Altered Proteolysis in Fibroblasts of Alzheimer Patients with Predictive Implications for Subjects at Risk of Disease

Figure 4

BACE1 activation by fibroblast culture conditions. Fibroblasts from two healthy aging control subjects (Cont 1 and Cont 2), from 6 probable AD patients (AD1-6), two of whom resulted negative to the TK-ab test (AD5 and AD6), and from two AD relatives (Rel 1 and Rel 2) were cultured under conditions favoring TK-ab production (positive) and under normal conditions (negative). Three immunoreactive bands of BACE1 protein were detected, corresponding to the precursor protein (inactive BACE1) (~50 KDa) and to two glycosylated active enzyme forms (active BACE1, within the range of 70–80 KDa), as shown in the insert. BACE1 proteins were quantified by densitometric analysis using GAPDH as the housekeeping; then the ratio between protein amounts in positive and negative culture conditions was calculated and reported for each subject.