scholarly journals PEX19 is a predominantly cytosolic chaperone and import receptor for class 1 peroxisomal membrane proteins

2004 ◽  
Vol 164 (1) ◽  
pp. 57-67 ◽  
Author(s):  
Jacob M. Jones ◽  
James C. Morrell ◽  
Stephen J. Gould
Keyword(s):  
Membrane Proteins ◽  
Protein Import ◽  
Dependent Manner ◽  
Peroxisomal Membrane ◽  
Class 1 ◽  
Targeting Signals ◽  
Import Receptor

Integral peroxisomal membrane proteins (PMPs) are synthesized in the cytoplasm and imported posttranslationally. Here, we demonstrate that PEX19 binds and stabilizes newly synthesized PMPs in the cytosol, binds to multiple PMP targeting signals (mPTSs), interacts with the hydrophobic domains of PMP targeting signals, and is essential for PMP targeting and import. These results show that PEX19 functions as both a chaperone and an import receptor for newly synthesized PMPs. We also demonstrate the existence of two PMP import mechanisms and two classes of mPTSs: class 1 mPTSs, which are bound by PEX19 and imported in a PEX19-dependent manner, and class 2 mPTSs, which are not bound by PEX19 and mediate protein import independently of PEX19.

scholarly journals PEX3 functions as a PEX19 docking factor in the import of class I peroxisomal membrane proteins

2004 ◽  
Vol 164 (6) ◽  
pp. 863-875 ◽  
Author(s):  
Yi Fang ◽  
James C. Morrell ◽  
Jacob M. Jones ◽  
Stephen J. Gould
Keyword(s):  
Membrane Proteins ◽  
Matrix Protein ◽  
Protein Import ◽  
Class Ii ◽  
Class I ◽  
Peroxisomal Membrane ◽  
Direct Role ◽  
Conserved Motif ◽  
Peroxisome Membrane ◽  
Import Receptor

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.

scholarly journals Peroxisomal Membrane Proteins Insert into the Endoplasmic Reticulum

2010 ◽  
Vol 21 (12) ◽  
pp. 2057-2065 ◽  
Author(s):  
Adabella van der Zand ◽  
Ineke Braakman ◽  
Henk F. Tabak
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Proteins ◽  
Functional Role ◽  
Protein Import ◽  
Mutant Gene ◽  
Dependent Manner ◽  
Wild Type ◽  
Peroxisomal Membrane ◽  
Trafficking Pathway ◽  
Mutant Cells

We show that a comprehensive set of 16 peroxisomal membrane proteins (PMPs) encompassing all types of membrane topologies first target to the endoplasmic reticulum (ER) in Saccharomyces cerevisiae. These PMPs insert into the ER membrane via the protein import complexes Sec61p and Get3p (for tail-anchored proteins). This trafficking pathway is representative for multiplying wild-type cells in which the peroxisome population needs to be maintained, as well as for mutant cells lacking peroxisomes in which new peroxisomes form after complementation with the wild-type version of the mutant gene. PMPs leave the ER in a Pex3p-Pex19p–dependent manner to end up in metabolically active peroxisomes. These results further extend the new concept that peroxisomes derive their basic framework (membrane and membrane proteins) from the ER and imply a new functional role for Pex3p and Pex19p.

scholarly journals Pex19 Binds Multiple Peroxisomal Membrane Proteins, Is Predominantly Cytoplasmic, and Is Required for Peroxisome Membrane Synthesis

2000 ◽  
Vol 148 (5) ◽  
pp. 931-944 ◽  
Author(s):  
Katherine A. Sacksteder ◽  
Jacob M. Jones ◽  
Sarah T. South ◽  
Xiaoling Li ◽  
Yifei Liu ◽  
...  
Keyword(s):  
Steady State ◽  
Membrane Proteins ◽  
Broad Spectrum ◽  
Matrix Protein ◽  
Protein Import ◽  
Nuclear Accumulation ◽  
Eukaryotic Cells ◽  
Membrane Synthesis ◽  
Peroxisomal Membrane ◽  
Peroxisome Membrane

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.

scholarly journals Multiple Distinct Targeting Signals in Integral Peroxisomal Membrane Proteins

2001 ◽  
Vol 153 (6) ◽  
pp. 1141-1150 ◽  
Author(s):  
Jacob M. Jones ◽  
James C. Morrell ◽  
Stephen J. Gould
Keyword(s):  
Membrane Proteins ◽  
Matrix Proteins ◽  
Membrane Biogenesis ◽  
Peroxisomal Membrane ◽  
Interesting Possibility ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Targeting Signals ◽  
Peroxisome Membrane ◽  
Metabolite Transporter

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.

scholarly journals Ubiquitination of the peroxisomal import receptor Pex5p

2004 ◽  
Vol 384 (1) ◽  
pp. 37-45 ◽  
Author(s):  
Harald W. PLATTA ◽  
Wolfgang GIRZALSKY ◽  
Ralf ERDMANN
Keyword(s):  
Protein Import ◽  
Ring Finger ◽  
Proteasomal Degradation ◽  
Peroxisomal Membrane ◽  
Peroxisomal Biogenesis ◽  
Peroxisomal Targeting ◽  
Ubiquitin Conjugating Enzyme ◽  
Targeting Signal ◽  
Import Receptor ◽  
In Cells

Proteins harbouring a peroxisomal targeting signal of type 1 (PTS1) are recognized by the import receptor Pex5p in the cytosol which directs them to a docking and translocation complex at the peroxisomal membrane. We demonstrate the ubiquitination of Pex5p in cells lacking components of the peroxisomal AAA (ATPases associated with various cellular activities) or Pex4p–Pex22p complexes of the peroxisomal protein import machinery and in cells affected in proteasomal degradation. In cells lacking components of the Pex4p–Pex22p complex, mono-ubiquitinated Pex5p represents the major modification, while in cells lacking components of the AAA complex polyubiquitinated forms are most prominent. Ubiquitination of Pex5p is shown to take place exclusively at the peroxisomal membrane after the docking step, and requires the presence of the RING-finger peroxin Pex10p. Mono- and poly-ubiquitination are demonstrated to depend on the ubiquitin-conjugating enzyme Ubc4p, suggesting that the ubiquitinated forms of Pex5p are targeted for proteasomal degradation. Accumulation of ubiquitinated Pex5p in proteasomal mutants demonstrates that the ubiquitination of Pex5p also takes place in strains which are not affected in peroxisomal biogenesis, indicating that the ubiquitination of Pex5p represents a genuine stage in the Pex5p receptor cycle.

The AAA peroxins Pex1p and Pex6p function as dislocases for the ubiquitinated peroxisomal import receptor Pex5p

2008 ◽  
Vol 36 (1) ◽  
pp. 99-104 ◽  
Author(s):  
Harald W. Platta ◽  
Mykhaylo O. Debelyy ◽  
Fouzi El Magraoui ◽  
Ralf Erdmann
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Matrix Proteins ◽  
Genetic Dissection ◽  
Cellular Functions ◽  
Peroxisomal Membrane ◽  
Aaa Atpase ◽  
Ubiquitin Conjugating Enzyme ◽  
Core Components ◽  
Import Receptor

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.

scholarly journals The peroxisome counteracts oxidative stresses by suppressing catalase import via Pex14 phosphorylation

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Kanji Okumoto ◽  
Mahmoud El Shermely ◽  
Masanao Natsui ◽  
Hidetaka Kosako ◽  
Ryuichi Natsuyama ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Protein Import ◽  
Protein Translocation ◽  
Central Component ◽  
Dependent Manner ◽  
Peroxisomal Membrane ◽  
Oxidative Stresses ◽  
Signal Type

Most of peroxisomal matrix proteins including a hydrogen peroxide (H2O2)-decomposing enzyme, catalase, are imported in a peroxisome-targeting signal type-1 (PTS1)-dependent manner. However, little is known about regulation of the membrane-bound protein import machinery. Here, we report that Pex14, a central component of the protein translocation complex in peroxisomal membrane, is phosphorylated in response to oxidative stresses such as H2O2 in mammalian cells. The H2O2-induced phosphorylation of Pex14 at Ser232 suppresses peroxisomal import of catalase in vivo and selectively impairs in vitro the interaction of catalase with the Pex14-Pex5 complex. A phosphomimetic mutant Pex14-S232D elevates the level of cytosolic catalase, but not canonical PTS1-proteins, conferring higher cell resistance to H2O2. We thus suggest that the H2O2-induced phosphorylation of Pex14 spatiotemporally regulates peroxisomal import of catalase, functioning in counteracting action against oxidative stress by the increase of cytosolic catalase.

scholarly journals Peroxisome Synthesis in the Absence of Preexisting Peroxisomes

1999 ◽  
Vol 144 (2) ◽  
pp. 255-266 ◽  
Author(s):  
Sarah T. South ◽  
Stephen J. Gould
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Matrix Protein ◽  
Protein Import ◽  
Zellweger Syndrome ◽  
Matrix Proteins ◽  
Peroxisomal Membrane ◽  
Peroxisomal Membrane Protein ◽  
The Matrix ◽  
Inactivating Mutations

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.

scholarly journals Interactions of Pex7p and Pex18p/Pex21p with the Peroxisomal Docking Machinery: Implications for the First Steps in PTS2 Protein Import

2002 ◽  
Vol 22 (17) ◽  
pp. 6056-6069 ◽  
Author(s):  
Katharina Stein ◽  
Annette Schell-Steven ◽  
Ralf Erdmann ◽  
Hanspeter Rottensteiner
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Dependent Manner ◽  
Binding Assays ◽  
Interaction Domain ◽  
Vitro Binding ◽  
Targeting Signal ◽  
Two Hybrid ◽  
Import Receptor

ABSTRACT Peroxisomal PTS2-dependent matrix protein import starts with the recognition of the PTS2 targeting signal by the import receptor Pex7p. Subsequently, the formed Pex7p/cargo complex is transported from the cytosol to the peroxisomal docking complex, consisting of Pex13p and Pex14p. In Saccharomyces cerevisiae, the latter event is thought to require the redundant Pex18p and Pex21p. Here we mapped the Pex7p interaction domain of Pex13p to its N-terminal 100 amino acids. Pex18p and Pex21p also interacted with this region, albeit only in the presence of Pex7p. Expression of an N-terminally deleted version of Pex13p in a pex13Δ mutant failed to restore growth on fatty acids due to a specific defect in the import of PTS2-containing proteins. We further show by yeast two-hybrid analysis, coimmunoprecipitation, and in vitro binding assays that Pex7p can bind Pex13p and Pex14p in the absence of Pex18p/Pex21p. The PTS2 protein thiolase was shown to interact with Pex14p but not with Pex13p in a Pex7p- and Pex18p/Pex21p-dependent manner, suggesting that only Pex14p binds cargo-loaded PTS2 receptor. We also found that the cytosolic Pex7p/thiolase-containing complex includes Pex18p. This complex accumulated in docking mutants but was absent in cells lacking Pex18p/Pex21p, indicating that Pex18p/Pex21p are required already before the docking event.

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