The Presence of Amyloid β-Protein in the Detergent-Insoluble Membrane Compartment of Human Neuroblastoma Cells

To investigate the intracellular compartmentalization of amyloid beta-protein (Abeta), human neuroblastoma SH-SY5Y cells were fractionated and the Abeta content in each fraction was quantitated by the well-characterized two-site enzyme-linked immunosorbent assay (ELISA). Subcellular fractionation of the cell revealed two distinct pools of Abeta within the cells: a Triton-soluble and a Triton-insoluble pools with the latter being larger than the former. Because Triton insolubility points to caveolae-like domains, we prepared detergent-insoluble, low-density membrane domains from SH-SY5Y cells using two different protocols. The low-density membrane fraction prepared by either protocol was found to contain a substantial proportion of intracellular Abeta40 and Abeta42. These results indicate that the distinct membrane domains are involved in the generation and/or trafficking of Abeta.