Intraperoxisomal Localization of Very-Long-Chain Fatty Acyl-CoA Synthetase: Implication in X-Adrenoleukodystrophy
ABSTRACT X-Adrenoleukodystrophy (X-ALD) is a demyelinating disorder characterized by the accumulation of saturated very-long-chain (VLC) fatty acids (>C22:0) due to the impaired activity of VLC acyl-CoA synthetase (VLCAS). The gene responsible for X-ALD was found to code for a peroxisomal integral membrane protein (ALDP) that belongs to the ATP binding cassette superfamily of transporters. To understand the function of ALDP and how ALDP and VLCAS interrelate in the peroxisomal β-oxidation of VLC fatty acids we investigated the peroxisomal topology of VLCAS protein. Antibodies raised against a peptide toward the C-terminus of VLCAS as well as against the N-terminus were used to define the intraperoxisomal localization and orientation of VLCAS in peroxisomes. Indirect immunofluorescent and electron microscopic studies show that peroxisomal VLCAS is localized on the matrix side. This finding was supported by protease protection assays and Western blot analysis of isolated peroxisomes. To further address the membrane topology of VLCAS, Western blot analysis of total membranes or integral membranes prepared from microsomes and peroxisomes indicates that VLCAS is a peripheral membrane-associated protein in peroxisomes, but an integral membrane in microsomes. Moreover, peroxisomes isolated from cultured skin fibroblasts from X-ALD patients with a mutation as well as a deletion in ALDP showed a normal amount of VLCAS. The consequence of VLCAS being localized to the luminal side of peroxisomes suggests that ALDP may be involved in stabilizing VLCAS activity, possibly through protein–protein interactions, and that loss or alterations in these interactions may account for the observed loss of peroxisomal VLCAS activity in X-ALD.
- SourceAvailable from: Ronald J A Wanders
[Show abstract] [Hide abstract]
- "It will be important to study the tissue and cellular pattern of ABCD1 expression to determine where and at which developmental period(s) the function of ALDP is necessary  . These studies and a comparison between human and mouse might offer an explanation as to why the same biochemical deficiency can lead to an inflammatory demyelinating disorder in humans but not in mice. "
ABSTRACT: Plasmalogens (1-O-alk-1'-enyl-2-acyl glycerophospholipids) constitute a special class of phospholipids characterized by the presence of a vinyl-ether bond at the sn-1 position. Although long considered as biological peculiarities, interest in this group of phospholipids has grown in recent years, thanks to the realization that plasmalogens are involved in different human diseases. In this review, we summarize the current state of knowledge with respect to the enzymatic synthesis of plasmalogens, the characteristic topology of the enzymes involved and the biological roles that have been assigned to plasmalogens.Biochimica et Biophysica Acta 04/2004; 1636(2-3):219-31. DOI:10.1016/j.bbalip.2003.12.010 · 4.66 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Peroxisomes are important organelles in plant metabolism, containing all the enzymes required for fatty acid beta-oxidation. More than 20 proteins are required for peroxisomal biogenesis and maintenance. The Arabidopsis pxa1 mutant, originally isolated because it is resistant to the auxin indole-3-butyric acid (IBA), developmentally arrests when germinated without supplemental sucrose, suggesting defects in fatty acid beta-oxidation. Because IBA is converted to the more abundant auxin, indole-3-acetic acid (IAA), in a mechanism that parallels beta-oxidation, the mutant is likely to be IBA resistant because it cannot convert IBA to IAA. Adult pxa1 plants grow slowly compared with wild type, with smaller rosettes, fewer leaves, and shorter inflorescence stems, indicating that PXA1 is important throughout development. We identified the molecular defect in pxa1 using a map-based positional approach. PXA1 encodes a predicted peroxisomal ATP-binding cassette transporter that is 42% identical to the human adrenoleukodystrophy (ALD) protein, which is defective in patients with the demyelinating disorder X-linked ALD. Homology to ALD protein and other human and yeast peroxisomal transporters suggests that PXA1 imports coenzyme A esters of fatty acids and IBA into the peroxisome for beta-oxidation. The pxa1 mutant makes fewer lateral roots than wild type, both in response to IBA and without exogenous hormones, suggesting that the IAA derived from IBA during seedling development promotes lateral root formation.Plant physiology 12/2001; 127(3):1266-78. DOI:10.1104/pp.127.3.1266 · 7.39 Impact Factor