Lipid rafts of purified mouse brain synaptosomes prepared with or without detergent reveal different lipid and protein domains.

Lipid rafts have been proposed to be important in a variety of functions including lipid transport, signal transduction and cell growth. There is increasing evidence that lipid rafts may play a role in cell functions in brain. Lipid rafts are typically isolated using a detergent such as Triton X-100. There has been, however, data from non-brain tissue indicating that preparation of lipid rafts using a detergent may represent different raft domains as compared with non-detergent preparation. The purpose of the present study was to compare protein and lipid markers of lipid rafts using a highly purified mouse synaptosomal fraction and non-detergent and detergent methods. The lipid raft marker proteins, alkaline phosphatase and flotillin, and the lipid markers, cholesterol and sphingomyelin, were highly enriched in lipid rafts prepared with detergent as compared with the non-detergent fraction. Enrichment of Na(+),K(+)-ATPase was greater in the non-detergent lipid raft fraction as compared with lipid rafts prepared with detergent. Lipid rafts from the nerve terminal of neurons prepared with or without detergents may represent different membrane domains each with unique specialized functions.