HUMAN IMR-32 NEUROBLASTOMA-CELLS AS A MODEL CELL-LINE IN ALZHEIMERS-DISEASE RESEARCH

The present study investigated expression and processing of amyloid pr ecursor protein by neuronally differentiated IMR-32 neuroblastoma cell s. APP mRNA in these cells was found to consist of approximately 58% A PP(695), 38% APP(751), and <4% APP(770). APP-immunoreactive bands dete cted in western blots of cellular protein extracts were only detected by anti-APP antibodies to peptides with strong homology to APLP2, sugg esting that these bands represent APP-like proteins and not APP itself . This result suggests that previous studies claiming immunodetection of cellular forms of APP may have to be re-evaluated. Four main specie s of C-terminal truncated, secreted APP were detected in blots of prot ein extracts from medium conditioned by these cells. The immunoreactiv e profile of these bands suggested a cleavage site N-terminal to the L ys(16)-Leu(17) bond of alpha-secretase. This, together with difference s in number and molecular mass of APP-immunoreactive bands between sec reted APP from IMR-32 cells and that from the commonly used PC-12 cell s, suggests differences in APP processing between these two neuronally differentiated cell lines. In theory, IMR-32 cells being of human neu ronal origin may be a more appropriate cell line to study APP-processi ng in relation to Alzheimer's disease than the rat phaeochromocytoma P C-12 cell line. Therefore, these detected differences warrant further investigation. Additionally IMR-32 cells under certain tissue culture conditions can form intracellular fibrillary material that reacts with anti-PHF specific antibodies. Neuronally differentiated IMR-32 cells could therefore be used as a model system to investigate possible inte ractions between APP-processing and PHF formation. (C) 1994 Wiley-Liss , Inc.