Inhibition of BACE1 Activity by a DNA Aptamer in an Alzheimer's Disease Cell Model

An initial step in amyloid-beta (A beta) production includes amyloid precursor protein (APP) cleavage via beta-Site amyloid precursor protein cleaving enzyme 1 (BACE1). Increased levels of brain A beta have been implicated in the pathogenesis of Alzheimer's disease (AD). Thus, beta-secretase represents a primary target for inhibitor drug development in AD. In this study, aptamers were obtained from combinatorial oligonucleotide libraries using a technology referred to as systematic evolution of ligands by exponential enrichment (SELEX). A purified human BACE1 extracellular domain was used as a target to conduct an in vitro selection process using SELEX. Two DNA aptamers were capable of binding to BACE1 with high affinity and good specificity, with Kd values in the nanomolar range. We subsequently confirmed that one aptamer, A1, exhibited a distinct inhibitory effect on BACE1 activity in an AD cell model. We detected the effects of M17-APPsw cells that stably expressed Swedish mutant APP after aptamer A1 treatment. A beta 40 and A beta 42 concentrations secreted by M17-APPsw cells decreased intracellularly and in culture media. Furthermore, Western blot analysis indicated that sAPP beta expression significantly decreased in the A1 treated versus control groups. These findings support the preliminary feasibility of an aptamer evolved from a SELEX strategy to function as a potential BACE1 inhibitor. To our knowledge, this is the first study to acquire a DNA aptamer that exhibited binding specificity to BACE1 and inhibited its activity.