Intraperoxisomal Localization of Very-Long-Chain Fatty Acyl-CoA Synthetase: Implication in X-Adrenoleukodystrophy

Department of Pediatrics, Medical University of South Carolina, Charleston, South Carolina, 29425
Experimental Cell Research (Impact Factor: 3.25). 03/2000; 254(2):309-320. DOI: 10.1006/excr.1999.4757


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.

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    • "Products include acetyl-CoA and a shortened (by two carbons) acyl-CoA; the latter becomes the substrate for subsequent rounds of β-oxidation (Fig. 3). Whether VLCFA are activated intraperoxisomally or outside the peroxisome (and then transported into the organelle as VLCFA-CoA) has been the subject of some debate [15] [16] [17] [18] [19]. "
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    ABSTRACT: Peroxisomes carry out many essential lipid metabolic functions. Nearly all of these functions require that an acyl group-either a fatty acid or the acyl side chain of a steroid derivative-be thioesterified to coenzyme A (CoA) for subsequent reactions to proceed. This thioesterification, or "activation", reaction, catalyzed by enzymes belonging to the acyl-CoA synthetase family, is thus central to cellular lipid metabolism. However, despite our rather thorough understanding of peroxisomal metabolic pathways, surprisingly little is known about the specific peroxisomal acyl-CoA synthetases that participate in these pathways. Of the 26 acyl-CoA synthetases encoded by the human and mouse genomes, only a few have been reported to be peroxisomal, including ACSL4, SLC27A2, and SLC27A4. In this review, we briefly describe the primary peroxisomal lipid metabolic pathways in which fatty acyl-CoAs participate. Then, we examine the evidence for presence and functions of acyl-CoA synthetases in peroxisomes, much of which was obtained before the existence of multiple acyl-CoA synthetase isoenzymes was known. Finally, we discuss the role(s) of peroxisome-specific acyl-CoA synthetase isoforms in lipid metabolism. This article is part of a Special Issue entitled: Metabolic Functions and Biogenesis of Peroxisomes in Health and Disease.
    Biochimica et Biophysica Acta 02/2012; 1822(9):1411-20. DOI:10.1016/j.bbadis.2012.02.010 · 4.66 Impact Factor
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    • "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 [16] [17]. 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. "
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    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
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