Figure 1.

Cholesterol depletion inhibits β-cleavage. (A) N2a cells were grown in the presence (+) or absence (−) of lovastatin/ mevalonate/delipidated FCS and 10 h after infection with adenoviruses to express wtAPP treated with 10 mM MβCD for the indicated times. Cells were then labeled with [³⁵S]methionine for 40 min and chased for 2 h. Immunoprecipitations of extracellular medium (Aβ; antibody 70JE) and cell lysate (total wtAPP; antibody IP60) revealed that Aβ secretion decreased after cholesterol depletion. The extent of cholesterol depletion was determined as described in Materials and methods. (B) 10 h after infection with adenoviruses to express swAPP, N2a cells were labeled for 30 min and chased for 30 min in the presence of 10 mM MβCD (leading to an ∼40–50% decrease in total cellular cholesterol). Immunoprecipitations from extracellular medium (antibody 6E10) and cell lysate (antibody IP60) showed a decreased production of Aβ and the COOH-terminal fragment generated by β-cleavage (βCTF). At the same time, the COOH-terminal fragment generated by α-cleavage (αCTF) and the soluble ectodomain generated by α-cleavage (αAPPs) were increased.