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Peroxisome synthesis in the absence of preexisting peroxisomes.

South ST, Gould SJ - J. Cell Biol. (1999)

Bottom Line: We also identified human PEX16, a novel integral peroxisomal membrane protein, and found that PBD061 had inactivating mutations in the PEX16 gene.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

ABSTRACT
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.

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The CG9 cell line lacks detectable peroxisomes. Human fibroblasts from representatives of nine different complementation  groups of the PBDs were processed for indirect immunofluorescence using rabbit antibodies specific for PMP70, and Texas red–labeled  goat anti–rabbit IgG secondary antibodies. Numerous peroxisomal structures were detected in (A) the PEX1-deficient CG1 cell line,  PBD009; (B) the PEX5-deficient CG2 cell line, PBD005; (C) the PEX12-deficient CG3 cell line, PBD097; (D) the PEX6-deficient CG4  cell line, PBD105; (E) the PEX10-deficient CG7 cell line, PBD100; (F) the CG8 cell line, PBD109; (G) the PEX2-deficient CG10 cell line,  PBD094; and (H) the CG13 cell line, PBD222. In contrast, (I) the CG9 cell line, PBD061, lacks detectable peroxisomes. Bar, 10 μm.
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Figure 1: The CG9 cell line lacks detectable peroxisomes. Human fibroblasts from representatives of nine different complementation groups of the PBDs were processed for indirect immunofluorescence using rabbit antibodies specific for PMP70, and Texas red–labeled goat anti–rabbit IgG secondary antibodies. Numerous peroxisomal structures were detected in (A) the PEX1-deficient CG1 cell line, PBD009; (B) the PEX5-deficient CG2 cell line, PBD005; (C) the PEX12-deficient CG3 cell line, PBD097; (D) the PEX6-deficient CG4 cell line, PBD105; (E) the PEX10-deficient CG7 cell line, PBD100; (F) the CG8 cell line, PBD109; (G) the PEX2-deficient CG10 cell line, PBD094; and (H) the CG13 cell line, PBD222. In contrast, (I) the CG9 cell line, PBD061, lacks detectable peroxisomes. Bar, 10 μm.

Mentions: Little is known about the mechanisms of PMP import or the synthesis of peroxisome membranes. To identify cell lines that are defective in these processes we screened skin fibroblasts from over 100 PBD patients for the presence of PMP-containing peroxisomal structures. Each cell line was processed for indirect immunofluorescence using antibodies specific for PMP70, an integral membrane protein of the peroxisome. Previous studies have reported that PBD cells contain peroxisomes and import PMPs (Santos et al., 1988a, 1988b) and we detected numerous PMP70-containing peroxisomes in virtually all cell lines examined. These included representatives of complementation groups 1, 2, 3, 4, 7, 8, 10, and 13 (Fig. 1). However, we did identify one cell line, PBD061, which failed to import PMP70 into peroxisomes (Fig. 1, I). This cell line was derived from a severely affected Zellweger syndrome patient and is the sole representative of PBD complementation group 9 (Moser et al., 1995). To test whether the absence of PMP70 staining in PBD061 cells reflected a generalized defect in PMP import or a peculiarity of PMP70 distribution, representatives of all complementation groups were also processed for indirect immunofluorescence using antibodies specific for other PMPs, including ALDP (Mosser et al., 1994), and P70R (Shani et al., 1997). These antibodies also revealed the presence of numerous PMP-containing peroxisomes in representatives of all complementation groups except for the CG9 cell line, PBD061 (data not shown).


Peroxisome synthesis in the absence of preexisting peroxisomes.

South ST, Gould SJ - J. Cell Biol. (1999)

The CG9 cell line lacks detectable peroxisomes. Human fibroblasts from representatives of nine different complementation  groups of the PBDs were processed for indirect immunofluorescence using rabbit antibodies specific for PMP70, and Texas red–labeled  goat anti–rabbit IgG secondary antibodies. Numerous peroxisomal structures were detected in (A) the PEX1-deficient CG1 cell line,  PBD009; (B) the PEX5-deficient CG2 cell line, PBD005; (C) the PEX12-deficient CG3 cell line, PBD097; (D) the PEX6-deficient CG4  cell line, PBD105; (E) the PEX10-deficient CG7 cell line, PBD100; (F) the CG8 cell line, PBD109; (G) the PEX2-deficient CG10 cell line,  PBD094; and (H) the CG13 cell line, PBD222. In contrast, (I) the CG9 cell line, PBD061, lacks detectable peroxisomes. Bar, 10 μm.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2132891&req=5

Figure 1: The CG9 cell line lacks detectable peroxisomes. Human fibroblasts from representatives of nine different complementation groups of the PBDs were processed for indirect immunofluorescence using rabbit antibodies specific for PMP70, and Texas red–labeled goat anti–rabbit IgG secondary antibodies. Numerous peroxisomal structures were detected in (A) the PEX1-deficient CG1 cell line, PBD009; (B) the PEX5-deficient CG2 cell line, PBD005; (C) the PEX12-deficient CG3 cell line, PBD097; (D) the PEX6-deficient CG4 cell line, PBD105; (E) the PEX10-deficient CG7 cell line, PBD100; (F) the CG8 cell line, PBD109; (G) the PEX2-deficient CG10 cell line, PBD094; and (H) the CG13 cell line, PBD222. In contrast, (I) the CG9 cell line, PBD061, lacks detectable peroxisomes. Bar, 10 μm.
Mentions: Little is known about the mechanisms of PMP import or the synthesis of peroxisome membranes. To identify cell lines that are defective in these processes we screened skin fibroblasts from over 100 PBD patients for the presence of PMP-containing peroxisomal structures. Each cell line was processed for indirect immunofluorescence using antibodies specific for PMP70, an integral membrane protein of the peroxisome. Previous studies have reported that PBD cells contain peroxisomes and import PMPs (Santos et al., 1988a, 1988b) and we detected numerous PMP70-containing peroxisomes in virtually all cell lines examined. These included representatives of complementation groups 1, 2, 3, 4, 7, 8, 10, and 13 (Fig. 1). However, we did identify one cell line, PBD061, which failed to import PMP70 into peroxisomes (Fig. 1, I). This cell line was derived from a severely affected Zellweger syndrome patient and is the sole representative of PBD complementation group 9 (Moser et al., 1995). To test whether the absence of PMP70 staining in PBD061 cells reflected a generalized defect in PMP import or a peculiarity of PMP70 distribution, representatives of all complementation groups were also processed for indirect immunofluorescence using antibodies specific for other PMPs, including ALDP (Mosser et al., 1994), and P70R (Shani et al., 1997). These antibodies also revealed the presence of numerous PMP-containing peroxisomes in representatives of all complementation groups except for the CG9 cell line, PBD061 (data not shown).

Bottom Line: We also identified human PEX16, a novel integral peroxisomal membrane protein, and found that PBD061 had inactivating mutations in the PEX16 gene.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.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Chemistry, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.

ABSTRACT
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.

Show MeSH
Related in: MedlinePlus