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Fig. 2. sAPP participates in the EGF-induced proliferation of neurospheres. (A)
Schematic structure of human APP (695 amino acid form) indicating the
positions of the epitopes of 22C11 and 6 E10 antibodies. 
-sAPP, soluble
APP; Aß, amyloid ß-peptide; TM, transmembrane region. (B)
sAPP-binding sites (red) are detected on plated undifferentiated NS as a
punctuate membrane staining. Nuclei are counterstained with DAPI. Scale bar: 5
µm. (C) A constant number of NS were seeded in media with different
concentrations of EGF (0, 2 or 20 ng/ml). Secreted (upper panel) and cellular
(lower panel) APP were detected by immunoblotting. Secretion of sAPP is
augmented by increasing concentrations of EGF (2 ng/ml, 3.5 fold; 20 ng/ml,
5.9 fold increase relative to EGF-free medium) while cellular APP remains
largely constant. (D) Percentage of BrdU-positive NS cells after 15 hours of
culture in medium containing EGF (2 ng/ml) and BrdU without (control) or with
antibodies directed against sAPP (22C11, 6E10). Both antibodies decrease
proliferation of NS cells. This decrease is abolished by pre-adsorption of the
antibodies with their epitopes or by co-incubating 22C11 and sAPP. Results are
shown as mean±s.e.m. of three independent experiments.
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