induced a decrease in HDAC1, but not in HDAC2, which were blocked by PKC inhibitors. Gln treatment resulted in an increase in global histone acetylation and methylation. In addition, Gln significantly reduced methylation of the Oct4 promoter region through decrease in DNMT1 and DNMT3a expression, which were blocked by PKC and HDAC inhibitors. In conclusion, Gln stimulates mESC proliferation and maintains mESC undifferentiation status through transcription regulation via the Akt, PKCE, and mTOR signaling pathways.Y
Human embryonic stem cell-specific role of YAP in maintenance of self-renewal and survival
No full textHuman embryonic stem cells (hESCs) have unique characteristics, such as self-renewal and pluripotency, which are distinct from those of other cell types. These characteristics of hESCs are tightly regulated by complex signaling mechanisms. In this study, we demonstrate that yes-associated protein (YAP) functions in an hESC-specific manner to maintain self-renewal and survival in hESCs. hESCs were highly sensitive to YAP downregulation to promote cell survival. Interestingly, hESCs displayed dynamic changes in YAP expression in response to YAP downregulation. YAP was critical for the maintenance of self-renewal. Additionally, the function of YAP in maintenance of self-renewal and cell survival was hESC-specific. Doxycycline upregulated YAP in hESCs and attenuated the decreased cell survival induced by YAP downregulation. However, decreased expression of self-renewal markers triggered by YAP downregulation and neural/cardiac differentiation were affected by doxycycline treatment. Collectively, the results reveal the mechanism underlying the role of YAP and the novel function of doxycycline in hESCs.Y
High glucose upregulates BACE1-mediated A beta production through ROS-dependent HIF-1 alpha and LXR alpha/ABCA1-regulated lipid raft reorganization in SK-N-MC cells
No full textThere is an accumulation of evidence indicating that the risk of Alzheimer's disease is associated with diabetes mellitus, an indicator of high glucose concentrations in blood plasma. This study investigated the effect of high glucose on BACE1 expression and amyloidogenesis in vivo, and we present details of the mechanism associated with those effects. Our results, using ZLC and ZDF rat models, showed that ZDF rats have high levels of amyloid-beta (A beta), phosphorylated tau, BACE1, and APP-C99. In vitro result with mouse hippocampal neuron and SK-N-MC, high glucose stimulated A beta secretion and apoptosis in a dose-dependent manner. In addition, high glucose increased BACE1 and APP-C99 expressions, which were reversed by a reactive oxygen species (ROS) scavenger. Indeed, high glucose increased intracellular ROS levels and HIF-1 alpha expression, associated with regulation of BACE1 and Liver X Receptor alpha (LXR alpha). In addition, high glucose induced ATP-binding cassette transporter A1 (ABCA1) down-regulation, was associated with LXR-induced lipid raft reorganization and BACE1 localization on the lipid raft. Furthermore, silencing of BACE1 expression was shown to regulate A beta secretion and apoptosis of SK-N-MC. In conclusion, high glucose upregulates BACE1 expression and activity through HIF-1 alpha and LXR alpha/ABCA1-regulated lipid raft reorganization, leading to A beta production and apoptosis of SK-N-MC.Y
Cellular Layer-by-Layer Coculture Platform Using Biodegradable, Nanoarchitectured Membranes for Stem Cell Therapy
No full textStem cells are regulated in vivo through interactions with the surrounding microenvironments in a three-dimensional (3D) manner. A coculture of stem cells with desired cell types, which recapitulates the complex in vivo cell cell communications, has been reported as an effective method to direct stem cell differentiation into specific lineage. However, conventional bilayer coculture systems employ membranes of microscale thickness and low porosity, which limit interaction between cocultured cells for efficient stem cell differentiation. Furthermore, conventional coculture systems require cell-impairing enzyme treatment to harvest the cells from the membranes. Here, we developed a cellular layer-by-layer (cLbL) coculture platform using biodegradable, nanothin, highly porous (BNTHP) membranes. Equipped with more porous and thinner membranes, the cLbL coculture platform better mimicked the in vivo 3D microenvironment and promoted cellular cross-talks between cocultured cells which occurred in nanoscale, resulting in more efficient stem cell differentiation compared to the conventional bilayer coculture systems. Furthermore, biodegradibility, biocompatibility, and highly flexibility of BNTHP membranes enabled conversion of the cell-attached membranes into implantable 3D cell constructs, thus avoiding harmful enzymatic harvesting of the cells. The cLbL platform may be an effective method to induce stem cell differentiation and facilitate cell implantation for stem cell therapy.OAIID:RECH_ACHV_DSTSH_NO:T201723063RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A004677CITE_RATE:9.89FILENAME:Cellular Layer-by-Layer Coculture Platform Using Biodegradable, Nanoarchitectured Membranes for Stem Cell Therapy.pdfDEPT_NM:화학생물공학부EMAIL:[email protected]_YN:YFILEURL:https://srnd.snu.ac.kr/eXrepEIR/fws/file/0902ae64-efb8-4dc6-93db-57052a2d2f0e/linkN
BICD1 mediates HIF1α nuclear translocation in mesenchymal stem cells during hypoxia adaptation
No full textHypoxia inducible factor 1 alpha (HIF1 alpha) is a master regulator leading to metabolic adaptation, an essential physiological process to maintain the survival of stem cells under hypoxia. However, it is poorly understood how HIF1 alpha translocates into the nucleus in stem cells under hypoxia. Here, we investigated the role of a motor adaptor protein Bicaudal D homolog 1 (BICD1) in dynein-mediated HIF1 alpha nuclear translocation and the effect of BICD1 regulation on hypoxia adaptation and its therapeutic potential on human umbilical cord blood-derived mesenchymal stem cells (UCB-MSCs). In our results, silencing of BICD1 but not BICD2 abolished HIF1 alpha nuclear translocation and its activity. BICD1 overexpression further enhanced hypoxia-induced HIF1 alpha nuclear translocation. Hypoxia stimulated direct bindings of HIF1 alpha to BICD1 and the intermediate chain of dynein (Dynein IC), which was abolished by BICD1 silencing. Akt inhibition reduced the binding of BICD1 to HIF1 alpha and nuclear translocation of HIF1 alpha. Conversely, Akt activation or GSK3 beta silencing further enhanced the hypoxia-induced HIF1 alpha nuclear translocation. Furthermore, BICD1 silencing abolished hypoxia-induced glycolytic reprogramming and increased mitochondrial ROS accumulation and apoptosis in UCB-MSCs under hypoxia. In the mouse skin wound healing model, the transplanted cell survival and skin wound healing capacities of hypoxia-pretreated UCB-MSCs were reduced by BICD1 silencing and further increased by GSK3 beta silencing. In conclusion, we demonstrated that BICD1-induced HIF1 alpha nuclear translocation is critical for hypoxia adaptation, which determines the regenerative potential of UCB-MSCs.Y
Palmitic Acid-BSA enhances Amyloid-β production through GPR40-mediated dual pathways in neuronal cells: Involvement of the Akt/mTOR/HIF-1α and Akt/NF-κB pathways
No full textAbstractThe pathophysiological actions of fatty acids (FAs) on Alzheimer’s disease (AD), which are possibly mediated by genomic effects, are widely known; however, their non-genomic actions remain elusive. The aim of this study was to investigate the non-genomic mechanism of extra-cellular palmitic acid (PA) regulating beta-amyloid peptide (Aβ) production, which may provide a link between obesity and the occurrence of AD. In an obese mouse model, a high-fat diet (HFD) significantly increased the expression levels of APP and BACE1 as well as the AD pathology in the mouse brain. We further found that PA conjugated with bovine serum albumin (PA-BSA) increased the expression of APP and BACE1 and the production of Aβ through the G protein-coupled receptor 40 (GPR40) in SK-N-MC cells. PA-BSA coupling with GPR40 significantly induced Akt activation which is required for mTOR/p70S6K1-mediated HIF-1α expression and NF-κB phosphorylation facilitating the transcriptional activity of the APP and BACE1 genes. In addition, silencing of APP and BACE1 expression significantly decreased the production of Aβ in SK-N-MC cells treated with PA-BSA. In conclusion, these results show that extra-cellular PA coupled with GPR40 induces the expression of APP and BACE1 to facilitate Aβ production via the Akt-mTOR-HIF-1α and Akt-NF-κB pathways in SK-N-MC cells.</jats:p
High glucose‐mediated PICALM and mTORC1 modulate processing of amyloid precursor protein via endosomal abnormalities
No full textBackground and Purpose Although diabetes mellitus (DM) is an important risk factor for Alzheimer's disease (AD), the detailed mechanism(s) by which DM regulates amyloid beta (A beta) processing is still unclear. The longer residence time of amyloid precursor protein (APP) in endosomes is critical for A beta production and DM is known to cause endosomal dysregulation. Here we have examined the effects of high glucose on APP-producing endosomes and related signaling pathways. Experimental Approach To identify the underlying mechanisms, we investigated the effects of high glucose on abnormalities in early endosomes and related signalling pathways in human neuroblastoma cells. In vivo, diabetic mice treated with pharmacological inhibitors were used to examine endosomal dysfunction. Key Results The hippocampus of diabetic animals presented endosomal abnormalities and A beta up-regulation. High glucose increased A beta production through early endosomal enlargement achieved by increased lipid raft-mediated APP endocytosis. High glucose induced ROS-stimulated Sp1 activation, up-regulating phosphatidylinositol binding clathrin assembly protein (PICALM), clathrin heavy chain, and adaptor-related protein complex 2 alpha 1. PICALM facilitated clathrin-mediated APP endocytosis resulting in early endosomal enlargement. Meanwhile, AMPK/mTORC1-mediated autophagy defect and ROS- and mTORC1-mediated lysosomal dysfunction aggravated early endosomal enlargement under high glucose. Moreover, the increased A beta production and cognitive deficits in diabetic mice were reversed by inhibition of early endosomal enlargement. Conclusion and Implications High glucose induces early endosomal abnormalities through PICALM-induced APP endocytosis and mTORC1-inhibited endosomal clearance, up-regulating A beta production. Thus, targeting PICALM and mTORC1 to prevent endosomal disorders is a promising strategy for managing diabetes-induced AD.Y
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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