HUMAN NEURONS DERIVED FROM A TERATOCARCINOMA CELL-LINE EXPRESS SOLELYTHE 695-AMINO ACID AMYLOID PRECURSOR PROTEIN AND PRODUCE INTRACELLULAR BETA-AMYLOID OR A4 PEPTIDES

The beta-amyloid or beta/A4 peptides that accumulate as filamentous ag gregates in the extracellular space of Alzheimer disease (AD) brains a re derived from one or more alternatively spliced amyloid precursor pr oteins (APPs). The more abundant APPs in the central nervous system ar e the 695- (APP695), 751- (APP751), and 770- (APP770) amino acid isofo rms, and each could be the source of beta/A4 peptide that accumulates in the AD brain. It is plausible that altered metabolism of these APPs by central nervous system neurons could lead to the release and depos ition of beta/A4 peptide in brain parenchyma. Thus, we examined the ex pression and processing of the three major brain APPs in nearly pure h uman neurons (NT2N cells) derived from a teratocarcinoma cell line (NT era2/c1.D1 or NT2 cells) after retinoic acid treatment. NT2N neurons e xpressed almost exclusively APP695, whereas NT2 cells expressed predom inantly APP751/770. Furthermore, the processing of the APPs in NT2N ce lls was distinct from NT2 and nonneuronal cells. Most significantly, t he NT2N neurons but not the NT2 cells constitutively generated intrace llular beta/A4 peptide and released it into the culture medium. This w ork demonstrates the intracellular production of beta/A4 peptide and s uggests that cultured NT2N cells may provide a unique model system for understanding the contribution of neurons and APP695 to amyloidogenes is in the AD brain.