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Protoplasma 2007Division and partitioning of microbodies (peroxisomes) of the green alga Klebsormidium flaccidum, whose cells contain a single microbody, were investigated by electron...
Division and partitioning of microbodies (peroxisomes) of the green alga Klebsormidium flaccidum, whose cells contain a single microbody, were investigated by electron microscopy. In interphase, the rod-shaped microbody is present between the nucleus and the single chloroplast, oriented perpendicular to the pole-to-pole direction of the future spindle. A centriole pair associates with one distal end of the microbody. In prophase, the microbody changes not only in shape, from a rodlike to a branched form, but also in orientation, from perpendicular to parallel to the future pole-to-pole direction. Duplicated centriole pairs are localized in close proximity to both distal ends of the microbody. In metaphase, the elongated microbody flanks the open spindle, with both distal ends close to the centriole pair at either spindle pole. The microbody further elongates in telophase and divides after septum formation (cytokinesis) has started. The association between the centrioles and both distal ends of the microbody is maintained throughout mitosis, resulting in the distal ends of the elongated microbody being fixed at the cellular poles. This configuration of the microbody may be favorable for faithful transmission of the organelle during cell division. After cytokinesis is completed, the microbody reverts to the perpendicular orientation by changing its shape. Microtubules radiating from the centrosomes flank the side of the microbody throughout mitosis. The close association of centrosomes and microtubules with the microbody is discussed in respect to the partitioning of the microbody in this alga.
Topics: Centrioles; Centrosome; Chlorophyta; Chromosomes; Microbodies; Microscopy, Electron; Microtubules; Mitosis; Spindle Apparatus
PubMed: 17922263
DOI: 10.1007/s00709-007-0267-6 -
Fungal Genetics and Biology : FG & B Mar 2009Fungal microbodies (peroxisomes) are inducible organelles that proliferate in response to nutritional cues. Proteins involved in peroxisome biogenesis/proliferation are...
Fungal microbodies (peroxisomes) are inducible organelles that proliferate in response to nutritional cues. Proteins involved in peroxisome biogenesis/proliferation are designated peroxins and are encoded by PEX genes. An autophagy-related process, termed pexophagy, is responsible for the selective removal of peroxisomes from the cell. Several genes involved in pexophagy are also required for autophagy and are collectively known as ATG genes. We have re-analysed the Aspergillus nidulans genome for the presence of PEX and ATG genes and have identified a number of previously missed genes. Also, we manually determined the correct intron positions in each identified gene. The data show that in A. nidulans and related fungi the basic set of genes involved in peroxisome biogenesis or degradation are conserved. However, both processes have features that more closely resemble organelle formation/degradation in mammals rather than yeast. Thus, filamentous fungi like A. nidulans are ideal model systems for peroxisome homeostasis in man.
Topics: Aspergillus nidulans; Conserved Sequence; Fungal Proteins; Introns; Microbodies
PubMed: 18694841
DOI: 10.1016/j.fgb.2008.07.009 -
Annual Review of Nutrition 1994Peroxisomes are present in virtually all eukaryotic cells. At present, they are known to contain more than 50 enzymes, more than half of which play a role in lipid... (Comparative Study)
Comparative Study Review
Peroxisomes are present in virtually all eukaryotic cells. At present, they are known to contain more than 50 enzymes, more than half of which play a role in lipid metabolism. During the past two decades, considerable knowledge has been gained about the role of peroxisomes in lipid metabolism, the implications of induction of hepatic peroxisome proliferation and the peroxisomal fatty acid beta-oxidation enzyme system in the development of hepatocellular carcinomas in rats and mice by structurally diverse groups of chemicals designated as peroxisome proliferators, and the biochemical basis for inheritable diseases in humans caused by disturbances and/or deficiencies in peroxisomal lipid metabolism. Nevertheless, many unanswered questions remain. The ontogeny and homeostatic interrelationships between the enzymes of the peroxisomal and mitochondrial lipid metabolism have yet to be fully elucidated. The mechanism(s) by which PPARs are activated also remains unclear. Information about the interplay between PPAR, RXR alpha, HSP72, and other possible regulatory molecules is necessary to elucidate the transcriptional activation of inducible peroxisomal genes. The assumption that multiple signaling pathways may be responsible for the pleiotropic responses induced by structurally different peroxisome proliferators requires further examination. Finally, studies to identify and characterize different PPARs and PPREs from inducible peroxisomal genes from a variety of species are also required for a clear understanding of the role of peroxisomal beta-oxidation enzyme system in the pathogenesis of hepatocellular carcinogenesis induced by peroxisome proliferators.
Topics: Animals; Fatty Acids; Glycerophosphates; Humans; Lipid Metabolism; Lipid Metabolism, Inborn Errors; Microbodies; Mitochondria; Oxidation-Reduction
PubMed: 7946524
DOI: 10.1146/annurev.nu.14.070194.002015 -
The Histochemical Journal Jul 1978The effects of detergents, organic lipid solvents, and several adjuvants used in cell fractionation on the ultrastructure of the peroxisomal (microbody) membrane and its...
The effects of detergents, organic lipid solvents, and several adjuvants used in cell fractionation on the ultrastructure of the peroxisomal (microbody) membrane and its permeability to catalase have been investigated. Chopper sections of glutaraldehyde-fixed liver were incubated in the presence of various agents, followed by cytochemical staining for catalase and processed for electron microscopy. Catalase activity was also determined biochemically in the incubation medium. Marked catalase diffusion was found after treatment with 1% or 0.5% Triton X-100 or deoxycholate, as well as with 50% ethanol or acetone or 20% propanol or t-butanol. In contrast, 1% digitonin and lower concentrations of the above agents, as well as sucrose or glycerine caused selective diffusion of catalase from a limited population of peroxisomes. Treatment with 10% polyvinylpyrrolidone (PVP), which has been used as a protective agent in the isolation of microbodies, did not produce any alteration in the fine structure and cytochemical appearance of peroxisomes. These findings concur with earlier biochemical studies on freshly isolated peroxisomes and demonstrate the susceptibility of microbodies, even in glutaraldehyde-fixed rat liver to the effects of various agents which affect the microbody membrane. A close correlation between the ultrastructural integrity of the microbody membrane and its permeability to catalase has been found. The significance of these observations for the assessment of the permeability characteristics of the microbody membrane is discussed.
Topics: Animals; Catalase; Deoxycholic Acid; Digitonin; Glycerol; Lipids; Male; Membranes; Microbodies; Organoids; Permeability; Polyethylene Glycols; Povidone; Quaternary Ammonium Compounds; Rats; Sucrose
PubMed: 669986
DOI: 10.1007/BF01003010 -
Molecular and Cellular Biochemistry Jan 1997In this article, the capabilities of peroxisomal involvement in the gluconeogenetic processes of vertebrate animals are reviewed in the light of recent findings on... (Review)
Review
In this article, the capabilities of peroxisomal involvement in the gluconeogenetic processes of vertebrate animals are reviewed in the light of recent findings on peroxisomal metabolism and proliferation. It is demonstrated that the participation of this organelle affords the potential of alternative pathways for the conversion of triacylglycerols to glucose, and for the conversion of amino acids and lactate to carbohydrate. Of interest in this connection, too, is that glyoxylate may act as a key intermediate in the gluconeogenetic functions of peroxisomes in both plants and animals. In addition, a close connection between peroxisomal function and the hormonal control of gluconeogenesis has been described, with these interrelationships extending to the associated phenomena of cellular signalling, gene expression, peroxisomal proliferation, and the function of insulin-like growth factors. The metabolic advantages of some of these alternative pathways for gluconeogenesis have been detailed, and suggestions made for the further testing of their quantitative relativities.
Topics: Amino Acids; Animals; Gene Expression Regulation; Gluconeogenesis; Glyoxylates; Insulin; Lactic Acid; Microbodies; Plants; Triglycerides
PubMed: 9046033
DOI: 10.1023/a:1006879111028 -
Journal of Cell Science Jul 2002All kinetoplastids contain membrane-bound microbodies known as glycosomes, in which several metabolic pathways including part of glycolysis are compartmentalized....
All kinetoplastids contain membrane-bound microbodies known as glycosomes, in which several metabolic pathways including part of glycolysis are compartmentalized. Peroxin 2 is essential for the import of many proteins into the microbodies of yeasts and mammals. The PEX2 gene of Trypanosoma brucei was identified and its expression was silenced by means of tetracycline-inducible RNA interference. Bloodstream-form trypanosomes, which rely exclusively on glycolysis for ATP generation, died rapidly upon PEX2 depletion. Insect-form (procyclic) trypanosomes do not rely solely on glycolysis for ATP synthesis. PEX2 depletion in procyclic forms resulted in relocation of most tested matrix proteins to the cytosol, and these mutants also died. Compartmentation of microbody enzymes is therefore essential for survival of bloodstream and procyclic T. brucei. In contrast, yeasts and cultured mammalian cells grow normally in the absence of peroxisomal membranes unless placed on selective media.
Topics: Animals; Cell Compartmentation; Down-Regulation; Gene Expression Regulation, Enzymologic; Genes, Lethal; Glyceraldehyde-3-Phosphate Dehydrogenases; Glycolysis; Membrane Proteins; Microbodies; Mutation; Peroxisomal Biogenesis Factor 2; Protein Transport; RNA, Double-Stranded; RNA, Messenger; Trypanosoma brucei brucei; Trypanosomiasis, African
PubMed: 12077356
DOI: 10.1242/jcs.115.13.2651 -
FEMS Microbiology Reviews Dec 1990This symposium marks the 15th anniversary of the discovery of microbodies in methylotrophic yeasts. In the intervening years much has been learned about the structure,... (Review)
Review
This symposium marks the 15th anniversary of the discovery of microbodies in methylotrophic yeasts. In the intervening years much has been learned about the structure, function and biogenesis of these organelles and these advances are described. As our endeavours continued, unexpected results have confused commonly held views. This was for instance the case when microbody-minus mutants of yeasts became available which showed that some microbody matrix enzymes may be functional when present in the cytosol while others are not. At the molecular level, our understanding of structure/function relationships is also expanding. Examples are structural elements which relate to protein topogenesis and function of enzymes in different cell compartments. Other, perhaps more unusual, adaptations have also been encountered; some involve protein-protein interactions or even modified cofactors which possibly have helped methylotrophic yeasts to establish and/or maintain themselves in natural ecosystems.
Topics: Methanol; Microbodies; Mutation; Structure-Activity Relationship; Yeasts
PubMed: 2094284
DOI: 10.1111/j.1574-6968.1990.tb04912.x -
Molecular Microbiology Dec 1992Eukaryotic cells have evolved a complex set of intracellular organelles, each of which possesses a specific complement of enzymes and performs unique metabolic... (Review)
Review
Eukaryotic cells have evolved a complex set of intracellular organelles, each of which possesses a specific complement of enzymes and performs unique metabolic functions. This compartmentalization of cellular functions provides a level of metabolic control not available to prokaryotes. However, it presents the eukaryotic cell with the problem of targeting proteins to their specific location(s). Proteins must be efficiently transported from their site of synthesis in the cytosol to their specific organelle(s). Such a process may require translocation across one or more hydrophobic membrane barriers and/or asymmetric integration into specific membranes. Proteins carry cis-acting amino acid sequences that serve to act as recognition motifs for protein sorting and for the cellular translocation machinery. Sequences that target proteins to the endoplasmic reticulum/secretory pathway, mitochondria, and chloroplasts are often present as cleavable amino-terminal extensions. In contrast, most peroxisomal proteins are synthesized at their mature size and are translocated to the organelle without any post-translational modification. This review will summarize what is known about how yeast solve the problem of specifically importing proteins into peroxisomes and will suggest future directions for investigations into peroxisome biogenesis in yeast.
Topics: Amino Acid Sequence; Biological Transport; Cell Compartmentation; Fungal Proteins; Microbodies; Molecular Sequence Data; Morphogenesis; Saccharomyces cerevisiae
PubMed: 1474890
DOI: 10.1111/j.1365-2958.1992.tb01780.x -
Clinica Chimica Acta; International... Mar 1988Peroxisomes have been shown to participate in a variety of pathological processes. Peroxisomal anomalities are central features of Zellweger's cerebro-hepato-renal... (Review)
Review
Peroxisomes have been shown to participate in a variety of pathological processes. Peroxisomal anomalities are central features of Zellweger's cerebro-hepato-renal syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease and several other genetic metabolic disorders (pseudo-Zellweger syndrome, Leber congenital amaurosis, cerebrotendinous xanthomatosis, rhizomelic chondrodysplasia punctata). In disorders with general loss of peroxisomal functions (Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease) an accumulation of very long-chain fatty acids and pathological bile acids are found. Patients have a defective synthesis of plasmalogens and show increased excretion of dicarboxylic acids of medium chain length and of pipecolic acid in the urine. These anomalities which are due to the lack of peroxisomal enzymes, supply the basis for clinical laboratory tests. The study of these peroxisomal disorders has presented valuable information on the normal function of peroxisomes.
Topics: Humans; Metabolic Diseases; Microbodies
PubMed: 3289796
DOI: 10.1016/0009-8981(88)90357-9 -
Current Opinion in Cell Biology Aug 2002Peroxisome development is a dynamic process that may involve organelle fusion and fission events. Cells contain different types of peroxisomes that vary in protein... (Review)
Review
Peroxisome development is a dynamic process that may involve organelle fusion and fission events. Cells contain different types of peroxisomes that vary in protein composition and capacity to incorporate membrane and matrix proteins. The protein import machinery is highly flexible and includes a cycling receptor that passes the peroxisomal membrane.
Topics: Animals; Extracellular Matrix Proteins; Humans; Membrane Proteins; Microbodies; Models, Biological; Neurospora crassa; Penicillium; Peroxisomes; Protein Transport; Proteins; Receptors, Cytoplasmic and Nuclear
PubMed: 12383803
DOI: 10.1016/s0955-0674(02)00354-x