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The Journal of Cell Biology Jan 2018Storage and consumption of neutral lipids in lipid droplets (LDs) are essential for energy homeostasis and tightly coupled to cellular metabolism. However, how metabolic...
Storage and consumption of neutral lipids in lipid droplets (LDs) are essential for energy homeostasis and tightly coupled to cellular metabolism. However, how metabolic cues are integrated in the life cycle of LDs is unclear. In this study, we characterize the function of Ldo16 and Ldo45, two splicing isoforms of the same protein in budding yeast. We show that Ldo proteins interact with the seipin complex, which regulates contacts between LDs and the endoplasmic reticulum (ER). Moreover, we show that the levels of Ldo16 and Ldo45 depend on the growth stage of cells and that deregulation of their relative abundance alters LD morphology, protein localization, and triglyceride content. Finally, we show that absence of Ldo proteins results in defects in LD morphology and consumption by lipophagy. Our findings support a model in which Ldo proteins modulate the activity of the seipin complex, thereby affecting LD properties. Moreover, we identify ER-LD contacts as regulatory targets coupling energy storage to cellular metabolism.
Topics: GTP-Binding Protein gamma Subunits; Lipid Droplets; Lipid Metabolism; Protein Isoforms; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins; Triglycerides
PubMed: 29187528
DOI: 10.1083/jcb.201704115 -
Molecular Cell Feb 2007Export of mature mRNA to the cytoplasm is the culmination of the nuclear portion of eukaryotic gene expression. After transport-competent mature mRNP export complexes... (Review)
Review
Export of mature mRNA to the cytoplasm is the culmination of the nuclear portion of eukaryotic gene expression. After transport-competent mature mRNP export complexes are formed in the nucleus, their passage through nuclear pore complexes (NPCs) is facilitated by the Mex67:Mtr2 heterodimer. At the NPC cytoplasmic face, mRNP remodeling prevents its return to the nucleus and so functions as a molecular ratchet imposing directionality on transport. In budding yeast, recent work suggests that the DEAD-box helicase Dbp5 remodels mRNPs at the NPC cytoplasmic face by removing Mex67 and that the Dbp5 ATPase is activated by Gle1 and inositol hexaphosphate (IP(6)).
Topics: Active Transport, Cell Nucleus; Carrier Proteins; Cell Nucleus; DEAD-box RNA Helicases; Dimerization; Membrane Transport Proteins; Models, Biological; Nuclear Pore Complex Proteins; Nuclear Proteins; Nucleocytoplasmic Transport Proteins; Phytic Acid; Protein Processing, Post-Translational; RNA Helicases; RNA, Messenger; RNA-Binding Proteins; Ribonucleoproteins; Saccharomyces cerevisiae Proteins
PubMed: 17289581
DOI: 10.1016/j.molcel.2007.01.016 -
FEBS Letters May 2007The evolutionarily conserved coat protein complex II (COPII) generates transport vesicles that mediate protein transport from the endoplasmic reticulum (ER). COPII coat... (Review)
Review
The evolutionarily conserved coat protein complex II (COPII) generates transport vesicles that mediate protein transport from the endoplasmic reticulum (ER). COPII coat is responsible for direct capture of cargo proteins and for the physical deformation of the ER membrane that drives the COPII vesicle formation. In addition to coat proteins, recent data have indicated that the Ras-like small GTPase Sar1 plays multiple roles, such as COPII coat recruitment, cargo sorting, and completion of the final fission. In the present review, we summarize current knowledge of COPII-mediated vesicle formation from the ER, as well as highlighting non-canonical roles of COPII components.
Topics: Biological Transport; COP-Coated Vesicles; Endoplasmic Reticulum; Exocytosis; Membrane Proteins; Monomeric GTP-Binding Proteins; Protein Transport; Saccharomyces cerevisiae Proteins; Vesicular Transport Proteins
PubMed: 17316621
DOI: 10.1016/j.febslet.2007.01.091 -
The International Journal of... Jan 2021Tumor necrosis factor-α-induced protein 8 (TNFAIP8) is a member of TIPE/TNFAIP8 family, has been involved in the development and progression of various human cancers....
Tumor necrosis factor-α-induced protein 8 (TNFAIP8) is a member of TIPE/TNFAIP8 family, has been involved in the development and progression of various human cancers. We hypothesized that TNFAIP8 promotes prostate cancer (PCa) progression via regulation of oxidative phosphorylation (OXPHOS) and glycolysis. Ectopic expression of TNFAIP8 increased PCa cell proliferation/migration/spheroid formation by enhancing cell metabolic activities. Mechanistically, TNFAIP8 activated the PI3K-AKT pathway and up-regulated PCa cell survival. TNFAIP8 was also found to regulate the expression of glucose metabolizing enzymes, enhancing glucose consumption, and endogenous ATP production. Treatment with a glycolysis inhibitor, 2-deoxyglucose (2-DG), reduced TNFAIP8 mediated glucose consumption, ATP production, spheroid formation, and PCa cell migration. By maintaining mitochondrial membrane potential, TNFAIP8 increased OXPHOS and glycolysis. Moreover, TNFAIP8 modulates the production of glycolytic metabolites in PCa cells. Collectively, our data suggest that TNFAIP8 exerts its oncogenic effects by enhancing glucose metabolism and by facilitating metabolic reprogramming in PCa cells. Therefore, TNFAIP8 may be a biomarker associated with prostate cancer and indicate a potential therapeutic target.
Topics: Apoptosis Regulatory Proteins; Cell Line, Tumor; Cell Movement; Cell Proliferation; Glycolysis; Humans; Male; Metabolism; Oxidative Phosphorylation; Prostatic Neoplasms; Signal Transduction
PubMed: 33227392
DOI: 10.1016/j.biocel.2020.105885 -
Advanced Drug Delivery Reviews Oct 2010Drug-metabolizing enzymes (DMEs) and transporters play pivotal roles in the disposition and detoxification of numerous foreign and endogenous chemicals. To accommodate... (Review)
Review
Drug-metabolizing enzymes (DMEs) and transporters play pivotal roles in the disposition and detoxification of numerous foreign and endogenous chemicals. To accommodate chemical challenges, the expression of many DMEs and transporters is up-regulated by a group of ligand-activated transcription factors namely nuclear receptors (NRs). The importance of NRs in xenobiotic metabolism and clearance is best exemplified by the most promiscuous xenobiotic receptors: pregnane X receptor (PXR, NR1I2) and constitutive androstane/activated receptor (CAR, NR1I3). Together, these two receptors govern the inductive expression of a largely overlapping array of target genes encoding phase I and II DMEs, and drug transporters. Moreover, PXR and CAR also represent two distinctive mechanisms of NR activation, whereby CAR demonstrates both constitutive and ligand-independent activation. In this review, recent advances in our understanding of PXR and CAR as xenosensors are discussed with emphasis placed on the differences rather than similarities of these two xenobiotic receptors in ligand recognition and target gene regulation.
Topics: Animals; Biological Transport; Carrier Proteins; Constitutive Androstane Receptor; Gene Expression Regulation; Humans; Inactivation, Metabolic; Ligands; Pregnane X Receptor; Receptors, Aryl Hydrocarbon; Receptors, Cytoplasmic and Nuclear; Receptors, Steroid; Transcription Factors; Xenobiotics
PubMed: 20727377
DOI: 10.1016/j.addr.2010.08.006 -
The Journal of Steroid Biochemistry and... May 2015CYP11A1 hydroxylates vitamin D3 producing 20S-hydroxyvitamin D3 [20(OH)D3] and 20S,23-dihydroxyvitamin D3 [20,23(OH)2D3] as the major and most characterized metabolites....
CYP11A1 hydroxylates vitamin D3 producing 20S-hydroxyvitamin D3 [20(OH)D3] and 20S,23-dihydroxyvitamin D3 [20,23(OH)2D3] as the major and most characterized metabolites. Both display immuno-regulatory and anti-cancer properties while being non-calcemic. A previous study indicated 20(OH)D3 can be metabolized by rat CYP24A1 to products including 20S,24-dihydroxyvitamin D3 [20,24(OH)2D3] and 20S,25-dihydroxyvitamin D3, with both producing greater inhibition of melanoma colony formation than 20(OH)D3. The aim of this study was to characterize the ability of rat and human CYP24A1 to metabolize 20(OH)D3 and 20,23(OH)2D3. Both isoforms metabolized 20(OH)D3 to the same dihydroxyvitamin D species with no secondary metabolites being observed. Hydroxylation at C24 produced both enantiomers of 20,24(OH)2D3. For rat CYP24A1 the preferred initial site of hydroxylation was at C24 whereas the human enzyme preferred C25. 20,23(OH)2D3 was initially metabolized to 20S,23,24-trihydroxyvitamin D3 and 20S,23,25-trihydroxyvitamin D3 by rat and human CYP24A1 as determined by NMR, with both isoforms showing a preference for initial hydroxylation at C25. CYP24A1 was able to further oxidize these metabolites in a series of reactions which included the cleavage of C23-C24 bond, as indicated by high resolution mass spectrometry of the products, analogous to the catabolism of 1,25(OH)2D3 via the C24-oxidation pathway. Similar catalytic efficiencies were observed for the metabolism of 20(OH)D3 and 20,23(OH)2D3 by human CYP24A1 and were lower than for the metabolism of 1,25(OH)2D3. We conclude that rat and human CYP24A1 metabolizes 20(OH)D3 producing only dihydroxyvitamin D3 species as products which retain biological activity, whereas 20,23(OH)2D3 undergoes multiple oxidations which include cleavage of the side chain.
Topics: Animals; Calcifediol; Dihydroxycholecalciferols; Humans; Hydroxylation; Oxidation-Reduction; Rats; Vitamin D; Vitamin D3 24-Hydroxylase
PubMed: 25727742
DOI: 10.1016/j.jsbmb.2015.02.010 -
Cell Cycle (Georgetown, Tex.) May 2013Here, we interrogated head and neck cancer (HNSCC) specimens (n = 12) to examine if different metabolic compartments (oxidative vs. glycolytic) co-exist in human tumors....
Here, we interrogated head and neck cancer (HNSCC) specimens (n = 12) to examine if different metabolic compartments (oxidative vs. glycolytic) co-exist in human tumors. A large panel of well-established biomarkers was employed to determine the metabolic state of proliferative cancer cells. Interestingly, cell proliferation in cancer cells, as marked by Ki-67 immunostaining, was strictly correlated with oxidative mitochondrial metabolism (OXPHOS) and the uptake of mitochondrial fuels, as detected via MCT1 expression (p < 0.001). More specifically, three metabolic tumor compartments were delineated: (1) proliferative and mitochondrial-rich cancer cells (Ki-67+/TOMM20+/COX+/MCT1+); (2) non-proliferative and mitochondrial-poor cancer cells (Ki-67-/TOMM20-/COX-/MCT1-); and (3) non-proliferative and mitochondrial-poor stromal cells (Ki-67-/TOMM20-/COX-/MCT1-). In addition, high oxidative stress (MCT4+) was very specific for cancer tissues. Thus, we next evaluated the prognostic value of MCT4 in a second independent patient cohort (n = 40). Most importantly, oxidative stress (MCT4+) in non-proliferating epithelial cancer cells predicted poor clinical outcome (tumor recurrence; p < 0.0001; log-rank test), and was functionally associated with FDG-PET avidity (p < 0.04). Similarly, oxidative stress (MCT4+) in tumor stromal cells was specifically associated with higher tumor stage (p < 0.03), and was a highly specific marker for cancer-associated fibroblasts (p < 0.001). We propose that oxidative stress is a key hallmark of tumor tissues that drives high-energy metabolism in adjacent proliferating mitochondrial-rich cancer cells, via the paracrine transfer of mitochondrial fuels (such as L-lactate and ketone bodies). New antioxidants and MCT4 inhibitors should be developed to metabolically target "three-compartment tumor metabolism" in head and neck cancers. It is remarkable that two "non-proliferating" populations of cells (Ki-67-/MCT4+) within the tumor can actually determine clinical outcome, likely by providing high-energy mitochondrial "fuels" for proliferative cancer cells to burn. Finally, we also show that in normal mucosal tissue, the basal epithelial "stem cell" layer is hyper-proliferative (Ki-67+), mitochondrial-rich (TOMM20+/COX+) and is metabolically programmed to use mitochondrial fuels (MCT1+), such as ketone bodies and L-lactate. Thus, oxidative mitochondrial metabolism (OXPHOS) is a common feature of both (1) normal stem cells and (2) proliferating cancer cells. As such, we should consider metabolically treating cancer patients with mitochondrial inhibitors (such as Metformin), and/or with a combination of MCT1 and MCT4 inhibitors, to target "metabolic symbiosis."
Topics: Aged; Aged, 80 and over; Biomarkers, Tumor; Cell Differentiation; Cell Proliferation; Epithelial Cells; Female; Fibroblasts; Glycolysis; Head and Neck Neoplasms; Humans; Kaplan-Meier Estimate; Ketone Bodies; Lactic Acid; Male; Membrane Transport Proteins; Middle Aged; Mitochondria; Mitochondrial Precursor Protein Import Complex Proteins; Monocarboxylic Acid Transporters; Muscle Proteins; Neoplasm Recurrence, Local; Neoplasm Staging; Neoplastic Stem Cells; Oxidative Phosphorylation; Oxidative Stress; Receptors, Cell Surface; Symporters
PubMed: 23574725
DOI: 10.4161/cc.24092 -
FEBS Letters Jun 2009Allosteric regulation of protein function occurs when the regulatory trigger, such as the binding of a small-molecule effector or inhibitor, takes place some distance... (Review)
Review
Allosteric regulation of protein function occurs when the regulatory trigger, such as the binding of a small-molecule effector or inhibitor, takes place some distance from the protein's, or protein complex's, active site. This distance can be a few A, or tens of A. Many proteins are regulated in this way and exhibit a variety of allosteric mechanisms. Here we review how analyses of experimentally determined models of protein 3D structures, using either X-ray crystallography or NMR spectroscopy, have revealed some of the mechanisms involved.
Topics: Allosteric Regulation; Catalytic Domain; Crystallography, X-Ray; Models, Molecular; Nuclear Magnetic Resonance, Biomolecular; Phosphorylation; Protein Binding; Protein Conformation; Proteins
PubMed: 19303011
DOI: 10.1016/j.febslet.2009.03.019 -
Current Biology : CB Jan 1996Recent studies of protein-dependent RNA splicing have provided new insights into the way RNA-protein interactions drive the stepwise assembly of catalytic RNA structures. (Review)
Review
Recent studies of protein-dependent RNA splicing have provided new insights into the way RNA-protein interactions drive the stepwise assembly of catalytic RNA structures.
Topics: Fungal Proteins; RNA; RNA Splicing; RNA-Binding Proteins; Ribonucleoproteins; Saccharomyces cerevisiae Proteins
PubMed: 8805212
DOI: 10.1016/s0960-9822(02)00412-8 -
Molecular Cell Feb 2018S-nitrosylation, the oxidative modification of Cys residues by nitric oxide (NO) to form S-nitrosothiols (SNOs), modifies all main classes of proteins and provides a...
S-nitrosylation, the oxidative modification of Cys residues by nitric oxide (NO) to form S-nitrosothiols (SNOs), modifies all main classes of proteins and provides a fundamental redox-based cellular signaling mechanism. However, in contrast to other post-translational protein modifications, S-nitrosylation is generally considered to be non-enzymatic, involving multiple chemical routes. We report here that endogenous protein S-nitrosylation in the model organism E. coli depends principally upon the enzymatic activity of the hybrid cluster protein Hcp, employing NO produced by nitrate reductase. Anaerobiosis on nitrate induces both Hcp and nitrate reductase, thereby resulting in the S-nitrosylation-dependent assembly of a large interactome including enzymes that generate NO (NO synthase), synthesize SNO-proteins (SNO synthase), and propagate SNO-based signaling (trans-nitrosylases) to regulate cell motility and metabolism. Thus, protein S-nitrosylation by NO in E. coli is essentially enzymatic, and the potential generality of the multiplex enzymatic mechanism that we describe may support a re-conceptualization of NO-based cellular signaling.
Topics: Cysteine; Escherichia coli; Escherichia coli Proteins; Nitric Oxide; Nitrosation; Oxidation-Reduction; Protein Processing, Post-Translational; Proteins; Proteolysis; Proteomics; S-Nitrosothiols; Signal Transduction
PubMed: 29358078
DOI: 10.1016/j.molcel.2017.12.025