scholarly journals Understanding the Molecular Basis of the Interaction between NDPK-A and AMPK α1

2006 ◽  
Vol 26 (15) ◽  
pp. 5921-5931 ◽  
Author(s):  
Russell M. Crawford ◽  
Kate J. Treharne ◽  
Sandrine Arnaud-Dabernat ◽  
Jean-Yves Daniel ◽  
Marc Foretz ◽  
...  
Keyword(s):  
Surrounding Medium ◽  
Nucleoside Diphosphate Kinase ◽  
Acid Synthesis ◽  
Cellular Fatty Acid ◽  
Energy Status ◽  
Substrate Channeling ◽  
Cellular Effects ◽  
Cellular Events ◽  
Necessary And Sufficient

ABSTRACT Nucleoside diphosphate kinase (NDPK) (nm23/awd) belongs to a multifunctional family of highly conserved proteins (∼16 to 20 kDa) including two well-characterized isoforms (NDPK-A and -B). NDPK catalyzes the conversion of nucleoside diphosphates to nucleoside triphosphates, regulates a diverse array of cellular events, and can act as a protein histidine kinase. AMP-activated protein kinase (AMPK) is a heterotrimeric protein complex that responds to the cellular energy status by switching off ATP-consuming pathways and switching on ATP-generating pathways when ATP is limiting. AMPK was first discovered as an activity that inhibited preparations of acetyl coenzyme A carboxylase 1 (ACC1), a regulator of cellular fatty acid synthesis. We recently reported that NDPK-A (but not NDPK-B) selectively regulates the α1 isoform of AMPK independently of the AMP concentration such that the manipulation of NDPK-A nucleotide trans-phosphorylation activity to generate ATP enhanced the activity of AMPK. This regulation occurred irrespective of the surrounding ATP concentration, suggesting that “substrate channeling” was occurring with the shielding of NDPK-generated ATP from the surrounding medium. We speculated that AMPK α1 phosphorylated NDPK-A during their interaction, and here, we identify two residues on NDPK-A targeted by AMPK α1 in vivo. We find that NDPK-A S122 and S144 are phosphorylated by AMPK α1 and that the phosphorylation status of S122, but not S144, determines whether substrate channeling can occur. We report the cellular effects of the S122 mutation on ACC1 phosphorylation and demonstrate that the presence of E124 (absent in NDPK-B) is necessary and sufficient to permit both AMPK α1 binding and substrate channeling.

scholarly journals A novel physical and functional association between nucleoside diphosphate kinase A and AMP-activated protein kinase α1 in liver and lung

2005 ◽  
Vol 392 (1) ◽  
pp. 201-209 ◽  
Author(s):  
Russell M. Crawford ◽  
Kate J. Treharne ◽  
O. Giles Best ◽  
Richmond Muimo ◽  
Claudia E. Riemen ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Mammalian Cells ◽  
Nucleoside Diphosphate Kinase ◽  
Cell Types ◽  
Acid Synthesis ◽  
Cellular Fatty Acid ◽  
Energy Status ◽  
Amp Activated Protein Kinase

Nucleoside diphosphate kinase (NDPK, NM23/awd) belongs to a multifunctional family of highly conserved proteins (∼16–20 kDa) containing two well-characterized isoforms (NM23-H1 and -H2; also known as NDPK A and B). NDPK catalyses the conversion of nucleoside diphosphates into nucleoside triphosphates, regulates a diverse array of cellular events and can act as a protein histidine kinase. AMPK (AMP-activated protein kinase) is a heterotrimeric protein complex that responds to cellular energy status by switching off ATP-consuming pathways and switching on ATP-generating pathways when ATP is limiting. AMPK was first discovered as an activity that inhibited preparations of ACC1 (acetyl-CoA carboxylase), a regulator of cellular fatty acid synthesis. We report that NM23-H1/NDPK A and AMPK α1 are associated in cytosol from two different tissue sources: rat liver and a human lung cell line (Calu-3). Co-immunoprecipitation and binding assay data from both cell types show that the H1/A (but not H2/B) isoform of NDPK is associated with AMPK complexes containing the α1 (but not α2) catalytic subunit. Manipulation of NM23-H1/NDPK A nucleotide transphosphorylation activity to generate ATP (but not GTP) enhances the activity of AMPK towards its specific peptide substrate in vitro and also regulates the phosphorylation of ACC1, an in vivo target for AMPK. Thus novel NM23-H1/NDPK A-dependent regulation of AMPK α1-mediated phosphorylation is present in mammalian cells.

scholarly journals E3 ubiquitin ligase Grail promotes hepatic steatosis through Sirt1 inhibition

2021 ◽  
Vol 12 (4) ◽  
Author(s):  
Pei-Yao Liu ◽  
Cheng-Cheung Chen ◽  
Chia-Ying Chin ◽  
Te-Jung Liu ◽  
Wen-Chiuan Tsai ◽  
...  
Keyword(s):  
Hepatic Steatosis ◽  
Lipid Accumulation ◽  
Acid Synthesis ◽  
Sirtuin 1 ◽  
Nonalcoholic Fatty Liver ◽  
Expression Of Genes ◽  
Hepatic Fat ◽  
Underlying Mechanisms

AbstractIn obese adults, nonalcoholic fatty liver disease (NAFLD) is accompanied by multiple metabolic dysfunctions. Although upregulated hepatic fatty acid synthesis has been identified as a crucial mediator of NAFLD development, the underlying mechanisms are yet to be elucidated. In this study, we reported upregulated expression of gene related to anergy in lymphocytes (GRAIL) in the livers of humans and mice with hepatic steatosis. Grail ablation markedly alleviated the high-fat diet-induced hepatic fat accumulation and expression of genes related to the lipid metabolism, in vitro and in vivo. Conversely, overexpression of GRAIL exacerbated lipid accumulation and enhanced the expression of lipid metabolic genes in mice and liver cells. Our results demonstrated that Grail regulated the lipid accumulation in hepatic steatosis via interaction with sirtuin 1. Thus, Grail poses as a significant molecular regulator in the development of NAFLD.

scholarly journals Isolation and structural elucidation of dimeric epigallocatechin-3-gallate autoxidation products and their antioxidant capacity

2021 ◽  
Author(s):  
Julian Alfke ◽  
Uta Kampermann ◽  
Svetlana Kalinina ◽  
Melanie Esselen
Keyword(s):  
Antioxidant Capacity ◽  
Antioxidant Properties ◽  
Cd Spectroscopy ◽  
Trolox Equivalent Antioxidant Capacity ◽  
Published Data ◽  
Dietary Polyphenols ◽  
Cellular Effects ◽  
The Impact

AbstractDietary polyphenols like epigallocatechin-3-gallate (EGCG)—which represents the most abundant flavan-3-ol in green tea—are subject of several studies regarding their bioactivity and health-related properties. On many occasions, cell culture or in vitro experiments form the basis of published data. Although the stability of these compounds is observed to be low, many reported effects are directly related to the parent compounds whereas the impact of EGCG degradation and autoxidation products is not yet understood and merely studied. EGCG autoxidation products like its dimers theasinensin A and D, “P2” and oolongtheanin are yet to be characterized in the same extent as their parental polyphenol. However, to investigate the bioactivity of autoxidation products—which would minimize the discrepancy between in vitro and in vivo data—isolation and structure elucidation techniques are urgently needed. In this study, a new protocol to acquire the dimers theasinensin A and D as well as oolongtheanin is depicted, including a variety of spectroscopic and quadrupole time-of-flight high-resolution mass spectrometric (qTOF-HRMS) data to characterize and assign these isolates. Through nuclear magnetic resonance (NMR) spectroscopy, polarimetry, and especially circular dichroism (CD) spectroscopy after enzymatic hydrolysis the complementary atropisomeric stereochemistry of the isolated theasinensins is illuminated and elucidated. Lastly, a direct comparison between the isolated EGCG autoxidation products and the monomer itself is carried out regarding their antioxidant properties featuring Trolox equivalent antioxidant capacity (TEAC) values. These findings help to characterize these products regarding their cellular effects and—which is of special interest in the flavonoid group—their redox properties.

scholarly journals NK cell activation through the NKG2D ligand MULT-1 is selectively prevented by the glycoprotein encoded by mouse cytomegalovirus gene m145

2005 ◽  
Vol 201 (2) ◽  
pp. 211-220 ◽  
Author(s):  
Astrid Krmpotic ◽  
Milena Hasan ◽  
Andrea Loewendorf ◽  
Tanja Saulig ◽  
Anne Halenius ◽  
...  
Keyword(s):  
Cell Activation ◽  
Nk Cell ◽  
Surface Expression ◽  
Viral Gene ◽  
Nkg2d Ligand ◽  
Mouse Cytomegalovirus ◽  
Mcmv Infection ◽  
Viral Survival ◽  
Necessary And Sufficient

The NK cell–activating receptor NKG2D interacts with three different cellular ligands, all of which are regulated by mouse cytomegalovirus (MCMV). We set out to define the viral gene product regulating murine UL16-binding protein-like transcript (MULT)-1, a newly described NKG2D ligand. We show that MCMV infection strongly induces MULT-1 gene expression, but surface expression of this glycoprotein is nevertheless completely abolished by the virus. Screening a panel of MCMV deletion mutants defined the gene m145 as the viral regulator of MULT-1. The MCMV m145-encoded glycoprotein turned out to be necessary and sufficient to regulate MULT-1 by preventing plasma membrane residence of MULT-1. The importance of MULT-1 in NK cell regulation in vivo was confirmed by the attenuating effect of the m145 deletion that was lifted after NK cell depletion. Our findings underline the significance of escaping MULT-1/NKG2D signaling for viral survival and maintenance.

scholarly journals LKB1 and AMPK maintain epithelial cell polarity under energetic stress

2007 ◽  
Vol 177 (3) ◽  
pp. 387-392 ◽  
Author(s):  
Vincent Mirouse ◽  
Lance L. Swick ◽  
Nevzat Kazgan ◽  
Daniel St Johnston ◽  
Jay E. Brenman
Keyword(s):  
Tumor Suppressor ◽  
Cell Polarity ◽  
Growth Control ◽  
Epithelial Polarity ◽  
Energy Status ◽  
Ampk Signaling ◽  
Cellular Energy ◽  
Energetic Stress ◽  
Stress Dependent

LKB1 is mutated in both familial and spontaneous tumors, and acts as a master kinase that activates the PAR-1 polarity kinase and the adenosine 5′monophosphate–activated kinase (AMPK). This has led to the hypothesis that LKB1 acts as a tumor suppressor because it is required to maintain cell polarity and growth control through PAR-1 and AMPK, respectively. However, the genetic analysis of LKB1–AMPK signaling in vertebrates has been complicated by the existence of multiple redundant AMPK subunits. We describe the identification of mutations in the single Drosophila melanogaster AMPK catalytic subunit AMPKα. Surprisingly, ampkα mutant epithelial cells lose their polarity and overproliferate under energetic stress. LKB1 is required in vivo for AMPK activation, and lkb1 mutations cause similar energetic stress–dependent phenotypes to ampkα mutations. Furthermore, lkb1 phenotypes are rescued by a phosphomimetic version of AMPKα. Thus, LKB1 signals through AMPK to coordinate epithelial polarity and proliferation with cellular energy status, and this might underlie the tumor suppressor function of LKB1.

scholarly journals Light and electron microscopical observations of the effects of high-density lipoprotein on growth of Plasmodium falciparum in vitro

Parasitology ◽  
2004 ◽  
Vol 128 (6) ◽  
pp. 577-584 ◽  
Author(s):  
H. IMRIE ◽  
D. J. P. FERGUSON ◽  
M. CARTER ◽  
J. DRAIN ◽  
A. SCHIFLETT ◽  
...  
Keyword(s):  
Plasmodium Falciparum ◽  
High Density Lipoprotein ◽  
Light And Electron Microscopy ◽  
Density Lipoprotein ◽  
Acid Synthesis ◽  
High Density ◽  
High Concentrations ◽  
Electron Microscopical ◽  
Necessary And Sufficient

Human serum high-density lipoprotein (HDL) is necessary and sufficient for the short-term maintenance of Plasmodium falciparum in in vitro culture. However, at high concentrations it is toxic to the parasite. A heat-labile component is apparently responsible for the stage-specific toxicity to parasites within infected erythrocytes 12–42 h after invasion, i.e. during trophozoite maturation. The effects of HDL on parasite metabolism (as determined by nucleic acid synthesis) are evident at about 30 h after invasion. Parasites treated with HDL show gross abnormalities by light and electron microscopy.

Migration of leukocytes through the vessel wall and beyond

2003 ◽  
Vol 90 (10) ◽  
pp. 598-606 ◽  
Author(s):  
Rashmi Yadav ◽  
Karen Larbi ◽  
Rebecca Young ◽  
Sussan Nourshargh
Keyword(s):  
Basement Membrane ◽  
Vessel Wall ◽  
International Workshop ◽  
Medical Science ◽  
Blood Stream ◽  
Primary Response ◽  
Leukocyte Migration ◽  
Leukocyte Transmigration ◽  
Cellular Events

SummaryThe migration of leukocytes from the vascular lumen to sites of infection and/or injury in the extravascular tissue involves a series of sequential and coordinated molecular and cellular events with the resultant primary response being that of reduced leukocyte velocity within the blood stream, followed by leukocyte firm adhesion to endothelial cells lining the vessel wall and eventually migration through the vessel wall. Despite the growing knowledge of the mechanisms that mediate initial interaction of leukocytes with the endothelium, very little is known about the mechanisms that mediate and regulate leukocyte migration through the venular wall, the endothelium and its associated perivascular basement membrane. This review, whilst giving a brief outline of the stepwise cascade of molecular interactions involved in this process and the methods employed to investigate leukocyte migration in vivo, focuses primarily on mechanisms of leukocyte transmigration, the final step in the process of leukocyte emigration. Furthermore, special emphasis is placed on discussing the process and the mechanisms involved in leukocyte migration through the basement membrane, a structure that presents significant impedance to transmigrating leukocytes but is seldom investigated in the context of leukocyte transmigration in vivo. The review also discusses the growing evidence supporting the concept that leukocyte transmigration is not only a response that describes the passage of leukocytes through the venular wall, but also acts as a means of regulating leukocyte responsiveness beyond the vessel wall, i.e. within the extravascular tissue.This publication was partially financed by Serono Foundation for the Advancement of Medical Science.Part of this paper was originally presented at the 2nd International Workshop on New Therapeutic Targets in Vascular Biology from February 6-9, 2003 in Geneva, Switzerland.

scholarly journals The ER–Golgi intermediate compartment is a key membrane source for the LC3 lipidation step of autophagosome biogenesis

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Liang Ge ◽  
David Melville ◽  
Min Zhang ◽  
Randy Schekman
Keyword(s):  
Autophagosome Formation ◽  
Functional Studies ◽  
A Cell ◽  
Intermediate Compartment ◽  
Membrane Isolation ◽  
Necessary And Sufficient ◽  
Organelle Membrane ◽  
Catabolic Process

Autophagy is a catabolic process for bulk degradation of cytosolic materials mediated by double-membraned autophagosomes. The membrane determinant to initiate the formation of autophagosomes remains elusive. Here, we establish a cell-free assay based on LC3 lipidation to define the organelle membrane supporting early autophagosome formation. In vitro LC3 lipidation requires energy and is subject to regulation by the pathways modulating autophagy in vivo. We developed a systematic membrane isolation scheme to identify the endoplasmic reticulum–Golgi intermediate compartment (ERGIC) as a primary membrane source both necessary and sufficient to trigger LC3 lipidation in vitro. Functional studies demonstrate that the ERGIC is required for autophagosome biogenesis in vivo. Moreover, we find that the ERGIC acts by recruiting the early autophagosome marker ATG14, a critical step for the generation of preautophagosomal membranes.

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