Maturation and pro-peptide cleavage of beta-secretase

Amyloid beta-peptide is generated by two sequential proteolytic cleavages m ediated by beta-secretase (BACE) and gamma-secretase. PACE was recently ide ntified as a membrane-associated aspartyl protease. We have now analyzed th e maturation and pro-peptide cleavage of BACE. Pulse-chase experiments reve aled that BACE is posttranslationally modified during transport to the cell surface, which can be monitored by a significant increase in the molecular mass. The increase in molecular mass is caused by complex N-glycosylation. Treatment with tunicamycin and N-glycosidase F led to a PACE derivative wi th a molecular weight corresponding to an unmodified version. In contrast, the mature form of BACE was resistant to endoglycosidase Il treatment. The cytoplasmic tail of PACE was required for efficient maturation and traffick ing through the Golgi; a BACE variant lacking the cytoplasmic tail undergoe s inefficient maturation. In contrast a soluble BACE variant that does not contain a membrane anchor matured more rapidly than full-length BACE. Pro-B ACE was predominantly located within the endoplasmic reticulum, Propeptide cleavage occurred immediately before full maturation and trafficking throug h the Golgi.