RCAN1 Inhibits BACE2 Turnover by Attenuating Proteasome-Mediated BACE2 Degradation

Amyloid-beta protein (A beta) is the main component of neuritic plaques, the pathological hallmark of Alzheimer's disease (AD).beta-site APP cleaving enzyme 1 (BACE1) is a major beta-secretase contributing to A beta generation.beta-site APP cleaving enzyme 2 (BACE2), the homolog of BACE1, is not only a theta-secretase but also a conditional beta-secretase. Previous studies showed that regulator of calcineurin 1 (RCAN1) is markedly increased by AD and promotes BACE1 expression. However, the role of RCAN1 in BACE2 regulation remains elusive. Here, we showed that RCAN1 increases BACE2 protein levels. Moreover, RCAN1 inhibits the turnover of BACE2 protein. Furthermore, RCAN1 attenuates proteasome-mediated BACE2 degradation, but not lysosome-mediated BACE2 degradation. Taken together, our work indicates that RCAN1 inhibits BACE2 turnover by attenuating proteasome-mediated BACE2 degradation. It advances our understanding of BACE2 regulation and provides a potential mechanism of BACE2 dysregulation in AD.