Components Involved in Peroxisome Import, Biogenesis, Proliferation, Turnover, and Movement

1998 ◽  
Vol 78 (1) ◽  
pp. 171-188 ◽  
Author(s):  
SURESH SUBRAMANI
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Peroxisomal Disorders ◽  
Peroxisomal Membrane ◽  
Peroxisomal Protein ◽  
Peroxisomal Targeting ◽  
Docking Proteins ◽  
Targeting Signal ◽  
Peroxisomal Targeting Signal

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.

scholarly journals Human peroxisomal targeting signal-1 receptor restores peroxisomal protein import in cells from patients with fatal peroxisomal disorders.

1995 ◽  
Vol 130 (1) ◽  
pp. 51-65 ◽  
Author(s):  
E A Wiemer ◽  
W M Nuttley ◽  
B L Bertolaet ◽  
X Li ◽  
U Francke ◽  
...  
Keyword(s):  
Protein Import ◽  
Zellweger Syndrome ◽  
Complementation Group ◽  
Cell System ◽  
Peroxisomal Disorders ◽  
Peroxisomal Membrane ◽  
Peroxisomal Protein ◽  
Peroxisomal Targeting ◽  
Targeting Signal

Two peroxisomal targeting signals, PTS1 and PTS2, are involved in the import of proteins into the peroxisome matrix. Human patients with fatal generalized peroxisomal deficiency disorders fall into at least nine genetic complementation groups. Cells from many of these patients are deficient in the import of PTS1-containing proteins, but the causes of the protein-import defect in these patients are unknown. We have cloned and sequenced the human cDNA homologue (PTS1R) of the Pichia pastoris PAS8 gene, the PTS1 receptor (McCollum, D., E. Monosov, and S. Subramani. 1993. J. Cell Biol. 121:761-774). The PTS1R mRNA is expressed in all human tissues examined. Antibodies to the human PTS1R recognize this protein in human, monkey, rat, and hamster cells. The protein is localized mainly in the cytosol but is also found to be associated with peroxisomes. Part of the peroxisomal PTS1R protein is tightly bound to the peroxisomal membrane. Antibodies to PTS1R inhibit peroxisomal protein-import of PTS1-containing proteins in a permeabilized CHO cell system. In vitro-translated PTS1R protein specifically binds a serine-lysine-leucine-peptide. A PAS8-PTS1R fusion protein complements the P. pastoris pas8 mutant. The PTS1R cDNA also complements the PTS1 protein-import defect in skin fibroblasts from patients--belonging to complementation group two--diagnosed as having neonatal adrenoleukodystrophy or Zellweger syndrome. The PTS1R gene has been localized to a chromosomal location where no other peroxisomal disorder genes are known to map. Our findings represent the only case in which the molecular basis of the protein-import deficiency in human peroxisomal disorders is understood.

Metabolic control of peroxisome abundance

1999 ◽  
Vol 112 (10) ◽  
pp. 1579-1590 ◽  
Author(s):  
C.C. Chang ◽  
S. South ◽  
D. Warren ◽  
J. Jones ◽  
A.B. Moser ◽  
...  
Keyword(s):  
Metabolic Control ◽  
Matrix Protein ◽  
Protein Import ◽  
Zellweger Syndrome ◽  
Mutant Gene ◽  
Peroxisomal Membrane ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Complementation Groups ◽  
Peroxisomal Targeting Signal

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.

scholarly journals Pex7p and Pex20p ofNeurospora crassaFunction Together in PTS2-dependent Protein Import into Peroxisomes

2003 ◽  
Vol 14 (2) ◽  
pp. 810-821 ◽  
Author(s):  
Martin Sichting ◽  
Annette Schell-Steven ◽  
Holger Prokisch ◽  
Ralf Erdmann ◽  
Hanspeter Rottensteiner
Keyword(s):  
Protein Import ◽  
Peroxisomal Membrane ◽  
Peroxisomal Targeting ◽  
Signal Type ◽  
Dependent Protein ◽  
Docking Proteins ◽  
Targeting Signal ◽  
Specific Factors ◽  
Species Specific

Recruiting matrix proteins with a peroxisomal targeting signal type 2 (PTS2) to the peroxisomal membrane requires species-specific factors. In Saccharomyces cerevisiae, the PTS2 receptor Pex7p acts in concert with the redundant Pex18p/Pex21p, whereas inYarrowia lipolytica, Pex20p might unite the function of both S. cerevisiae peroxins. Herein, the genome of the filamentous fungus Neurospora crassa was analyzed for peroxin-encoding genes. We identified a set of 18 peroxins that resembles that of Y. lipolytica rather than that ofS. cerevisiae. Interestingly, proteins homologous to both S. cerevisiae Pex7p and Y. lipolytica Pex20p exist in N. crassa. We report on the isolation of these PTS2-specific peroxins and demonstrate thatNcPex20p can substitute for S. cerevisiaePex18p/Pex21p, but not for ScPex7p. Like Pex18p,NcPex20p did not bind PTS2 protein or the docking proteins in the absence of ScPex7p. Rather,NcPex20p was required before docking to form an import-competent complex of cargo-loaded PTS2 receptors.NcPex7p did not functionally replace yeast Pex7p, probably because the N. crassa PTS2 receptor failed to associate with Pex18p/Pex21p. However, once NcPex7p andNcPex20p had been coexpressed, it proved possible to replace yeast Pex7p. Pex20p and Pex18p/Pex21p are therefore true orthologues, both of which are in need of Pex7p for PTS2 protein import.

scholarly journals The peroxisomal protein import machinery displays a preference for monomeric substrates

Open Biology ◽  
2015 ◽  
Vol 5 (4) ◽  
pp. 140236 ◽  
Author(s):  
Marta O. Freitas ◽  
Tânia Francisco ◽  
Tony A. Rodrigues ◽  
Celien Lismont ◽  
Pedro Domingues ◽  
...  
Keyword(s):  
Protein Import ◽  
Urate Oxidase ◽  
Experimental Conditions ◽  
Peroxisomal Membrane ◽  
Oligomeric Proteins ◽  
Peroxisomal Protein ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Monomeric Proteins

Peroxisomal matrix proteins are synthesized on cytosolic ribosomes and transported by the shuttling receptor PEX5 to the peroxisomal membrane docking/translocation machinery, where they are translocated into the organelle matrix. Under certain experimental conditions this protein import machinery has the remarkable capacity to accept already oligomerized proteins, a property that has heavily influenced current models on the mechanism of peroxisomal protein import. However, whether or not oligomeric proteins are really the best and most frequent clients of this machinery remain unclear. In this work, we present three lines of evidence suggesting that the peroxisomal import machinery displays a preference for monomeric proteins. First, in agreement with previous findings on catalase, we show that PEX5 binds newly synthesized (monomeric) acyl-CoA oxidase 1 (ACOX1) and urate oxidase (UOX), potently inhibiting their oligomerization. Second, in vitro import experiments suggest that monomeric ACOX1 and UOX are better peroxisomal import substrates than the corresponding oligomeric forms. Finally, we provide data strongly suggesting that although ACOX1 lacking a peroxisomal targeting signal can be imported into peroxisomes when co-expressed with ACOX1 containing its targeting signal, this import pathway is inefficient.

scholarly journals Involvement of Pex13p in Pex14p Localization and Peroxisomal Targeting Signal 2–dependent Protein Import into Peroxisomes

1999 ◽  
Vol 144 (6) ◽  
pp. 1151-1162 ◽  
Author(s):  
Wolfgang Girzalsky ◽  
Peter Rehling ◽  
Katharina Stein ◽  
Julia Kipper ◽  
Lars Blank ◽  
...  
Keyword(s):  
Binding Sites ◽  
Protein Import ◽  
Sh3 Domain ◽  
Loss Of Function ◽  
Peroxisomal Membrane ◽  
Peroxisomal Targeting ◽  
Dependent Protein ◽  
Targeting Signal ◽  
Docking Protein ◽  
Peroxisomal Targeting Signal

Pex13p is the putative docking protein for peroxisomal targeting signal 1 (PTS1)-dependent protein import into peroxisomes. Pex14p interacts with both the PTS1- and PTS2-receptor and may represent the point of convergence of the PTS1- and PTS2-dependent protein import pathways. We report the involvement of Pex13p in peroxisomal import of PTS2-containing proteins. Like Pex14p, Pex13p not only interacts with the PTS1-receptor Pex5p, but also with the PTS2-receptor Pex7p; however, this association may be direct or indirect. In support of distinct peroxisomal binding sites for Pex7p, the Pex7p/Pex13p and Pex7p/ Pex14p complexes can form independently. Genetic evidence for the interaction of Pex7p and Pex13p is provided by the observation that overexpression of Pex13p suppresses a loss of function mutant of Pex7p. Accordingly, we conclude that Pex7p and Pex13p functionally interact during PTS2-dependent protein import into peroxisomes. NH2-terminal regions of Pex13p are required for its interaction with the PTS2-receptor while the COOH-terminal SH3 domain alone is sufficient to mediate its interaction with the PTS1-receptor. Reinvestigation of the topology revealed both termini of Pex13p to be oriented towards the cytosol. We also found Pex13p to be required for peroxisomal association of Pex14p, yet the SH3 domain of Pex13p may not provide the only binding site for Pex14p at the peroxisomal membrane.

scholarly journals The Peroxisome Biogenesis Factors Pex4p, Pex22p, Pex1p, and Pex6p Act in the Terminal Steps of Peroxisomal Matrix Protein Import

2000 ◽  
Vol 20 (20) ◽  
pp. 7516-7526 ◽  
Author(s):  
Cynthia S. Collins ◽  
Jennifer E. Kalish ◽  
James C. Morrell ◽  
J. Michael McCaffery ◽  
Stephen J. Gould
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Protein Translocation ◽  
Matrix Proteins ◽  
Peroxisome Biogenesis ◽  
Peroxisomal Membrane ◽  
The Matrix ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Mutant Cells

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.

scholarly journals 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.

1996 ◽  
Vol 135 (6) ◽  
pp. 1763-1774 ◽  
Author(s):  
G Dodt ◽  
S J Gould
Keyword(s):  
Protein Import ◽  
Protein Translocation ◽  
Bimodal Distribution ◽  
Atp Depletion ◽  
Peroxisome Biogenesis ◽  
Direct Role ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Peroxisomal Targeting Signal

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.

scholarly journals Expression of the Cymbidium Ringspot Virus 33-Kilodalton Protein in Saccharomyces cerevisiae and Molecular Dissection of the Peroxisomal Targeting Signal

2004 ◽  
Vol 78 (9) ◽  
pp. 4744-4752 ◽  
Author(s):  
Beatriz Navarro ◽  
Luisa Rubino ◽  
Marcello Russo
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Fluorescent Protein ◽  
Ringspot Virus ◽  
Intermediate Step ◽  
Cell Organelles ◽  
Peroxisomal Membrane ◽  
Essential Components ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Peroxisomal Targeting Signal

ABSTRACT Open reading frame 1 in the viral genome of Cymbidium ringspot virus encodes a 33-kDa protein (p33), which was previously shown to localize to the peroxisomal membrane in infected and transgenic plant cells. To determine the sequence requirements for the organelle targeting and membrane insertion, the protein was expressed in the yeast Saccharomyces cerevisiae in native form (33K) or fused to the green fluorescent protein (33KGFP). Cell organelles were identified by immunolabeling of marker proteins. In addition, peroxisomes were identified by simultaneous expression of the red fluorescent protein DsRed containing a peroxisomal targeting signal and mitochondria by using the dye MitoTracker. Fluorescence microscopy showed the 33KGFP fusion protein concentrated in a few large bodies colocalizing with peroxisomes. These bodies were shown by electron microscopy to be composed by aggregates of peroxisomes, a few mitochondria and endoplasmic reticulum (ER) strands. In immunoelectron microscopy, antibodies to p33 labeled the peroxisomal clumps. Biochemical analysis suggested that p33 is anchored to the peroxisomal membrane through a segment of ca. 7 kDa, which corresponds to the sequence comprising two hydrophobic transmembrane domains and a hydrophilic interconnecting loop. Analysis of deletion mutants confirmed these domains as essential components of the p33 peroxisomal targeting signal, together with a cluster of three basic amino acids (KRR). In yeast mutants lacking peroxisomes p33 was detected in the ER. The possible involvement of the ER as an intermediate step for the integration of p33 into the peroxisomal membrane is discussed.

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