Apoptotic cell death and amyloid precursor protein signaling in neuroblastoma SH-SY5Y cells.
We have recently shown that the amyloid precursor protein (APP) and a subset of its C-terminal fragments (CTFs) are tyrosine phosphorylated in human brain and in cultured cells. Tyrosine phosphorylation generates a substrate that is sequentially bound by the adaptor proteins ShcA and Grb2, and this interaction is significantly enhanced in Alzheimer's disease brains. Here we have studied the APP/CTFs phosphorylation and ShcA activation in a human neuroblastoma cell line, SH-SY5Y, under basal and apoptotic conditions. To commit these cells to apoptosis, we used staurosporin, a well-known apoptotic inducer and protein kinase C blocker. Our data suggest the following: (1) in normally proliferating SH-SY5Y cells, full-length APP is complexed with Grb2[Q3], likely through its SH2 domain; (2) upon induction of apoptosis, APP is degraded and ShcA-Grb2 coimmunoprecipitates with CTFs recognized by anti-APP antibodies; and (3) caspase inhibitors partially block the degradation of APP and the coprecipitation of CTFs with ShcA-Grb2 adaptors. In summary, our data suggest that in SH-SY5Y cells, tyrosine-phosphorylated APP is involved in a complex with ShcA-Grb2 adaptors that is disrupted during apoptosis. The abnormal degradation of APP and consequent increased levels of CTFs (as has been observed in Alzheimer's disease and Down's syndrome) generate a complex between tyrosine-phosphorylated CTFs and intracellular adaptors. The signaling through APP and its CTFs may have significant relevance for apoptotic cell death in Alzheimer's disease.
Venezia
Valentina
V
Sezione di Farmacologia, Dipartimento Oncologia Biologia e Genetica, Università degli Studi di Genova, Italy.
Russo
Claudio
C
Repetto
Emanuela
E
Nizzari
Mario
M
Violani
Elisabetta
E
Carlo
Pia
P
Marchetti
Bianca
B
Schettini
Gennaro
G
D000544:Alzheimer Disease / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D017209:Apoptosis; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction
D016564:Amyloid beta-Protein Precursor