Dataset Information

Alzheimer's disease-linked mutations in presenilin-1 result in a drastic loss of activity in purified ?-secretase complexes.

ABSTRACT:

Background

Mutations linked to early onset, familial forms of Alzheimer's disease (FAD) are found most frequently in PSEN1, the gene encoding presenilin-1 (PS1). Together with nicastrin (NCT), anterior pharynx-defective protein 1 (APH1), and presenilin enhancer 2 (PEN2), the catalytic subunit PS1 constitutes the core of the ?-secretase complex and contributes to the proteolysis of the amyloid precursor protein (APP) into amyloid-beta (A?) peptides. Although there is a growing consensus that FAD-linked PS1 mutations affect A? production by enhancing the A?1-42/A?1-40 ratio, it remains unclear whether and how they affect the generation of APP intracellular domain (AICD). Moreover, controversy exists as to how PS1 mutations exert their effects in different experimental systems, by either increasing A?1-42 production, decreasing A?1-40 production, or both. Because it could be explained by the heterogeneity in the composition of ?-secretase, we purified to homogeneity complexes made of human NCT, APH1aL, PEN2, and the pathogenic PS1 mutants L166P, ?E9, or P436Q.

Methodology/principal findings

We took advantage of a mouse embryonic fibroblast cell line lacking PS1 and PS2 to generate different stable cell lines overexpressing human ?-secretase complexes with different FAD-linked PS1 mutations. A multi-step affinity purification procedure was used to isolate semi-purified or highly purified ?-secretase complexes. The functional characterization of these complexes revealed that all PS1 FAD-linked mutations caused a loss of ?-secretase activity phenotype, in terms of A?1-40, A?1-42 and APP intracellular domain productions in vitro.

Conclusion/significance

Our data support the view that PS1 mutations lead to a strong ?-secretase loss-of-function phenotype and an increased A?1-42/A?1-40 ratio, two mechanisms that are potentially involved in the pathogenesis of Alzheimer's disease.

SUBMITTER: Cacquevel M

PROVIDER: S-EPMC3329438 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Publications

Alzheimer's disease-linked mutations in presenilin-1 result in a drastic loss of activity in purified γ-secretase complexes.

Cacquevel Matthias M Aeschbach Lorène L Houacine Jemila J Fraering Patrick C PC

PloS one 20120418 4

<h4>Background</h4>Mutations linked to early onset, familial forms of Alzheimer's disease (FAD) are found most frequently in PSEN1, the gene encoding presenilin-1 (PS1). Together with nicastrin (NCT), anterior pharynx-defective protein 1 (APH1), and presenilin enhancer 2 (PEN2), the catalytic subunit PS1 constitutes the core of the γ-secretase complex and contributes to the proteolysis of the amyloid precursor protein (APP) into amyloid-beta (Aβ) peptides. Although there is a growing consensus t ...[more]

PMID: 22529981

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Project description:Neurexins are a large family of neuronal plasma membrane proteins, which function as trans-synaptic receptors during synaptic differentiation. The binding of presynaptic neurexins to postsynaptic partners, such as neuroligins, has been proposed to participate in a signaling pathway that regulates synapse formation/stabilization. The identification of mutations in neurexin genes associated with autism and mental retardation suggests that dysfunction of neurexins may underlie synaptic defects associated with brain disorders. However, the mechanisms that regulate neurexin function at synapses are still unclear. Here, we show that neurexins are proteolytically processed by presenilins (PS), the catalytic components of the γ-secretase complex that mediates the intramembraneous cleavage of several type I membrane proteins. Inhibition of PS/γ-secretase by using pharmacological and genetic approaches induces a drastic accumulation of neurexin C-terminal fragments (CTFs) in cultured rat hippocampal neurons and mouse brain. Neurexin-CTFs accumulate mainly at the presynaptic terminals of PS conditional double knockout (PS cDKO) mice lacking both PS genes in glutamatergic neurons of the forebrain. The fact that loss of PS function enhances neurexin accumulation at glutamatergic terminals mediated by neuroligin-1 suggests that PS regulate the processing of neurexins at glutamatergic synapses. Interestingly, presenilin 1 (PS1) is recruited to glutamatergic terminals mediated by neuroligin-1, thus concentrating PS1 at terminals containing β-neurexins. Furthermore, familial Alzheimer's disease (FAD)-linked PS1 mutations differentially affect β-neurexin-1 processing. Expression of PS1 M146L and PS1 H163R mutants in PS-/- cells rescues the processing of β-neurexin-1, whereas PS1 C410Y and PS1 ΔE9 fail to rescue the processing defect. These results suggest that PS regulate the synaptic function and processing of neurexins at glutamatergic synapses, and that impaired neurexin processing by PS may play a role in FAD.