title: Inhibition of prolylendopeptidase does not affect gamma-secretase processing of amyloid precursor protein in a human neuroblastoma cell line.
abstract: Abeta peptides are major components of the amyloid plaques that characterize Alzheimer's disease. The enzyme activities (beta- and gamma-secretases) involved in generating Abeta from amyloid precursor protein (APP) are unidentified. It has been suggested that prolylendopeptidase (PEP), an oligopeptidase that normally cleaves after proline residues, could also cleave after the alanine at position 42 of Abeta to generate Abeta42. We investigated whether inhibition of PEP activity in human neuroblastoma cells affected Abeta levels in cell culture media. An SH-SY5Y cell line expressing SPA4CT, encoding the C-terminal 100 residues of APP and the signal sequence, was used. Only gamma-secretase activity is required for Abeta production in this cell line. The PEP inhibitor Fmoc-AlaPro-CN (10 microM) reduced PEP activity in these cells by approximately 95% in the absence of significant toxicity, but had no effect on Abeta40 or Abeta42 levels in cell culture media. We conclude that PEP is unlikely to be involved in gamma-secretase processing of APP.
authors.affiliation: The Queens University of Belfast, School of Biology and Biochemistry, Medical Biology Centre, Northern Ireland, UK. j.a.johnston@qub.ac.uk
authors.forename: J A
authors.initials: JA
authors.lastname: Johnston
authors.forename: M
authors.initials: M
authors.lastname: Jensen
authors.forename: L
authors.initials: L
authors.lastname: Lannfelt
authors.forename: B
authors.initials: B
authors.lastname: Walker
authors.forename: C H
authors.initials: CH
authors.lastname: Williams
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000187:drug effects* / Q000378:metabolism*; D016282:Aspartic Acid Endopeptidases; D001932:Brain Neoplasms / Q000201:enzymology*; D010450:Endopeptidases / Q000187:drug effects* / Q000378:metabolism*; D005449:Fluorenes / Q000494:pharmacology; D006801:Humans; D009447:Neuroblastoma / Q000201:enzymology*; D009842:Oligopeptides / Q000037:antagonists & inhibitors* / Q000187:drug effects* / Q000378:metabolism; D014407:Tumor Cells, Cultured / Q000187:drug effects* / Q000201:enzymology*
chemical_list: D000596:Amino Acids; D016564:Amyloid beta-Protein Precursor; D005449:Fluorenes; C016456:N(alpha)-fluorenylmethyloxycarbonylamino acids; D009842:Oligopeptides; C073248:Peptamen; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases; D016282:Aspartic Acid Endopeptidases; C509280:BACE1 protein, human