Adrenoleukodystrophy protein enhances association of very long-chain acyl-coenzyme A synthetase with the peroxisome

Objective: To clarify the function of adrenoleukodystrophy protein (ALDP) using our ALDP-deficient mice established by gene targeting. Background: X-linked adrenoleukodystrophy (ALD) is characterized biochemically by the accumulation of very long-chain fatty acids (VLCFA) in tissues and body fluids, and is caused by impairment of peroxisomal β-oxidation. In ALD, very long-chain acyl-coenzyme A synthetase (VLACS), which is necessary for peroxisomal β-oxidation, does not function. Methods: The ALDP-deficient mice and C57BL/6J mice were used. VLACS or ALDP were transiently expressed by lipofection in murine fibroblasts, and VLCFA β-oxidation was assayed. Liver peroxisomes were purified by sequential centrifugations and a Nycodenz gradient centrifugation. The peroxisomal localization of VLACS was compared between the mutant and control mice using a Western blot analysis. Results: Impairment of VLCFA β-oxidation in ALDP-deficient fibroblasts was not corrected by the additional expression of VLACS alone but was by the coexpression of VLACS and ALDP. Although the tissue-specific expression of VLACS was similar in ALDP-deficient and normal mice, peroxisomal VLACS was clearly lower in ALDP-deficient than in normal mice. Conclusions: ALDP plays a role in the peroxisomal localization of VLACS, and VLACS does not function unless localized in the peroxisome.