Degradation of the Amyloid beta-Protein by the Novel Mitochondrial Peptidasome, PreP

Department of Biochemistry and Biophysics , Stockholm University, Tukholma, Stockholm, Sweden
Journal of Biological Chemistry (Impact Factor: 4.57). 10/2006; 281(39):29096-104. DOI: 10.1074/jbc.M602532200
Source: PubMed


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
β-protein (Aβ). 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 Aβ. We have cloned, overexpressed, and purified recombinant hPreP and its mutant with catalytic base Glu78 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 Aβ-(1-42), Aβ-(1-40), and Aβ 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 Å
resolution of AtPreP allowed us to identify Cys90 and Cys527 that form disulfide bridges under oxidized conditions and might be involved in redox regulation of the enzyme. Degradation
of the mitochondrial Aβ by hPreP may potentially be of importance in the pathology of Alzheimer disease.

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Available from: Pavel f Pavlov, Jan 05, 2016
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    • "The work byBrunetti et al (2015)in this issue of EMBO Molecular Medicine provides a novel link between Ab accumulation and mitochondria. Intracellular degradation of Ab is performed by two enzymes of the pitrilysin oligopeptidase family: the human insulin-degrading enzyme (IDE) and a mitochondrial-specific pitrilysin metallopeptidase 1 (PITRM1), which also digests the mitochondrial targeting sequences (MTS) of imported proteins across the inner mitochondrial membrane (Falkevall et al, 2006). Decreased PITRM1 proteolytic activity contributes to Ab accumulation in the mitochondria , leading to neuronal death that is exacerbated in AD (Alikhani et al, 2011).Brunetti et al (2015)now identify a homozygous PITRM1 mutation (c.548G>A, p.Arg183Gln) in two siblings from an isolated population in Norway, presenting with mild intellectual disability, spinocerebellar ataxia, cognitive decline and psychosis by homozygosity mapping and whole exome sequencing. "

    Preview · Article · Jan 2016 · EMBO Molecular Medicine
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    • "Not only is the brain a major target in primary, genetically determined mitochondrial disease, but mitochondrial dysfunction is also a prominent feature in many of the most prevalent neurodegenerative diseases including Parkinson's disease (PD) and Alzheimer's dementia (AD) (Manczak et al, 2006; Morais & De Strooper, 2010; Friedland-Leuner et al, 2014). For instance, AD is characterised by the accumulation of the amyloid beta (Ab) peptide as plaques in the neuropil, and recent work has suggested that Ab is present in the inner compartment of mitochondria (Falkevall et al, 2006; Manczak et al, 2006; Hansson Petersen et al, 2008). The mitochondrial fraction of Ab is quantitatively digested by the pitrilysin metallopeptidase 1 (PITRM1) (Hansson Petersen et al, 2008; Pagani & Eckert, 2011; Pinho et al, 2014). "
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    ABSTRACT: Mitochondrial dysfunction and altered proteostasis are central features of neurodegenerative diseases. The pitrilysin metallopeptidase 1 (PITRM1) is a mitochondrial matrix enzyme, which digests oligopeptides, including the mitochondrial targeting sequences that are cleaved from proteins imported across the inner mitochondrial membrane and the mitochondrial fraction of amyloid beta (Aβ). We identified two siblings carrying a homozygous PITRM1 missense mutation (c.548G>A, p.Arg183Gln) associated with an autosomal recessive, slowly progressive syndrome characterised by mental retardation, spinocerebellar ataxia, cognitive decline and psychosis. The pathogenicity of the mutation was tested in vitro, in mutant fibroblasts and skeletal muscle, and in a yeast model. A Pitrm1(+/-) heterozygous mouse showed progressive ataxia associated with brain degenerative lesions, including accumulation of Aβ-positive amyloid deposits. Our results show that PITRM1 is responsible for significant Aβ degradation and that impairment of its activity results in Aβ accumulation, thus providing a mechanistic demonstration of the mitochondrial involvement in amyloidotic neurodegeneration.
    Full-text · Article · Dec 2015 · EMBO Molecular Medicine
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    • "By virtue of their distinctive subcellular localizations and pH optima, AβDPs constitute powerful tools for manipulating different pools of Aβ and, thereby, gaining fresh insight into their potential involvement in the pathogenesis of AD (Leissring and Turner, 2013). AβDPs are present in a diverse range of subcellular compartments: insulin-degrading enzyme (IDE) in cytosol (Roth, 2004), IDE and presequence peptidase in mitochondria (Leissring et al., 2004; Falkevall et al., 2006), BACE-2 and endothelin-converting enzymes 1-and -2 in endosomes (Eckman et al., 2001; Abdul- Hay et al., 2012), and in cathepsins B and D in lysosomes (Gan et al., 2004; Leissring et al., 2009) (see Saido and Leissring, 2012; Leissring and Turner, 2013 for comprehensive reviews). Collectively, these AβDPs represent a diverse set of experimental tools for selectively manipulating different pools of Aβ. "

    Full-text · Article · Aug 2014 · Frontiers in Aging Neuroscience
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