title: Independent relationship between amyloid precursor protein (APP) dimerization and γ-secretase processivity.
abstract: Altered production of β-amyloid (Aβ) from the amyloid precursor protein (APP) is closely associated with Alzheimer's disease (AD). APP has a number of homo- and hetero-dimerizing domains, and studies have suggested that dimerization of β-secretase derived APP carboxyl terminal fragment (CTFβ, C99) impairs processive cleavage by γ-secretase increasing production of long Aβs (e.g., Aβ1-42, 43). Other studies report that APP CTFβ dimers are not γ-secretase substrates. We revisited this issue due to observations made with an artificial APP mutant referred to as 3xK-APP, which contains three lysine residues at the border of the APP ectodomain and transmembrane domain (TMD). This mutant, which dramatically increases production of long Aβ, was found to form SDS-stable APP dimers, once again suggesting a mechanistic link between dimerization and increased production of long Aβ. To further evaluate how multimerization of substrate affects both initial γ-secretase cleavage and subsequent processivity, we generated recombinant wild type- (WT) and 3xK-C100 substrates, isolated monomeric, dimeric and trimeric forms of these proteins, and evaluated both ε-cleavage site utilization and Aβ production. These show that multimerization significantly impedes γ-secretase cleavage, irrespective of substrate sequence. Further, the monomeric form of the 3xK-C100 mutant increased long Aβ production without altering the initial ε-cleavage utilization. These data confirm and extend previous studies showing that dimeric substrates are not efficient γ-secretase substrates, and demonstrate that primary sequence determinants within APP substrate alter γ-secretase processivity.
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America; McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Joo In
authors.initials: JI
authors.lastname: Jung
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; College of Pharmacy, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Sasha
authors.initials: S
authors.lastname: Premraj
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America; McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Pedro E
authors.initials: PE
authors.lastname: Cruz
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America; McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Ladd
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Yewon
authors.initials: Y
authors.lastname: Kwak
authors.affiliation: Department of Neuroscience, University of California San Diego, La Jolla, California, United States of America.
authors.forename: Edward H
authors.initials: EH
authors.lastname: Koo
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America; McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Kevin M
authors.initials: KM
authors.lastname: Felsenstein
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America; McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Todd E
authors.initials: TE
authors.lastname: Golde
authors.affiliation: Center for Translational Research in Neurodegenerative Disease, University of Florida, Gainesville, Florida, United States of America; Department of Neuroscience, University of Florida, Gainesville, Florida, United States of America; McKnight Brain Institute, College of Medicine, University of Florida, Gainesville, Florida, United States of America.
authors.forename: Yong
authors.initials: Y
authors.lastname: Ran
mesh_terms: D053829:Amyloid Precursor Protein Secretases / Q000378:metabolism*; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D017077:Culture Media, Conditioned / Q000737:chemistry; D004797:Enzyme-Linked Immunosorbent Assay; D013058:Mass Spectrometry; D009154:Mutation; D055503:Protein Multimerization; D017434:Protein Structure, Tertiary; D011994:Recombinant Proteins / Q000737:chemistry
chemical_list: C545487:APP protein, human; D016564:Amyloid beta-Protein Precursor; D017077:Culture Media, Conditioned; D011994:Recombinant Proteins; D053829:Amyloid Precursor Protein Secretases