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 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 Inhibitors of Copi and Copii Do Not Block PEX3-Mediated Peroxisome Synthesis

2000 ◽  
Vol 149 (7) ◽  
pp. 1345-1360 ◽  
Author(s):  
Sarah T. South ◽  
Katherine A. Sacksteder ◽  
Xiaoling Li ◽  
Yifei Liu ◽  
Stephen J. Gould
Keyword(s):  
Membrane Proteins ◽  
Zellweger Syndrome ◽  
Brefeldin A ◽  
Membrane Traffic ◽  
Dominant Negative ◽  
Peroxisome Biogenesis ◽  
Membrane Synthesis ◽  
Peroxisomal Membrane ◽  
Peroxisome Membrane ◽  
Inactivating Mutations

In humans, defects in peroxisome biogenesis are the cause of lethal diseases typified by Zellweger syndrome. Here, we show that inactivating mutations in human PEX3 cause Zellweger syndrome, abrogate peroxisome membrane synthesis, and result in reduced abundance of peroxisomal membrane proteins (PMPs) and/or mislocalization of PMPs to the mitochondria. Previous studies have suggested that PEX3 may traffic through the ER en route to the peroxisome, that the COPI inhibitor, brefeldin A, leads to accumulation of PEX3 in the ER, and that PEX3 overexpression alters the morphology of the ER. However, we were unable to detect PEX3 in the ER at early times after expression. Furthermore, we find that inhibition of COPI function by brefeldin A has no effect on trafficking of PEX3 to peroxisomes and does not inhibit PEX3-mediated peroxisome biogenesis. We also find that inhibition of COPII-dependent membrane traffic by a dominant negative SAR1 mutant fails to block PEX3 transport to peroxisomes and PEX3-mediated peroxisome synthesis. Based on these results, we propose that PEX3 targeting to peroxisomes and PEX3-mediated peroxisome membrane synthesis may occur independently of COPI- and COPII-dependent membrane traffic.

scholarly journals Reevaluation of the role of Pex1 and dynamin-related proteins in peroxisome membrane biogenesis

2015 ◽  
Vol 211 (5) ◽  
pp. 1041-1056 ◽  
Author(s):  
Alison M. Motley ◽  
Paul C. Galvin ◽  
Lakhan Ekal ◽  
James M. Nuttall ◽  
Ewald H. Hettema
Keyword(s):  
Protein Delivery ◽  
Matrix Protein ◽  
Protein Import ◽  
De Novo ◽  
Primary Role ◽  
Peroxisome Biogenesis ◽  
Peroxisomal Membrane ◽  
Related Proteins ◽  
Peroxisome Membrane

A recent model for peroxisome biogenesis postulates that peroxisomes form de novo continuously in wild-type cells by heterotypic fusion of endoplasmic reticulum–derived vesicles containing distinct sets of peroxisomal membrane proteins. This model proposes a role in vesicle fusion for the Pex1/Pex6 complex, which has an established role in matrix protein import. The growth and division model proposes that peroxisomes derive from existing peroxisomes. We tested these models by reexamining the role of Pex1/Pex6 and dynamin-related proteins in peroxisome biogenesis. We found that induced depletion of Pex1 blocks the import of matrix proteins but does not affect membrane protein delivery to peroxisomes; markers for the previously reported distinct vesicles colocalize in pex1 and pex6 cells; peroxisomes undergo continued growth if fission is blocked. Our data are compatible with the established primary role of the Pex1/Pex6 complex in matrix protein import and show that peroxisomes in Saccharomyces cerevisiae multiply mainly by growth and division.

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.

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 Pex24 and Pex32 are required to tether peroxisomes to the ER for organelle biogenesis, positioning and segregation in yeast

2020 ◽  
Vol 133 (16) ◽  
pp. jcs246983 ◽  
Author(s):  
Fei Wu ◽  
Rinse de Boer ◽  
Arjen M. Krikken ◽  
Arman Akşit ◽  
Nicola Bordin ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Membrane Protein ◽  
Matrix Protein ◽  
Protein Import ◽  
Hansenula Polymorpha ◽  
Major Effect ◽  
Organelle Biogenesis ◽  
Peroxisomal Membrane ◽  
Contact Sites ◽  
Membrane Growth

ABSTRACTThe yeast Hansenula polymorpha contains four members of the Pex23 family of peroxins, which characteristically contain a DysF domain. Here we show that all four H. polymorpha Pex23 family proteins localize to the endoplasmic reticulum (ER). Pex24 and Pex32, but not Pex23 and Pex29, predominantly accumulate at peroxisome–ER contacts. Upon deletion of PEX24 or PEX32 – and to a much lesser extent, of PEX23 or PEX29 – peroxisome–ER contacts are lost, concomitant with defects in peroxisomal matrix protein import, membrane growth, and organelle proliferation, positioning and segregation. These defects are suppressed by the introduction of an artificial peroxisome–ER tether, indicating that Pex24 and Pex32 contribute to tethering of peroxisomes to the ER. Accumulation of Pex32 at these contact sites is lost in cells lacking the peroxisomal membrane protein Pex11, in conjunction with disruption of the contacts. This indicates that Pex11 contributes to Pex32-dependent peroxisome–ER contact formation. The absence of Pex32 has no major effect on pre-peroxisomal vesicles that occur in pex3 atg1 deletion cells.

scholarly journals The Peroxin Pex19p Interacts with Multiple, Integral Membrane Proteins at the Peroxisomal Membrane

2000 ◽  
Vol 149 (6) ◽  
pp. 1171-1178 ◽  
Author(s):  
William B. Snyder ◽  
Antonius Koller ◽  
A. Jobu Choy ◽  
Suresh Subramani
Keyword(s):  
Membrane Proteins ◽  
Multiple Integral ◽  
Integral Membrane Proteins ◽  
Peroxisome Biogenesis ◽  
Yeast Two Hybrid ◽  
Peroxisomal Membrane ◽  
Site Of Action ◽  
Peroxisome Membrane ◽  
Two Hybrid ◽  
New Protein

Pex19p is a protein required for the early stages of peroxisome biogenesis, but its precise function and site of action are unknown. We tested the interaction between Pex19p and all known Pichia pastoris Pex proteins by the yeast two-hybrid assay. Pex19p interacted with six of seven known integral peroxisomal membrane proteins (iPMPs), and these interactions were confirmed by coimmunoprecipitation. The interactions were not reduced upon inhibition of new protein synthesis, suggesting that they occur with preexisting, and not newly synthesized, pools of iPMPs. By mapping the domains in six iPMPs that interact with Pex19p and the iPMP sequences responsible for targeting to the peroxisome membrane (mPTSs), we found the majority of these sites do not overlap. Coimmunoprecipitation of Pex19p from fractions that contain peroxisomes or cytosol revealed that the interactions between predominantly cytosolic Pex19p and the iPMPs occur in the organelle pellet that contains peroxisomes. These data, taken together, suggest that Pex19p may have a chaperone-like role at the peroxisome membrane and that it is not the receptor for targeting of iPMPs to the peroxisome.

Pex5p stabilizes Pex14p: a study using a newly isolated pex5 CHO cell mutant, ZPEG101

2012 ◽  
Vol 449 (1) ◽  
pp. 195-207 ◽  
Author(s):  
Ryuichi Natsuyama ◽  
Kanji Okumoto ◽  
Yukio Fujiki
Keyword(s):  
Matrix Protein ◽  
Protein Import ◽  
Chinese Hamster ◽  
Ovary Cell ◽  
Cell Mutant ◽  
Peroxisomal Membrane ◽  
Multiple Binding Sites ◽  
Multiple Binding ◽  
Signal Type ◽  
Mutant Phenotypes

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.

scholarly journals Pex13p is an SH3 protein of the peroxisome membrane and a docking factor for the predominantly cytoplasmic PTs1 receptor.

1996 ◽  
Vol 135 (1) ◽  
pp. 85-95 ◽  
Author(s):  
S J Gould ◽  
J E Kalish ◽  
J C Morrell ◽  
J Bjorkman ◽  
A J Urquhart ◽  
...  
Keyword(s):  
Steady State ◽  
Matrix Proteins ◽  
Cytoplasmic Protein ◽  
Peroxisomal Membrane ◽  
Peroxisomal Targeting ◽  
Targeting Signal ◽  
Peroxisome Membrane ◽  
Peroxisomal Targeting Signal

Import of newly synthesized PTS1 proteins into the peroxisome requires the PTS1 receptor (Pex5p), a predominantly cytoplasmic protein that cycles between the cytoplasm and peroxisome. We have identified Pex13p, a novel integral peroxisomal membrane from both yeast and humans that binds the PTS1 receptor via a cytoplasmically oriented SH3 domain. Although only a small amount of Pex5p is bound to peroxisomes at steady state (< 5%), loss of Pex13p further reduces the amount of peroxisome-associated Pex5p by approximately 40-fold. Furthermore, loss of Pex13p eliminates import of peroxisomal matrix proteins that contain either the type-1 or type-2 peroxisomal targeting signal but does not affect targeting and insertion of integral peroxisomal membrane proteins. We conclude that Pex13p functions as a docking factor for the predominantly cytoplasmic PTS1 receptor.

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