BACE2 degradation is mediated by both the proteasome and lysosome pathways

Background Alzheimer's disease is the most common neurodegenerative disease in the elderly. Amyloid-beta protein (A beta) is the major component of neuritic plaques which are the hallmark of AD pathology. beta-site APP cleaving enzyme 1 (BACE1) is the major beta-secretase contributing to A beta generation. beta-site APP-cleaving enzyme 2 (BACE2), the homolog of BACE1, might play a complex role in the pathogenesis of Alzheimer's disease as it is not only a theta-secretase but also a conditional beta-secretase. Dysregulation of BACE2 is observed in Alzheimer's disease. However, the regulation of BACE2 is less studied compared with BACE1, including its degradation pathways. In this study, we investigated the turnover rates and degradation pathways of BACE2 in both neuronal cells and non-neuronal cells. Results Both lysosomal inhibition and proteasomal inhibition cause a time- and dose-dependent increase of transiently overexpressed BACE2 in HEK293 cells. The half-life of transiently overexpressed BACE2 protein is approximately 6 h. Moreover, the half-life of endogenous BACE2 protein is approximately 4 h in both HEK293 cells and mouse primary cortical neurons. Furthermore, both lysosomal inhibition and proteasomal inhibition markedly increases endogenous BACE2 in HEK293 cells and mouse primary cortical neurons. Conclusions This study demonstrates that BACE2 is degraded by both the proteasome and lysosome pathways in both neuronal and non-neuronal cells at endogenous level and in transient overexpression system. It indicates that BACE2 dysregulation might be mediated by the proteasomal and lysosomal impairment in Alzheimer's disease. This study advances our understanding of the regulation of BACE2 and provides a potential mechanism of its dysregulation in Alzheimer's disease.