Membrane inserted APP fragments containing the beta A4 sequence of Alzheimer's disease do not aggregate

Previously we have shown that the COOH-terminal fragment (A4CT) of the Alzheimer amyloid protein precursor (APP), which at the NH2-terminus carries the sequence of the amyloid beta A4 protein, forms highly insoluble aggregates [EMBO J. (1988) 7, 949-957]. Here we report that aggregation is prevented if A4CT is expressed in vitro with a signal sequence at the NH2-terminus (SPA4CT) under conditions which allow membrane insertion. Aggregates from SPA4CT are obtained after removal of membranes by chloroform/methanol extraction or heating.