Familial Alzheimer disease–linked mutations specifically disrupt Ca2+ leak function of presenilin 1
Omar Nelson, … , Bart de Strooper, Ilya Bezprozvanny
Omar Nelson, … , Bart de Strooper, Ilya Bezprozvanny
Published May 1, 2007
Citation Information: J Clin Invest. 2007;117(5):1230-1239. https://doi.org/10.1172/JCI30447.
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Research Article Neuroscience

Familial Alzheimer disease–linked mutations specifically disrupt Ca2+ leak function of presenilin 1

Abstract

Mutations in presenilins are responsible for approximately 40% of all early-onset familial Alzheimer disease (FAD) cases in which a genetic cause has been identified. In addition, a number of mutations in presenilin-1 (PS1) have been suggested to be associated with the occurrence of frontal temporal dementia (FTD). Presenilins are highly conserved transmembrane proteins that support cleavage of the amyloid precursor protein by γ-secretase. Recently, we discovered that presenilins also function as passive ER Ca2+ leak channels. Here we used planar lipid bilayer reconstitution assays and Ca2+ imaging experiments with presenilin-null mouse embryonic fibroblasts to analyze ER Ca2+ leak function of 6 FAD-linked PS1 mutants and 3 known FTD-associated PS1 mutants. We discovered that L166P, A246E, E273A, G384A, and P436Q FAD mutations in PS1 abolished ER Ca2+ leak function of PS1. In contrast, A79V FAD mutation or FTD-associated mutations (L113P, G183V, and Rins352) did not appear to affect ER Ca2+ leak function of PS1 in our experiments. We validated our findings in Ca2+ imaging experiments with primary fibroblasts obtained from an FAD patient possessing mutant PS1-A246E. Our results indicate that many FAD mutations in presenilins are loss-of-function mutations affecting ER Ca2+ leak activity. In contrast, none of the FTD-associated mutations affected ER Ca2+ leak function of PS1, indicating that the observed effects are disease specific. Our observations are consistent with the potential role of disturbed Ca2+ homeostasis in Alzheimer disease pathogenesis.

Authors

Omar Nelson, Huiping Tu, Tianhua Lei, Mostafa Bentahir, Bart de Strooper, Ilya Bezprozvanny

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Figure 1

Recombinant presenilins form Ca2+ channels in BLMs.

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Recombinant presenilins form Ca2+ channels in BLMs. (A) ...
(A) Molecular model of presenilins (3, 4). The 9 transmembrane domains (TM1–TM9) of presenilins, the γ-secretase catalytic aspartate residues (yellow dots), and the site of the endoproteolytic cleavage (scissors) are shown. The positions of PS1 FAD mutants A79V, L166P, A246E, E273A, G384A, and P436Q examined in our study are shown (red dots, black letters). Also shown are positions of M146V, ′ˆ†E9 FAD mutations in PS1, and N141I FAD mutations in PS2 analyzed in ref. 10 (red dots, green letters). Also shown is D257A "γ-secretase" mutation in PS1, which was analyzed in ref. 10 (yellow dot, orange letters) and FTD-associated PS1 mutations L113P, G183V, and Rins352 examined in our study (blue dots, blue letters). (B) Expression of PS1 and PS1 mutants in Sf9 cells. The ER microsomes from noninfected Sf9 cells and from Sf9 cells infected with WT and FAD mutant PS1-encoding baculoviruses were analyzed by Western blotting with anti-PS1 monoclonal antibodies. The position of PS1 holoprotein is indicated by an arrow. Actin was used as the loading control. (C) The Ba2+ currents recorded at +10 mV, 0 mV, and –10 mV holding potentials are shown for the empty BLM and for BLM fused with ER microsomal preparations from Sf9 cells infected with the WT and FAD mutant PS1-encoding baculoviruses. Similar results were obtained in at least 5 independent BLM experiments with each PS1 mutant.