title: Novel beta-secretase cleavage of beta-amyloid precursor protein in the endoplasmic reticulum/intermediate compartment of NT2N cells.
abstract: Previous studies have demonstrated that NT2N neurons derived from a human embryonal carcinoma cell line (NT2) constitutively process the endogenous wild-type beta-amyloid precursor protein (APP) to amyloid beta peptide in an intracellular compartment. These studies indicate that other proteolytic fragments generated by intracellular processing must also be present in these cells. Here we show that the NH2-terminal fragment of APP generated by beta-secretase cleavage (APPbeta) is indeed produced from the endogenous full length APP (APPFL). Pulse-chase studies demonstrated a precursor-product relationship between APPFL and APPbeta as well as intracellular and secreted APPbeta fragments. In addition, trypsin digestion of intact NT2N cells at 4 degrees C did not abolish APPbeta recovered from the cell lysates. Furthermore, the production of intracellular APPbeta from wild-type APP appears to be a unique characteristic of postmitotic neurons, since intracellular APPbeta was not detected in several non-neuronal cell lines. Significantly, production of APPbeta occurred even when APP was retained in the ER/ intermediate compartment by inhibition with brefeldin A, incubation at 15 degrees C, or by expression of exogenous APP bearing the dilysine ER retrieval motif.
authors.affiliation: Department of Pathology and Laboratory Medicine, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: A S
authors.initials: AS
authors.lastname: Chyung
authors.forename: B D
authors.initials: BD
authors.lastname: Greenberg
authors.forename: D G
authors.initials: DG
authors.lastname: Cook
authors.forename: R W
authors.initials: RW
authors.lastname: Doms
authors.forename: V M
authors.initials: VM
authors.lastname: Lee
mesh_terms: D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D016282:Aspartic Acid Endopeptidases; D020126:Brefeldin A; D016466:CHO Cells; D002451:Cell Compartmentation; D006224:Cricetinae; D003517:Cyclopentanes / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism*; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006801:Humans; D009474:Neurons / Q000201:enzymology / Q000378:metabolism*; D010446:Peptide Fragments / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D014407:Tumor Cells, Cultured
chemical_list: D016564:Amyloid beta-Protein Precursor; D003517:Cyclopentanes; D010446:Peptide Fragments; D020126:Brefeldin A; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human