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1
South, Sarah T. y Stephen J. Gould. "Peroxisome Synthesis in the Absence of Preexisting Peroxisomes". Journal of Cell Biology 144, n.º 2 (25 de enero de 1999): 255–66. http://dx.doi.org/10.1083/jcb.144.2.255.
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Zellweger syndrome and related diseases are caused by defective import of peroxisomal matrix proteins. In all previously reported Zellweger syndrome cell lines the defect could be assigned to the matrix protein import pathway since peroxisome membranes were present, and import of integral peroxisomal membrane proteins was normal. However, we report here a Zellweger syndrome patient (PBD061) with an unusual cellular phenotype, an inability to import peroxisomal membrane proteins. We also identified human PEX16, a novel integral peroxisomal membrane protein, and found that PBD061 had inactivating mutations in the PEX16 gene. Previous studies have suggested that peroxisomes arise from preexisting peroxisomes but we find that expression of PEX16 restores the formation of new peroxisomes in PBD061 cells. Peroxisome synthesis and peroxisomal membrane protein import could be detected within 2–3 h of PEX16 injection and was followed by matrix protein import. These results demonstrate that peroxisomes do not necessarily arise from division of preexisting peroxisomes. We propose that peroxisomes may form by either of two pathways: one that involves PEX11-mediated division of preexisting peroxisomes, and another that involves PEX16-mediated formation of peroxisomes in the absence of preexisting peroxisomes.
2
Voorn-Brouwer, Tineke, Astrid Kragt, Henk F. Tabak y Ben Distel. "Peroxisomal membrane proteins are properly targeted to peroxisomes in the absence of COPI- and COPII-mediated vesicular transport". Journal of Cell Science 114, n.º 11 (1 de junio de 2001): 2199–204. http://dx.doi.org/10.1242/jcs.114.11.2199.
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The classic model for peroxisome biogenesis states that new peroxisomes arise by the fission of pre-existing ones and that peroxisomal matrix and membrane proteins are recruited directly from the cytosol. Recent studies challenge this model and suggest that some peroxisomal membrane proteins might traffic via the endoplasmic reticulum to peroxisomes. We have studied the trafficking in human fibroblasts of three peroxisomal membrane proteins, Pex2p, Pex3p and Pex16p, all of which have been suggested to transit the endoplasmic reticulum before arriving in peroxisomes. Here, we show that targeting of these peroxisomal membrane proteins is not affected by inhibitors of COPI and COPII that block vesicle transport in the early secretory pathway. Moreover, we have obtained no evidence for the presence of these peroxisomal membrane proteins in compartments other than peroxisomes and demonstrate that COPI and COPII inhibitors do not affect peroxisome morphology or integrity. Together, these data fail to provide any evidence for a role of the endoplasmic reticulum in peroxisome biogenesis.
3
Knoops, Kèvin, Rinse de Boer, Anita Kram y Ida J. van der Klei. "Yeast pex1 cells contain peroxisomal ghosts that import matrix proteins upon reintroduction of Pex1". Journal of Cell Biology 211, n.º 5 (7 de diciembre de 2015): 955–62. http://dx.doi.org/10.1083/jcb.201506059.
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Pex1 and Pex6 are two AAA-ATPases that play a crucial role in peroxisome biogenesis. We have characterized the ultrastructure of the Saccharomyces cerevisiae peroxisome-deficient mutants pex1 and pex6 by various high-resolution electron microscopy techniques. We observed that the cells contained peroxisomal membrane remnants, which in ultrathin cross sections generally appeared as double membrane rings. Electron tomography revealed that these structures consisted of one continuous membrane, representing an empty, flattened vesicle, which folds into a cup shape. Immunocytochemistry revealed that these structures lack peroxisomal matrix proteins but are the sole sites of the major peroxisomal membrane proteins Pex2, Pex10, Pex11, Pex13, and Pex14. Upon reintroduction of Pex1 in Pex1-deficient cells, these peroxisomal membrane remnants (ghosts) rapidly incorporated peroxisomal matrix proteins and developed into peroxisomes. Our data support earlier views that Pex1 and Pex6 play a role in peroxisomal matrix protein import.
4
Walton, P. A., P. E. Hill y S. Subramani. "Import of stably folded proteins into peroxisomes." Molecular Biology of the Cell 6, n.º 6 (junio de 1995): 675–83. http://dx.doi.org/10.1091/mbc.6.6.675.
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By virtue of their synthesis in the cytoplasm, proteins destined for import into peroxisomes are obliged to traverse the single membrane of this organelle. Because the targeting signal for most peroxisomal matrix proteins is a carboxy-terminal tripeptide sequence (SKL or its variants), these proteins must remain import competent until their translation is complete. We sought to determine whether stably folded proteins were substrates for peroxisomal import. Prefolded proteins stabilized with disulfide bonds and chemical cross-linkers were shown to be substrates for peroxisomal import, as were mature folded and disulfide-bonded IgG molecules containing the peroxisomal targeting signal. In addition, colloidal gold particles conjugated to proteins bearing the peroxisomal targeting signal were translocated into the peroxisomal matrix. These results support the concept that proteins may fold in the mammalian cytosol, before their import into the peroxisome, and that protein unfolding is not a prerequisite for peroxisomal import.
5
Szilard, R. K., V. I. Titorenko, M. Veenhuis y R. A. Rachubinski. "Pay32p of the yeast Yarrowia lipolytica is an intraperoxisomal component of the matrix protein translocation machinery." Journal of Cell Biology 131, n.º 6 (15 de diciembre de 1995): 1453–69. http://dx.doi.org/10.1083/jcb.131.6.1453.
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Pay mutants of the yeast Yarrowia lipolytica fail to assemble functional peroxisomes. One mutant strain, pay32-1, has abnormally small peroxisomes that are often found in clusters surrounded by membraneous material. The functionally complementing gene PAY32 encodes a protein, Pay32p, of 598 amino acids (66,733 D) that is a member of the tetratricopeptide repeat family. Pay32p is intraperoxisomal. In wild-type peroxisomes, Pay32p is associated primarily with the inner surface of the peroxisomal membrane, but approximately 30% of Pay32p is localized to the peroxisomal matrix. The majority of Pay32p in the matrix is complexed with two polypeptides of 62 and 64 kD recognized by antibodies to SKL (peroxisomal targeting signal-1). In contrast, in peroxisomes of the pay32-1 mutant, Pay32p is localized exclusively to the matrix and forms no complex. Biochemical characterization of the mutants pay32-1 and pay32-KO (a PAY32 gene disruption strain) showed that Pay32p is a component of the peroxisomal translocation machinery. Mutations in the PAY32 gene prevent the translocation of most peroxisome-bound proteins into the peroxisomal matrix. These proteins, including the 62-kD anti-SKL-reactive polypeptide, are trapped in the peroxisomal membrane at an intermediate stage of translocation in pay32 mutants. Our results suggest that there are at least two distinct translocation machineries involved in the import of proteins into peroxisomes.
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Anteghini, Marco, Vitor Martins dos Santos y Edoardo Saccenti. "In-Pero: Exploiting Deep Learning Embeddings of Protein Sequences to Predict the Localisation of Peroxisomal Proteins". International Journal of Molecular Sciences 22, n.º 12 (15 de junio de 2021): 6409. http://dx.doi.org/10.3390/ijms22126409.
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Peroxisomes are ubiquitous membrane-bound organelles, and aberrant localisation of peroxisomal proteins contributes to the pathogenesis of several disorders. Many computational methods focus on assigning protein sequences to subcellular compartments, but there are no specific tools tailored for the sub-localisation (matrix vs. membrane) of peroxisome proteins. We present here In-Pero, a new method for predicting protein sub-peroxisomal cellular localisation. In-Pero combines standard machine learning approaches with recently proposed multi-dimensional deep-learning representations of the protein amino-acid sequence. It showed a classification accuracy above 0.9 in predicting peroxisomal matrix and membrane proteins. The method is trained and tested using a double cross-validation approach on a curated data set comprising 160 peroxisomal proteins with experimental evidence for sub-peroxisomal localisation. We further show that the proposed approach can be easily adapted (In-Mito) to the prediction of mitochondrial protein localisation obtaining performances for certain classes of proteins (matrix and inner-membrane) superior to existing tools.
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Brown, Trevor W., Vladimir I. Titorenko y Richard A. Rachubinski. "Mutants of theYarrowia lipolytica PEX23Gene Encoding an Integral Peroxisomal Membrane Peroxin Mislocalize Matrix Proteins and Accumulate Vesicles Containing Peroxisomal Matrix and Membrane Proteins". Molecular Biology of the Cell 11, n.º 1 (enero de 2000): 141–52. http://dx.doi.org/10.1091/mbc.11.1.141.
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pex mutants are defective in peroxisome assembly. The mutant strain pex23-1 of the yeast Yarrowia lipolytica lacks morphologically recognizable peroxisomes and mislocalizes all peroxisomal matrix proteins investigated preferentially to the cytosol. pex23 strains accumulate vesicular structures containing both peroxisomal matrix and membrane proteins. The PEX23 gene was isolated by functional complementation of the pex23-1 strain and encodes a protein, Pex23p, of 418 amino acids (47,588 Da). Pex23p exhibits high sequence similarity to two hypothetical proteins of the yeastSaccharomyces cerevisiae. Pex23p is an integral membrane protein of peroxisomes that is completely, or nearly completely, sequestered from the cytosol. Pex23p is detected at low levels in cells grown in medium containing glucose, and its levels are significantly increased by growth in medium containing oleic acid, the metabolism of which requires intact peroxisomes.
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Ma, Changle, Gaurav Agrawal y Suresh Subramani. "Peroxisome assembly: matrix and membrane protein biogenesis". Journal of Cell Biology 193, n.º 1 (4 de abril de 2011): 7–16. http://dx.doi.org/10.1083/jcb.201010022.
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The biogenesis of peroxisomal matrix and membrane proteins is substantially different from the biogenesis of proteins of other subcellular compartments, such as mitochondria and chloroplasts, that are of endosymbiotic origin. Proteins are targeted to the peroxisome matrix through interactions between specific targeting sequences and receptor proteins, followed by protein translocation across the peroxisomal membrane. Recent advances have shed light on the nature of the peroxisomal translocon in matrix protein import and the molecular mechanisms of receptor recycling. Furthermore, the endoplasmic reticulum has been shown to play an important role in peroxisomal membrane protein biogenesis. Defining the molecular events in peroxisome assembly may enhance our understanding of the etiology of human peroxisome biogenesis disorders.
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Bascom, Roger A., Honey Chan y Richard A. Rachubinski. "Peroxisome Biogenesis Occurs in an Unsynchronized Manner in Close Association with the Endoplasmic Reticulum in Temperature-sensitiveYarrowia lipolyticaPex3p Mutants". Molecular Biology of the Cell 14, n.º 3 (marzo de 2003): 939–57. http://dx.doi.org/10.1091/mbc.e02-10-0633.
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Pex3p is a peroxisomal integral membrane protein required early in peroxisome biogenesis, and Pex3p-deficient cells lack identifiable peroxisomes. Two temperature-sensitive pex3 mutant strains of the yeast Yarrowia lipolytica were made to investigate the role of Pex3p in the early stages of peroxisome biogenesis. In glucose medium at 16°C, these mutants underwent de novo peroxisome biogenesis and exhibited early matrix protein sequestration into peroxisome-like structures found at the endoplasmic reticulum-rich periphery of cells or sometimes associated with nuclei. The de novo peroxisome biogenesis seemed unsynchronized, with peroxisomes occurring at different stages of development both within cells and between cells. Cells with peripheral nascent peroxisomes and cells with structures morphologically distinct from peroxisomes, such as semi/circular tubular structures that immunostained with antibodies to peroxisomal matrix proteins and to the endoplasmic reticulum-resident protein Kar2p, and that surrounded lipid droplets, were observed during up-regulation of peroxisome biogenesis in cells incubated in oleic acid medium at 16°C. These structures were not detected in wild-type or Pex3p-deficient cells. Their role in peroxisome biogenesis remains unclear. Targeting of peroxisomal matrix proteins to these structures suggests that Pex3p directly or indirectly sequesters components of the peroxisome biogenesis machinery. Such a role is consistent with Pex3p overexpression producing cells with fewer, larger, and clustered peroxisomes.
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Gould, S. J., J. E. Kalish, J. C. Morrell, J. Bjorkman, A. J. Urquhart y D. I. Crane. "Pex13p is an SH3 protein of the peroxisome membrane and a docking factor for the predominantly cytoplasmic PTs1 receptor." Journal of Cell Biology 135, n.º 1 (1 de octubre de 1996): 85–95. http://dx.doi.org/10.1083/jcb.135.1.85.
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Import of newly synthesized PTS1 proteins into the peroxisome requires the PTS1 receptor (Pex5p), a predominantly cytoplasmic protein that cycles between the cytoplasm and peroxisome. We have identified Pex13p, a novel integral peroxisomal membrane from both yeast and humans that binds the PTS1 receptor via a cytoplasmically oriented SH3 domain. Although only a small amount of Pex5p is bound to peroxisomes at steady state (< 5%), loss of Pex13p further reduces the amount of peroxisome-associated Pex5p by approximately 40-fold. Furthermore, loss of Pex13p eliminates import of peroxisomal matrix proteins that contain either the type-1 or type-2 peroxisomal targeting signal but does not affect targeting and insertion of integral peroxisomal membrane proteins. We conclude that Pex13p functions as a docking factor for the predominantly cytoplasmic PTS1 receptor.
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Titorenko, Vladimir I. y Richard A. Rachubinski. "Mutants of the Yeast Yarrowia lipolyticaDefective in Protein Exit from the Endoplasmic Reticulum Are Also Defective in Peroxisome Biogenesis". Molecular and Cellular Biology 18, n.º 5 (1 de mayo de 1998): 2789–803. http://dx.doi.org/10.1128/mcb.18.5.2789.
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ABSTRACT Mutations in the SEC238 and SRP54 genes of the yeast Yarrowia lipolytica not only cause temperature-sensitive defects in the exit of the precursor form of alkaline extracellular protease and of other secretory proteins from the endoplasmic reticulum and in protein secretion but also lead to temperature-sensitive growth in oleic acid-containing medium, the metabolism of which requires the assembly of functionally intact peroxisomes. The sec238A andsrp54KO mutations at the restrictive temperature significantly reduce the size and number of peroxisomes, affect the import of peroxisomal matrix and membrane proteins into the organelle, and significantly delay, but do not prevent, the exit of two peroxisomal membrane proteins, Pex2p and Pex16p, from the endoplasmic reticulum en route to the peroxisomal membrane. Mutations in the PEX1 and PEX6 genes, which encode members of the AAA family of N-ethylmaleimide-sensitive fusion protein-like ATPases, not only affect the exit of precursor forms of secretory proteins from the endoplasmic reticulum but also prevent the exit of the peroxisomal membrane proteins Pex2p and Pex16p from the endoplasmic reticulum and cause the accumulation of an extensive network of endoplasmic reticulum membranes. None of the peroxisomal matrix proteins tested associated with the endoplasmic reticulum in sec238A,srp54KO, pex1-1, and pex6KO mutant cells. Our data provide evidence that the endoplasmic reticulum is required for peroxisome biogenesis and suggest that inY. lipolytica, the trafficking of some membrane proteins, but not matrix proteins, to the peroxisome occurs via the endoplasmic reticulum, results in their glycosylation within the lumen of the endoplasmic reticulum, does not involve transport through the Golgi, and requires the products encoded by the SEC238, SRP54,PEX1, and PEX6 genes.
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Woodward, Andrew W. y Bonnie Bartel. "The Arabidopsis Peroxisomal Targeting Signal Type 2 Receptor PEX7 Is Necessary for Peroxisome Function and Dependent on PEX5". Molecular Biology of the Cell 16, n.º 2 (febrero de 2005): 573–83. http://dx.doi.org/10.1091/mbc.e04-05-0422.
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Plant peroxisomal proteins catalyze key metabolic reactions. Several peroxisome biogenesis PEROXIN (PEX) genes encode proteins acting in the import of targeted proteins necessary for these processes into the peroxisomal matrix. Most peroxisomal matrix proteins bear characterized Peroxisomal Targeting Signals (PTS1 or PTS2), which are bound by the receptors PEX5 or PEX7, respectively, for import into peroxisomes. Here we describe the isolation and characterization of an Arabidopsis peroxin mutant, pex7-1, which displays peroxisome-defective phenotypes including reduced PTS2 protein import. We also demonstrate that the pex5-1 PTS1 receptor mutant, which contains a lesion in a domain conserved among PEX7-binding proteins from various organisms, is defective not in PTS1 protein import, but rather in PTS2 protein import. Combining these mutations in a pex7-1 pex5-1 double mutant abolishes detectable PTS2 protein import and yields seedlings that are entirely sucrose-dependent for establishment, suggesting a severe block in peroxisomal fatty acid β-oxidation. Adult pex7-1 pex5-1 plants have reduced stature and bear abnormally shaped seeds, few of which are viable. The pex7-1 pex5-1 seedlings that germinate have dramatically fewer lateral roots and often display fused cotyledons, phenotypes associated with reduced auxin response. Thus PTS2-directed peroxisomal import is necessary for normal embryonic development, seedling establishment, and vegetative growth.
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Collins, Cynthia S., Jennifer E. Kalish, James C. Morrell, J. Michael McCaffery y Stephen J. Gould. "The Peroxisome Biogenesis Factors Pex4p, Pex22p, Pex1p, and Pex6p Act in the Terminal Steps of Peroxisomal Matrix Protein Import". Molecular and Cellular Biology 20, n.º 20 (15 de octubre de 2000): 7516–26. http://dx.doi.org/10.1128/mcb.20.20.7516-7526.2000.
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ABSTRACT Peroxisomes are independent organelles found in virtually all eukaryotic cells. Genetic studies have identified more than 20PEX genes that are required for peroxisome biogenesis. The role of most PEX gene products, peroxins, remains to be determined, but a variety of studies have established that Pex5p binds the type 1 peroxisomal targeting signal and is the import receptor for most newly synthesized peroxisomal matrix proteins. The steady-state abundance of Pex5p is unaffected in mostpex mutants of the yeast Pichia pastorisbut is severely reduced in pex4 andpex22 mutants and moderately reduced in pex1and pex6 mutants. We used these subphenotypes to determine the epistatic relationships among several groups ofpex mutants. Our results demonstrate that Pex4p acts after the peroxisome membrane synthesis factor Pex3p, the Pex5p docking factors Pex13p and Pex14p, the matrix protein import factors Pex8p, Pex10p, and Pex12p, and two other peroxins, Pex2p and Pex17p. Pex22p and the interacting AAA ATPases Pex1p and Pex6p were also found to act after Pex10p. Furthermore, Pex1p and Pex6p were found to act upstream of Pex4p and Pex22p. These results suggest that Pex1p, Pex4p, Pex6p, and Pex22p act late in peroxisomal matrix protein import, after matrix protein translocation. This hypothesis is supported by the phenotypes of the corresponding mutant strains. As has been shown previously for P. pastoris pex1,pex6, and pex22 mutant cells, we show here thatpex4Δ mutant cells contain peroxisomal membrane protein-containing peroxisomes that import residual amounts of peroxisomal matrix proteins.
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Lambkin, Gareth R. y Richard A. Rachubinski. "Yarrowia lipolyticaCells Mutant for the Peroxisomal Peroxin Pex19p Contain Structures Resembling Wild-Type Peroxisomes". Molecular Biology of the Cell 12, n.º 11 (noviembre de 2001): 3353–64. http://dx.doi.org/10.1091/mbc.12.11.3353.
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PEX genes encode peroxins, which are proteins required for peroxisome assembly. The PEX19 gene of the yeast Yarrowia lipolytica was isolated by functional complementation of the oleic acid-nonutilizing strainpex19-1 and encodes Pex19p, a protein of 324 amino acids (34,822 Da). Subcellular fractionation and immunofluorescence microscopy showed Pex19p to be localized primarily to peroxisomes. Pex19p is detected in cells grown in glucose-containing medium, and its levels are not increased by incubation of cells in oleic acid–containing medium, the metabolism of which requires intact peroxisomes. pex19 cells preferentially mislocalize peroxisomal matrix proteins and the peripheral intraperoxisomal membrane peroxin Pex16p to the cytosol, although small amounts of these proteins could be reproducibly localized to a subcellular fraction enriched for peroxisomes. In contrast, the peroxisomal integral membrane protein Pex2p exhibits greatly reduced levels inpex19 cells compared with its levels in wild-type cells. Importantly, pex19 cells were shown by electron microscopy to contain structures that resemble wild-type peroxisomes in regards to size, shape, number, and electron density. Subcellular fractionation and isopycnic density gradient centrifugation confirmed the presence of vesicular structures in pex19 mutant strains that were similar in density to wild-type peroxisomes and that contained profiles of peroxisomal matrix and membrane proteins that are similar to, yet distinct from, those of wild-type peroxisomes. Because peroxisomal structures form in pex19 cells, Pex19p apparently does not function as a peroxisomal membrane protein receptor in Y. lipolytica. Our results are consistent with a role for Y. lipolytica Pex19p in stabilizing the peroxisomal membrane.
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Smith, Jennifer J., Marcello Marelli, Rowan H. Christmas, Franco J. Vizeacoumar, David J. Dilworth, Trey Ideker, Timothy Galitski, Krassen Dimitrov, Richard A. Rachubinski y John D. Aitchison. "Transcriptome profiling to identify genes involved in peroxisome assembly and function". Journal of Cell Biology 158, n.º 2 (22 de julio de 2002): 259–71. http://dx.doi.org/10.1083/jcb.200204059.
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Yeast cells were induced to proliferate peroxisomes, and microarray transcriptional profiling was used to identify PEX genes encoding peroxins involved in peroxisome assembly and genes involved in peroxisome function. Clustering algorithms identified 224 genes with expression profiles similar to those of genes encoding peroxisomal proteins and genes involved in peroxisome biogenesis. Several previously uncharacterized genes were identified, two of which, YPL112c and YOR084w, encode proteins of the peroxisomal membrane and matrix, respectively. Ypl112p, renamed Pex25p, is a novel peroxin required for the regulation of peroxisome size and maintenance. These studies demonstrate the utility of comparative gene profiling as an alternative to functional assays to identify genes with roles in peroxisome biogenesis.
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Hosoi, Ken-ichiro, Non Miyata, Satoru Mukai, Satomi Furuki, Kanji Okumoto, Emily H. Cheng y Yukio Fujiki. "The VDAC2–BAK axis regulates peroxisomal membrane permeability". Journal of Cell Biology 216, n.º 3 (7 de febrero de 2017): 709–22. http://dx.doi.org/10.1083/jcb.201605002.
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Peroxisomal biogenesis disorders (PBDs) are fatal genetic diseases consisting of 14 complementation groups (CGs). We previously isolated a peroxisome-deficient Chinese hamster ovary cell mutant, ZP114, which belongs to none of these CGs. Using a functional screening strategy, VDAC2 was identified as rescuing the peroxisomal deficiency of ZP114 where VDAC2 expression was not detected. Interestingly, knockdown of BAK or overexpression of the BAK inhibitors BCL-XL and MCL-1 restored peroxisomal biogenesis in ZP114 cells. Although VDAC2 is not localized to the peroxisome, loss of VDAC2 shifts the localization of BAK from mitochondria to peroxisomes, resulting in peroxisomal deficiency. Introduction of peroxisome-targeted BAK harboring the Pex26p transmembrane region into wild-type cells resulted in the release of peroxisomal matrix proteins to cytosol. Moreover, overexpression of BAK activators PUMA and BIM permeabilized peroxisomes in a BAK-dependent manner. Collectively, these findings suggest that BAK plays a role in peroxisomal permeability, similar to mitochondrial outer membrane permeabilization.
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Eitzen, Gary A., Rachel K. Szilard y Richard A. Rachubinski. "Enlarged Peroxisomes Are Present in Oleic Acid–grown Yarrowia lipolytica Overexpressing the PEX16 Gene Encoding an Intraperoxisomal Peripheral Membrane Peroxin". Journal of Cell Biology 137, n.º 6 (16 de junio de 1997): 1265–78. http://dx.doi.org/10.1083/jcb.137.6.1265.
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Pex mutants of the yeast Yarrowia lipolytica are defective in peroxisome assembly. The mutant strain pex16-1 lacks morphologically recognizable peroxisomes. Most peroxisomal proteins are mislocalized to a subcellular fraction enriched for cytosol in pex16 strains, but a subset of peroxisomal proteins is localized at, or near, wild-type levels to a fraction typically enriched for peroxisomes. The PEX16 gene was isolated by functional complementation of the pex16-1 strain and encodes a protein, Pex16p, of 391 amino acids (44,479 D). Pex16p has no known homologues. Pex16p is a peripheral protein located at the matrix face of the peroxisomal membrane. Substitution of the carboxylterminal tripeptide Ser-Thr-Leu, which is similar to the consensus sequence of peroxisomal targeting signal 1, does not affect targeting of Pex16p to peroxisomes. Pex16p is synthesized in wild-type cells grown in glucose-containing media, and its levels are modestly increased by growth of cells in oleic acid–containing medium. Overexpression of the PEX16 gene in oleic acid– grown Y. lipolytica leads to the appearance of a small number of enlarged peroxisomes, which contain the normal complement of peroxisomal proteins at levels approaching those of wild-type peroxisomes.
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Waterham, H. R., V. I. Titorenko, P. Haima, J. M. Cregg, W. Harder y M. Veenhuis. "The Hansenula polymorpha PER1 gene is essential for peroxisome biogenesis and encodes a peroxisomal matrix protein with both carboxy- and amino-terminal targeting signals." Journal of Cell Biology 127, n.º 3 (1 de noviembre de 1994): 737–49. http://dx.doi.org/10.1083/jcb.127.3.737.
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We describe the cloning of the Hansenula polymorpha PER1 gene and the characterization of the gene and its product, PER1p. The gene was cloned by functional complementation of a per1 mutant of H. polymorpha, which was impaired in the import of peroxisomal matrix proteins (Pim- phenotype). The DNA sequence of PER1 predicts that PER1p is a polypeptide of 650 amino acids with no significant sequence similarity to other known proteins. PER1 expression was low but significant in wild-type H. polymorpha growing on glucose and increased during growth on any one of a number of substrates which induce peroxisome proliferation. PER1p contains both a carboxy- (PTS1) and an amino-terminal (PTS2) peroxisomal targeting signal which both were demonstrated to be capable of directing bacterial beta-lactamase to the organelle. In wild-type H. polymorpha PER1p is a protein of low abundance which was demonstrated to be localized in the peroxisomal matrix. Our results suggest that the import of PER1p into peroxisomes is a prerequisite for the import of additional matrix proteins and we suggest a regulatory function of PER1p on peroxisomal protein support.
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SUBRAMANI, SURESH. "Components Involved in Peroxisome Import, Biogenesis, Proliferation, Turnover, and Movement". Physiological Reviews 78, n.º 1 (1 de enero de 1998): 171–88. http://dx.doi.org/10.1152/physrev.1998.78.1.171.
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Subramani, Suresh. Components Involved in Peroxisome Import, Biogenesis, Proliferation, Turnover, and Movement. Physiol. Rev. 78: 171–188, 1998. — In the decade that has elapsed since the discovery of the first peroxisomal targeting signal (PTS), considerable information has been obtained regarding the mechanism of protein import into peroxisomes. The PTSs responsible for the import of matrix and membrane proteins to peroxisomes, the receptors for several of these PTSs, and docking proteins for the PTS1 and PTS2 receptors are known. Many peroxins involved in peroxisomal protein import and biogenesis have been characterized genetically and biochemically. These studies have revealed important new insights regarding the mechanism of protein translocation across the peroxisomal membrane, the conservation of PEX genes through evolution, the role of peroxins in fatal human peroxisomal disorders, and the biogenesis of the organelle. It is clear that peroxisomal protein import and biogenesis have many features unique to this organelle alone. More recent studies on peroxisome degradation, division, and movement highlight newer aspects of the biology of this organelle that promise to be just as exciting and interesting as import and biogenesis.
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Thoms, Sven. "Import of proteins into peroxisomes: piggybacking to a new home away from home". Open Biology 5, n.º 11 (noviembre de 2015): 150148. http://dx.doi.org/10.1098/rsob.150148.
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Peroxisomes are capable of importing folded and oligomeric proteins. However, it is a matter of dispute whether oligomer import by peroxisomes is the exception or the rule. Here, I argue for a clear distinction between homo-oligomeric proteins that are essentially peroxisomal, and dually localized hetero-oligomers that access the peroxisome by piggyback import, localizing there in limited number, whereas the majority remain in the cytosol. Homo-oligomeric proteins comprise the majority of all peroxisomal matrix proteins. There is evidence that binding by Pex5 in the cytosol can regulate their oligomerization state before import. The hetero-oligomer group is made up of superoxide dismutase and lactate dehydrogenase. These proteins have evolved mechanisms that render import inefficient and retain the majority of proteins in the cytosol.
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Jones, Jacob M., James C. Morrell y Stephen J. Gould. "Multiple Distinct Targeting Signals in Integral Peroxisomal Membrane Proteins". Journal of Cell Biology 153, n.º 6 (4 de junio de 2001): 1141–50. http://dx.doi.org/10.1083/jcb.153.6.1141.
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Peroxisomal proteins are synthesized on free polysomes and then transported from the cytoplasm to peroxisomes. This process is mediated by two short well-defined targeting signals in peroxisomal matrix proteins, but a well-defined targeting signal has not yet been described for peroxisomal membrane proteins (PMPs). One assumption in virtually all prior studies of PMP targeting is that a given protein contains one, and only one, distinct targeting signal. Here, we show that the metabolite transporter PMP34, an integral PMP, contains at least two nonoverlapping sets of targeting information, either of which is sufficient for insertion into the peroxisome membrane. We also show that another integral PMP, the peroxin PEX13, also contains two independent sets of peroxisomal targeting information. These results challenge a major assumption of most PMP targeting studies. In addition, we demonstrate that PEX19, a factor required for peroxisomal membrane biogenesis, interacts with the two minimal targeting regions of PMP34. Together, these results raise the interesting possibility that PMP import may require novel mechanisms to ensure the solubility of integral PMPs before their insertion in the peroxisome membrane, and that PEX19 may play a central role in this process.
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Platta, Harald W., Mykhaylo O. Debelyy, Fouzi El Magraoui y Ralf Erdmann. "The AAA peroxins Pex1p and Pex6p function as dislocases for the ubiquitinated peroxisomal import receptor Pex5p". Biochemical Society Transactions 36, n.º 1 (22 de enero de 2008): 99–104. http://dx.doi.org/10.1042/bst0360099.
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The discovery of the peroxisomal ATPase Pex1p triggered the beginning of the research on AAA (ATPase associated with various cellular activities) proteins and the genetic dissection of peroxisome biogenesis. Peroxisomes are virtually ubiquitous organelles, which are connected to diverse cellular functions. The highly diverse and adaptive character of peroxisomes is accomplished by modulation of their enzyme content, which is mediated by dynamically operating protein-import machineries. The import of matrix proteins into the peroxisomal lumen has been described as the ATP-consuming step, but the corresponding reaction, as well as the ATPase responsible, had been obscure for nearly 15 years. Recent work using yeast and human fibroblast cells has identified the peroxisomal AAA proteins Pex1p and Pex6p as mechano-enzymes and core components of a complex which dislocates the cycling import receptor Pex5p from the peroxisomal membrane back to the cytosol. This AAA-mediated process is regulated by the ubiquitination status of the receptor. Pex4p [Ubc10p (ubiquitin-conjugating enzyme 10)]-catalysed mono-ubiquitination of Pex5p primes the receptor for recycling, thereby enabling further rounds of matrix protein import, whereas Ubc4p-catalysed polyubiquitination targets Pex5p to proteasomal degradation.
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Hashiguchi, Noriyo, Tomoko Kojidani, Tsuneo Imanaka, Tokuko Haraguchi, Yasushi Hiraoka, Eveline Baumgart, Sadaki Yokota, Toshiro Tsukamoto y Takashi Osumi. "Peroxisomes Are Formed from Complex Membrane Structures inPEX6-deficient CHO Cells upon Genetic Complementation". Molecular Biology of the Cell 13, n.º 2 (febrero de 2002): 711–22. http://dx.doi.org/10.1091/mbc.01-10-0479.
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Pex6p belongs to the AAA family of ATPases. Its CHO mutant, ZP92, lacks normal peroxisomes but contains peroxisomal membrane remnants, so called peroxisomal ghosts, which are detected with anti–70-kDa peroxisomal membrane protein (PMP70) antibody. No peroxisomal matrix proteins were detected inside the ghosts, but exogenously expressed green fluorescent protein (GFP) fused to peroxisome targeting signal-1 (PTS-1) accumulated in the areas adjacent to the ghosts. Electron microscopic examination revealed that PMP70-positive ghosts in ZP92 were complex membrane structures, rather than peroxisomes with reduced matrix protein import ability. In a typical case, a set of one central spherical body and two layers of double-membraned loops were observed, with endoplasmic reticulum present alongside the outer loop. In the early stage of complementation by PEX6 cDNA, catalase and acyl-CoA oxidase accumulated in the lumen of the double-membraned loops. Biochemical analysis revealed that almost all the peroxisomal ghosts were converted into peroxisomes upon complementation. Our results indicate that 1) Peroxisomal ghosts are complex membrane structures; and 2) The complex membrane structures become import competent and are converted into peroxisomes upon complementation with PEX6.
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Tam, Yuen Yi C. y Richard A. Rachubinski. "Yarrowia lipolyticaCells Mutant for thePEX24Gene Encoding a Peroxisomal Membrane Peroxin Mislocalize Peroxisomal Proteins and Accumulate Membrane Structures Containing Both Peroxisomal Matrix and Membrane Proteins". Molecular Biology of the Cell 13, n.º 8 (agosto de 2002): 2681–91. http://dx.doi.org/10.1091/mbc.e02-02-0117.
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Peroxins are proteins required for peroxisome assembly and are encoded by the PEX genes. Functional complementation of the oleic acid–nonutilizing strain mut1-1 of the yeastYarrowia lipolytica has identified the novel gene,PEX24. PEX24 encodes Pex24p, a protein of 550 amino acids (61,100 Da). Pex24p is an integral membrane protein of peroxisomes that exhibits high sequence homology to two hypothetical proteins encoded by the open reading frames YHR150W andYDR479C of the Saccharomyces cerevisiaegenome. Pex24p is detectable in wild-type cells grown in glucose-containing medium, and its levels are significantly increased by incubation of cells in oleic acid–containing medium, the metabolism of which requires intact peroxisomes. pex24 mutants are compromised in the targeting of both matrix and membrane proteins to peroxisomes. Although pex24 mutants fail to assemble functional peroxisomes, they do harbor membrane structures that contain subsets of peroxisomal proteins.
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Ali, Ameena M., Jack Atmaj, Alaa Adawy, Sergey Lunev, Niels Van Oosterwijk, Sun Rei Yan, Chris Williams y Matthew R. Groves. "The Pex4p–Pex22p complex fromHansenula polymorpha: biophysical analysis, crystallization and X-ray diffraction characterization". Acta Crystallographica Section F Structural Biology Communications 74, n.º 2 (26 de enero de 2018): 76–81. http://dx.doi.org/10.1107/s2053230x17018428.
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Peroxisomes are a major cellular compartment of eukaryotic cells, and are involved in a variety of metabolic functions and pathways according to species, cell type and environmental conditions. Their biogenesis relies on conserved genes known asPEXgenes that encode peroxin proteins. Peroxisomal membrane proteins and peroxisomal matrix proteins are generated in the cytosol and are subsequently imported into the peroxisome post-translationally. Matrix proteins containing a peroxisomal targeting signal type 1 (PTS1) are recognized by the cycling receptor Pex5p and transported to the peroxisomal lumen. Pex5p docking, release of the cargo into the lumen and recycling involve a number of peroxins, but a key player is the Pex4p–Pex22p complex described in this manuscript. Pex4p from the yeastSaccharomyces cerevisiaeis a ubiquitin-conjugating enzyme that is anchored on the cytosolic side of the peroxisomal membrane through its binding partner Pex22p, which acts as both a docking site and a co-activator of Pex4p. As Pex5p undergoes recycling and release, the Pex4p–Pex22p complex is essential for monoubiquitination at the conserved cysteine residue of Pex5p. The absence of Pex4p–Pex22p inhibits Pex5p recycling and hence PTS1 protein import. This article reports the crystallization of Pex4p and of the Pex4p–Pex22p complex from the yeastHansenula polymorpha,and data collection from their crystals to 2.0 and 2.85 Å resolution, respectively. The resulting structures are likely to provide important insights to understand the molecular mechanism of the Pex4p–Pex22p complex and its role in peroxisome biogenesis.
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Chang, C. C., S. South, D. Warren, J. Jones, A. B. Moser, H. W. Moser y S. J. Gould. "Metabolic control of peroxisome abundance". Journal of Cell Science 112, n.º 10 (15 de mayo de 1999): 1579–90. http://dx.doi.org/10.1242/jcs.112.10.1579.
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Zellweger syndrome and related disorders represent a group of lethal, genetically heterogeneous diseases. These peroxisome biogenesis disorders (PBDs) are characterized by defective peroxisomal matrix protein import and comprise at least 10 complementation groups. The genes defective in seven of these groups and more than 90% of PBD patients are now known. Here we examine the distribution of peroxisomal membrane proteins in fibroblasts from PBD patients representing the seven complementation groups for which the mutant gene is known. Peroxisomes were detected in all PBD cells, indicating that the ability to form a minimal peroxisomal structure is not blocked in these mutants. We also observed that peroxisome abundance was reduced fivefold in PBD cells that are defective in the PEX1, PEX5, PEX12, PEX6, PEX10, and PEX2 genes. These cell lines all display a defect in the import of proteins with the type-1 peroxisomal targeting signal (PTS1). In contrast, peroxisome abundance was unaffected in cells that are mutated in PEX7 and are defective only in the import of proteins with the type-2 peroxisomal targeting signal. Interestingly, a fivefold reduction in peroxisome abundance was also observed for cells lacking either of two PTS1-targeted peroxisomal beta-oxidation enzymes, acyl-CoA oxidase and 2-enoyl-CoA hydratase/D-3-hydroxyacyl-CoA dehydrogenase. These results indicate that reduced peroxisome abundance in PBD cells may be caused by their inability to import these PTS1-containing enzymes. Furthermore, the fact that peroxisome abundance is influenced by peroxisomal 105-oxidation activities suggests that there may be metabolic control of peroxisome abundance.
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Motley, Alison M., Paul C. Galvin, Lakhan Ekal, James M. Nuttall y Ewald H. Hettema. "Reevaluation of the role of Pex1 and dynamin-related proteins in peroxisome membrane biogenesis". Journal of Cell Biology 211, n.º 5 (7 de diciembre de 2015): 1041–56. http://dx.doi.org/10.1083/jcb.201412066.
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A recent model for peroxisome biogenesis postulates that peroxisomes form de novo continuously in wild-type cells by heterotypic fusion of endoplasmic reticulum–derived vesicles containing distinct sets of peroxisomal membrane proteins. This model proposes a role in vesicle fusion for the Pex1/Pex6 complex, which has an established role in matrix protein import. The growth and division model proposes that peroxisomes derive from existing peroxisomes. We tested these models by reexamining the role of Pex1/Pex6 and dynamin-related proteins in peroxisome biogenesis. We found that induced depletion of Pex1 blocks the import of matrix proteins but does not affect membrane protein delivery to peroxisomes; markers for the previously reported distinct vesicles colocalize in pex1 and pex6 cells; peroxisomes undergo continued growth if fission is blocked. Our data are compatible with the established primary role of the Pex1/Pex6 complex in matrix protein import and show that peroxisomes in Saccharomyces cerevisiae multiply mainly by growth and division.
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Perry, Ryan J., Fred D. Mast y Richard A. Rachubinski. "Endoplasmic Reticulum-Associated Secretory Proteins Sec20p, Sec39p, and Dsl1p Are Involved in Peroxisome Biogenesis". Eukaryotic Cell 8, n.º 6 (3 de abril de 2009): 830–43. http://dx.doi.org/10.1128/ec.00024-09.
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ABSTRACT Two pathways have been identified for peroxisome formation: (i) growth and division and (ii) de novo synthesis. Recent experiments determined that peroxisomes originate at the endoplasmic reticulum (ER). Although many proteins have been implicated in the peroxisome biogenic program, no proteins in the eukaryotic secretory pathway have been identified as having roles in peroxisome formation. Using the yeast Saccharomyces cerevisiae regulatable Tet promoter Hughes clone collection, we found that repression of the ER-associated secretory proteins Sec20p and Sec39p resulted in mislocalization of the peroxisomal matrix protein chimera Pot1p-green fluorescent protein (GFP) to the cytosol. Likewise, the peroxisomal membrane protein chimera Pex3p-GFP localized to tubular-vesicular structures in cells suppressed for Sec20p, Sec39p, and Dsl1p, which form a complex at the ER. Loss of Sec39p attenuated formation of Pex3p-derived peroxisomal structures following galactose induction of Pex3p-GFP expression from the GAL1 promoter. Expression of Sec20p, Sec39p, and Dsl1p was moderately increased in yeast grown under conditions that proliferate peroxisomes, and Sec20p, Sec39p, and Dsl1p were found to cofractionate with peroxisomes and colocalize with Pex3p-monomeric red fluorescent protein under these conditions. Our results show that SEC20, SEC39, and DSL1 are essential secretory genes involved in the early stages of peroxisome assembly, and this work is the first to identify and characterize an ER-associated secretory machinery involved in peroxisome biogenesis.
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Geuze, Hans J., Jean Luc Murk, An K. Stroobants, Janice M. Griffith, Monique J. Kleijmeer, Abraham J. Koster, Arie J. Verkleij, Ben Distel y Henk F. Tabak. "Involvement of the Endoplasmic Reticulum in Peroxisome Formation". Molecular Biology of the Cell 14, n.º 7 (julio de 2003): 2900–2907. http://dx.doi.org/10.1091/mbc.e02-11-0734.
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The traditional view holds that peroxisomes are autonomous organelles multiplying by growth and division. More recently, new observations have challenged this concept. Herein, we present evidence supporting the involvement of the endoplasmic reticulum (ER) in peroxisome formation by electron microscopy, immunocytochemistry and three-dimensional image reconstruction of peroxisomes and associated compartments in mouse dendritic cells. We found the peroxisomal membrane protein Pex13p and the ATP-binding cassette transporter protein PMP70 present in specialized subdomains of the ER that were continuous with a peroxisomal reticulum from which mature peroxisomes arose. The matrix proteins catalase and thiolase were only detectable in the reticula and peroxisomes. Our results suggest the existence of a maturation pathway from the ER to peroxisomes and implicate the ER as a major source from which the peroxisomal membrane is derived.
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Sacksteder, Katherine A., Jacob M. Jones, Sarah T. South, Xiaoling Li, Yifei Liu y Stephen J. Gould. "Pex19 Binds Multiple Peroxisomal Membrane Proteins, Is Predominantly Cytoplasmic, and Is Required for Peroxisome Membrane Synthesis". Journal of Cell Biology 148, n.º 5 (6 de marzo de 2000): 931–44. http://dx.doi.org/10.1083/jcb.148.5.931.
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Peroxisomes are components of virtually all eukaryotic cells. While much is known about peroxisomal matrix protein import, our understanding of how peroxisomal membrane proteins (PMPs) are targeted and inserted into the peroxisome membrane is extremely limited. Here, we show that PEX19 binds a broad spectrum of PMPs, displays saturable PMP binding, and interacts with regions of PMPs required for their targeting to peroxisomes. Furthermore, mislocalization of PEX19 to the nucleus leads to nuclear accumulation of newly synthesized PMPs. At steady state, PEX19 is bimodally distributed between the cytoplasm and peroxisome, with most of the protein in the cytoplasm. We propose that PEX19 may bind newly synthesized PMPs and facilitate their insertion into the peroxisome membrane. This hypothesis is supported by the observation that the loss of PEX19 results in degradation of PMPs and/or mislocalization of PMPs to the mitochondrion.
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Titorenko, Vladimir I., Jennifer J. Smith, Rachel K. Szilard y Richard A. Rachubinski. "Pex20p of the Yeast Yarrowia lipolytica Is Required for the Oligomerization of Thiolase in the Cytosol and for Its Targeting to the Peroxisome". Journal of Cell Biology 142, n.º 2 (27 de julio de 1998): 403–20. http://dx.doi.org/10.1083/jcb.142.2.403.
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Pex mutants are defective in peroxisome assembly. In the pex20-1 mutant strain of the yeast Yarrowia lipolytica, the peroxisomal matrix protein thiolase is mislocalized exclusively to the cytosol, whereas the import of other peroxisomal proteins is unaffected. The PEX20 gene was isolated by functional complementation of the pex20-1 strain and encodes a protein, Pex20p, of 424 amino acids (47,274 D). Despite its role in the peroxisomal import of thiolase, which is targeted by an amino-terminal peroxisomal targeting signal-2 (PTS2), Pex20p does not exhibit homology to Pex7p, which acts as the PTS2 receptor. Pex20p is mostly cytosolic, whereas 4–8% is associated with high-speed (200,000 g) pelletable peroxisomes. In the wild-type strain, all newly synthesized thiolase is associated with Pex20p in a heterotetrameric complex composed of two polypeptide chains of each protein. This association is independent of PTS2. Pex20p is required for both the oligomerization of thiolase in the cytosol and its targeting to the peroxisome. Our data suggest that monomeric Pex20p binds newly synthesized monomeric thiolase in the cytosol and promotes the formation of a heterotetrameric complex of these two proteins, which could further bind to the peroxisomal membrane. Translocation of the thiolase homodimer into the peroxisomal matrix would release Pex20p monomers back to the cytosol, thereby permitting a new cycle of binding-oligomerization-targeting-release for Pex20p and thiolase.
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Erdmann, R. y G. Blobel. "Giant peroxisomes in oleic acid-induced Saccharomyces cerevisiae lacking the peroxisomal membrane protein Pmp27p." Journal of Cell Biology 128, n.º 4 (15 de febrero de 1995): 509–23. http://dx.doi.org/10.1083/jcb.128.4.509.
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We have purified peroxisomal membranes from Saccharomyces cerevisiae after induction of peroxisomes in oleic acid-containing media. About 30 distinct proteins could be discerned among the HPLC- and SDS-PAGE-separated proteins of the high salt-extracted peroxisomal membranes. The most abundant of these, Pmp27p, was purified and the corresponding gene PMP27 was cloned and sequenced. Its primary structure is 32% identical to PMP31 and PMP32 of the yeast Candida biodinii (Moreno, M., R. Lark, K. L. Campbell, and M. J. Goodman. 1994. Yeast. 10:1447-1457). Immunoelectron microscopic localization of Pmp27p showed labeling of the peroxisomal membrane, but also of matrix-less and matrix containing tubular membranes nearby. Electronmicroscopical data suggest that some of these tubular extensions might interconnect peroxisomes to form a peroxisomal reticulum. Cells with a disrupted PMP27 gene (delta pmp27) still grew well on glucose or ethanol, but they failed to grow on oleate although peroxisomes were still induced by transfer to oleate-containing media. The induced peroxisomes of delta pmp27 cells were fewer but considerably larger than those of wild-type cells, suggesting that Pmp27p may be involved in parceling of peroxisomes into regular quanta. delta pmp27 cells cultured in oleate-containing media form multiple buds, of which virtually all are peroxisome deficient. The growth defect of delta pmp27 cells on oleic acid appears to result from the inability to segregate the giant peroxisomes to daughter cells.
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Stewart, Mary Q., Renee D. Esposito, Jehangir Gowani y Joel M. Goodman. "Alcohol oxidase and dihydroxyacetone synthase, the abundant peroxisomal proteins of methylotrophic yeasts, assemble in different cellular compartments". Journal of Cell Science 114, n.º 15 (1 de agosto de 2001): 2863–68. http://dx.doi.org/10.1242/jcs.114.15.2863.
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Alcohol oxidase (AO) and dihydroxyacetone synthase (DHAS) constitute the bulk of matrix proteins in methylotrophic yeasts, model organisms for the study of peroxisomal assembly. Both are homooligomers; AO is a flavin-containing octamer, whereas DHAS is a thiamine pyrophosphate-containing dimer. Experiments in recent years have demonstrated that assembly of peroxisomal oligomers can occur before import; indeed the absence of chaperones within the peroxisomal matrix calls into question the ability of this compartment to assemble proteins at all. We have taken a direct pulse-chase approach to monitor import and assembly of the two major proteins of peroxisomes in Candida boidinii. Oligomers of AO are not observed in the cytosol, consistent with the proteins inability to undergo piggyback import. Indeed, oligomerization of AO can be followed within the peroxisomal matrix, directly demonstrating the capacity of this compartment for protein assembly. By contrast, DHAS quickly dimerizes in the cytosol before import. Binding and import was slowed at 15°C; the effect on AO was more dramatic. In conclusion, our data indicate that peroxisomes assemble AO in the matrix, while DHAS undergoes dimerization prior to import.
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Verner, Zdeněk, Vojtěch Žárský, Tien Le, Ravi Kumar Narayanasamy, Petr Rada, Daniel Rozbeský, Abhijith Makki et al. "Anaerobic peroxisomes in Entamoeba histolytica metabolize myo-inositol". PLOS Pathogens 17, n.º 11 (15 de noviembre de 2021): e1010041. http://dx.doi.org/10.1371/journal.ppat.1010041.
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Entamoeba histolytica is believed to be devoid of peroxisomes, like most anaerobic protists. In this work, we provided the first evidence that peroxisomes are present in E. histolytica, although only seven proteins responsible for peroxisome biogenesis (peroxins) were identified (Pex1, Pex6, Pex5, Pex11, Pex14, Pex16, and Pex19). Targeting matrix proteins to peroxisomes is reduced to the PTS1-dependent pathway mediated via the soluble Pex5 receptor, while the PTS2 receptor Pex7 is absent. Immunofluorescence microscopy showed that peroxisomal markers (Pex5, Pex14, Pex16, Pex19) are present in vesicles distinct from mitosomes, the endoplasmic reticulum, and the endosome/phagosome system, except Pex11, which has dual localization in peroxisomes and mitosomes. Immunoelectron microscopy revealed that Pex14 localized to vesicles of approximately 90–100 nm in diameter. Proteomic analyses of affinity-purified peroxisomes and in silico PTS1 predictions provided datasets of 655 and 56 peroxisomal candidates, respectively; however, only six proteins were shared by both datasets, including myo-inositol dehydrogenase (myo-IDH). Peroxisomal NAD-dependent myo-IDH appeared to be a dimeric enzyme with high affinity to myo-inositol (Km 0.044 mM) and can utilize also scyllo-inositol, D-glucose and D-xylose as substrates. Phylogenetic analyses revealed that orthologs of myo-IDH with PTS1 are present in E. dispar, E. nutalli and E. moshkovskii but not in E. invadens, and form a monophyletic clade of mostly peroxisomal orthologs with free-living Mastigamoeba balamuthi and Pelomyxa schiedti. The presence of peroxisomes in E. histolytica and other archamoebae breaks the paradigm of peroxisome absence in anaerobes and provides a new potential target for the development of antiparasitic drugs.
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Evers, M. E., V. I. Titorenko, I. J. van der Klei, W. Harder y M. Veenhuis. "Assembly of alcohol oxidase in peroxisomes of the yeast Hansenula polymorpha requires the cofactor flavin adenine dinucleotide." Molecular Biology of the Cell 5, n.º 8 (agosto de 1994): 829–37. http://dx.doi.org/10.1091/mbc.5.8.829.
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The peroxisomal flavoprotein alcohol oxidase (AO) is an octamer (600 kDa) consisting of eight identical subunits, each of which contains one flavin adenine dinucleotide molecule as a cofactor. Studies on a riboflavin (Rf) auxotrophic mutant of the yeast Hansenula polymorpha revealed that limitation of the cofactor led to drastic effects on AO import and assembly as well as peroxisome proliferation. Compared to wild-type control cells Rf-limitation led to 1) reduced levels of AO protein, 2) reduced levels of correctly assembled and activated AO inside peroxisomes, 3) a partial inhibition of peroxisomal protein import, leading to the accumulation of precursors of matrix proteins in the cytosol, and 4) a significant increase in peroxisome number. We argue that the inhibition of import may result from the saturation of a peroxisomal molecular chaperone under conditions that normal assembly of a major matrix protein inside the target organelle is prevented.
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Hill, P. E. y P. A. Walton. "Import of microinjected proteins bearing the SKL peroxisomal targeting sequence into the peroxisomes of a human fibroblast cell line: evidence that virtually all peroxisomes are import-competent". Journal of Cell Science 108, n.º 4 (1 de abril de 1995): 1469–76. http://dx.doi.org/10.1242/jcs.108.4.1469.
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Peroxisomes import virtually all of their membrane and matrix proteins post-translationally. It is presently unknown whether, in mammalian cells, their exists a pool of mature peroxisomes which have received their complement of proteins and are import-incompetent. Previous work has shown that fibroblasts are capable of importing microinjected peroxisomal proteins into peroxisomes. This report describes the import of a hybrid peroxisomal protein into virtually all peroxisomes of the microinjected cell. The peroxisomal import was uniform in both short and long incubations. Pretreatment of the cells with cycloheximide did not affect the import of the peroxisomal protein, nor was there any difference in the distribution of the imported protein. Sequential microinjection experiments demonstrated that peroxisomes that had imported luciferase were capable of importing another peroxisomal protein injected 24 hours later. These results suggest that, in fibroblasts, all peroxisomes have associated protein-import machinery; this evidence does not support the hypothesis that there exists a pool of import-incompetent peroxisomes.
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Walton, P. A., M. Wendland, S. Subramani, R. A. Rachubinski y W. J. Welch. "Involvement of 70-kD heat-shock proteins in peroxisomal import." Journal of Cell Biology 125, n.º 5 (1 de junio de 1994): 1037–46. http://dx.doi.org/10.1083/jcb.125.5.1037.
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This report describes the involvement of 70-kD heat-shock proteins (hsp70) in the import of proteins into mammalian peroxisomes. Employing a microinjection-based assay (Walton, P. A., S. J. Gould, J. R. Feramisco, and S. Subramani. 1992. Mol. Cell Biol. 12:531-541), we demonstrate that proteins of the hsp70 family were associated with proteins being imported into the peroxisomal matrix. Import of peroxisomal proteins could be inhibited by coinjection of antibodies directed against the constitutive hsp70 proteins (hsp73). In a permeabilized-cell assay (Wendland and Subramani. 1993. J. Cell Biol. 120:675-685), antibodies directed against hsp70 proteins were shown to inhibit peroxisomal protein import. Inhibition could be overcome by the addition of exogenous hsp70 proteins. Purified rat liver peroxisomes were shown to have associated hsp70 proteins. The amount of associated hsp70 was increased under conditions of peroxisomal proliferation. Furthermore, proteinase protection assays indicated that the hsp70 molecules were located on the outside of the peroxisomal membrane. Finally, the process of heat-shocking cells resulted in a considerable delay in the import of peroxisomal proteins. Taken together, these results indicate that heat-shock proteins of the cytoplasmic hsp70 family are involved in the import of peroxisomal proteins.
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Slawecki, M. L., G. Dodt, S. Steinberg, A. B. Moser, H. W. Moser y S. J. Gould. "Identification of three distinct peroxisomal protein import defects in patients with peroxisome biogenesis disorders". Journal of Cell Science 108, n.º 5 (1 de mayo de 1995): 1817–29. http://dx.doi.org/10.1242/jcs.108.5.1817.
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Zellweger syndrome, neonatal adrenoleukodystrophy, infantile Refsum's disease, and classical rhizomelic chondrodysplasia punctata are lethal genetic disorders caused by defects in peroxisome biogenesis. We report here a characterization of the peroxisomal matrix protein import capabilities of fibroblasts from 62 of these peroxisome biogenesis disorder patients representing all ten known complementation groups. Using an immunofluorescence microscopy assay, we identified three distinct peroxisomal protein import defects among these patients. Type-1 cells have a specific inability to import proteins containing the PTS1 peroxisomal targeting signal, type-2 cells have a specific defect in import of proteins containing the PTS2 signal, and type-3 cells exhibit a loss of, or reduction in, the import of both PTS1 and PTS2 proteins. Considering that the common cellular phenotype of Zellweger syndrome, neonatal adrenoleukodystrophy and infantile Refsum's disease has been proposed to be a complete defect in peroxisomal matrix protein import, the observation that 85% (40/47) of the type-3 cell lines imported a low but detectable amount of both PTS1 and PTS2 proteins was surprising. Furthermore, different cell lines with the type-3 defect exhibited a broad spectrum of different phenotypes; some showed a complete absence of matrix protein import while others contained 50–100 matrix protein-containing peroxisomes per cell. We also noted certain relationships between the import phenotypes and clinical diagnoses: both type-1 cell lines were from neonatal adrenoleukodystrophy patients, all 13 type-2 cell lines were from classical rhizomelic chondrodysplasia punctata patients, and the type-3 import defect was found in the vast majority of Zellweger syndrome (22/22), neonatal adrenoleukodytrophy (17/19), and infantile Refsum's disease (7/7) patients. Our finding that all type-1 cell lines were from the second complementation group (CG2), all 13 type-2 cell lines were from CG11, and that cells from the eight remaining complementation groups only exhibit the type-3 defect indicates that mutations in particular genes give rise to the different types of peroxisomal protein import defects. This hypothesis is further supported by correlations between certain complementation groups and particular type-3 subphenotypes: all patient cell lines belonging to CG3 and CG10 showed a complete absence of peroxisomal matrix protein import while those from CG6, CG7, and CG8 imported some peroxisomal matrix proteins. However, the fact that cell lines from within particular complementation groups (CG1, CG4) could have different matrix protein import characteristics suggests that allelic heterogeneity also plays an important role in generating different import phenotypes in certain patients.(ABSTRACT TRUNCATED AT 400 WORDS)
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Kalish, J. E., C. Theda, J. C. Morrell, J. M. Berg y S. J. Gould. "Formation of the peroxisome lumen is abolished by loss of Pichia pastoris Pas7p, a zinc-binding integral membrane protein of the peroxisome." Molecular and Cellular Biology 15, n.º 11 (noviembre de 1995): 6406–19. http://dx.doi.org/10.1128/mcb.15.11.6406.
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We have cloned and sequenced PAS7, a gene required for peroxisome assembly in the yeast Pichia pastoris. The product of this gene, Pas7p, is a member of the C3HC4 superfamily of zinc-binding proteins. Point mutations that alter conserved residues of the C3HC4 motif abolish PAS7 activity and reduce zinc binding, suggesting that Pas7p binds zinc in vivo and that zinc binding is essential for PAS7 function. As with most pas mutants, pas7 cells exhibit a pronounced deficiency in import of peroxisomal matrix proteins that contain either the type 1 peroxisomal targeting signal (PTS1) or the type 2 PTS (PTS2). However, while other yeast and mammalian pas mutants accumulate ovoid, vesicular peroxisomal intermediates, loss of Pas7p leads to accumulation of membrane sheets and vesicles which lack a recognizable lumen. Thus, Pas7p appears to be essential for protein translocation into peroxisomes as well as formation of the lumen of the organelle. Consistent with these data, we find that Pas7p is an integral peroxisomal membrane protein which is entirely resistant to exogenous protease and thus appears to reside completely within the peroxisome. Our observations suggest that the function of Pas7p defines a previously unrecognized step in peroxisome assembly: formation of the peroxisome lumen. Furthermore, because the peroxisomal intermediates in the pas7 delta mutant proliferate in response to peroxisome-inducing environmental conditions, we conclude that Pas7p is not required for peroxisome proliferation.
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Fang, Yi, James C. Morrell, Jacob M. Jones y Stephen J. Gould. "PEX3 functions as a PEX19 docking factor in the import of class I peroxisomal membrane proteins". Journal of Cell Biology 164, n.º 6 (8 de marzo de 2004): 863–75. http://dx.doi.org/10.1083/jcb.200311131.
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PEX19 is a chaperone and import receptor for newly synthesized, class I peroxisomal membrane proteins (PMPs). PEX19 binds these PMPs in the cytoplasm and delivers them to the peroxisome for subsequent insertion into the peroxisome membrane, indicating that there may be a PEX19 docking factor in the peroxisome membrane. Here we show that PEX3 is required for PEX19 to dock at peroxisomes, interacts specifically with the docking domain of PEX19, and is required for recruitment of the PEX19 docking domain to peroxisomes. PEX3 is also sufficient to dock PEX19 at heterologous organelles and binds PEX19 via a conserved motif that is essential for this docking activity and for PEX3 function in general. Not surprisingly, transient inhibition of PEX3 abrogates class I PMP import but has no effect on class II PMP import or peroxisomal matrix protein import. Taken together, these results suggest that PEX3 plays a selective, essential, and direct role in PMP import as a docking factor for PEX19.
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Guo, Tong, Yuriy Y. Kit, Jean-Marc Nicaud, Marie-Therese Le Dall, S. Kelly Sears, Hojatollah Vali, Honey Chan, Richard A. Rachubinski y Vladimir I. Titorenko. "Peroxisome division in the yeast Yarrowia lipolytica is regulated by a signal from inside the peroxisome". Journal of Cell Biology 162, n.º 7 (22 de septiembre de 2003): 1255–66. http://dx.doi.org/10.1083/jcb.200305055.
Texto completoResumen
We describe an unusual mechanism for organelle division. In the yeast Yarrowia lipolytica, only mature peroxisomes contain the complete set of matrix proteins. These mature peroxisomes assemble from several immature peroxisomal vesicles in a multistep pathway. The stepwise import of distinct subsets of matrix proteins into different immature intermediates along the pathway causes the redistribution of a peroxisomal protein, acyl-CoA oxidase (Aox), from the matrix to the membrane. A significant redistribution of Aox occurs only in mature peroxisomes. Inside mature peroxisomes, the membrane-bound pool of Aox interacts with Pex16p, a membrane-associated protein that negatively regulates the division of early intermediates in the pathway. This interaction inhibits the negative action of Pex16p, thereby allowing mature peroxisomes to divide.
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Gonzalez, Kim L., Sarah E. Ratzel, Kendall H. Burks, Charles H. Danan, Jeanne M. Wages, Bethany K. Zolman y Bonnie Bartel. "A pex1 missense mutation improves peroxisome function in a subset of Arabidopsis pex6 mutants without restoring PEX5 recycling". Proceedings of the National Academy of Sciences 115, n.º 14 (19 de marzo de 2018): E3163—E3172. http://dx.doi.org/10.1073/pnas.1721279115.
Texto completoResumen
Peroxisomes are eukaryotic organelles critical for plant and human development because they house essential metabolic functions, such as fatty acid β-oxidation. The interacting ATPases PEX1 and PEX6 contribute to peroxisome function by recycling PEX5, a cytosolic receptor needed to import proteins targeted to the peroxisomal matrix. Arabidopsis pex6 mutants exhibit low PEX5 levels and defects in peroxisomal matrix protein import, oil body utilization, peroxisomal metabolism, and seedling growth. These defects are hypothesized to stem from impaired PEX5 retrotranslocation leading to PEX5 polyubiquitination and consequent degradation of PEX5 via the proteasome or of the entire organelle via autophagy. We recovered a pex1 missense mutation in a screen for second-site suppressors that restore growth to the pex6-1 mutant. Surprisingly, this pex1-1 mutation ameliorated the metabolic and physiological defects of pex6-1 without restoring PEX5 levels. Similarly, preventing autophagy by introducing an atg7-null allele partially rescued pex6-1 physiological defects without restoring PEX5 levels. atg7 synergistically improved matrix protein import in pex1-1 pex6-1, implying that pex1-1 improves peroxisome function in pex6-1 without impeding autophagy of peroxisomes (i.e., pexophagy). pex1-1 differentially improved peroxisome function in various pex6 alleles but worsened the physiological and molecular defects of a pex26 mutant, which is defective in the tether anchoring the PEX1–PEX6 hexamer to the peroxisome. Our results support the hypothesis that, beyond PEX5 recycling, PEX1 and PEX6 have additional functions in peroxisome homeostasis and perhaps in oil body utilization.
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Motley, A., E. Hettema, B. Distel y H. Tabak. "Differential protein import deficiencies in human peroxisome assembly disorders." Journal of Cell Biology 125, n.º 4 (15 de mayo de 1994): 755–67. http://dx.doi.org/10.1083/jcb.125.4.755.
Texto completoResumen
Two peroxisome targeting signals (PTSs) for matrix proteins have been well defined to date. PTS1 comprises a COOH-terminal tripeptide, SKL, and has been found in several matrix proteins, whereas PTS2 has been found only in peroxisomal thiolase and is contained within an NH2-terminal cleavable presequence. We have investigated the functional integrity of the import routes for PTS1 and PTS2 in fibroblasts from patients suffering from peroxisome assembly disorders. Three of the five complementation groups tested showed a general loss of PTS1 and PTS2 import. Two complementation groups showed a differential loss of peroxisomal protein import: group I cells were able to import a PTS1- but not a PTS2- containing reporter protein into their peroxisomes, and group IV cells were able to import the PTS2 but not the PTS1 reporter into aberrant, peroxisomal ghostlike structures. The observation that the PTS2 import pathway is intact only in group IV cells is supported by the protection of endogenous thiolase from protease degradation in group IV cells and its sensitivity in the remaining complementation groups, including the partialized disorder of group I. The functionality of the PTS2 import pathway and colocalization of endogenous thiolase with the peroxisomal membranes in group IV cells was substantiated further using immunofluorescence, subcellular fractionation, and immunoelectron microscopy. The phenotypes of group I and IV cells provide the first evidence for differential import deficiencies in higher eukaryotes. These phenotypes are analogous to those found in Saccharomyces cerevisiae peroxisome assembly mutants.
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Usuda, N., M. I. Usman, M. K. Reddy, T. Hashimoto, J. K. Reddy y M. S. Rao. "Immunocytochemical localization of urate oxidase, fatty acyl-CoA oxidase, and catalase in bovine kidney peroxisomes." Journal of Histochemistry & Cytochemistry 36, n.º 3 (marzo de 1988): 253–58. http://dx.doi.org/10.1177/36.3.3343509.
Texto completoResumen
We investigated the localization of urate oxidase, peroxisomal fatty acyl-CoA oxidase, and catalase in bovine kidney by immunoblot analysis and protein A-gold immunocytochemistry, using the respective polyclonal monospecific antibodies raised against the enzymes purified from rat liver. By immunoblot analysis, these three proteins were detected in bovine kidney and bovine liver homogenates. Subcellular localization of these three enzymes in kidney was ascertained by protein A-gold immunocytochemical staining of Lowicryl K4M-embedded tissue. Peroxisomes in bovine kidney cortical epithelium possessed crystalloid cores or nucleoids, which were found to be the exclusive sites of urate oxidase localization. The limiting membrane, the marginal plate, and the matrix of renal peroxisomes were negative for urate oxidase staining. In contrast, catalase and fatty acyl-CoA oxidase were found in the peroxisome matrix. These results demonstrate that, unlike rat kidney peroxisomes which lack urate oxidase, peroxisomes of bovine kidney contain this enzyme as well as peroxisomal fatty acyl-CoA oxidase.
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Zaar, K., A. Völkl y H. D. Fahimi. "d-aspartate oxidase in rat, bovine and sheep kidney cortex is localized in peroxisomes". Biochemical Journal 261, n.º 1 (1 de julio de 1989): 233–38. http://dx.doi.org/10.1042/bj2610233.
Texto completoResumen
D-Aspartate oxidase (EC 1.4.3.1) was assayed in subcellular fractions and in highly purified peroxisomes from rat, bovine and sheep kidney cortex as well as from rat liver. During all steps of subcellular-fractionation procedures, D-aspartate oxidase co-fractionated with peroxisomal marker enzymes. In highly purified preparations of peroxisomes, the enrichment of D-aspartate oxidase activity over the homogenate is about 32-fold, being comparable with that of the peroxisomal marker enzymes catalase and D-amino acid oxidase. Disruption of the peroxisomes by freezing and thawing released more than 90% of the enzyme activity, which is typical for soluble peroxisomal-matrix proteins. Our findings provide strong evidence that in these tissues D-aspartate oxidase is a peroxisomal-matrix protein and should be added as an additional flavoprotein oxidase to the known set of peroxisomal oxidases.
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Koller, Antonius, William B. Snyder, Klaas Nico Faber, Thibaut J. Wenzel, Linda Rangell, Gilbert A. Keller y Suresh Subramani. "Pex22p of Pichia pastoris, Essential for Peroxisomal Matrix Protein Import, Anchors the Ubiquitin-Conjugating Enzyme, Pex4p, on the Peroxisomal Membrane". Journal of Cell Biology 146, n.º 1 (12 de julio de 1999): 99–112. http://dx.doi.org/10.1083/jcb.146.1.99.
Texto completoResumen
We isolated a Pichia pastoris mutant that was unable to grow on the peroxisome-requiring media, methanol and oleate. Cloning the gene by complementation revealed that the encoded protein, Pex22p, is a new peroxin. A Δpex22 strain does not grow on methanol or oleate and is unable to import peroxisomal matrix proteins. However, this strain targets peroxisomal membrane proteins to membranes, most likely peroxisomal remnants, detectable by fluorescence and electron microscopy. Pex22p, composed of 187 amino acids, is an integral peroxisomal membrane protein with its NH2 terminus in the matrix and its COOH terminus in the cytosol. It contains a 25–amino acid peroxisome membrane-targeting signal at its NH2 terminus. Pex22p interacts with the ubiquitin-conjugating enzyme Pex4p, a peripheral peroxisomal membrane protein, in vivo, and in a yeast two-hybrid experiment. Pex22p is required for the peroxisomal localization of Pex4p and in strains lacking Pex22p, the Pex4p is cytosolic and unstable. Therefore, Pex22p anchors Pex4p at the peroxisomal membrane. Strains that do not express Pex4p or Pex22p have similar phenotypes and lack Pex5p, suggesting that Pex4p and Pex22p act at the same step in peroxisome biogenesis. The Saccharomyces cerevisiae hypothetical protein, Yaf5p, is the functional homologue of P. pastoris Pex22p.
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Alexson, S. E., Y. Fujiki, H. Shio y P. B. Lazarow. "Partial disassembly of peroxisomes." Journal of Cell Biology 101, n.º 1 (1 de julio de 1985): 294–304. http://dx.doi.org/10.1083/jcb.101.1.294.
Texto completoResumen
Rat liver peroxisomes were subjected to a variety of procedures intended to partially disassemble or damage them; the effects were analyzed by recentrifugation into sucrose gradients, enzyme analyses, electron microscopy, and SDS PAGE. Freezing and thawing or mild sonication released some matrix proteins and produced apparently intact peroxisomal "ghosts" with crystalloid cores and some fuzzy fibrillar content. Vigorous sonication broke open the peroxisomes but the membranes remained associated with cores and fibrillar and amorphous matrix material. The density of both ghosts and more severely damaged peroxisomes was approximately 1.23. Pyrophosphate (pH 9) treatment solubilized the fibrillar content, yielding ghosts that were empty except for cores. Some matrix proteins such as catalase and thiolase readily leak from peroxisomes. Other proteins were identified that remain in mechanically damaged peroxisomes but are neither core nor membrane proteins because they can be released by pyrophosphate treatment. These constitute a class of poorly soluble matrix proteins that appear to correspond to the fibrillar material observed morphologically. All of the peroxisomal beta-oxidation enzymes are located in the matrix, but they vary greatly in how easily they leak out. Palmitoyl coenzyme A synthetase is in the membrane, based on its co-distribution with the 22-kilodalton integral membrane polypeptide.
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Mu, Yizhu, Yunash Maharjan, Raghbendra Kumar Dutta, Xiaofan Wei, Jin Hwi Kim, Jinbae Son, Channy Park y Raekil Park. "Pharmacological inhibition of catalase induces peroxisome leakage and suppression of LPS induced inflammatory response in Raw 264.7 cell". PLOS ONE 16, n.º 2 (19 de febrero de 2021): e0245799. http://dx.doi.org/10.1371/journal.pone.0245799.
Texto completoResumen
Peroxisomes are metabolically active organelles which are known to exert anti-inflammatory effects especially associated with the synthesis of mediators of inflammation resolution. However, the role of catalase and effects of peroxisome derived reactive oxygen species (ROS) caused by lipid peroxidation through 4-hydroxy-2-nonenal (4-HNE) on lipopolysaccharide (LPS) mediated inflammatory pathway are largely unknown. Here, we show that inhibition of catalase by 3-aminotriazole (3-AT) results in the generation of peroxisomal ROS, which contribute to leaky peroxisomes in RAW264.7 cells. Leaky peroxisomes cause the release of matrix proteins to the cytosol, which are degraded by ubiquitin proteasome system. Furthermore, 3-AT promotes the formation of 4HNE-IκBα adduct which directly interferes with LPS induced NF-κB activation. Even though, a selective degradation of peroxisome matrix proteins and formation of 4HNE- IκBα adduct are not directly related with each other, both of them are could be the consequences of lipid peroxidation occurring at the peroxisome membrane.
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Zaar, K. y H. D. Fahimi. "Immunoelectron microscopic localization of the isozymes of L-alpha-hydroxyacid oxidase in renal peroxisomes of beef and sheep: evidence of distinct intraorganellar subcompartmentation." Journal of Histochemistry & Cytochemistry 39, n.º 6 (junio de 1991): 801–8. http://dx.doi.org/10.1177/39.6.2033239.
Texto completoResumen
L-alpha-hydroxyacid oxidase (HAOX), a peroxisomal marker enzyme in mammals, exists in two isozymic forms, HAOX A (EC 1.1.3.1) and HAOX B (EC 1.3.4.2), which differ in their substrate specificity. In rat tissues HAOX A is found exclusively in hepatocyte peroxisomes and HAOX B in renal peroxisomes. Recently we found enzymatic evidence that highly purified peroxisome preparations from beef and sheep kidney cortex contain both isozymes. In situ, the peroxisomes in the proximal tubule cells of both species exhibit peculiar angular outlines apparently due to the presence of multiple marginal plates. Marginal plates are plate-like crystalline matrix inclusions which are apposed to the inner aspect of the peroxisomal membrane. In this study monospecific antibodies against HAOX A and B proteins purified from rat liver and kidney, respectively, were raised in rabbits and used to study the intraorganellar localization of each isozyme in beef and sheep kidney cortex peroxisomes. Incubation of ultra-thin sections of LR White-embedded tissue with anti-HAOX A or B followed by protein A-gold revealed that in both species HAOX A is present diffusely in the peroxisomal matrix, whereas HAOX B is localized almost exclusively in the membrane associated marginal plates. This is the first report on the in situ immunocytochemical characterization of marginal plates, which are the most common inclusions in the matrix of renal peroxisomes.
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Chang, Chia-Che, Daniel S. Warren, Katherine A. Sacksteder y Stephen J. Gould. "Pex12 Interacts with Pex5 and Pex10 and Acts Downstream of Receptor Docking in Peroxisomal Matrix Protein Import". Journal of Cell Biology 147, n.º 4 (15 de noviembre de 1999): 761–74. http://dx.doi.org/10.1083/jcb.147.4.761.
Texto completoResumen
Peroxisomal matrix protein import requires PEX12, an integral peroxisomal membrane protein with a zinc ring domain at its carboxy terminus. Mutations in human PEX12 result in Zellweger syndrome, a lethal neurological disorder, and implicate the zinc ring domain in PEX12 function. Using two-hybrid studies, blot overlay assays, and coimmunoprecipitation experiments, we observed that the zinc-binding domain of PEX12 binds both PEX5, the PTS1 receptor, and PEX10, another integral peroxisomal membrane protein required for peroxisomal matrix protein import. Furthermore, we identified a patient with a missense mutation in the PEX12 zinc-binding domain, S320F, and observed that this mutation reduces the binding of PEX12 to PEX5 and PEX10. Overexpression of either PEX5 or PEX10 can suppress this PEX12 mutation, providing genetic evidence that these interactions are biologically relevant. PEX5 is a predominantly cytoplasmic protein and previous PEX5-binding proteins have been implicated in docking PEX5 to the peroxisome surface. However, we find that loss of PEX12 or PEX10 does not reduce the association of PEX5 with peroxisomes, demonstrating that these peroxins are not required for receptor docking. These and other results lead us to propose that PEX12 and PEX10 play direct roles in peroxisomal matrix protein import downstream of the receptor docking event.