title: The Kunitz-protease inhibitor domain in amyloid precursor protein reduces cellular mitochondrial enzymes expression and function.
abstract: Mitochondrial dysfunction is a prominent feature of Alzheimer's disease (AD) and this can be contributed by aberrant metabolic enzyme function. But, the mechanism causing this enzymatic impairment is unclear. Amyloid precursor protein (APP) is known to be alternatively spliced to produce three major isoforms in the brain (APP695, APP751, APP770). Both APP770 and APP751 contain the Kunitz Protease Inhibitory (KPI) domain, but the former also contain an extra OX-2 domain. APP695 on the other hand, lacks both domains. In AD, up-regulation of the KPI-containing APP isoforms has been reported. But the functional contribution of this elevation is unclear. In the present study, we have expressed and compared the effect of the non-KPI containing APP695 and the KPI-containing APP751 on mitochondrial function. We found that the KPI-containing APP751 significantly decreased the expression of three major mitochondrial metabolic enzymes; citrate synthase, succinate dehydrogenase and cytochrome c oxidase (COX IV). This reduction lowers the NAD(+)/NADH ratio, COX IV activity and mitochondrial membrane potential. Overall, this study demonstrated that up-regulation of the KPI-containing APP isoforms is likely to contribute to the impairment of metabolic enzymes and mitochondrial function in AD.
authors.affiliation: Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Li-Min
authors.initials: LM
authors.lastname: Chua
authors.forename: Mei-Li
authors.initials: ML
authors.lastname: Lim
authors.forename: Boon-Seng
authors.initials: BS
authors.lastname: Wong
mesh_terms: D000544:Alzheimer Disease / Q000378:metabolism; D016564:Amyloid beta-Protein Precursor / Q000378:metabolism*; D002460:Cell Line; D002950:Citrate (si)-Synthase / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000378:metabolism; D005786:Gene Expression Regulation; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D008928:Mitochondria / Q000378:metabolism*; D009154:Mutation; D010446:Peptide Fragments / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D054730:Protein Interaction Domains and Motifs; D013385:Succinate Dehydrogenase / Q000378:metabolism; D015854:Up-Regulation
chemical_list: D016564:Amyloid beta-Protein Precursor; D018076:DNA, Complementary; D010446:Peptide Fragments; C093597:amyloid beta-protein precursor 695 (18-38); D013385:Succinate Dehydrogenase; D003576:Electron Transport Complex IV; D002950:Citrate (si)-Synthase
keywords: APP; KPI; Metabolic enzymes; Mitochondrial function