Journal articles: 'Pex5'

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Miyata, Non, and Yukio Fujiki. "Shuttling Mechanism of Peroxisome Targeting Signal Type 1 Receptor Pex5: ATP-Independent Import and ATP-Dependent Export." Molecular and Cellular Biology 25, no. 24 (December 15, 2005): 10822–32. http://dx.doi.org/10.1128/mcb.25.24.10822-10832.2005.

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ABSTRACT Peroxisomal matrix proteins are posttranslationally imported into peroxisomes with the peroxisome-targeting signal 1 receptor, Pex5. The longer isoform of Pex5, Pex5L, also transports Pex7-PTS2 protein complexes. After unloading the cargoes, Pex5 returns to the cytosol. To address molecular mechanisms underlying Pex5 functions, we constructed a cell-free Pex5 translocation system with a postnuclear supernatant fraction from CHO cell lines. In assays using the wild-type CHO-K1 cell fraction, 35S-labeled Pex5 was specifically imported into and exported from peroxisomes with multiple rounds. 35S-Pex5 import was also evident using peroxisomes isolated from rat liver. ATP was not required for 35S-Pex5 import but was indispensable for export. 35S-Pex5 was imported neither to peroxisome remnants from RING peroxin-deficient cell mutants nor to those from pex14 cells lacking a Pex5-docking site. In contrast, 35S-Pex5 was imported into the peroxisome remnants of PEX1-, PEX6-, and PEX26-defective cell mutants, including those from patients with peroxisome biogenesis disorders, from which, however, 35S-Pex5 was not exported, thereby indicating that Pex1 and Pex6 of the AAA ATPase family and their recruiter, Pex26, were essential for Pex5 export. Moreover, we analyzed the 35S-Pex5-associated complexes on peroxisomal membranes by blue-native polyacrylamide gel electrophoresis. 35S-Pex5 was in two distinct, 500- and 800-kDa complexes comprising different sets of peroxins, such as Pex14 and Pex2, implying that Pex5 transited between the subcomplexes. Together, results indicated that Pex5 most likely enters peroxisomes, changes its interacting partners, and then exits using ATP energy.

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Min, Kyunghun, Hokyoung Son, Jungkwan Lee, Gyung Ja Choi, Jin-Cheol Kim, and Yin-Won Lee. "Peroxisome Function Is Required for Virulence and Survival of Fusarium graminearum." Molecular Plant-Microbe Interactions® 25, no. 12 (December 2012): 1617–27. http://dx.doi.org/10.1094/mpmi-06-12-0149-r.

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Peroxisomes are organelles that are involved in a number of important cellular metabolic processes, including the β-oxidation of fatty acids, biosynthesis of secondary metabolites, and detoxification of reactive oxygen species (ROS). In this study, the role of peroxisomes was examined in Fusarium graminearum by targeted deletion of three genes (PEX5, PEX6, and PEX7) encoding peroxin (PEX) proteins required for peroxisomal protein import. PEX5 and PEX7 deletion mutants were unable to localize the fluorescently tagged peroxisomal targeting signal type 1 (PTS1)- and PTS2-containing proteins to peroxisomes, respectively, whereas the PEX6 mutant failed to localize both fluorescent proteins. Deletion of PEX5 and PEX6 resulted in retarded growth on long-chain fatty acids and butyrate, while the PEX7 deletion mutants utilized fatty acids other than butyrate. Virulence on wheat heads was greatly reduced in the PEX5 and PEX6 deletion mutants, and they were defective in spreading from inoculated florets to the adjacent spikelets through rachis. Deletion of PEX5 and PEX6 dropped survivability of aged cells in planta and in vitro due to the accumulation of ROS followed by necrotic cell death. These results demonstrate that PTS1-dependent peroxisomal protein import mediated by PEX5 and PEX6 are critical to virulence and survival of F. graminearum.

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Gonzalez, Kim L., Sarah E. Ratzel, Kendall H. Burks, Charles H. Danan, Jeanne M. Wages, Bethany K. Zolman, and 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, no. 14 (March 19, 2018): E3163—E3172. http://dx.doi.org/10.1073/pnas.1721279115.

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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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Platta, Harald W., Fouzi El Magraoui, Bastian E. Bäumer, Daniel Schlee, Wolfgang Girzalsky, and Ralf Erdmann. "Pex2 and Pex12 Function as Protein-Ubiquitin Ligases in Peroxisomal Protein Import." Molecular and Cellular Biology 29, no. 20 (August 17, 2009): 5505–16. http://dx.doi.org/10.1128/mcb.00388-09.

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ABSTRACT The PTS1-dependent peroxisomal matrix protein import is facilitated by the receptor protein Pex5 and can be divided into cargo recognition in the cytosol, membrane docking of the cargo-receptor complex, cargo release, and recycling of the receptor. The final step is controlled by the ubiquitination status of Pex5. While polyubiquitinated Pex5 is degraded by the proteasome, monoubiquitinated Pex5 is destined for a new round of the receptor cycle. Recently, the ubiquitin-conjugating enzymes involved in Pex5 ubiquitination were identified as Ubc4 and Pex4 (Ubc10), whereas the identity of the corresponding protein-ubiquitin ligases remained unknown. Here we report on the identification of the protein-ubiquitin ligases that are responsible for the ubiquitination of the peroxisomal protein import receptor Pex5. It is demonstrated that each of the three RING peroxins Pex2, Pex10, and Pex12 exhibits ubiquitin-protein isopeptide ligase activity. Our results show that Pex2 mediates the Ubc4-dependent polyubiquitination whereas Pex12 facilitates the Pex4-dependent monoubiquitination of Pex5.

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Ramón, Naxhiely Martínez, and Bonnie Bartel. "Interdependence of the Peroxisome-targeting Receptors in Arabidopsis thaliana: PEX7 Facilitates PEX5 Accumulation and Import of PTS1 Cargo into Peroxisomes." Molecular Biology of the Cell 21, no. 7 (April 2010): 1263–71. http://dx.doi.org/10.1091/mbc.e09-08-0672.

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Peroxisomes compartmentalize certain metabolic reactions critical to plant and animal development. The import of proteins from the cytosol into the organelle matrix depends on more than a dozen peroxin (PEX) proteins, with PEX5 and PEX7 serving as receptors that shuttle proteins bearing one of two peroxisome-targeting signals (PTSs) into the organelle. PEX5 is the PTS1 receptor; PEX7 is the PTS2 receptor. In plants and mammals, PEX7 depends on PEX5 binding to deliver PTS2 cargo into the peroxisome. In this study, we characterized a pex7 missense mutation, pex7-2, that disrupts both PEX7 cargo binding and PEX7-PEX5 interactions in yeast, as well as PEX7 protein accumulation in plants. We examined localization of peroxisomally targeted green fluorescent protein derivatives in light-grown pex7 mutants and observed not only the expected defects in PTS2 protein import but also defects in PTS1 import. These PTS1 import defects were accompanied by reduced PEX5 accumulation in light-grown pex7 seedlings. Our data suggest that PEX5 and PTS1 import depend on the PTS2 receptor PEX7 in Arabidopsis and that the environment may influence this dependence. These data advance our understanding of the biogenesis of these essential organelles and provide a possible rationale for the retention of the PTS2 pathway in some organisms.

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Hagstrom, Danielle, Changle Ma, Soumi Guha-Polley, and Suresh Subramani. "The unique degradation pathway of the PTS2 receptor, Pex7, is dependent on the PTS receptor/coreceptor, Pex5 and Pex20." Molecular Biology of the Cell 25, no. 17 (September 2014): 2634–43. http://dx.doi.org/10.1091/mbc.e13-12-0716.

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Peroxisomal matrix protein import uses two peroxisomal targeting signals (PTSs). Most matrix proteins use the PTS1 pathway and its cargo receptor, Pex5. The PTS2 pathway is dependent on another receptor, Pex7, and its coreceptor, Pex20. We found that during the matrix protein import cycle, the stability and dynamics of Pex7 differ from those of Pex5 and Pex20. In Pichia pastoris, unlike Pex5 and Pex20, Pex7 is constitutively degraded in wild-type cells but is stabilized in pex mutants affecting matrix protein import. Degradation of Pex7 is more prevalent in cells grown in methanol, in which the PTS2 pathway is nonessential, in comparison with oleate, suggesting regulation of Pex7 turnover. Pex7 must shuttle into and out of peroxisomes before it is polyubiquitinated and degraded by the proteasome. The shuttling of Pex7, and consequently its degradation, is dependent on the receptor recycling pathways of Pex5 and Pex20 and relies on an interaction between Pex7 and Pex20. We also found that blocking the export of Pex20 from peroxisomes inhibits PTS1-mediated import, suggesting sharing of limited components in the export of PTS receptors/coreceptors. The shuttling and stability of Pex7 are divergent from those of Pex5 and Pex20, exemplifying a novel interdependence of the PTS1 and PTS2 pathways.

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Woodward, Andrew W., and 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, no. 2 (February 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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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, no. 11 (November 15, 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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Ma, Changle, Danielle Hagstrom, Soumi Guha Polley, and Suresh Subramani. "Redox-regulated Cargo Binding and Release by the Peroxisomal Targeting Signal Receptor, Pex5." Journal of Biological Chemistry 288, no. 38 (July 31, 2013): 27220–31. http://dx.doi.org/10.1074/jbc.m113.492694.

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In its role as a mobile receptor for peroxisomal matrix cargo containing a peroxisomal targeting signal called PTS1, the protein Pex5 shuttles between the cytosol and the peroxisome lumen. Pex5 binds PTS1 proteins in the cytosol via its C-terminal tetratricopeptide domains and delivers them to the peroxisome lumen, where the receptor·cargo complex dissociates. The cargo-free receptor is exported to the cytosol for another round of import. How cargo release and receptor recycling are regulated is poorly understood. We found that Pex5 functions as a dimer/oligomer and that its protein interactions with itself (homo-oligomeric) and with Pex8 (hetero-oligomeric) control the binding and release of cargo proteins. These interactions are controlled by a redox-sensitive amino acid, cysteine 10 of Pex5, which is essential for the formation of disulfide bond-linked Pex5 forms, for high affinity cargo binding, and for receptor recycling. Disulfide bond-linked Pex5 showed the highest affinity for PTS1 cargo. Upon reduction of the disulfide bond by dithiothreitol, Pex5 transitioned to a noncovalent dimer, concomitant with the partial release of PTS1 cargo. Additionally, dissipation of the redox balance between the cytosol and the peroxisome lumen caused an import defect. A hetero-oligomeric interaction between the N-terminal domain (amino acids 1–110) of Pex5 and a conserved motif at the C terminus of Pex8 further facilitates cargo release, but only under reducing conditions. This interaction is also important for the release of PTS1 proteins. We suggest a redox-regulated model for Pex5 function during the peroxisomal matrix protein import cycle.

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Titorenko, V. I., D. M. Ogrydziak, and R. A. Rachubinski. "Four distinct secretory pathways serve protein secretion, cell surface growth, and peroxisome biogenesis in the yeast Yarrowia lipolytica." Molecular and Cellular Biology 17, no. 9 (September 1997): 5210–26. http://dx.doi.org/10.1128/mcb.17.9.5210.

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We have identified and characterized mutants of the yeast Yarrowia lipolytica that are deficient in protein secretion, in the ability to undergo dimorphic transition from the yeast to the mycelial form, and in peroxisome biogenesis. Mutations in the SEC238, SRP54, PEX1, PEX2, PEX6, and PEX9 genes affect protein secretion, prevent the exit of the precursor form of alkaline extracellular protease from the endoplasmic reticulum, and compromise peroxisome biogenesis. The mutants sec238A, srp54KO, pex2KO, pex6KO, and pex9KO are also deficient in the dimorphic transition from the yeast to the mycelial form and are affected in the export of only plasma membrane and cell wall-associated proteins specific for the mycelial form. Mutations in the SEC238, SRP54, PEX1, and PEX6 genes prevent or significantly delay the exit of two peroxisomal membrane proteins, Pex2p and Pex16p, from the endoplasmic reticulum en route to the peroxisomal membrane. Mutations in the PEX5, PEX16, and PEX17 genes, which have previously been shown to be essential for peroxisome biogenesis, affect the export of plasma membrane and cell wall-associated proteins specific for the mycelial form but do not impair exit from the endoplasmic reticulum of either Pex2p and Pex16p or of proteins destined for secretion. Biochemical analyses of these mutants provide evidence for the existence of four distinct secretory pathways that serve to deliver proteins for secretion, plasma membrane and cell wall synthesis during yeast and mycelial modes of growth, and peroxisome biogenesis. At least two of these secretory pathways, which are involved in the export of proteins to the external medium and in the delivery of proteins for assembly of the peroxisomal membrane, diverge at the level of the endoplasmic reticulum.

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SZILARD, Rachel K., and Richard A. RACHUBINSKI. "Tetratricopeptide repeat domain of Yarrowia lipolytica Pex5p is essential for recognition of the type 1 peroxisomal targeting signal but does not confer full biological activity on Pex5p." Biochemical Journal 346, no. 1 (February 8, 2000): 177–84. http://dx.doi.org/10.1042/bj3460177.

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Peroxins are proteins required for peroxisome assembly and are encoded by the PEX genes. The Yarrowia lipolytica pex5-1 mutant fails to import a subset of peroxisomal matrix proteins, including those with a type 1 peroxisomal targeting signal (PTS1). Pex5p family members interact with a PTS1 through their characteristic tetratricopeptide repeat (TPR) domain. We used binding assays in vitro to investigate the nature of the association of Y. lipolytica Pex5p (YlPex5p) with the PTS1 signal. A purified recombinant YlPex5p fusion protein interacted specifically, directly and autonomously with a protein terminating in a PTS1. Wild-type YlPex5p translated in vitro recognized functional PTS1s specifically. This activity is abrogated by the substitution of an aspartic residue for a conserved glycine residue in the TPR domain (G455D) of YlPex5p encoded by the pex5-1 allele. Deletion analysis demonstrated that an intact TPR domain of YlPex5p is necessary but not sufficient for both interaction with a PTS1 and functional complementation of a strain lacking YlPex5p.

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Miyata, Non, Kanji Okumoto, Satoru Mukai, Masafumi Noguchi, and Yukio Fujiki. "AWP1/ZFAND6 Functions in Pex5 Export by Interacting with Cys-Monoubiquitinated Pex5 and Pex6 AAA ATPase." Traffic 13, no. 1 (November 9, 2011): 168–83. http://dx.doi.org/10.1111/j.1600-0854.2011.01298.x.

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Chang, C. C., S. South, D. Warren, J. Jones, A. B. Moser, H. W. Moser, and S. J. Gould. "Metabolic control of peroxisome abundance." Journal of Cell Science 112, no. 10 (May 15, 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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Bottger, Gina, Phil Barnett, AndréT J. Klein, Astrid Kragt, Henk F. Tabak, and Ben Distel. "Saccharomyces cerevisiae PTS1 Receptor Pex5p Interacts with the SH3 Domain of the Peroxisomal Membrane Protein Pex13p in an Unconventional, Non-PXXP–related Manner." Molecular Biology of the Cell 11, no. 11 (November 2000): 3963–76. http://dx.doi.org/10.1091/mbc.11.11.3963.

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A number of peroxisome-associated proteins have been described that are involved in the import of proteins into peroxisomes, among which is the receptor for peroxisomal targeting signal 1 (PTS1) proteins Pex5p, the integral membrane protein Pex13p, which contains an Src homology 3 (SH3) domain, and the peripheral membrane protein Pex14p. In the yeast Saccharomyces cerevisiae, both Pex5p and Pex14p are able to bind Pex13p via its SH3 domain. Pex14p contains the classical SH3 binding motif PXXP, whereas this sequence is absent in Pex5p. Mutation of the conserved tryptophan in the PXXP binding pocket of Pex13-SH3 abolished interaction with Pex14p, but did not affect interaction with Pex5p, suggesting that Pex14p is the classical SH3 domain ligand and that Pex5p binds the SH3 domain in an alternative way. To identify the SH3 binding site in Pex5p, we screened a randomly mutagenized PEX5 library for loss of interaction with Pex13-SH3. Such mutations were all located in a small region in the N-terminal half of Pex5p. One of the altered residues (F208) was part of the sequence W204XXQF208, that is conserved between Pex5 proteins of different species. Site-directed mutagenesis of Trp204 confirmed the essential role of this motif in recognition of the SH3 domain. The Pex5p mutants could only partially restore PTS1-protein import in pex5Δ cells in vivo. In vitro binding studies showed that these Pex5p mutants failed to interact with Pex13-SH3 in the absence of Pex14p, but regained their ability to bind in the presence of Pex14p, suggesting the formation of a heterotrimeric complex consisting of Pex5p, Pex14p, and Pex13-SH3. In vivo, these Pex5p mutants, like wild-type Pex5p, were still found to be associated with peroxisomes. Taken together, this indicates that in the absence of Pex13-SH3 interaction, other protein(s) is able to bind Pex5p at the peroxisome; Pex14p is a likely candidate for this function.

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Bonnet, Crystel, Eric Espagne, Denise Zickler, Stéphanie Boisnard, Anne Bourdais, and Véronique Berteaux-Lecellier. "The peroxisomal import proteins PEX2, PEX5 and PEX7 are differently involved in Podospora anserina sexual cycle." Molecular Microbiology 62, no. 1 (October 2006): 157–69. http://dx.doi.org/10.1111/j.1365-2958.2006.05353.x.

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Mbekeani, Alison, Will Stanley, Vishal Kalel, Noa Dahan, Einat Zalckvar, Lilach Sheiner, Wolfgang Schliebs, Ralf Erdmann, Ehmke Pohl, and Paul Denny. "Functional Analyses of a Putative, Membrane-Bound, Peroxisomal Protein Import Mechanism from the Apicomplexan Protozoan Toxoplasma gondii." Genes 9, no. 9 (August 29, 2018): 434. http://dx.doi.org/10.3390/genes9090434.

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Peroxisomes are central to eukaryotic metabolism, including the oxidation of fatty acids—which subsequently provide an important source of metabolic energy—and in the biosynthesis of cholesterol and plasmalogens. However, the presence and nature of peroxisomes in the parasitic apicomplexan protozoa remains controversial. A survey of the available genomes revealed that genes encoding peroxisome biogenesis factors, so-called peroxins (Pex), are only present in a subset of these parasites, the coccidia. The basic principle of peroxisomal protein import is evolutionarily conserved, proteins harbouring a peroxisomal-targeting signal 1 (PTS1) interact in the cytosol with the shuttling receptor Pex5 and are then imported into the peroxisome via the membrane-bound protein complex formed by Pex13 and Pex14. Surprisingly, whilst Pex5 is clearly identifiable, Pex13 and, perhaps, Pex14 are apparently absent from the coccidian genomes. To investigate the functionality of the PTS1 import mechanism in these parasites, expression of Pex5 from the model coccidian Toxoplasma gondii was shown to rescue the import defect of Pex5-deleted Saccharomyces cerevisiae. In support of these data, green fluorescent protein (GFP) bearing the enhanced (e)PTS1 known to efficiently localise to peroxisomes in yeast, localised to peroxisome-like bodies when expressed in Toxoplasma. Furthermore, the PTS1-binding domain of Pex5 and a PTS1 ligand from the putatively peroxisome-localised Toxoplasma sterol carrier protein (SCP2) were shown to interact in vitro. Taken together, these data demonstrate that the Pex5–PTS1 interaction is functional in the coccidia and indicate that a nonconventional peroxisomal import mechanism may operate in the absence of Pex13 and Pex14.

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Natsuyama, Ryuichi, Kanji Okumoto, and Yukio Fujiki. "Pex5p stabilizes Pex14p: a study using a newly isolated pex5 CHO cell mutant, ZPEG101." Biochemical Journal 449, no. 1 (December 7, 2012): 195–207. http://dx.doi.org/10.1042/bj20120911.

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Pex5p [PTS (peroxisome-targeting signal) type 1 receptor] plays an essential role in peroxisomal matrix protein import. In the present study, we isolated a novel PEX5-deficient CHO (Chinese-hamster ovary) cell mutant, termed ZPEG101, showing typical peroxisomal import defects of both PTS1 and PTS2 proteins. ZPEG101 is distinct from other known pex5 CHO mutants in its Pex5p expression. An undetectable level of Pex5p in ZPEG101 results in unstable Pex14p, which is due to inefficient translocation to the peroxisomal membrane. All of the mutant phenotypes of ZPEG101 are restored by expression of wild-type Pex5pL, a longer form of Pex5p, suggesting a role for Pex5p in sustaining the levels of Pex14p in addition to peroxisomal matrix protein import. Complementation analysis using various Pex5p mutants revealed that in the seven pentapeptide WXXXF/Y motifs in Pex5pL, known as the multiple binding sites for Pex14p, the fifth motif is an auxiliary binding site for Pex14p and is required for Pex14p stability. Furthermore, we found that Pex5p–Pex13p interaction is essential for the import of PTS1 proteins as well as catalase, but not for that of PTS2 proteins. Therefore ZPEG101 with no Pex5p would be a useful tool for investigating Pex5p function and delineating the mechanisms underlying peroxisomal matrix protein import.

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Schell-Steven, Annette, Katharina Stein, Mara Amoros, Christiane Landgraf, Rudolf Volkmer-Engert, Hanspeter Rottensteiner, and Ralf Erdmann. "Identification of a Novel, Intraperoxisomal Pex14-Binding Site in Pex13: Association of Pex13 with the Docking Complex Is Essential for Peroxisomal Matrix Protein Import." Molecular and Cellular Biology 25, no. 8 (April 15, 2005): 3007–18. http://dx.doi.org/10.1128/mcb.25.8.3007-3018.2005.

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ABSTRACT The peroxisomal docking complex is a key component of the import machinery for matrix proteins. The core protein of this complex, Pex14, is thought to represent the initial docking site for the import receptors Pex5 and Pex7. Associated with this complex is a fraction of Pex13, another essential component of the import machinery. Here we demonstrate that Pex13 directly binds Pex14 not only via its SH3 domain but also via a novel intraperoxisomal site. Furthermore, we demonstrate that Pex5 also contributes to the association of Pex13 with Pex14. Peroxisome function was affected only mildly by mutations within the novel Pex14 interaction site of Pex13 or by the non-Pex13-interacting mutant Pex5W204A. However, when these constructs were tested in combination, PTS1-dependent import and growth on oleic acid were severely compromised. When the SH3 domain-mediated interaction of Pex13 with Pex14 was blocked on top of that, PTS2-dependent matrix protein import was completely compromised and Pex13 was no longer copurified with the docking complex. We conclude that the association of Pex13 with Pex14 is an essential step in peroxisomal protein import that is enabled by two direct interactions and by one that is mediated by Pex5, a result which indicates a novel, receptor-independent function of Pex5.

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Wang, Wei, Zhi-Jie Xia, Jean-Claude Farré, and Suresh Subramani. "TRIM37, a novel E3 ligase for PEX5-mediated peroxisomal matrix protein import." Journal of Cell Biology 216, no. 9 (July 19, 2017): 2843–58. http://dx.doi.org/10.1083/jcb.201611170.

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Most proteins destined for the peroxisomal matrix depend on the peroxisomal targeting signals (PTSs), which require the PTS receptor PEX5, whose deficiency causes fatal human peroxisomal biogenesis disorders (PBDs). TRIM37 gene mutations cause muscle–liver–brain–eye (mulibrey) nanism. We found that TRIM37 localizes in peroxisomal membranes and ubiquitylates PEX5 at K464 by interacting with its C-terminal 51 amino acids (CT51), which is required for PTS protein import. PEX5 mutations (K464A or ΔCT51), or TRIM37 depletion or mutation, reduce PEX5 abundance by promoting its proteasomal degradation, thereby impairing its functions in cargo binding and PTS protein import in human cells. TRIM37 or PEX5 depletion induces apoptosis and enhances sensitivity to oxidative stress, underscoring the cellular requirement for functional peroxisomes. Therefore, TRIM37-mediated ubiquitylation stabilizes PEX5 and promotes peroxisomal matrix protein import, suggesting that mulibrey nanism is a new PBD.

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AMERY, Leen, Hideki SANO, Guy P. MANNAERTS, Jamie SNIDER, Jeroen van LOOY, Marc FRANSEN, and Paul P. van VELDHOVEN. "Identification of PEX5p-related novel peroxisome-targeting signal 1 (PTS1)-binding proteins in mammals." Biochemical Journal 357, no. 3 (July 25, 2001): 635–46. http://dx.doi.org/10.1042/bj3570635.

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Based on peroxin protein 5 (Pex5p) homology searches in the expressed sequence tag database and sequencing of large full-length cDNA inserts, three novel and related human cDNAs were identified. The brain-derived cDNAs coded for two related proteins that differ only slightly at their N-terminus, and exhibit 39.8% identity to human PEX5p. The shorter liver-derived cDNA coded for the C-terminal tetratricopeptide repeat-containing domain of the brain cDNA-encoded proteins. Since these three proteins specifically bind to various C-terminal peroxisome-targeting signals in a manner indistinguishable from Pex5p and effectively compete with Pex5p in an in vitro peroxisome-targeting signal 1 (PTS1)-binding assay, we refer to them as ‘Pex5p-related proteins’ (Pex5Rp). In contrast to Pex5p, however, human PEX5Rp did not bind to Pex14p or to the RING finger motif of Pex12p, and could not restore PTS1 protein import in Pex5−/− mouse fibroblasts. Immunofluorescence analysis of epitope-tagged PEX5Rp in Chinese hamster ovary cells suggested an exclusively cytosolic localization. Northern-blot analysis showed that the PEX5R gene, which is localized to chromosome 3q26.2–3q27, is expressed preferentially in brain. Mouse PEX5Rp was also delineated. In addition, experimental evidence established that the closest-related yeast homologue, YMR018wp, did not bind PTS1. Based on its subcellular localization and binding properties, Pex5Rp may function as a regulator in an early step of the PTS1 protein import process.

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Collins, Cynthia S., Jennifer E. Kalish, James C. Morrell, J. Michael McCaffery, and 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, no. 20 (October 15, 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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Dodt, G., and S. J. Gould. "Multiple PEX genes are required for proper subcellular distribution and stability of Pex5p, the PTS1 receptor: evidence that PTS1 protein import is mediated by a cycling receptor." Journal of Cell Biology 135, no. 6 (December 15, 1996): 1763–74. http://dx.doi.org/10.1083/jcb.135.6.1763.

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PEX5 encodes the type-1 peroxisomal targeting signal (PTS1) receptor, one of at least 15 peroxins required for peroxisome biogenesis. Pex5p has a bimodal distribution within the cell, mostly cytosolic with a small amount bound to peroxisomes. This distribution indicates that Pex5p may function as a cycling receptor, a mode of action likely to require interaction with additional peroxins. Loss of peroxins required for protein translocation into the peroxisome (PEX2 or PEX12) resulted in accumulation of Pex5p at docking sites on the peroxisome surface. Pex5p also accumulated on peroxisomes in normal cells under conditions which inhibit protein translocation into peroxisomes (low temperature or ATP depletion), returned to the cytoplasm when translocation was restored, and reaccumulated on peroxisomes when translocation was again inhibited. Translocation inhibiting conditions did not result in Pex5p redistribution in cells that lack detectable peroxisomes. Thus, it appears that Pex5p can cycle repeatedly between the cytoplasm and peroxisome. Altered activity of the peroxin defective in CG7 cells leads to accumulation of Pex5p within the peroxisome, indicating that Pex5p may actually enter the peroxisome lumen at one point in its cycle. In addition, we found that the PTS1 receptor was extremely unstable in the peroxin-deficient CG1, CG4, and CG8 cells. Altered distribution or stability of the PTS1 receptor in all cells with a defect in PTS1 protein import implies that the genes mutated in these cell lines encode proteins with a direct role in peroxisomal protein import.

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Chang, Chia-Che, Daniel S. Warren, Katherine A. Sacksteder, and 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, no. 4 (November 15, 1999): 761–74. http://dx.doi.org/10.1083/jcb.147.4.761.

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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.

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Di Cara, Francesca, Richard A. Rachubinski, and Andrew J. Simmonds. "Distinct Roles for Peroxisomal Targeting Signal Receptors Pex5 and Pex7 in Drosophila." Genetics 211, no. 1 (November 2, 2018): 141–49. http://dx.doi.org/10.1534/genetics.118.301628.

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Pedrosa, Ana G., Tânia Francisco, Diana Bicho, Ana F. Dias, Aurora Barros-Barbosa, Vera Hagmann, Gabriele Dodt, Tony A. Rodrigues, and Jorge E. Azevedo. "Peroxisomal monoubiquitinated PEX5 interacts with the AAA ATPases PEX1 and PEX6 and is unfolded during its dislocation into the cytosol." Journal of Biological Chemistry 293, no. 29 (June 8, 2018): 11553–63. http://dx.doi.org/10.1074/jbc.ra118.003669.

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Piacentini, Diego, Federica Della Rovere, Ilaria Bertoldi, Lorenzo Massimi, Adriano Sofo, Maria Maddalena Altamura, and Giuseppina Falasca. "Peroxisomal PEX7 Receptor Affects Cadmium-Induced ROS and Auxin Homeostasis in Arabidopsis Root System." Antioxidants 10, no. 9 (September 20, 2021): 1494. http://dx.doi.org/10.3390/antiox10091494.

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Peroxisomes are important in plant physiological functions and stress responses. Through the production of reactive oxygen and nitrogen species (ROS and RNS), and antioxidant defense enzymes, peroxisomes control cellular redox homeostasis. Peroxin (PEX) proteins, such as PEX7 and PEX5, recognize peroxisome targeting signals (PTS1/PTS2) important for transporting proteins from cytosol to peroxisomal matrix. pex7-1 mutant displays reduced PTS2 protein import and altered peroxisomal metabolism. In this research we analyzed the role of PEX7 in the Arabidopsis thaliana root system exposed to 30 or 60 μM CdSO4. Cd uptake and translocation, indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) levels, and reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels and catalase activity were analyzed in pex7-1 mutant primary and lateral roots in comparison with the wild type (wt). The peroxisomal defect due to PEX7 mutation did not reduce Cd-uptake but reduced its translocation to the shoot and the root cell peroxisomal signal detected by 8-(4-Nitrophenyl) Bodipy (N-BODIPY) probe. The trend of nitric oxide (NO) and peroxynitrite in pex7-1 roots, exposed/not exposed to Cd, was as in wt, with the higher Cd-concentration inducing higher levels of these RNS. By contrast, PEX7 mutation caused changes in Cd-induced hydrogen peroxide (H2O2) and superoxide anion (O2●−) levels in the roots, delaying ROS-scavenging. Results show that PEX7 is involved in counteracting Cd toxicity in Arabidopsis root system by controlling ROS metabolism and affecting auxin levels. These results add further information to the important role of peroxisomes in plant responses to Cd.

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Romano, Fabian B., Neil B. Blok, and Tom A. Rapoport. "Peroxisome protein import recapitulated in Xenopus egg extracts." Journal of Cell Biology 218, no. 6 (April 10, 2019): 2021–34. http://dx.doi.org/10.1083/jcb.201901152.

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Peroxisomes import their luminal proteins from the cytosol. Most substrates contain a C-terminal Ser-Lys-Leu (SKL) sequence that is recognized by the receptor Pex5. Pex5 binds to peroxisomes via a docking complex containing Pex14, and recycles back into the cytosol following its mono-ubiquitination at a conserved Cys residue. The mechanism of peroxisome protein import remains incompletely understood. Here, we developed an in vitro import system based on Xenopus egg extracts. Import is dependent on the SKL motif in the substrate and on the presence of Pex5 and Pex14, and is sustained by ATP hydrolysis. A protein lacking an SKL sequence can be coimported, providing strong evidence for import of a folded protein. The conserved cysteine in Pex5 is not essential for import or to clear import sites for subsequent rounds of translocation. This new in vitro assay will be useful for further dissecting the mechanism of peroxisome protein import.

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Schäfer, Antje, Daniela Kerssen, Marten Veenhuis, Wolf-H. Kunau, and Wolfgang Schliebs. "Functional Similarity between the Peroxisomal PTS2 Receptor Binding Protein Pex18p and the N-Terminal Half of the PTS1 Receptor Pex5p." Molecular and Cellular Biology 24, no. 20 (October 15, 2004): 8895–906. http://dx.doi.org/10.1128/mcb.24.20.8895-8906.2004.

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ABSTRACT Within the extended receptor cycle of peroxisomal matrix import, the function of the import receptor Pex5p comprises cargo recognition and transport. While the C-terminal half (Pex5p-C) is responsible for PTS1 binding, the contribution of the N-terminal half of Pex5p (Pex5p-N) to the receptor cycle has been less clear. Here we demonstrate, using different techniques, that in Saccharomyces cerevisiae Pex5p-N alone facilitates the import of the major matrix protein Fox1p. This finding suggests that Pex5p-N is sufficient for receptor docking and cargo transport into peroxisomes. Moreover, we found that Pex5p-N can be functionally replaced by Pex18p, one of two auxiliary proteins of the PTS2 import pathway. A chimeric protein consisting of Pex18p (without its Pex7p binding site) fused to Pex5p-C is able to partially restore PTS1 protein import in a PEX5 deletion strain. On the basis of these results, we propose that the auxiliary proteins of the PTS2 import pathway fulfill roles similar to those of the N-terminal half of Pex5p in the PTS1 import pathway.

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Sargent, Graeme, Tim van Zutphen, Tatiana Shatseva, Ling Zhang, Valeria Di Giovanni, Robert Bandsma, and Peter Kijun Kim. "PEX2 is the E3 ubiquitin ligase required for pexophagy during starvation." Journal of Cell Biology 214, no. 6 (September 5, 2016): 677–90. http://dx.doi.org/10.1083/jcb.201511034.

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Peroxisomes are metabolic organelles necessary for anabolic and catabolic lipid reactions whose numbers are highly dynamic based on the metabolic need of the cells. One mechanism to regulate peroxisome numbers is through an autophagic process called pexophagy. In mammalian cells, ubiquitination of peroxisomal membrane proteins signals pexophagy; however, the E3 ligase responsible for mediating ubiquitination is not known. Here, we report that the peroxisomal E3 ubiquitin ligase peroxin 2 (PEX2) is the causative agent for mammalian pexophagy. Expression of PEX2 leads to gross ubiquitination of peroxisomes and degradation of peroxisomes in an NBR1-dependent autophagic process. We identify PEX5 and PMP70 as substrates of PEX2 that are ubiquitinated during amino acid starvation. We also find that PEX2 expression is up-regulated during both amino acid starvation and rapamycin treatment, suggesting that the mTORC1 pathway regulates pexophagy by regulating PEX2 expression levels. Finally, we validate our findings in vivo using an animal model.

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Wang, Jiaoyu, Xiaoyan Wu, Zhen Zhang, Xinfa Du, Xueqin Mao, and Guochang Sun. "Fluorescence localization of PTS1 and PTS2 in PEX5 and PEX7 mutants of Magnaporthe grisea." Journal of Biotechnology 136 (October 2008): S221. http://dx.doi.org/10.1016/j.jbiotec.2008.07.467.

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Han, Ji Seul, Kyung Hee Han, and Jae Bum Kim. "Peroxisomal-PEX5 Controls Fasting-Induced Lipolysis." Contact 3 (January 2020): 251525642096030. http://dx.doi.org/10.1177/2515256420960303.

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Lipid droplets (LDs) are dynamic subcellular organelles which play critical roles for lipid homeostasis upon change of nutritional state. Although several organelles such as mitochondria and peroxisomes are involved in lipid metabolism, physiological roles and mediators involved in the spatiotemporal regulation of these subcellular organelles for energy metabolism has largely remained elusive. Our recent study implicates the importance of peroxisomes in the translocation of lipases onto LDs upon fasting cues. Also, we found that peroxisomal protein PEX5 modulates PKA-induced lipolysis by escorting ATGL toward LDs. This is accompanied by KIFC3-mediated migration of peroxisomes, leading to the physical contact between peroxisomes and LDs. In adipocyte-specific PEX5-knockout mice, fasting induced lipolysis is attenuated due to defective ATGL recruitment onto LDs. These results show that PEX5 plays a pivotal role in PKA induced lipolysis that occurs upon nutritional deprivation. We further speculate that the contact between LDs and peroxisomes could facilitate lipid metabolism via exchange of lipid metabolites between the organelles in response to nutritional changes.

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Rosenthal, Mira, Eyal Metzl-Raz, Jérôme Bürgi, Eden Yifrach, Layla Drwesh, Amir Fadel, Yoav Peleg, et al. "Uncovering targeting priority to yeast peroxisomes using an in-cell competition assay." Proceedings of the National Academy of Sciences 117, no. 35 (August 17, 2020): 21432–40. http://dx.doi.org/10.1073/pnas.1920078117.

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Approximately half of eukaryotic proteins reside in organelles. To reach their correct destination, such proteins harbor targeting signals recognized by dedicated targeting pathways. It has been shown that differences in targeting signals alter the efficiency in which proteins are recognized and targeted. Since multiple proteins compete for any single pathway, such differences can affect the priority for which a protein is catered. However, to date the entire repertoire of proteins with targeting priority, and the mechanisms underlying it, have not been explored for any pathway. Here we developed a systematic tool to study targeting priority and used the Pex5-mediated targeting to yeast peroxisomes as a model. We titrated Pex5 out by expressing high levels of a Pex5-cargo protein and examined how the localization of each peroxisomal protein is affected. We found that while most known Pex5 cargo proteins were outcompeted, several cargo proteins were not affected, implying that they have high targeting priority. This priority group was dependent on metabolic conditions. We dissected the mechanism of priority for these proteins and suggest that targeting priority is governed by different parameters, including binding affinity of the targeting signal to the cargo factor, the number of binding interfaces to the cargo factor, and more. This approach can be modified to study targeting priority in various organelles, cell types, and organisms.

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Schliebs, Wolfgang, Jürgen Saidowsky, Bogos Agianian, Gabriele Dodt, Friedrich W. Herberg, and Wolf-H. Kunau. "Recombinant Human Peroxisomal Targeting Signal Receptor PEX5." Journal of Biological Chemistry 274, no. 9 (February 26, 1999): 5666–73. http://dx.doi.org/10.1074/jbc.274.9.5666.

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Loughran, Patricia A., Donna B. Stolz, Simon C. Watkins, Richard L. Simmons, and Timothy R. Billiar. "P183. Inducible nitric oxide synthase localization to peroxisomes in hepatocytes is modulated by PEX5 and PEX7." Nitric Oxide 14, no. 4 (June 2006): 76. http://dx.doi.org/10.1016/j.niox.2006.04.253.

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Gualdrón-López, Melisa, Nathalie Chevalier, Patrick Van Der Smissen, Pierre J. Courtoy, Daniel J. Rigden, and Paul A. M. Michels. "Ubiquitination of the glycosomal matrix protein receptor PEX5 in Trypanosoma brucei by PEX4 displays novel features." Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 1833, no. 12 (December 2013): 3076–92. http://dx.doi.org/10.1016/j.bbamcr.2013.08.008.

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Knoops, Kèvin, Rinse de Boer, Anita Kram, and Ida J. van der Klei. "Yeast pex1 cells contain peroxisomal ghosts that import matrix proteins upon reintroduction of Pex1." Journal of Cell Biology 211, no. 5 (December 7, 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.

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Brown, Aidan I., Peter K. Kim, and Andrew D. Rutenberg. "PEX5 and Ubiquitin Dynamics on Mammalian Peroxisome Membranes." PLoS Computational Biology 10, no. 1 (January 16, 2014): e1003426. http://dx.doi.org/10.1371/journal.pcbi.1003426.

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Gatto,, Gregory J., Ernest L. Maynard, Anthony L. Guerrerio, Brian V. Geisbrecht, Stephen J. Gould, and Jeremy M. Berg. "Correlating Structure and Affinity for PEX5:PTS1 Complexes†." Biochemistry 42, no. 6 (February 2003): 1660–66. http://dx.doi.org/10.1021/bi027034z.

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Hochreiter, Bernhard, Cheng-Shoong Chong, Andreas Hartig, Sebastian Maurer-Stroh, Johannes Berger, Johannes A. Schmid, and Markus Kunze. "A Novel FRET Approach Quantifies the Interaction Strength of Peroxisomal Targeting Signals and Their Receptor in Living Cells." Cells 9, no. 11 (October 30, 2020): 2381. http://dx.doi.org/10.3390/cells9112381.

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Measuring Förster–resonance–energy–transfer (FRET) efficiency allows the investigation of protein–protein interactions (PPI), but extracting quantitative measures of affinity necessitates highly advanced technical equipment or isolated proteins. We demonstrate the validity of a recently suggested novel approach to quantitatively analyze FRET-based experiments in living mammalian cells using standard equipment using the interaction between different type-1 peroxisomal targeting signals (PTS1) and their soluble receptor peroxin 5 (PEX5) as a model system. Large data sets were obtained by flow cytometry coupled FRET measurements of cells expressing PTS1-tagged EGFP together with mCherry fused to the PTS1-binding domain of PEX5, and were subjected to a fitting algorithm extracting a quantitative measure of the interaction strength. This measure correlates with results obtained by in vitro techniques and a two-hybrid assay, but is unaffected by the distance between the fluorophores. Moreover, we introduce a live cell competition assay based on this approach, capable of depicting dose- and affinity-dependent modulation of the PPI. Using this system, we demonstrate the relevance of a sequence element next to the core tripeptide in PTS1 motifs for the interaction strength between PTS1 and PEX5, which is supported by a structure-based computational prediction of the binding energy indicating a direct involvement of this sequence in the interaction.

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Lyman, Kyle A., Ye Han, Robert J. Heuermann, Xiangying Cheng, Jonathan E. Kurz, Reagan E. Lyman, Paul P. Van Veldhoven, and Dane M. Chetkovich. "Allostery between two binding sites in the ion channel subunit TRIP8b confers binding specificity to HCN channels." Journal of Biological Chemistry 292, no. 43 (September 8, 2017): 17718–30. http://dx.doi.org/10.1074/jbc.m117.802256.

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Tetratricopeptide repeat (TPR) domains are ubiquitous structural motifs that mediate protein–protein interactions. For example, the TPR domains in the peroxisomal import receptor PEX5 enable binding to a range of type 1 peroxisomal targeting signal motifs. A homolog of PEX5, tetratricopeptide repeat–containing Rab8b-interacting protein (TRIP8b), binds to and functions as an auxiliary subunit of hyperpolarization-activated cyclic nucleotide (HCN)–gated channels. Given the similarity between TRIP8b and PEX5, this difference in function raises the question of what mechanism accounts for their binding specificity. In this report, we found that the cyclic nucleotide–binding domain and the C terminus of the HCN channel are critical for conferring specificity to TRIP8b binding. We show that TRIP8b binds the HCN cyclic nucleotide–binding domain through a 37-residue domain and the HCN C terminus through the TPR domains. Using a combination of fluorescence polarization– and co-immunoprecipitation–based assays, we establish that binding at either site increases affinity at the other. Thus, allosteric coupling of the TRIP8b TPR domains both promotes binding to HCN channels and limits binding to type 1 peroxisomal targeting signal substrates. These results raise the possibility that other TPR domains may be similarly influenced by allosteric mechanisms as a general feature of protein–protein interactions.

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Jardim, Armando, Wei Liu, Ekaterina Zheleznova, and Buddy Ullman. "Peroxisomal Targeting Signal-1 Receptor Protein PEX5 fromLeishmania donovani." Journal of Biological Chemistry 275, no. 18 (April 28, 2000): 13637–44. http://dx.doi.org/10.1074/jbc.275.18.13637.

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Baker, Alison, Thomas Lanyon Hogg, and Stuart L. Warriner. "Peroxisome protein import: a complex journey." Biochemical Society Transactions 44, no. 3 (June 9, 2016): 783–89. http://dx.doi.org/10.1042/bst20160036.

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The import of proteins into peroxisomes possesses many unusual features such as the ability to import folded proteins, and a surprising diversity of targeting signals with differing affinities that can be recognized by the same receptor. As understanding of the structure and function of many components of the protein import machinery has grown, an increasingly complex network of factors affecting each step of the import pathway has emerged. Structural studies have revealed the presence of additional interactions between cargo proteins and the PEX5 receptor that affect import potential, with a subtle network of cargo-induced conformational changes in PEX5 being involved in the import process. Biochemical studies have also indicated an interdependence of receptor–cargo import with release of unloaded receptor from the peroxisome. Here, we provide an update on recent literature concerning mechanisms of protein import into peroxisomes.

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Otera, Hidenori, Kiyoko Setoguchi, Maho Hamasaki, Toshitaka Kumashiro, Nobuhiro Shimizu, and Yukio Fujiki. "Peroxisomal Targeting Signal Receptor Pex5p Interacts with Cargoes and Import Machinery Components in a Spatiotemporally Differentiated Manner: Conserved Pex5p WXXXF/Y Motifs Are Critical for Matrix Protein Import." Molecular and Cellular Biology 22, no. 6 (March 15, 2002): 1639–55. http://dx.doi.org/10.1128/mcb.22.6.1639-1655.2002.

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ABSTRACT Two isoforms of the peroxisomal targeting signal type 1 (PTS1) receptor, termed Pex5pS and (37-amino-acid-longer) Pex5pL, are expressed in mammals. Pex5pL transports PTS1 proteins and Pex7p-PTS2 cargo complexes to the initial Pex5p-docking site, Pex14p, on peroxisome membranes, while Pex5pS translocates only PTS1 cargoes. Here we report functional Pex5p domains responsible for interaction with peroxins Pex7p, Pex13p, and Pex14p. An N-terminal half, such as Pex5pL(1-243), comprising amino acid residues 1 to 243, bound to Pex7p, Pex13p, and Pex14p and was sufficient for restoring the impaired PTS2 import of pex5 cell mutants, while the C-terminal tetratricopeptide repeat motifs were required for PTS1 binding. N-terminal Pex5p possessed multiple Pex14p-binding sites. Alanine-scanning analysis of the highly conserved seven (six in Pex5pS) pentapeptide WXXXF/Y motifs residing at the N-terminal region indicated that these motifs were essential for the interaction of Pex5p with Pex14p and Pex13p. Moreover, mutation of several WXXXF/Y motifs did not affect the PTS import-restoring activity of Pex5p, implying that the binding of Pex14p to all of the WXXXF/Y sites was not a prerequisite for the translocation of Pex5p-cargo complexes. Pex5p bound to Pex13p at the N-terminal part, not to the C-terminal SH3 region, via WXXXF/Y motifs 2 to 4. PTS1 and PTS2 import required the interaction of Pex5p with Pex14p but not with Pex13p, while Pex5p binding to Pex13p was essential for import of catalase with PTS1-like signal KANL. Pex5p recruited PTS1 proteins to Pex14p but not to Pex13p. Pex14p and Pex13p formed a complex with PTS1-loaded Pex5p but dissociated in the presence of cargo-unloaded Pex5p, implying that PTS cargoes are released from Pex5p at a step downstream of Pex14p and upstream of Pex13p. Thus, Pex14p and Pex13p very likely form mutually and temporally distinct subcomplexes involved in peroxisomal matrix protein import.

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Baumgart, E., M. Grabenbauer, M. Baes, and H. D. Fahimi. "347 Mitochondrial alterations in PEX5-/--knockout mice with Zellweger syndrome." European Journal of Paediatric Neurology 3, no. 6 (January 1999): A88. http://dx.doi.org/10.1016/s1090-3798(99)91221-7.

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Wang, Wei, and Suresh Subramani. "Role of PEX5 ubiquitination in maintaining peroxisome dynamics and homeostasis." Cell Cycle 16, no. 21 (September 21, 2017): 2037–45. http://dx.doi.org/10.1080/15384101.2017.1376149.

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Galland, Nathalie, Fabian Demeure, Véronique Hannaert, Emilie Verplaetse, Didier Vertommen, Patrick Van Der Smissen, Pierre J. Courtoy, and Paul A. M. Michels. "Characterization of the role of the receptors PEX5 and PEX7 in the import of proteins into glycosomes of Trypanosoma brucei." Biochimica et Biophysica Acta (BBA) - Molecular Cell Research 1773, no. 4 (April 2007): 521–35. http://dx.doi.org/10.1016/j.bbamcr.2007.01.006.

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Gurvitz, Aner, Sigrid Langer, Martin Piskacek, Barbara Hamilton, Helmut Ruis, and Andreas Hartig. "Predicting the Function and Subcellular Location of Caenorhabditis elegans Proteins Similar to Saccharomyces cerevisiae β-Oxidation Enzymes." Yeast 1, no. 3 (January 1, 2000): 188–200. http://dx.doi.org/10.1155/2000/596562.

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The role of peroxisomal processes in the maintenance of neurons has not been thoroughly investigated. We propose using Caenorhabditis elegans as a model organism for studying the molecular basis underlying neurodegeneration in certain human peroxisomal disorders, e.g. Zellweger syndrome, since the nematode neural network is well characterized and relatively simple in function. Here we have identified C. elegans PEX-5 (C34C6.6) representing the receptor for peroxisomal targeting signal type 1 (PTS1), defective in patients with such disorders. PEX-5 interacted strongly in a two-hybrid assay with Gal4p–SKL, and a screen using PEX-5 identified interaction partners that were predominantly terminated with PTS1 or its variants. A list of C. elegans proteins with similarities to well-characterized yeast β-oxidation enzymes was compiled by homology probing. The possible subcellular localization of these orthologues was predicted using an algorithm based on trafficking signals. Examining the C termini of selected nematode proteins for PTS1 function substantiated predictions made regarding the proteins' peroxisomal location. It is concluded that the eukaryotic PEX5-dependent route for importing PTS1-containing proteins into peroxisomes is conserved in nematodes. C. elegans might emerge as an attractive model system for studying the importance of peroxisomes and affiliated processes in neurodegeneration, and also for studying a β-oxidation process that is potentially compartmentalized in both mitochondria and peroxisomes.

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Li, Xiaoling, Eveline Baumgart, James C. Morrell, Gerardo Jimenez-Sanchez, David Valle, and Stephen J. Gould. "PEX11β Deficiency Is Lethal and Impairs Neuronal Migration but Does Not Abrogate Peroxisome Function." Molecular and Cellular Biology 22, no. 12 (June 15, 2002): 4358–65. http://dx.doi.org/10.1128/mcb.22.12.4358-4365.2002.

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ABSTRACT Zellweger syndrome is a lethal neurological disorder characterized by severe defects in peroxisomal protein import. The resulting defects in peroxisome metabolism and the accumulation of peroxisomal substrates are thought to cause the other Zellweger syndrome phenotypes, including neuronal migration defects, hypotonia, a developmental delay, and neonatal lethality. These phenotypes are also manifested in mouse models of Zellweger syndrome generated by disruption of the PEX5 or PEX2 gene. Here we show that mice lacking peroxisomal membrane protein PEX11β display several pathologic features shared by these mouse models of Zellweger syndrome, including neuronal migration defects, enhanced neuronal apoptosis, a developmental delay, hypotonia, and neonatal lethality. However, PEX11β deficiency differs significantly from Zellweger syndrome and Zellweger syndrome mice in that it is not characterized by a detectable defect in peroxisomal protein import and displays only mild defects in peroxisomal fatty acid β-oxidation and peroxisomal ether lipid biosynthesis. These results demonstrate that the neurological pathologic features of Zellweger syndrome can occur without peroxisomal enzyme mislocalization and challenge current models of Zellweger syndrome pathogenesis.

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Ahmad, Tanbir, Amin Ismail, Siti Aqlima Ahmad, Khalilah Abdul Khalil, Elmutaz Atta Awad, Muhammad Tayyab Akhtar, and Awis Qurni Sazili. "Recovery of Gelatin from Bovine Skin with the Aid of Pepsin and Its Effects on the Characteristics of the Extracted Gelatin." Polymers 13, no. 10 (May 12, 2021): 1554. http://dx.doi.org/10.3390/polym13101554.

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Pepsin enzyme was used to pretreat the bovine skin at the rate of 5, 15, and 25 units of enzyme/g of skin to recover gelatin, and the recovered gelatins were referred to as Pe5, Pe15, and Pe25, respectively. The gelatin yield increased significantly (p < 0.05) from 18.17% for Pe5 to 24.67% for Pe25 as the level of pepsin increased, but the corresponding gel strength and viscosity decreased significantly (p < 0.05) from 215.49 to 56.06 g and 9.17 to 8.17 mPa·s for Pe5 and Pe25, respectively. β- and α1- and α2-chains were degraded entirely in all the gelatins samples as observed in protein pattern elaborated by gel electrophoresis. 1H nuclear magnetic resonance (1H NMR) analysis indicated the coiled structure of gelatin protein chains. The lowest amide III amplitude of Pe25 as found by Fourier transform infrared (FTIR) spectroscopy indicated that α-helix structure of protein chains were lost to more irregular coiled structure. Thus, it could be summarized that pepsin might be used at the lower level (5 units/g of wet skin) to extract gelatin from bovine skin with good functional properties and at higher level (15/25 units/g of wet skin) to obtain gelatin of industrial grade with high yield.

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Ebberink, Merel S., Petra A. W. Mooyer, Janet Koster, Conny J. M. Dekker, François J. M. Eyskens, Carlo Dionisi-Vici, Peter T. Clayton, Peter G. Barth, Ronald J. A. Wanders, and Hans R. Waterham. "Genotype-phenotype correlation in PEX5-deficient peroxisome biogenesis defective cell lines." Human Mutation 30, no. 1 (January 2009): 93–98. http://dx.doi.org/10.1002/humu.20833.

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Journal articles on the topic 'Pex5'

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