MODULATED INDUCTION OF TAU-PROTEIN IN CULTURED HUMAN NEUROBLASTOMA-CELLS

Previous studies indicated that a chemically-defined, differentiation medium (DM) induces neuroblastoma cells, especially IMR32K cells, to e xhibit phenotypes of mature neurons (including neurite outgrowth and s ynthesis of neurofilament polypeptides) and develop certain attributes of the neurons which are affected by neurofibrillary degeneration in Alzheimer's disease, such as expression of tangle-associated epitopes and accumulation of paired helical filaments-(PHF-) like fibrils. Immu nocytochemical staining suggested that this cytoskeletal abnormality m ost likely results from altered expression of tau proteins. In the cur rent study, we addressed this issue by analyzing tau-enriched preparat ions of IMR32K cells that were previously exposed to different incubat ion media using a panel of antibodies specific to tau and related micr otubule-associated proteins. These cultured cells exhibited three grou ps of tau immunoreactivities which differ in molecular weight. Among t hem the level of high molecular weight tau (MW 90-112 kDa) was selecti vely augmented after DM incubation. The tau proteins produced in these neuron-like cells shared phosphorylated sites with PHF-tau and fetal tau, but differed from PHF-tau in their lack of the N-terminal insert which characterizes adult isoforms.