title: gamma-Cleavage is dependent on zeta-cleavage during the proteolytic processing of amyloid precursor protein within its transmembrane domain.
abstract: beta-Amyloid precursor protein apparently undergoes at least three major cleavages, gamma-, epsilon-, and the newly identified zeta-cleavage, within its transmembrane domain to produce secreted beta-amyloid protein (Abeta). However, the roles of epsilon- and zeta-cleavages in the formation of secreted Abeta and the relationship among these three cleavages, namely epsilon-, zeta-, and gamma-cleavages, remain elusive. We investigated these issues by attempting to determine the formation and turnover of the intermediate products generated by these cleavages, in the presence or absence of known gamma-secretase inhibitors. By using a differential inhibition strategy, our data demonstrate that Abeta(46) is an intermediate precursor of secreted Abeta. Our co-immunoprecipitation data also reveal that, as an intermediate, Abeta(46) is tightly associated with presenilin in intact cells. Furthermore, we identified a long Abeta species that is most likely the long sought after intermediate product, Abeta(49), generated by epsilon-cleavage, and this Abeta(49) is further processed by zeta- and gamma-cleavages to generate Abeta(46) and ultimately the secreted Abeta(40/42). More interestingly, our data demonstrate that gamma-cleavage not only occurs last but also depends on zeta-cleavage occurring prior to it, indicating that zeta-cleavage is crucial for the formation of secreted Abeta. Thus, we conclude that the C terminus of secreted Abeta is most likely generated by a series of sequential cleavages, namely first epsilon-cleavage which is then followed by zeta- and gamma-cleavages, and that Abeta(46) produced by zeta-cleavage is the precursor of secreted Abeta(40/42).
authors.affiliation: Department of Pathobiology, College of Veterinary Medicine, the University of Tennessee, Knoxville, 37996, USA.
authors.forename: Guojun
authors.initials: G
authors.lastname: Zhao
authors.forename: Mei-Zhen
authors.initials: MZ
authors.lastname: Cui
authors.forename: Guozhang
authors.initials: G
authors.lastname: Mao
authors.forename: Yunzhou
authors.initials: Y
authors.lastname: Dong
authors.forename: Jianxin
authors.initials: J
authors.lastname: Tan
authors.forename: Longsheng
authors.initials: L
authors.lastname: Sun
authors.forename: Xuemin
authors.initials: X
authors.lastname: Xu
mesh_terms: D053829:Amyloid Precursor Protein Secretases; D016564:Amyloid beta-Protein Precursor / Q000737:chemistry* / Q000378:metabolism*; D000818:Animals; D002219:Carbamates / Q000494:pharmacology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D002474:Cell-Free System; D004151:Dipeptides / Q000494:pharmacology; D010450:Endopeptidases / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D011499:Protein Processing, Post-Translational; D017434:Protein Structure, Tertiary
chemical_list: D016564:Amyloid beta-Protein Precursor; D002219:Carbamates; D004151:Dipeptides; D004791:Enzyme Inhibitors; C410009:L 685458; D053829:Amyloid Precursor Protein Secretases; D010450:Endopeptidases