title: Aminopeptidase A contributes to the N-terminal truncation of amyloid beta-peptide.
abstract: Several lines of data previously indicated that N-terminally truncated forms of amyloid-beta (Abeta) peptides are likely the earliest and more abundant species immunohistochemically detectable in Alzheimer's disease-affected brains. It is noteworthy that the free N-terminal residue of full-length Abeta (fl-Abeta) is an aspartyl residue, suggesting that Abeta could be susceptible to exopeptidasic attack by aminopeptidase A (APA)-like proteases. In this context, we have examined whether APA could target Abeta peptides in both cell-free and cellular models. We first show that the general aminopeptidase inhibitor amastatin as well as two distinct aminopeptidase A inhibitors EC33 and pl302 both significantly increase the recovery of genuine fl-Abeta peptides generated by cells over-expressing Swedish-mutated beta amyloid precursor protein (APP) while the aminopeptidase N blocker pl250 did not modify fl-Abeta recovery. In agreement with this observation, we establish that over-expressed APA drastically reduces, in a calcium dependent manner, fl-Abeta but not APP IntraCellular Domain in a cell-free model of Abeta production. In agreement with the above data, we show that recombinant APA degrades fl-Abeta in a pl302-sensitive manner. Interestingly, we also show that EC33 and pl302 lower staurosporine-stimulated activation of caspase-3 in wild-type fibroblasts but not in betaAPP/beta-amyloid precursor protein-like protein 2 (APLP2) double knockout fibroblasts, suggesting that protecting endogenous fl-Abeta physiological production triggers neuroprotective phenotype. By contrast, EC33 does not modify staurosporine-induced caspase-3 activation in wild-type and Swedish-mutated betaAPP-HEK293 expressing cells that display exacerbated production of Abeta. Overall, our data establish that APA contributes to the N-terminal truncation of Abeta and suggest that this cleavage is likely abrogating a protective function associated with physiological but not supraphysiological levels of genuine fl-Abeta peptides.
authors.affiliation: Institut de Pharmacologie Moléculaire et Cellulaire and Institut de NeuroMédecine Moléculaire, UMR6097 CNRS/UNSA, Equipe labellisée Fondation pour la Recherche Médicale, Sophia-Antipolis, Valbonne, France.
authors.forename: Jean
authors.initials: J
authors.lastname: Sevalle
authors.forename: Audrey
authors.initials: A
authors.lastname: Amoyel
authors.forename: Philippe
authors.initials: P
authors.lastname: Robert
authors.forename: Marie-Claude
authors.initials: MC
authors.lastname: Fournié-Zaluski
authors.forename: Bernard
authors.initials: B
authors.lastname: Roques
authors.forename: Frédéric
authors.initials: F
authors.lastname: Checler
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002460:Cell Line; D043384:Glutamyl Aminopeptidase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D006801:Humans; D051379:Mice; D018345:Mice, Knockout; D010446:Peptide Fragments / Q000737:chemistry* / Q000378:metabolism*; D010455:Peptides / Q000502:physiology; D017434:Protein Structure, Tertiary
chemical_list: D016229:Amyloid beta-Peptides; D010446:Peptide Fragments; D010455:Peptides; C016977:amastatin; D043384:Glutamyl Aminopeptidase