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PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca²⁺ homeostasis.

ABSTRACT: PSEN2 (presenilin 2) is one of the 3 proteins that, when mutated, causes early onset familial Alzheimer disease (FAD) cases. In addition to its well-known role within the ?-secretase complex (the enzyme ultimately responsible for A? peptides formation), PSEN2 is endowed with some ?-secretase-independent functions in distinct cell signaling pathways, such as the modulation of intracellular Ca²⁺ homeostasis. Here, by using different FAD-PSEN2 cell models, we demonstrate that mutated PSEN2 impairs autophagy by causing a block in the degradative flux at the level of the autophagosome-lysosome fusion step. The defect does not depend on an altered lysosomal functionality but rather on a decreased recruitment of the small GTPase RAB7 to autophagosomes, a key event for normal autophagy progression. Importantly, FAD-PSEN2 action on autophagy is unrelated to its ?-secretase activity but depends on its previously reported ability to partially deplete ER Ca²⁺ content, thus reducing cytosolic Ca²⁺ response upon IP3-linked cell stimulations. Our data sustain the pivotal role for Ca²⁺ signaling in autophagy and reveal a novel mechanism by which FAD-linked presenilins alter the degradative process, reinforcing the view of a causative role for a dysfunctional quality control pathway in AD neurodegeneration.Abbreviations: A?: amyloid ?; AD: Alzheimer disease; ACTB: actin beta; AMPK: AMP-activated protein kinase; APP: amyloid-beta precursor protein; BafA: bafilomycin A₁; BAPTA-AM: 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester; CFP: cyan fluorescent protein; EGTA-AM: ethylene glycol-bis(?-aminoethyl ether)-N,N,N',N'-tetraacetic acid acetoxymethyl ester; ER: endoplasmic reticulum; EGFP-HDQ74: enhanced GFP-huntingtin exon 1 containing 74 polyglutamine repeats; FAD: familial Alzheimer disease; FCS: fetal calf serum; FRET: fluorescence/Förster resonance energy transfer; GFP: green fluorescent protein; IP3: inositol trisphosphate; KD: knockdown; LAMP1: lysosomal associated membrane protein 1; MAP1LC3-II/LC3-II: lipidated microtubule-associated protein 1 light chain 3; MCU: mitochondrial calcium uniporter; MICU1: mitochondrial calcium uptake 1; MEFs: mouse embryonic fibroblasts; MFN2: mitofusin 2; MTOR: mechanistic target of rapamycin kinase; MTORC1: MTOR complex 1; SQSTM1/p62: sequestosome 1; PSEN1: presenilin 1; PSEN2: presenilin 2; RAB7: RAB7A: member RAS oncogene family; RFP: red fluorescent protein; ATP2A/SERCA: ATPase sarcoplasmic/endoplasmic reticulum Ca²⁺ transporting; siRNA: small interference RNA; V-ATPase: vacuolar-type H⁺-ATPase; WT: wild type.

SUBMITTER: Fedeli C

PROVIDER: S-EPMC6844518 | biostudies-literature | 2019 Dec

REPOSITORIES: biostudies-literature

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PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca<sup>2+</sup> homeostasis.

Fedeli Chiara C Filadi Riccardo R Rossi Alice A Mammucari Cristina C Pizzo Paola P

Autophagy 20190327 12

PSEN2 (presenilin 2) is one of the 3 proteins that, when mutated, causes early onset familial Alzheimer disease (FAD) cases. In addition to its well-known role within the γ-secretase complex (the enzyme ultimately responsible for Aβ peptides formation), PSEN2 is endowed with some γ-secretase-independent functions in distinct cell signaling pathways, such as the modulation of intracellular Ca<sup>2+</sup> homeostasis. Here, by using different FAD-PSEN2 cell models, we demonstrate that mutated PSE ...[more]

PMID: 30892128

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Project description:BackgroundAmyloid protein precursor (APP), presenilin-1 (PSEN1), and presenilin-2 (PSEN2) mutations cause autosomal dominant forms of early-onset Alzheimer disease (AD-EOAD). Although these genes were identified in the 1990s, variant classification remains a challenge, highlighting the need to colligate mutations from large series.Methods and findingsWe report here a novel update (2012-2016) of the genetic screening of the large AD-EOAD series ascertained across 28 French hospitals from 1993 onwards, bringing the total number of families with identified mutations to n = 170. Families were included when at least two first-degree relatives suffered from early-onset Alzheimer disease (EOAD) with an age of onset (AOO) ≤65 y in two generations. Furthermore, we also screened 129 sporadic cases of Alzheimer disease with an AOO below age 51 (44% males, mean AOO = 45 ± 2 y). APP, PSEN1, or PSEN2 mutations were identified in 53 novel AD-EOAD families. Of the 129 sporadic cases screened, 17 carried a PSEN1 mutation and 1 carried an APP duplication (13%). Parental DNA was available for 10 sporadic mutation carriers, allowing us to show that the mutation had occurred de novo in each case. Thirteen mutations (12 in PSEN1 and 1 in PSEN2) identified either in familial or in sporadic cases were previously unreported. Of the 53 mutation carriers with available cerebrospinal fluid (CSF) biomarkers, 46 (87%) had all three CSF biomarkers-total tau protein (Tau), phospho-tau protein (P-Tau), and amyloid β (Aβ)42-in abnormal ranges. No mutation carrier had the three biomarkers in normal ranges. One limitation of this study is the absence of functional assessment of the possibly and probably pathogenic variants, which should help their classification.ConclusionsOur findings suggest that a nonnegligible fraction of PSEN1 mutations occurs de novo, which is of high importance for genetic counseling, as PSEN1 mutational screening is currently performed in familial cases only. Among the 90 distinct mutations found in the whole sample of families and isolated cases, definite pathogenicity is currently established for only 77%, emphasizing the need to pursue the effort to classify variants.

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PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca²⁺ homeostasis.

Publications

PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca<sup>2+</sup> homeostasis.

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PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca2+ homeostasis.

Publications

PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca<sup>2+</sup> homeostasis.

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OmicsDI is part of the ELIXIR infrastructure

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PSEN2 (presenilin 2) mutants linked to familial Alzheimer disease impair autophagy by altering Ca²⁺ homeostasis.