Article |
Address correspondence to Stephen J. Gould, Dept. of Biological Chemistry, The Johns Hopkins University School of Medicine, 725 North Wolfe St., Baltimore, MD 21205. Tel.: (410) 9553424. Fax: (410) 9550215. E-mail: sgould{at}jhmi.edu
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key Words: peroxisome biogenesis; fatty acid oxidation; organelle division; peroxisomal membrane protein; Zellweger syndrome
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Peroxisome division is poorly understood. We previously established that defects in peroxisomal fatty acid ß-oxidation reduce peroxisome abundance in mammalian cells, indicating that there may be metabolic control of peroxisome division (Chang et al., 1999). PEX11 proteins have also been implicated in the regulation of peroxisome abundance. Studies in yeast demonstrated that loss of PEX11 caused a signification reduction in peroxisome abundance and that PEX11 overexpression caused a pronounced increase in their abundance (Erdmann and Blobel, 1995; Marshall et al., 1995; Sakai et al., 1995). A similar ability to promote peroxisome proliferation was also reported for human (Abe and Fujiki, 1998; Abe et al., 1998; Schrader et al., 1998), rodent (Passreiter et al., 1998; Schrader et al., 1998), and protozoan (Lorenz et al., 1998; Maier et al., 2001) forms of PEX11. These results have previously been interpreted to support a direct role for PEX11 in peroxisome division (Gould and Valle, 2000). However, recent studies have demonstrated that loss of yeast PEX11 blocks the peroxisomal oxidation of medium chain fatty acids (MCFAs)* and that other defects in MCFA oxidation reduce peroxisome abundance (van Roermund et al., 2000, 2001). In fact, van Roermund et al. (2000) proposed that the role of PEX11 in peroxisome division is a secondary, indirect consequence of its role in MCFA oxidation. Furthermore, they suggested that flux of MCFAs through the peroxisomal ß-oxidation pathway generates a signaling molecule that promotes peroxisome division.
We tested this hypothesis of PEX11 function in mammalian cells and yeast. We demonstrated that PEX11 proteins are able to drive peroxisome division in the absence of peroxisome metabolism, and that the loss of murine PEX11ß causes a reduction in peroxisome abundance in the absence of peroxisomal metabolic substrates. These results, together with the fact that the loss of PEX11 proteins affects multiple, unrelated peroxisomal metabolic activities, suggest a revised model of PEX11 function. We propose that PEX11 proteins play a direct role in peroxisome division and that their loss inhibits peroxisome metabolism indirectly, perhaps due to altered membrane structure or dynamics.
![]() |
Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
|
|
PBD005 cells were transfected with either pcDNA3-PEX11ßmyc or pcDNA3-PMP34myc, incubated for 2 d, processed for indirect immunofluorescence, and observed by confocal immunofluorescence microscopy. Peroxisome abundance was thirty times higher in PBD005 cells overexpressing PEX11ßmyc (979 ± 388 pps) as compared with untransfected cells (32 ± 16 pps), and was unaffected by overexpression of PMP34myc (35 ± 15 pps) (Fig. 3). Thus, the peroxisome-proliferating activity of human PEX11ß is not dependent on peroxisomal ß-oxidation activities. Furthermore, because PBD005 cells are defective in all known peroxisomal metabolic activities and are unable to import peroxisomal matrix enzymes (Dodt et al., 1995), we can conclude that the peroxisome-proliferating activity of human PEX11ß is independent of all peroxisomal metabolic activities. In a previous study (Chang et al., 1999), we reported that defects in peroxisomal ß-oxidation, due to either (a) isolated defects in the acyl-CoA oxidase 1 (Poll-The et al., 1988) or the D-bifunctional protein (D-BP) (van Grunsven et al., 1998) genes, or (b) defects in genes that are required for peroxisomal matrix protein import (e.g., PEX5) (Dodt et al., 1995), cause a significant reduction in peroxisome abundance. Thus, it was expected that peroxisome abundance would be reduced in untransfected PBD005 cells (32 ± 16 pps) as compared with untransfected normal human fibroblasts (94 ± 36 pps) (Fig. 3).
|
|
Peroxisome abundance increased merely by releasing cells from glucose repression (Fig. 4, C and D). This is not surprising given the role of ADR1 in glucose repression and the fact that ADR1 regulates the expression of many peroxisomal protein-encoding genes (Gurvitz et al., 2000; Ramil et al., 2000). Galactose-induced expression of PEX13 (Fig. 4 E) or YPR128C (Fig. 4 F) failed to increase peroxisome abundance beyond what was observed in galactose-grown XLY1 cells carrying the empty vector (Fig. 4 D), indicating that overexpression of PMPs alone is not sufficient to increase peroxisome abundance. In contrast, galactose-induced expression of PEX11 increased peroxisome abundance to levels that were observed in oleate-grown BY4733 cells (Fig. 4 G). The absence of fatty acids from the growth media (S-Gal) makes it extremely unlikely that there was any significant flux of substrates through the peroxisomal fatty acid ß-oxidation pathway in these experiments. Thus, our results suggest that S. cerevisiae Pex11p has intrinsic peroxisome-proliferating activity. As an alternative test of this hypothesis, we repeated these experiments in XLY2 cells, a pox1 derivative of XLY1. POX1 encodes the peroxisomal acyl-CoA oxidase, which catalyzes the first committed step in fatty acid ß-oxidation and is essential for ß-oxidation of all fatty acids in S. cerevisiae (Wang et al., 1994). Galactose-induced expression of PEX13 had no effect on peroxisome abundance in XLY2 cells (Fig. 4 H). In contrast, galactose-induced expression of PEX11 in XLY2 cells increased peroxisome abundance to levels that were similar to PEX11-expressing XLY1 cells and oleate-grown BY4733 cells (Fig. 4 I).
Loss of mouse PEX11ß has an indirect effect on peroxisome metabolism
The ability of human and yeast PEX11 proteins to promote peroxisome division independent of peroxisomal fatty acid ß-oxidation, combined with the fact that loss of yeast PEX11 reduces peroxisomal MCFA oxidation, suggests two possible models of PEX11 function: either PEX11 proteins have multiple, independent functions in both peroxisome division and MCFA oxidation, or the effect of PEX11 deficiency on peroxisome metabolism is indirect. We recently generated mice lacking the PEX11ß gene (unpublished data). If PEX11ß functions primarily in fatty acid oxidation, then peroxisome abundance should be the same in PEX11ß+/+ and PEX11ß-/- cells when these two cell lines are grown in serum-free medium, which is devoid of lipids and lacks substrates of the peroxisomal fatty acid oxidation pathway. However, if PEX11ß functions primarily in peroxisome division, peroxisome abundance should be reduced in PEX11ß-/- cells relative to PEX11ß+/+ cells.
Mouse embryonic fibroblasts from PEX11ß+/+ and PEX11ß-/- mice were generated. After a 24-h incubation in serum-free medium, the cells were fixed, permeabilized, and processed for immunofluorescence using antibodies specific for the peroxisomal enzyme catalase and the PMP PEX14 (Fig. 5). Peroxisome abundance was quantified by counting the number of peroxisomes per section in 60 cells. For PEX11ß+/+ cells grown under these conditions, we detected an average peroxisome abundance of 230 ± 52 pps. Peroxisome abundance in PEX11ß-/- cells grown under identical conditions was approximately half of that wild-type cells, 128 ± 32 pps, indicating that loss of PEX11ß affects peroxisome abundance independently of peroxisomal metabolism.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
We first tested whether PEX11 overexpression was sufficient to promote peroxisome division in the absence of any peroxisome proliferating stimulus. Of more than 10 human integral PMPs tested, only PEX11 overexpression was sufficient to promote peroxisome division. We next tested whether the peroxisome-proliferating effect of PEX11ß overexpression required metabolically active peroxisomes. We observed that the peroxisome division-promoting effect of PEX11ß was the same or even greater in PEX5-deficient PBD005 fibroblasts, which are unable to import peroxisomal matrix enzymes and are defective in all peroxisomal metabolic functions (Dodt et al., 1995). We also observed that PEX11 overexpression in yeast was sufficient to promote peroxisome division. Our final test was to assess the effects of PEX11ß deficiency on peroxisome division in fibroblasts grown in chemically defined, serum-free medium, which lacks peroxisomal fatty acid oxidation substrates and contains glucose and essential amino acids as the sole carbon sources. We observed that PEX11ß-/- cells have only half the peroxisome abundance of their WT counterparts. Taken together, these results demonstrate that PEX11 proteins promote peroxisome division regardless of the metabolic state of peroxisomes.
The simplest interpretation of these results is that PEX11 proteins play direct roles in promoting peroxisome division. But what of the unquestionable requirement for yeast PEX11 in MCFA oxidation? Does this reflect a direct or indirect role for PEX11 proteins in peroxisome metabolic pathways? Although we cannot exclude a direct role for yeast PEX11 in peroxisomal MCFA oxidation, it is curious that the loss of yeast PEX11 also causes a significant reduction in the peroxisomal oxidation of long chain fatty acids (van Roermund et al., 2000), substrates that are thought to be imported by a distinct pathway (Hettema and Tabak, 2000). It is also notable that loss of mammalian PEX11ß affects both the peroxisomal fatty acid ß-oxidation and peroxisomal ether lipid synthesis pathways (unpublished data), two pathways that do not share even a single biochemical step (Wanders et al., 2001a). In fact, current diagnostic procedures for human peroxisomal diseases use a deficiency of both pathways as the means for differentiating between mere metabolic defects and defects in peroxisome biogenesis (Wanders et al., 2001a). One possible mechanism to explain the impairment of multiple peroxisomal metabolic pathways in pex11 mutant cells is that loss of PEX11 proteins may alter the physical properties of the peroxisome membrane. If true, this could impair metabolite transport across the peroxisome membrane. It is also possible that such an alteration could affect different transport systems to different degrees, explaining the near total defect in MCFA oxidation but only partial defect in long chain fatty acid oxidation in yeast (van Roermund et al., 2000), and the partial defects in fatty acid ß-oxidation and ether lipid synthesis in mammalian cells (unpublished data). Our hypothesis of PEX11's role in peroxisomal metabolism is also consistent with the fact that the defect in MCFA oxidation can be overcome by permeabilizing the peroxisome membrane (van Roermund et al., 2000) and that PEX11 lacks structural similarities to known fatty acid and nucleotide transporters (Coe et al., 1999; Saier, 2000).
Although the available evidence points to a direct role for PEX11 proteins in peroxisome division, what is the nature of this role? The strong correlation between PEX11 protein levels and peroxisome abundance within the cell (Erdmann and Blobel, 1995; Marshall et al., 1995; Sakai et al., 1995) suggests that peroxisome division may be sensitive to PEX11 concentrations in the peroxisome membrane, although there is also evidence that PEX11 activity may be affected by posttranslational modification (Marshall et al., 1996). Although peroxisome division is a poorly understood process, Hoepfner et al. (Hoepfner et al., 2001) have recently established that the dynamin-related protein VPS1 is required for peroxisome division and that peroxisome motility requires the class V myosin, MYO2. It will be interesting to determine whether PEX11 proteins participate in VPS1-mediated peroxisome division or whether they act in some distinct process, such as a coat-mediated peroxisome budding process (Passreiter et al., 1998; Kirchhausen, 2000). In addition to resolving these questions, future studies of peroxisome division should explore the role of PEX11-interacting proteins in the division process, as well as the possibility that PEX11 proteins may modify peroxisome lipids or recruit lipid-modifying activities to the peroxisome membranes.
One last point of discussion is the role of peroxisome metabolism in regulating peroxisome abundance. The existence of metabolic control over peroxisome abundance was established by the observation that isolated defects in the human peroxisomal ß-oxidation enzymes acyl-CoA oxidase or 2-enoyl-CoA hydratase/D-3-hydroxyacyl-CoA dehydrogenase bifunctional enzyme cause an 80% reduction in peroxisome abundance in human fibroblasts (Chang et al., 1999). The van Roermund et al. (2000) report clearly extended this observation to yeast, indicating that the phenomenon is evolutionarily conserved. Like the mechanism of PEX11-mediated peroxisome division, this phenomenon is poorly understood. One attractive hypothesis is that metabolite flux through peroxisomal ß-oxidation pathways generates signaling molecules that in turn regulate PEX11 activity. However, the levels of human PEX11ß mRNA are not altered in human cells that lack either acyl-CoA oxidase or the 2-enoyl-CoA hydratase/D-3-hydroxyacyl-CoA dehydrogenase binfunctional enzyme (Chang et al., 1999) and S. cerevisiae PEX11 protein levels are not altered in peroxisomal fatty acid oxidation mutants (van Roermund et al., 2000). Although it is formally possible that PEX11 activity and fatty acid oxidation might be linked by posttranslational mechanisms, the sole report on posttranslational regulation of PEX11 proposes that PEX11 activity should decrease with increasing peroxisomal fatty acid oxidation activity (Marshall et al., 1996). Thus, it may be that eukaryotic cells utilize two mechanisms for controlling peroxisome division, one that acts through PEX11 proteins, and another, PEX11-independent mechanism that is sensitive to metabolic flux through peroxisomal fatty acid ß-oxidation pathways.
![]() |
Materials and methods |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Cell lines, transfection, microinjection, immunofluorescence, and antibodies
The wild-type human skin fibroblast GM5756 and the PEX5-deficient cell line PBD005 (Dodt et al., 1995) were cultured under standard conditions (Slawecki et al., 1995), as were fibroblasts derived from PEX11ß+/+ and PEX11ß-/- mouse embryos (unpublished data). All transfections were performed by electroporation (Chang et al., 1997) and microinjections were performed with DNA at a concentration of 0.1 µg/ml in reverse PBS buffer (4 mM NaHPO4, 1 mM KH2PO4, 140 mM KCl, pH 7.3) (South and Gould, 1999). For immunofluorescence, cells were fixed in 3% formaldehyde in Dulbecco's modified PBS (DPBS) (Life Technologies), pH 7.1, for 20 min, and then permeabilized in 25 µg/ml digitonin or 1% Triton X-100 in DPBS for 5 min. Cells were then incubated with primary antibodies for 30 min, washed extensively in DPBS, incubated with fluorescently labeled secondary antibodies for 10 min, washed extensively in DPBS, and mounted on slides. Rabbit antibodies against PEX14 have been described (Sacksteder et al., 2000). Monoclonal antibodies to the myc epitope were obtained from the tissue culture supernatant of the hybridoma 19E10 (Evan et al., 1985). Sheep antihuman catalase antibodies were obtained from The Binding Site. Secondary antibodies specific for rabbit and mouse antibodies were obtained from commercial sources.
Yeast strains and culture conditions
Yeast strains used in this study were based on S. cerevisiae strain BY4733 (MATa, his3200, leu2
0, met15
0, trp1
63, ura3
0). The strain XLY1 was generated by one-step PCR-mediated disruption of the PEX11 gene in BY4733 using kanMX4 as the selectable maker (Baker-Brachmann et al., 1998), followed by transformation with the URA3-based replicating vector pPGK1-GFP/PTS1. The XLY2 strain was generated from XLY1 by one-step PCR-mediated disruption of the POX1 gene using HIS3 as the selectable maker. Plasmid transformations were performed using the LiOAc procedure (Guthrie and Fink, 1991). All strains were cultured in minimal S medium (0.17% yeast nitrogen base without ammonium sulfate [Sigma-Aldrich]; 0.5% ammonium sulfate) with glucose (2%), galactose (1%), or oleic acid/Tween 40 (0.2%, 0.02%) as carbon source. Media were supplemented with amino acids, uracil, and adenine as required (Guthrie and Fink, 1991).
Peroxisome abundance measurements
To determine peroxisome abundance in human and mouse fibroblasts, cells were examined by confocal fluorescence microscopy and fluorescence images were captured under identical conditions using an UltraVIEW confocal imaging system (Nikon). Images were then analyzed by IPLab-spectrum software (Scanalytics) and peroxisomes were automatically identified as segments comprised of pixels with limiting range of intensity. Segments in each cell were automatically counted, the sum of which equaled the pps for that cell. For human fibroblasts, at least 30 randomly selected cells were examined for each sample. For the analysis of mouse fibroblasts, cells were grown for 24 h in chemically defined, serum-free medium lacking lipids (DME; GIBCO BRL), and supplemented with 0.25% BSA, 6.25 x 10-8 M transferrin, 8.3 x 10-7 M insulin, 3 x 10-8 M selenium, 2 x 10-8 M progesteron, and 10-4 M putrescine (all from Sigma-Aldrich) (Bottenstein et al., 1980), and peroxisome abundance in 60 randomly selected cells was determined. To determine the peroxisome abundance in yeast, yeast strains BY4733, XLY1, and XLY2 transformed with either pRS425/GAL1, or its derivatives pRS524/GAL1-PEX11, pRS425/GAL1-PEX13, or pRS425/GAL1-YPR128C were grown in glucose, galactose, or oleic acid medium. Cells were washed with DPBS buffer twice, fixed with 3% formaldehyde for 30 min, and then examined under an Olympus fluorescence microscope. Peroxisome abundance was determined in 120 cells from each sample.
![]() |
Footnotes |
---|
![]() |
Acknowledgments |
---|
Submitted: 7 December 2001
Revised: 7 December 2001
Accepted: 4 January 2002
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
Abe, I., K. Okumoto, S. Tamura, and Y. Fujiki. 1998. Clofibrate-inducible, 28-kDa peroxisomal integral membrane protein is encoded by PEX11. FEBS Lett. 431:468472.[CrossRef][Medline]
Bjorkman, J., G. Stetten, C.S. Moore, S.J. Gould, and D.I. Crane. 1998. Genomic structure of PEX13, a candidate peroxisome biogenesis disorder gene. Genomics. 54:521528.[CrossRef][Medline]
Chang, C.C., W.H. Lee, H.W. Moser, D. Valle, and S.J. Gould. 1997. Isolation of the human PEX12 gene, mutated in group 3 of the peroxisome biogenesis disorders. Nat. Genet. 15:385388.[Medline]
Chang, C.C., S. South, D. Warren, J. Jones, A.B. Moser, H.W. Moser, and S.J. Gould. 1999. Metabolic control of peroxisome abundance. J. Cell Sci. 112:15791590.
Coe, N.R., A.J. Smith, B.I. Frohnert, P.A. Watkins, and D.A. Bernlohr. 1999. The fatty acid transport protein (FATP1) is a very long chain acyl-CoA synthetase. J. Biol. Chem. 274:3630036304.
Elgersma, Y., L. Kwast, A. Klein, T. Voorn-Brouwer, M. van den Berg, B. Metzig, T. America, H.F. Tabak, and B. Distel. 1996. The SH3 domain of the Saccharomyces cerevisiae peroxisomal membrane protein Pex13p functions as a docking site for Pex5p, a mobile receptor for the import of PTS1 containing proteins. J. Cell Biol. 135:97109.[Abstract]
Erdmann, R., and G. Blobel. 1995. Giant peroxisomes in oleic acid-induced Saccharomyces cerevisiae lacking the peroxisomal membrane protein Pmp27p. J. Cell Biol. 128:509523.[Abstract]
Erdmann, R., and G. Blobel. 1996. Identification of Pex13p, a peroxisomal membrane receptor for the PTS1 recognition factor. J. Cell Biol. 135:111121.[Abstract]
Erdmann, R., M. Veenhuis, D. Mertens, and W.H. Kunau. 1989. Isolation of peroxisome-deficient mutants of Saccharomyces cerevisiae. Proc. Natl. Acad. Sci. USA. 86:54195423.[Abstract]
Fransen, M., S.R. Terlecky, and S. Subramani. 1998. Identification of a human PTS1 receptor docking protein directly required for peroxisomal protein import. Proc. Natl. Acad. Sci. USA. 95:80878092.
Gould, S.J., and D. Valle. 2000. The genetics and cell biology of the peroxisome biogenesis disorders. Trends Genet. 16:340344.[CrossRef][Medline]
Gould, S.J., J.E. Kalish, J.C. Morrell, J. Bjorkman, A.J. Urquhart, and D.I. Crane. 1996. PEX13p is an SH3 protein in the peroxisome membrane and a docking factor for the PTS1 receptor. J. Cell Biol. 135:8595.[Abstract]
Gould, S.G., D. Valle, and G.V. Raymond. 2001. The peroxisome biogenesis disorders. The Metabolic and Molecular Bases of Inherited Disease. Vol. 2. C.R. Scriver, A.L. Beaudet, W.S. Sly, and D. Valle, editors. McGraw-Hill, New York. 31813217.
Guthrie, C., and G.R. Fink. 1991. Guide to Yeast Genetics and Molecular Biology. Academic Press, San Diego. 933 pp.
Hettema, E.H., and H.F. Tabak. 2000. Transport of fatty acids and metabolites across the peroxisomal membrane. Biochim. Biophys. Acta. 1486:1827.[Medline]
Hoepfner, D., M. van den Berg, P. Philippsen, H.F. Tabak, and E.H. Hettema. 2001. A role for Vps1p, actin, and the myo2p motor in peroxisome abundance and inheritance in Saccharomyces cerevisiae. J. Cell Biol. 155:979990.
Jones, J.M., J.C. Morrell, and S.J. Gould. 2001. Multiple distinct targeting signals in integral peroxisomal membrane proteins. J. Cell Biol. 153:11411150.
Kalish, J.E., G.A. Keller, J.C. Morrell, S.J. Mihalik, B. Smith, J.M. Cregg, and S.J. Gould. 1996. Characterization of a novel component of the peroxisomal protein import apparatus using fluorescent peroxisomal proteins. EMBO J. 15:32753285.[Abstract]
Kim, J., and D.J. Klionsky. 2000. Autophagy, cytoplasm-to-vacuole targeting pathway, and pexophagy in yeast and mammalian cells. Annu. Rev. Biochem. 69:303342.[CrossRef][Medline]
Kunau, W.-H., A. Beyer, T. Franken, K. Gotte, M. Marzioch, J. Saidowsky, A. Skaletz-Rorowski, and F.F. Wiebel. 1993. Two complementary approaches to study peroxisome biogenesis in Saccharomyces cerevisiae: forward and reversed genetics. Biochimie. 75:209224.[CrossRef][Medline]
Lombard-Platet, G., S. Savary, C.O. Sarde, J.L. Mandel, and G. Chimini. 1996. A close relative of the adrenoileukodystrophy (ALD) gene codes for a peroxisomal protein with a specific expression pattern. Proc. Natl. Acad. Sci. USA. 93:12651269.
Lorenz, P., A.G. Maier, E. Baumgart, R. Erdmann, and C. Clayton. 1998. Elongation and clustering of glycosomes in Trypanosoma brucei overexpressing the glycosomal Pex11p. EMBO J. 17:35423555.
Marshall, P., Y. Krimkevich, R. Lark, J. Dyer, M. Veenhuis, and J. Goodman. 1995. Pmp27 promotes peroxisomal proliferation. J. Cell Biol. 129:345355.[Abstract]
Marshall, P.A., J.M. Dyer, M.E. Quick, and J.M. Goodman. 1996. Redox-sensitive homodimerization of Pex11p: a proposed mechanism to regulate peroxisomal division. J. Cell Biol. 135:123137.[Abstract]
Palmieri, L., H. Rottensteiner, W. Girzalsky, P. Scarcia, F. Palmieri, and R. Erdmann. 2001. Identification and functional reconstitution of the yeast peroxisomal adenine nucleotide transporter. EMBO J. 20:50495059.
Passreiter, M., M. Anton, D. Lay, R. Frank, C. Harter, F.T. Wieland, K. Gorgas, and W.W. Just. 1998. Peroxisome biogenesis: involvement of ARF and coatomer. J. Cell Biol. 141:373383.
Purdue, P.E., and P.B. Lazarow. 2001. Peroxisome biogenesis. Annu. Rev. Cell Dev. Biol. 17:701752.[CrossRef][Medline]
Reguenga, C., M.E. Oliveira, A.M. Gouveia, C. Eckerskorn, C. Sa-Miranda, and J.E. Azevedo. 1999. Identification of a 24 kDa intrinsic membrane proteins from mammalian peroxisomes. Biochim. Biophys. Acta. 1445:337341.[Medline]
Sacksteder, K.A., J.M. Jones, S.T. South, X. Li, Y. Liu, and S.J. Gould. 2000. PEX19 binds multiple peroxisomal membrane proteins, is predominantly cytoplasmic, and is required for peroxisome membrane synthesis. J. Cell Biol. 148:931944.
Saier, M.H., Jr. 2000. A functional-phylogenetic classification system for transmembrane solute transporters. Microbiol. Mol. Biol. Rev. 64:354411.
Sakai, Y., P.A. Marshall, A. Saiganji, K. Takabe, H. Saiki, N. Kato, and J.M. Goodman. 1995. The Candida boidinii peroxisomal membrane protein Pmp30 has a role in peroxisomal proliferation and is functionally homologous to Pmp27 from Saccharomyces cerevisiae. J. Bacteriol. 177:67736781.[Abstract]
Schrader, M., B.E. Reuber, J.C. Morrell, G. Jimenez-Sanchez, C. Obie, T. Stroh, D. Valle, T.A. Schroer, and S.J. Gould. 1998. Expression of PEX11ß mediates peroxisome proliferation in the absence of extracellular stimuli. J. Biol. Chem. 273:2960729614.
Shani, N., G. Jimenez-Sanchez, G. Steel, M. Dean, and D. Valle. 1997. Identification of a fourth half ABC transporter in the human peroxisomal membrane. Hum. Mol. Genet. 6:19251931.
Shimizu, N., R. Itoh, Y. Hirono, H. Otera, K. Ghaedi, K. Tateishi, S. Tamura, K. Okumoto, T. Harano, S. Mukai, and Y. Fujiki. 1999. The peroxin Pex14p. cDNA cloning by functional complementation on a Chinese hamster ovary cell mutant, characterization, and functional analysis. J. Biol. Chem. 274:1259312604.
Sikorski, R.S., and P. Hieter. 1989. A system of shuttle vectors and yeast host strains designed for efficient manipulation of DNA in Saccharomyces cerevisiae. Genetics. 122:1927.
Slawecki, M., G. Dodt, S. Steinberg, A.B. Moser, H.W. Moser, and S.J. Gould. 1995. Identification of three distinct peroxisomal protein import defects in patients with peroxisomal biogenesis disorders. J. Cell Sci. 108:18171829.
South, S.T., and S.J. Gould. 1999. Peroxisome synthesis in the absence of preexisting peroxisomes. J. Cell Biol. 144:255266.
Tabak, H.F., I. Braakman, and B. Distel. 1999. Peroxisomes: simple function but complex in maintenance. Trends Cell Biol. 9:447453.[CrossRef][Medline]
van Grunsven, E.G., E. van Berkel, L. Ijlst, P. Vreken, J.B. de Klerk, J. Adamski, H. Lemonde, P.T. Clayton, D.A. Cuebas, and R.J. Wanders. 1998. Peroxisomal D-hydroxyacl-CoA dehydrogenase deficiency: resolution of the enzyme defect and its molecular basis in bifunctional protein deficiency. Proc. Natl. Acad. Sci. USA. 95:21282133.
van Roermund, C.W., H.F. Tabak, M. van Den Berg, R.J. Wanders, and E.H. Hettema. 2000. Pex11p plays a primary role in medium-chain fatty acid oxidation, a process that affects peroxisome number and size in Saccharomyces cerevisiae. J. Cell Biol. 150:489498.
van Roermund, C.W., R. Drissen, M. van Den Berg, L. Ijlst, E.H. Hettema, H.F. Tabak, H.R. Waterham, and R.J. Wanders. 2001. Identification of a peroxisomal ATP carrier required for medium-chain fatty acid beta-oxidation and normal peroxisome proliferation in Saccharomyces cerevisiae. Mol. Cell. Biol. 21:43214329.
Wanders, R.J.A., P.G. Barth, and H.S.A. Heymans. 2001a. Single peroxisomal enzyme deficiencies. The Metabolic and Molecular Bases of Inherited Disease. Vol. 2. C.R. Scriver, A.L. Beaudet, W.S. Sly, and D. Valle, editors. McGraw-Hill, New York. 32193256.
Wang, T., Y. Luo, and G.M. Small. 1994. The POX1 gene encoding peroxisomal acyl-CoA oxidase in Saccharomyces cerevisiae is under the control of multiple regulatory elements. J. Biol. Chem. 269:2448024485.
Will, G.K., M. Soukupova, X. Hong, K.S. Erdmann, J.A. Kiel, G. Dodt, W.H. Kunau, and R. Erdmann. 1999. Identification and characterization of the human orthologue of yeast Pex14p. Mol. Cell. Biol. 19:22652277.
Wylin, T., M. Baes, C. Brees, G.P. Mannaerts, M. Fransen, and P.P. Van Veldhoven. 1999. Identification and characterization of human PMP34, a protein closely related to the peroxisomal integral membrane protein PMP47 of Candida boidinii. Eur. J. Biochem. 258:332338.[Abstract]