Amyloid-beta is a neurotoxic peptide which Is implicated In the pathogenesis of Alzheimer’s disease. It binds an intracellular polypeptide known as ERAB, thought to be a hydroxysteroid dehydrogenase enzyme, which Is expressed in normal tissues, but is overexpressed In neurons affected In Alzheimer’s disease, ERAB immunoprecipitates with amyloid-beta, and when cell cultures are exposed to amyloid-beta, ERAB inside the cell is rapidly redistributed to the plasma membrane, The toxic effect of amyloid-beta on these cells is prevented by blocking ERAB and is enhanced by overexpression of ERAB. By Interacting with intracellular amyloid-beta, ERAB may therefore contribute to the neuronal dysfunction associated with Alzheimer’s disease.