digitonin and Adrenoleukodystrophy

In the yeast Saccharomyces cerevisiae, fatty acid beta-oxidation is restricted to peroxisomes. Previous studies have shown two possible routes by which fatty acids enter the peroxisome. The first route involves transport of medium-chain fatty acids across the peroxisomal membrane as free fatty acids, followed by activation within the peroxisome by Faa2p, an acyl-CoA synthetase. The second route involves transport of long-chain fatty acids. Long-chain fatty acids enter the peroxisome via a route that involves activation in the extraperoxisomal space, followed by transport across the peroxisomal membrane. It has been suggested that this transport is dependent upon the peroxisomal ATP-binding-cassette transporters Pxa1p and Pxa2p. In this paper we investigated whether Pxa2p is directly responsible for the transport of C18:1-CoA, a long-chain acyl-CoA ester. Using protoplasts in which the plasma membrane has been selectively permeabilised by digitonin, we show that C18:1-CoA, but not C8:0-CoA, enters the peroxisome via Pxa2p, in an ATP-dependent fashion. The results obtained may contribute to the elucidation of the primary defect in the human disease X-linked adrenoleukodystrophy.

Topics: Acyl Coenzyme A; Adenosine Triphosphate; Adrenoleukodystrophy; ATP-Binding Cassette Transporters; Biological Transport; Cell Membrane Permeability; Digitonin; Fatty Acids; Fungal Proteins; Humans; Microbodies; Oxidation-Reduction; Protoplasts; Saccharomyces cerevisiae; Saccharomyces cerevisiae Proteins

We have used complementation analysis after somatic cell fusion to investigate the genetic relationships among various genetic diseases in humans in which there is a simultaneous impairment of several peroxisomal functions. The activity of acyl-coenzyme A:dihydroxyacetonephosphate acyltransferase, which is deficient in these diseases, was used as an index of complementation. In some of these diseases peroxisomes are deficient and catalase is present in the cytosol, so that the appearance of particle-bound catalase could be used as an index of complementation. The cell lines studied can be divided into at least five complementation groups. Group 1 is represented by a cell line from a patient with the rhizomelic form of chondrodysplasia punctata. Group 2 consists of cell lines from four patients with the Zellweger syndrome, a patient with the infantile form of Refsum disease and a patient with hyperpipecolic acidemia. Group 3 comprises one cel line from a patient with the Zellweger syndrome, group 4 one cell line from a patient with the neonatal form of adrenoleukodystrophy, and group 5 one cell line from a patient with the Zellweger syndrome. We conclude that at least five genes are required for the assembly of a functional peroxisome.

Topics: Acyltransferases; Adrenoleukodystrophy; Catalase; Cell Fusion; Cell Line; Centrifugation, Density Gradient; Chondrodysplasia Punctata; Digitonin; Fibroblasts; Genetic Complementation Test; Humans; Metabolism, Inborn Errors; Microbodies; Refsum Disease; Syndrome