Structural characterization of variant forms of arylsulfatase A that associate with alcoholism.

Several electrophoretic forms of human platelet arylsulfatase A (ASA), including variant type IIIa and normal type IV(a), have been identified by nondenaturing polyacrylamide gel electrophoresis. An alcoholic population that we have analyzed is enriched in variant type IIIa compared with nonalcoholic psychiatric and normal controls. Individuals with the IIIa enzyme possess greatly reduced levels of ASA activity. To understand further the structural basis for the differences and their potential biological consequences, the nature of the ASA variant expressed by fibroblasts from different individuals was explored. The electrophoretic patterns of fibroblast ASA from the IIIa and IV(a) individuals differ in degree of phosphorylation. Furthermore, fibroblast ASA from IIIa individuals lacks an N-linked glycan found in ASA from IV(a) individuals. In addition, differences in peptide and/or posttranslational modification unrelated to the N-linked carbohydrate or phosphorylation exist between the fibroblast ASA from IIIa and IV(a) individuals. The finding that both fibroblasts and platelets exhibit related electrophoretic isoform patterns characteristic of the donor's ASA type allows for the use of fibroblasts to study the impact of ethanol on the metabolism of cells possessing different ASA types.