Fig. 2

Developmental expression of PS1 fragments in transgenic and nontransgenic hippocampal neurons. (A) Extracts from normal nontransgenic neuronal cultures were probed with the anti-PS1 C-terminal antibody 17.2 at different stages of development ranging from 4 hr to 12 days post-plating (lanes 1–5) to demonstrate the initial appearance of the proteolytic fragment and the later appearance of the full-length protein at ∼50 kD. An additional PS1 cross-reactive ∼98 kD band was observed at 4 hr (lane 1). Western blot analysis of cultures from transgenic animals expressing wtPS1 (lane 6) or M146L PS1 (lane 7) following differentiation for 12 days is also shown. (B) Homogenates of control nontransgenic neurons were probed with the N-terminal Ab14 antiserum at various stages of development, from 4 hr to 12 days (lanes 1–5). (C) PS1 immunoreactivity was examined in cultured transgenic neurons using the specific NT1 antibody which revealed that the human protein existed primarily in its cleaved form in wild-type (lanes 1, 2) and M146L mutants (lanes 3, 4). An additional and possibly nonspecific band at ∼64 kD was observed in the wtPS1 at day 12 (lane 2) which was not detected in the M146L mutant neurons.