Amyloid beta (Abeta) is a pathological hallmark of Alzheimer's disease (AD). It is derived from the amyloid precursor protein (APP) by two sequential proteolytic cleavages, which also generate the APP intracellular domain (AICD). The precise cellular function(s) of AICD still remain obscure. To elucidate the roles of AICD in the development of AD, a yeast two-hybrid system was used to screen a human brain cDNA library for proteins interacting directly with AICD. One of the potential AICD-interacting proteins identified from our screening result is a lipid raft-associated protein, flotillin-1. The interaction was confirmed by glutathione S-transferase pull-down and coimmunoprecipitation studies. Since lipid raft has been suggested to play an important role in signal transduction as well as the pathogenic development of neurodegenerative diseases, it is proposed that flotillin-1 may recruit APP to lipid rafts and therefore participate in the localization and processing of APP.