Temperature-Sensitive Mutation of PEX6 in Peroxisome Biogenesis Disorders in Complementation Group C (CG-C): Comparative Study of PEX6 and PEX1

Imamura, Atsushi; Shimozawa, Nobuyuki; Suzuki, Yasuyuki; Zhang, Zhongyi; Tsukamoto, Tomoko; Fujiki, Yukio; Orii, Tadao; Osumi, Takashi; Wanders, Ronald J. A.; Kondo, Naomi

doi:10.1203/00006450-200010000-00020

Cited by 20 publications

(12 citation statements)

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“…In these cells, peroxisomes were formed when cells were cultured at 301C and peroxisomal parameters and the import of peroxisomal enzymes were restored. This phenomenon has been reported for patients belonging to CG1 (PEX1) [Imamura et al, 1998a], CG4 (PEX6) [Imamura et al, 2000b], CG8 (PEX26) [Imamura et al, 2001], CG10 (PEX2) [Imamura et al, 1998b], and CG13 (PEX13) [Shimozawa et al, 1999].…”

Section: Introductionsupporting

confidence: 60%

Identification of the molecular defect in patients with peroxisomal mosaicism using a novel method involving culturing of cells at 40°C: Implications for other inborn errors of metabolism

et al. 2004

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The peroxisome biogenesis disorders (PBDs), which comprise Zellweger syndrome (ZS), neonatal adrenoleukodystrophy, and infantile Refsum disease (IRD), represent a spectrum of disease severity, with ZS being the most severe, and IRD the least severe disorder. The PBDs are caused by mutations in one of the at least 12 different PEX genes encoding proteins involved in the biogenesis of peroxisomes. We report the biochemical characteristics and molecular basis of a subset of atypical PBD patients. These patients were characterized by abnormal peroxisomal plasma metabolites, but otherwise normal to very mildly abnormal peroxisomal parameters in cultured skin fibroblasts, including a mosaic catalase immunofluorescence pattern in fibroblasts. Since this latter feature made standard complementation analysis impossible, we developed a novel complementation technique in which fibroblasts were cultured at 40 degrees C, which exacerbates the defect in peroxisome biogenesis. Using this method, we were able to assign eight patients to complementation group 3 (CG3), followed by the identification of a single homozygous c.959C>T (p.S320F) mutation in their PEX12 gene. We also investigated various peroxisomal biochemical parameters in fibroblasts at 30 degrees C, 37 degrees C, and 40 degrees C, and found that all parameters showed a temperature-dependent behavior. The principle of culturing cells at elevated temperatures to exacerbate the defect in peroxisome biogenesis, and thereby preventing certain mutations from being missed, may well have a much wider applicability for a range of different inborn errors of metabolism.

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Section: Introductionsupporting

confidence: 60%

Identification of the molecular defect in patients with peroxisomal mosaicism using a novel method involving culturing of cells at 40°C: Implications for other inborn errors of metabolism

et al. 2004

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“…Moreover, a large proportion of Pex13p is unfolded even at a normal body temperature, but the residual adaptor activity by correctly folded proteins can somehow maintain peroxisomal functions as shown in the residual activity of the fatty acid metabolism (4,8). In PBD, TS phenotypes in Pex1, Pex2, and Pex6 with milder forms have been reported (26,27) and therapeutic effects have been reported in cells from patients with milder phenotypes, but not those with the severe phenotype, ZS (28). Treatment of PBD fibroblasts with 4-phenylbutyrate showed an induction of peroxisomes having a 2-fold increase in transcription of related genes.…”

Section: Discussionmentioning

confidence: 99%

Molecular Mechanism of a Temperature-Sensitive Phenotype in Peroxisomal Biogenesis Disorder

et al. 2005

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Peroxisomal biogenesis disorders include Zellweger syndrome and milder phenotypes, such as neonatal adrenoleukodystrophy (NALD). Our previous study of a NALD patient with a marked deterioration by a fever revealed a mutation (Ile326Thr) within a SH3 domain of PEX13 protein (Pex13p), showing a temperature-sensitive (TS) phenotype in peroxisomal biogenesis. Clinical TS phenotypes also have been reported in several genetic diseases, but the molecular mechanisms still remain to be clarified. The immunofluorescent staining with anti-Pex13p antibody also revealed TS phenotype of the I326T mutant protein itself in the patient cells. Protease digestion of the recombinant Pex13p-SH3 domain showed an increase of protease susceptibility, suggesting a problem of mutant protein fold. Conformational analyses against urea denaturation using urea gradient gel electrophoresis or fluorescence emission from tryptophan residue revealed that the mutant protein should be easily unfolded. Far-UV circular dichroism (CD) spectra demonstrated that both wild-type and the mutant protein have antiparallel beta-sheets as their secondary structure with slightly different extent. The thermal unfolding profiles measured by CD showed a marked lower melting temperature for I326T protein compared with that of wild-type protein. Analysis of the protein 3D-structure indicated that the Ile326 should be a core residue for folding kinetics and the substitution of Ile326 by threonine should directly alter the kinetic equilibrium, suggesting a marked increase of the unfolded molecules when the patient had a high fever. Peroxisomal disorders represent an expanding group of genetic disorders in humans and comprise ‫02ف‬ different disorders (1,2). Generally, peroxisomal disorders are divided into two groups; PBD (MIM#601539) and single peroxisomal enzyme deficiencies. PBD include ZS (MIM#214100), NALD (MIM#202370), infantile Refsum disease (MIM#266510), and rhizomelic chondrodysplasia punctata type 1 (MIM#215100). Our recent studies have shown that there is genetic heterogeneity among these patients, as concluded from complementation studies that have so far shown 13 different groups (3). The exact functional role of these different PEX gene products (peroxins) is largely unknown, but recent studies have revealed part of the importing mechanisms of peroxisomal proteins in association with peroxisome targeting signal receptors 1 and 2 (4).A central role in the peroxisomal assembly is played by the PEX13 protein (Pex13p)

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“…In terms of potential therapies, studies of cell lines from severe and mildly affected patients in other Zellweger spectrum complementation groups have shown that PEX gene-dependent, temperature-sensitive cell phenotypes are widespread among mildly affected patients [Imamura et al, 1998b[Imamura et al, , 2000a[Imamura et al, , 2000b. It is now generally accepted that the observed improvement in PEX1 protein function in these cells at permissive temperatures may reflect an increased stability of the residual mutated protein.…”

Section: Future Prospectsmentioning

confidence: 99%

PEX1mutations in the Zellweger spectrum of the peroxisome biogenesis disorders

2005

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Diseases of the Zellweger spectrum represent a major subgroup of the peroxisome biogenesis disorders, a group of autosomal-recessive diseases that are characterized by widespread tissue pathology, including neurodegeneration. The Zellweger spectrum represents a clinical continuum, with Zellweger syndrome (ZS) having the most severe phenotype, and neonatal adrenoleukodystrophy (NALD) and infantile Refsum disease (IRD) having progressively milder phenotypes. Mutations in the PEX1 gene, which encodes a 143-kDa AAA ATPase protein required for peroxisome biogenesis, are the most common cause of the Zellweger spectrum diseases. The PEX1 mutations identified to date comprise insertions, deletions, nonsense, missense, and splice site mutations. Mutations that produce premature truncation codons (PTCs) are distributed throughout the PEX1 gene, whereas the majority of missense mutations segregate with the two essential AAA domains of the PEX1 protein. Severity at the two ends of the Zellweger spectrum correlates broadly with mutation type and impact (i.e., the severe ZS correlates with PTCs on both alleles, and the milder phenotypes correlate with missense mutations), but exceptions to these general correlations exist. This article provides an overview of the currently known PEX1 mutations, and includes, when necessary, revised mutation nomenclature and genotype-phenotype correlations that may be useful for clinical diagnosis.

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Temperature-Sensitive Mutation of PEX6 in Peroxisome Biogenesis Disorders in Complementation Group C (CG-C): Comparative Study of PEX6 and PEX1

Cited by 20 publications

References 32 publications

Identification of the molecular defect in patients with peroxisomal mosaicism using a novel method involving culturing of cells at 40°C: Implications for other inborn errors of metabolism

Identification of the molecular defect in patients with peroxisomal mosaicism using a novel method involving culturing of cells at 40°C: Implications for other inborn errors of metabolism

Molecular Mechanism of a Temperature-Sensitive Phenotype in Peroxisomal Biogenesis Disorder

PEX1mutations in the Zellweger spectrum of the peroxisome biogenesis disorders

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