scholarly journals Coenzyme Q10 deficiencies: pathways in yeast and humans

2018 ◽  
Vol 62 (3) ◽  
pp. 361-376 ◽  
Author(s):  
Agape M. Awad ◽  
Michelle C. Bradley ◽  
Lucía Fernández-del-Río ◽  
Anish Nag ◽  
Hui S. Tsui ◽  
...  
Keyword(s):  
Biosynthetic Pathway ◽  
De Novo ◽  
Human Gene ◽  
Coenzyme Q ◽  
Human Cells ◽  
Yeast Cells ◽  
Gene Products ◽  
Functional Conservation ◽  
Hydrophobic Lipid ◽  
Yeast Genes

Coenzyme Q (ubiquinone or CoQ) is an essential lipid that plays a role in mitochondrial respiratory electron transport and serves as an important antioxidant. In human and yeast cells, CoQ synthesis derives from aromatic ring precursors and the isoprene biosynthetic pathway. Saccharomyces cerevisiae coq mutants provide a powerful model for our understanding of CoQ biosynthesis. This review focusses on the biosynthesis of CoQ in yeast and the relevance of this model to CoQ biosynthesis in human cells. The COQ1–COQ11 yeast genes are required for efficient biosynthesis of yeast CoQ. Expression of human homologs of yeast COQ1–COQ10 genes restore CoQ biosynthesis in the corresponding yeast coq mutants, indicating profound functional conservation. Thus, yeast provides a simple yet effective model to investigate and define the function and possible pathology of human COQ (yeast or human gene involved in CoQ biosynthesis) gene polymorphisms and mutations. Biosynthesis of CoQ in yeast and human cells depends on high molecular mass multisubunit complexes consisting of several of the COQ gene products, as well as CoQ itself and CoQ intermediates. The CoQ synthome in yeast or Complex Q in human cells, is essential for de novo biosynthesis of CoQ. Although some human CoQ deficiencies respond to dietary supplementation with CoQ, in general the uptake and assimilation of this very hydrophobic lipid is inefficient. Simple natural products may serve as alternate ring precursors in CoQ biosynthesis in both yeast and human cells, and these compounds may act to enhance biosynthesis of CoQ or may bypass certain deficient steps in the CoQ biosynthetic pathway.

scholarly journals Surprising Arginine Biosynthesis: a Reappraisal of the Enzymology and Evolution of the Pathway in Microorganisms

2007 ◽  
Vol 71 (1) ◽  
pp. 36-47 ◽  
Author(s):  
Ying Xu ◽  
Bernard Labedan ◽  
Nicolas Glansdorff
Keyword(s):  
Biosynthetic Pathway ◽  
De Novo ◽  
Single Gene ◽  
Metabolic Function ◽  
Gene Products ◽  
Arginine Biosynthesis ◽  
Acetyl Coenzyme A ◽  
Bacterial Phyla ◽  
Acetyl Group ◽  
Acetylglutamate Synthase

SUMMARY Major aspects of the pathway of de novo arginine biosynthesis via acetylated intermediates in microorganisms must be revised in light of recent enzymatic and genomic investigations. The enzyme N-acetylglutamate synthase (NAGS), which used to be considered responsible for the first committed step of the pathway, is present in a limited number of bacterial phyla only and is absent from Archaea. In many Bacteria, shorter proteins related to the Gcn5-related N-acetyltransferase family appear to acetylate l-glutamate; some are clearly similar to the C-terminal, acetyl-coenzyme A (CoA) binding domain of classical NAGS, while others are more distantly related. Short NAGSs can be single gene products, as in Mycobacterium spp. and Thermus spp., or fused to the enzyme catalyzing the last step of the pathway (argininosuccinase), as in members of the Alteromonas-Vibrio group. How these proteins bind glutamate remains to be determined. In some Bacteria, a bifunctional ornithine acetyltransferase (i.e., using both acetylornithine and acetyl-CoA as donors of the acetyl group) accounts for glutamate acetylation. In many Archaea, the enzyme responsible for glutamate acetylation remains elusive, but possible connections with a novel lysine biosynthetic pathway arose recently from genomic investigations. In some Proteobacteria (notably Xanthomonadaceae) and Bacteroidetes, the carbamoylation step of the pathway appears to involve N-acetylornithine or N-succinylornithine rather than ornithine. The product N-acetylcitrulline is deacetylated by an enzyme that is also involved in the provision of ornithine from acetylornithine; this is an important metabolic function, as ornithine itself can become essential as a source of other metabolites. This review insists on the biochemical and evolutionary implications of these findings.

scholarly journals Multiple Blocks to Human Immunodeficiency Virus Type 1 Replication in Rodent Cells

2000 ◽  
Vol 74 (21) ◽  
pp. 9868-9877 ◽  
Author(s):  
Paul D. Bieniasz ◽  
Bryan R. Cullen
Keyword(s):  
Gene Expression ◽  
Human Immunodeficiency Virus ◽  
Cell Lines ◽  
Infectious Virus ◽  
Human Gene ◽  
Human Cells ◽  
Gene Products ◽  
Immunodeficiency Virus ◽  
Hiv 1

ABSTRACT The recent identification of human gene products that are required for early steps in the human immunodeficiency virus type 1 (HIV-1) life cycle has raised the possibility that rodents might be engineered to support HIV-1 infection. Therefore, we have examined the ability of modified mouse, rat, and hamster cell lines to support productive HIV-1 replication. Rodent cells, engineered to support Tat function by stable expression of a permissive cyclin T1 protein, proved to be able to support reverse transcription, integration, and early gene expression at levels comparable to those observed in human cell lines. Surprisingly, however, levels of CD4- and coreceptor-dependent virus entry were reduced to a variable but significant extent in both mouse and rat fibroblast cell lines. Additional posttranscriptional defects were observed, including a reduced level of unspliced HIV-1 genomic RNA and reduced structural gene expression. Furthermore, the HIV-1 Gag precursor is generally inefficiently processed and is poorly secreted from mouse and rat cells in a largely noninfectious form. These posttranscriptional defects, together, resulted in a dramatically reduced yield of infectious virus (up to 10,000-fold) over a single cycle of HIV-1 replication, as compared to human cells. Interestingly, these defects were less pronounced in one hamster cell line, CHO, which not only was able to produce infectious HIV-1 particles at a level close to that observed in human cells, but also could support transient, low-level HIV-1 replication. Importantly, the blocks to infectious virus production in mouse and rat cells are recessive, since they can be substantially suppressed by fusion with uninfected human cells. These studies imply the existence of one or more human gene products, either lacking or nonfunctional in most rodent cells that are critical for infectious HIV-1 virion morphogenesis.

scholarly journals Human to yeast pathway transplantation: cross-species dissection of the adenine de novo pathway regulatory node

2017 ◽  
Author(s):  
Neta Agmon ◽  
Jasmine Temple ◽  
Zuojian Tang ◽  
Tobias Schraink ◽  
Maayan Baron ◽  
...  
Keyword(s):  
Yeast Strain ◽  
Transcriptional Control ◽  
De Novo ◽  
Enzyme Level ◽  
Yeast Cells ◽  
Protein Coding ◽  
Coding Regions ◽  
Human Proteins ◽  
Human Ortholog ◽  
Yeast Genes

AbstractPathway transplantation from one organism to another represents a means to a more complete understanding of a biochemical or regulatory process. The purine biosynthesis pathway, a core metabolic function, was transplanted from human to yeast. We replaced the entireSaccharomyces cerevisiaeadenine de novo pathway with the cognate human pathway components. A yeast strain was “humanized” for the full pathway by deleting all relevant yeast genes completely and then providing the human pathway in trans using a neochromosome expressing the human protein coding regions under the transcriptional control of their cognate yeast promoters and terminators. The “humanized” yeast strain grows in the absence of adenine, indicating complementation of the yeast pathway by the full set of human proteins. While the strain with the neochromosome is indeed prototrophic, it grows slowly in the absence of adenine. Dissection of the phenotype revealed that the human ortholog ofADE4, PPAT, shows only partial complementation. We have used several strategies to understand this phenotype, that point toPPAT/ADE4as the central regulatory node. Pathway metabolites are responsible for regulatingPPAT’sprotein abundance through transcription and proteolysis as well as its enzymatic activity by allosteric regulation in these yeast cells. Extensive phylogenetic analysis of PPATs from diverse organisms hints at adaptations of the enzyme-level regulation to the metabolite levels in the organism. Finally, we isolated specific mutations in PPAT as well as in other genes involved in the purine metabolic network that alleviate incomplete complementation byPPATand provide further insight into the complex regulation of this critical metabolic pathway.

scholarly journals Inverse regulation of the yeast COX5 genes by oxygen and heme.

1989 ◽  
Vol 9 (5) ◽  
pp. 1958-1964 ◽  
Author(s):  
M R Hodge ◽  
G Kim ◽  
K Singh ◽  
M G Cumsky
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Environmental Conditions ◽  
Physiological Response ◽  
Biosynthetic Pathway ◽  
Yeast Cells ◽  
Yeast Mitochondria ◽  
Aerobic Growth ◽  
Yeast Strains ◽  
Yeast Genes

The COX5a and COX5b genes encode divergent forms of yeast cytochrome c oxidase subunit V. Although the polypeptide products of the two genes are functionally interchangeable, it is the Va subunit that is normally found in preparations of yeast mitochondria and cytochrome c oxidase. We show here that the predominance of subunit Va stems in part from the differential response of the two genes to the presence of molecular oxygen. Our results indicate that during aerobic growth, COX5a levels were high, while COX5b levels were low. Anaerobically, the pattern was reversed; COX5a levels dropped sevenfold, while those of COX5b were elevated sevenfold. Oxygen appeared to act at the level of transcription through heme, since the addition of heme restored an aerobic pattern of transcription to anaerobically grown cells and the effect of anaerobiosis on COX5 transcription was reproduced in strains containing a mutation in the heme-biosynthetic pathway (hem1). In conjunction with the oxygen-heme response, we determined that the product of the ROX1 gene, a trans-acting regulator of several yeast genes controlled by oxygen, is also involved in COX5 expression. These results, as well as our observation that COX5b expression varied significantly in certain yeast strains, indicate that the COX5 genes undergo a complex pattern of regulation. This regulation, especially the increase in COX5b levels anaerobically, may reflect an attempt to modulate the activity of a key respiratory enzyme in response to varying environmental conditions. The results presented here, as well as those from other laboratories, suggest that the induction or derepression of certain metabolic enzymes during anaerobiosis may be a common and important physiological response in yeast cells.

scholarly journals TRPM5-mediated calcium uptake regulates mucin secretion from human colon goblet cells

eLife ◽  
2013 ◽  
Vol 2 ◽  
Author(s):  
Sandra Mitrovic ◽  
Cristina Nogueira ◽  
Gerard Cantero-Recasens ◽  
Kerstin Kiefer ◽  
José M Fernández-Fernández ◽  
...  
Keyword(s):  
Calcium Uptake ◽  
De Novo ◽  
Human Gene ◽  
Colonic Cancer ◽  
Secretory Granules ◽  
Human Colon ◽  
Goblet Cells ◽  
Gene Products ◽  
Mucin Secretion ◽  
The Difference

Mucin 5AC (MUC5AC) is secreted by goblet cells of the respiratory tract and, surprisingly, also expressed de novo in mucus secreting cancer lines. siRNA-mediated knockdown of 7343 human gene products in a human colonic cancer goblet cell line (HT29-18N2) revealed new proteins, including a Ca2+-activated channel TRPM5, for MUC5AC secretion. TRPM5 was required for PMA and ATP-induced secretion of MUC5AC from the post-Golgi secretory granules. Stable knockdown of TRPM5 reduced a TRPM5-like current and ATP-mediated Ca2+ signal. ATP-induced MUC5AC secretion depended strongly on Ca2+ influx, which was markedly reduced in TRPM5 knockdown cells. The difference in ATP-induced Ca2+ entry between control and TRPM5 knockdown cells was abrogated in the absence of extracellular Ca2+ and by inhibition of the Na+/Ca2+ exchanger (NCX). Accordingly, MUC5AC secretion was reduced by inhibition of NCX. Thus TRPM5 activation by ATP couples TRPM5-mediated Na+ entry to promote Ca2+ uptake via an NCX to trigger MUC5AC secretion.

Inverse regulation of the yeast COX5 genes by oxygen and heme

1989 ◽  
Vol 9 (5) ◽  
pp. 1958-1964
Author(s):  
M R Hodge ◽  
G Kim ◽  
K Singh ◽  
M G Cumsky
Keyword(s):  
Cytochrome C ◽  
Cytochrome C Oxidase ◽  
Environmental Conditions ◽  
Physiological Response ◽  
Biosynthetic Pathway ◽  
Yeast Cells ◽  
Yeast Mitochondria ◽  
Aerobic Growth ◽  
Yeast Strains ◽  
Yeast Genes

The COX5a and COX5b genes encode divergent forms of yeast cytochrome c oxidase subunit V. Although the polypeptide products of the two genes are functionally interchangeable, it is the Va subunit that is normally found in preparations of yeast mitochondria and cytochrome c oxidase. We show here that the predominance of subunit Va stems in part from the differential response of the two genes to the presence of molecular oxygen. Our results indicate that during aerobic growth, COX5a levels were high, while COX5b levels were low. Anaerobically, the pattern was reversed; COX5a levels dropped sevenfold, while those of COX5b were elevated sevenfold. Oxygen appeared to act at the level of transcription through heme, since the addition of heme restored an aerobic pattern of transcription to anaerobically grown cells and the effect of anaerobiosis on COX5 transcription was reproduced in strains containing a mutation in the heme-biosynthetic pathway (hem1). In conjunction with the oxygen-heme response, we determined that the product of the ROX1 gene, a trans-acting regulator of several yeast genes controlled by oxygen, is also involved in COX5 expression. These results, as well as our observation that COX5b expression varied significantly in certain yeast strains, indicate that the COX5 genes undergo a complex pattern of regulation. This regulation, especially the increase in COX5b levels anaerobically, may reflect an attempt to modulate the activity of a key respiratory enzyme in response to varying environmental conditions. The results presented here, as well as those from other laboratories, suggest that the induction or derepression of certain metabolic enzymes during anaerobiosis may be a common and important physiological response in yeast cells.

Arabidopsis 4-COUMAROYL-COA LIGASE 8 contributes to the biosynthesis of the benzenoid ring of coenzyme Q in peroxisomes

2019 ◽  
Vol 476 (22) ◽  
pp. 3521-3532
Author(s):  
Eric Soubeyrand ◽  
Megan Kelly ◽  
Shea A. Keene ◽  
Ann C. Bernert ◽  
Scott Latimer ◽  
...  
Keyword(s):  
Oxidative Metabolism ◽  
Time Course ◽  
Reverse Genetics ◽  
De Novo ◽  
Coenzyme Q ◽  
Control Level ◽  
Wild Type ◽  
Fluorescent Reporters ◽  
Coa Ligase ◽  
Peroxisomal Targeting

Plants have evolved the ability to derive the benzenoid moiety of the respiratory cofactor and antioxidant, ubiquinone (coenzyme Q), either from the β-oxidative metabolism of p-coumarate or from the peroxidative cleavage of kaempferol. Here, isotopic feeding assays, gene co-expression analysis and reverse genetics identified Arabidopsis 4-COUMARATE-COA LIGASE 8 (4-CL8; At5g38120) as a contributor to the β-oxidation of p-coumarate for ubiquinone biosynthesis. The enzyme is part of the same clade (V) of acyl-activating enzymes than At4g19010, a p-coumarate CoA ligase known to play a central role in the conversion of p-coumarate into 4-hydroxybenzoate. A 4-cl8 T-DNA knockout displayed a 20% decrease in ubiquinone content compared with wild-type plants, while 4-CL8 overexpression boosted ubiquinone content up to 150% of the control level. Similarly, the isotopic enrichment of ubiquinone's ring was decreased by 28% in the 4-cl8 knockout as compared with wild-type controls when Phe-[Ring-13C6] was fed to the plants. This metabolic blockage could be bypassed via the exogenous supply of 4-hydroxybenzoate, the product of p-coumarate β-oxidation. Arabidopsis 4-CL8 displays a canonical peroxisomal targeting sequence type 1, and confocal microscopy experiments using fused fluorescent reporters demonstrated that this enzyme is imported into peroxisomes. Time course feeding assays using Phe-[Ring-13C6] in a series of Arabidopsis single and double knockouts blocked in the β-oxidative metabolism of p-coumarate (4-cl8; at4g19010; at4g19010 × 4-cl8), flavonol biosynthesis (flavanone-3-hydroxylase), or both (at4g19010 × flavanone-3-hydroxylase) indicated that continuous high light treatments (500 µE m−2 s−1; 24 h) markedly stimulated the de novo biosynthesis of ubiquinone independently of kaempferol catabolism.

New insights into heparan sulphate biosynthesis from the study of mutant mice

2002 ◽  
Vol 69 ◽  
pp. 47-57 ◽  
Author(s):  
Catherine L. R. Merry ◽  
John T. Gallagher
Keyword(s):  
Growth Factors ◽  
Biosynthetic Pathway ◽  
Heparan Sulphate ◽  
Mutant Mice ◽  
Gene Products ◽  
Multiple Gene ◽  
Adhesion Proteins ◽  
Ligand Interactions

Heparan sulphate (HS) is an essential co-receptor for a number of growth factors, morphogens and adhesion proteins. The biosynthetic modifications involved in the generation of a mature HS chain may determine the strength and outcome of HS–ligand interactions. These modifications are catalysed by a complex family of enzymes, some of which occur as multiple gene products. Various mutant mice have now been generated, which lack the function of isolated components of the HS biosynthetic pathway. In this discussion, we outline the key findings of these studies, and use them to put into context our own work concerning the structure of the HS generated by the Hs2st-/- mice.

scholarly journals EXO1 Plays a Role in Generating Type I and Type II Survivors in Budding Yeast

Genetics ◽  
2004 ◽  
Vol 166 (4) ◽  
pp. 1641-1649
Author(s):  
Laura Maringele ◽  
David Lydall
Keyword(s):  
Homologous Recombination ◽  
Budding Yeast ◽  
Human Cells ◽  
Telomere Maintenance ◽  
Recombination Process ◽  
Yeast Cells ◽  
Type I ◽  
Type Ii ◽  
Recombination Proteins

Abstract Telomerase-defective budding yeast cells escape senescence by using homologous recombination to amplify telomeric or subtelomeric structures. Similarly, human cells that enter senescence can use homologous recombination for telomere maintenance, when telomerase cannot be activated. Although recombination proteins required to generate telomerase-independent survivors have been intensively studied, little is known about the nucleases that generate the substrates for recombination. Here we demonstrate that the Exo1 exonuclease is an initiator of the recombination process that allows cells to escape senescence and become immortal in the absence of telomerase. We show that EXO1 is important for generating type I survivors in yku70Δ mre11Δ cells and type II survivors in tlc1Δ cells. Moreover, in tlc1Δ cells, EXO1 seems to contribute to the senescence process itself.

scholarly journals A Nucleolar Protein That Affects Mating Efficiency in Saccharomyces cerevisiae by Altering the Morphological Response to Pheromone

Genetics ◽  
1998 ◽  
Vol 149 (2) ◽  
pp. 795-805
Author(s):  
Jinah Kim ◽  
Jeanne P Hirsch
Keyword(s):  
Growth Regulation ◽  
Subcellular Location ◽  
Null Alleles ◽  
Temperature Sensitive ◽  
Gene Products ◽  
Morphological Response ◽  
Mating Efficiency ◽  
Yeast Genes ◽  
Transcriptional Induction ◽  
In Cells

Abstract SSF1 and SSF2 are redundant essential yeast genes that, when overexpressed, increase the mating efficiency of cells containing a defective Ste4p Gβ subunit. To identify the precise function of these genes in mating, different responses to pheromone were assayed in cells that either lacked or overexpressed SSF gene products. Cells containing null alleles of both SSF1 and SSF2 displayed the normal transcriptional induction response to pheromone but were unable to form mating projections. Overexpression of SSF1 conferred the ability to form mating projections on cells containing a temperature-sensitive STE4 allele, but had only a small effect on transcriptional induction. SSF1 overexpression preferentially increased the mating efficiency of a strain containing a null allele of SPA2, a gene that functions specifically in cell morphology. To investigate whether Ssf1p plays a direct physical role in mating projection formation, its subcellular location was determined. An Ssf1p-GFP fusion was found to localize to the nucleolus, implying that the role of SSF gene products in projection formation is indirect. The region of Ssf1p-GFP localization in cells undergoing projection formation was larger and more diffuse, and was often present in a specific orientation with respect to the projection. Although the function of Ssf1p appears to originate in the nucleus, it is likely that it ultimately acts on one or more of the proteins that is directly involved in the morphological response to pheromone. Because many of the proteins required for projection formation during mating are also required for bud formation during vegetative growth, regulation of the activity or amount of one or more of these proteins by Ssf1p could explain its role in both mating and dividing cells.

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