Amyloid beta-protein precursor (APP) of cultured cells: secretory and non-secretory forms of APP.

Overproduction or aberrant catabolism of the predicted amyloid beta-protein precursor (APP) is suspected as the cause of amyloid deposition in Alzheimer's disease and Down's syndrome brains. For possible in vitro experiments of amyloid formation, we have examined the expression of APP in various cultured cells. We found two types of APP producing cell lines. PC12h (rat pheochromocytoma) and HL-60 (human acute promyelocytic leukemia) cells produce a secretory form that is released into the culture medium, while Bu-17 (human glioma) cells synthesize only a non-secretory form that accumulates at the cell surface. APP immunoreactivity on the latter cells was detected at the tips of cell processes or growth cones. These observations indicate that the nonsecretory form of APP may play a role in cell contact or adhesion.