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Degradation of the amyloid beta-protein by the novel mitochondrial peptidasome, PreP.
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. (E. Glaser)
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. (E. Glaser)
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. (E. Glaser)
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics. (E. Glaser)
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2006 (English)In: Journal of Biological Chemistry, ISSN 0021-9258, Vol. 281, no 39, 29096-29104 p.Article in journal (Refereed) Published
Abstract [en]

Recently we have identified the novel mitochondrial peptidase responsible for degrading presequences and other short unstructured peptides in mitochondria, the presequence peptidase, which we named PreP peptidasome. In the present study we have identified and characterized the human PreP homologue, hPreP, in brain mitochondria, and we show its capacity to degrade the amyloid beta-protein (Abeta). PreP belongs to the pitrilysin oligopeptidase family M16C containing an inverted zinc-binding motif. We show that hPreP is localized to the mitochondrial matrix. In situ immuno-inactivation studies in human brain mitochondria using anti-hPreP antibodies showed complete inhibition of proteolytic activity against Abeta. We have cloned, overexpressed, and purified recombinant hPreP and its mutant with catalytic base Glu(78) in the inverted zinc-binding motif replaced by Gln. In vitro studies using recombinant hPreP and liquid chromatography nanospray tandem mass spectrometry revealed novel cleavage specificities against Abeta-(1-42), Abeta-(1-40), and Abeta Arctic, a protein that causes increased protofibril formation an early onset familial variant of Alzheimer disease. In contrast to insulin degrading enzyme, which is a functional analogue of hPreP, hPreP does not degrade insulin but does degrade insulin B-chain. Molecular modeling of hPreP based on the crystal structure at 2.1 A resolution of AtPreP allowed us to identify Cys(90) and Cys(527) that form disulfide bridges under oxidized conditions and might be involved in redox regulation of the enzyme. Degradation of the mitochondrial Abeta by hPreP may potentially be of importance in the pathology of Alzheimer disease.

Place, publisher, year, edition, pages
2006. Vol. 281, no 39, 29096-29104 p.
Keyword [en]
Aged, Aged; 80 and over, Amino Acid Sequence, Amyloid beta-Protein/*chemistry/metabolism, Animals, Cerebral Cortex/pathology, Humans, Male, Middle Aged, Mitochondria/*metabolism, Mitochondrial Proteins/chemistry/*physiology, Molecular Sequence Data, Peptides/*chemistry, Protein Binding, Rats, Rats; Sprague-Dawley, Sequence Homology; Amino Acid, Serine Endopeptidases/chemistry/*physiology, Submitochondrial Particles/*chemistry
URN: urn:nbn:se:su:diva-8748DOI: 10.1074/jbc.M602532200PubMedID: 16849325OAI: diva2:175267
Available from: 2007-12-21 Created: 2007-12-21 Last updated: 2009-08-24Bibliographically approved
In thesis
1. The Mitochondrial Peptidasome, PreP, relation to Alzheimer Disease
Open this publication in new window or tab >>The Mitochondrial Peptidasome, PreP, relation to Alzheimer Disease
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Amyloid-β (Aβ) is the toxic peptide implicated in the pathogenesis of Alzheimer Disease (AD). Accumulation of Aβ has been shown in brain mitochondria from AD patients and AD mice models. The occurrence of Aβ in the mitochondrial matrix leads to free radical generation and apoptosis in neurons.

In our studies, Aβ was found in brain mitochondria of living patients with plaque pathology. Extracellular Aβ was taken up by neuroblastoma cells and was found in the mitochondria. Moreover, we showed that Aβ40 and Aβ42 are transported into mitochondria via the Translocase of the Outer Membrane, the TOM machinery.

We have identified the mitochondrial Aβ-degrading protease hPreP, in human brain mitochondrial matrix. PreP is a metalloprotease, originally identified as presequence protease, but was also shown to degrade other unstructured peptides including Aβ. Immunoinactivation of PreP in human brain mitochondria revealed PreP to be the protease responsible for Aβ degradation in mitochondria.

Also, we have investigated if genetic variation in the gene encoding hPreP is associated with AD by genotyping 19 single nucleotide polymorphisms (SNPs) in the Swedish population. The study did not show a genetic association between any of the genotyped SNPs and the risk to AD. However, the biochemical analysis of four SNPs selected on the basis of their location within a structural homology model of hPreP revealed a decreased activity compared to wildtype.

Interestingly, the activity of PreP in human brain mitochondrial matrix in AD individuals was significantly lower compared to non-dement aged-matched controls. These findings were also confirmed in brain mitochondrial matrix of AD mouse models. These results suggest that a decreased PreP activity may contribute to Aβ aggregation and accumulation inside mitochondria leading to neuronal death in AD. In summary, our findings show that the degradation of Aβ by hPreP may be of importance in the pathology of AD.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm University, 2009. 64 p.
National Category
Medical Biotechnology (with a focus on Cell Biology (including Stem Cell Biology), Molecular Biology, Microbiology, Biochemistry or Biopharmacy)
Research subject
urn:nbn:se:su:diva-29044 (URN)978-91-7155-918-0 (pp. 1-64) (ISBN)
Public defence
2009-09-25, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 12 A, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Submitted. Paper 4: In progress. Available from: 2009-09-03 Created: 2009-08-07 Last updated: 2009-08-24Bibliographically approved

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