[presenilin-2[/genes/[psen2[/genes/[psen2[/genes/[psen2[/genes/[psen2--TEMP--/genes)--FIX-- (Psen2) is an important component in the neurobiology of neurodegenerative [diseases[/[diseases[/[diseases[/[diseases[/[diseases[/[diseases[/[diseases[/[diseases[/diseases. This page provides detailed information about its structure, function, and role in disease processes.
Presenilin 2 (PSEN2) is a polytopic transmembrane protein that, together with [presenilin-1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- 1
The PSEN2 gene is located on chromosome 1q42.13 and encodes a 448-amino acid protein. Approximately 45 pathogenic mutations have been identified, with the N141I "Volga German" mutation being the best characterized. A distinctive feature of PSEN2 mutations compared to [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- is their later average age of onset and notable incomplete penetrance, suggesting that genetic and environmental modifiers play a greater role in PSEN2-associated FAD.
¶ Gene and Protein Structure
- Chromosomal location: 1q42.13
- Gene size: ~25 kb
- Exons: 12 coding exons
- Protein: 448 amino acids (~50 kDa)
- Homology: 67% amino acid identity with [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- (467 amino acids)
PSEN2 is a nine-transmembrane domain (9-TMD) protein:
- N-terminus and C-terminus: Both cytoplasmic
- Large cytoplasmic loop: Between TMD6 and TMD7; site of endoproteolytic cleavage into N-terminal fragment (NTF) and C-terminal fragment (CTF) during [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- maturation
- Catalytic aspartates: D263 (TMD6) and D366 (TMD7) form the active site of the aspartyl protease
- PAL motif: Conserved Pro-Ala-Leu sequence near the active site, essential for catalysis
| Feature |
[PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- |
PSEN2 |
| Chromosome |
14q24.3 |
1q42.13 |
| Protein length |
467 aa |
448 aa |
| Known pathogenic mutations |
>300 |
~45 |
| Expression |
Ubiquitous; high in [neurons[/entities/[neurons[/entities/[neurons[/entities/[neurons[/entities/[neurons--TEMP--/entities)--FIX-- |
More restricted; highest in [neurons[/entities/[neurons[/entities/[neurons[/entities/[neurons[/entities/[neurons--TEMP--/entities)--FIX--, heart, pancreas |
| Predominant subcellular localization |
ER, Golgi, plasma membrane, endosomes |
Primarily ER and [late[/diseases/[late[/diseases/[late[/diseases/[late[/diseases/[late--TEMP--/diseases)--FIX-- endosomes/lysosomes |
| Age of onset (mean) |
30-55 years |
50-70 years |
| Penetrance |
Nearly complete (~100%) |
Incomplete (some carriers unaffected to age 80+) |
| Aβ42/40 ratio effect |
Generally stronger increase |
Moderate increase; higher baseline Aβ43 production |
PSEN2 assembles into a [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- complex with the same accessory subunits as [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX--:
- PSEN2 (catalytic subunit) — mutually exclusive with [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX--
- Nicastrin (substrate recognition)
- APH-1 (scaffolding; APH-1A or APH-1B variants)
- PEN-2 (PSEN activation via endoproteolysis)
Each cell contains both [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX--- and PSEN2-containing complexes. [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- complexes account for the majority (~70-80%) of total [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- activity; PSEN2 complexes contribute the remaining ~20-30%.
PSEN2-containing complexes differ from [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX---containing complexes:
- Subcellular localization: PSEN2 complexes are enriched in late endosomes and lysosomes, while [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- complexes are more broadly distributed (ER, Golgi, plasma membrane)
- Aβ] product line: PSEN2 complexes may produce relatively more Aβ43 (a highly amyloidogenic species) compared to [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- complexes
- Substrate processing: PSEN2 complexes process [APP[/genes/[app[/genes/[app[/genes/[app[/genes/[app--TEMP--/genes)--FIX--
- Endosomal [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- production: Because PSEN2 complexes localize to late endosomes, they generate [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- in an endosomal compartment where conditions favor aggregation
PSEN2 has important functions beyond [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- catalysis:
- ER calcium regulation: PSEN2 modulates ER calcium content independently of its protease activity
- Mitochondria-ER contact sites (MAMs): PSEN2 is enriched at MAMs where it regulates calcium transfer between ER and mitochondria
- [autophagy[/entities/[autophagy[/entities/[autophagy[/entities/[autophagy[/entities/[autophagy--TEMP--/entities)--FIX-- regulation: PSEN2 modulates autophagosome-lysosome fusion through calcium-dependent mechanisms
- Inflammatory signaling: PSEN2 modulates [NLRP3 inflammasome[/mechanisms/[nlrp3-inflammasome[/mechanisms/[nlrp3-inflammasome[/mechanisms/[nlrp3-inflammasome[/mechanisms/[nlrp3-inflammasome--TEMP--/mechanisms)--FIX-- activation in [Microglia[/entities/microglia.[/entities/microglia.[/entities/microglia.[/entities/microglia.--TEMP--/entities)--FIX--
~45 PSEN2 mutations have been identified. Most are missense mutations concentrated in the transmembrane domains:
| Mutation |
Population |
Age of Onset (mean) |
Key Features |
| N141I |
Volga German kindred |
~55 years |
Most common PSEN2 mutation; founding mutation from 1760s Germany; also Fulda German families |
| M239V |
Italian families |
~50 years |
Aggressive phenotype; prominent CAA |
| T122R |
Italian families |
~50 years |
Severe early-onset |
| M239I |
Italian families |
~55 years |
Variable presentation |
| A85V |
African American |
~60 years |
One of few reported in non-European populations |
| N141Y |
Japanese family |
~68 years |
Same codon as N141I; distinct substitution |
PSEN2 FAD mutations cause disease through qualitative shifts in [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- cleavage:
- Reduced overall [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- processivity (partial loss of function)
- Increased Aβ42/Aβ40 and Aβ43/Aβ40 ratios (qualitative gain of toxic function)
- The longer [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- species (Aβ42, Aβ43) are more aggregation-prone and seed plaque formation
- This "qualitative shift" model explains why PSEN2 mutations increase AD risk despite often reducing total [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- production
The N141I mutation is the most extensively studied PSEN2 variant:
- History: Identified in 1995 in families of Volga German descent; traced to a common ancestor from the Hesse region of Germany (~1760s, before emigration to Russia)
- Effect: Asparagine-to-isoleucine substitution at position 141 (TMD2)
- [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- effect: Increases Aβ42 secretion by ~2-fold; increases Aβ42/40 ratio
- Penetrance: Notably incomplete — some carriers remain cognitively normal into their 80s
- Modifiers: [APOE[/[cortex[/[cortex[/[cortex[/[cortex[/[cortex[/[cortex[/[cortex[/cortex]
- Cotton wool plaques in some cases (similar to certain [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- mutations)
A distinctive feature of PSEN2 mutations:
- Some N141I carriers remain cognitively unimpaired beyond age 80
- This contrasts with [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX-- mutations, which have ~100% penetrance
- Modifying factors include [APOE genotype, protective variants (e.g., APOE2, Christchurch), and possibly lifestyle factors
- Incomplete penetrance complicates genetic counseling and risk assessment
¶ Cellular and Molecular Mechanisms
PSEN2 FAD mutations profoundly affect ER calcium homeostasis:
- PSEN2 normally forms low-conductance ER calcium leak channels (independent of [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- activity)
- FAD mutations (N141I) partially deplete ER calcium stores
- Reduced ER calcium alters [ryanodine receptor[/entities/[ryanodine-receptor[/entities/[ryanodine-receptor[/entities/[ryanodine-receptor[/entities/[ryanodine-receptor--TEMP--/entities)--FIX-- and IP3 receptor signaling
- Disrupted calcium signaling affects synaptic plasticity, gene expression, and cell survival
- ER calcium depletion reduces cytosolic calcium transients needed for synaptic vesicle fusion
A 2024 study demonstrated critical endolysosomal roles for PSEN2 3):
- Both PSEN2 knockout and N141I knock-in accelerate AD pathology in APPKI mice
- PSEN2 dysfunction causes endolysosomal swelling and impaired acidification
- Reduced surface expression of synaptic [proteins[/[proteins[/[proteins[/[proteins[/[proteins[/[proteins[/[proteins[/[proteins[/proteins (AMPA receptors, neuroligins)
- Circuit-level hyperexcitability in hippocampal CA1 [neurons[/entities/[neurons[/entities/[neurons[/entities/[neurons[/entities/[neurons--TEMP--/entities)--FIX--
- These effects are sex-dependent, with female mice more severely affected
FAD-PSEN2 mutations impair autophagy through a calcium-dependent mechanism:
- Partial ER calcium depletion reduces cytoplasmic calcium levels
- Reduced calcium impairs autophagosome-lysosome fusion (SNARE-mediated)
- Result: Block in autophagic flux at the fusion step, not at autophagosome formation
- Accumulated autophagosomes contain undegraded cargo including [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- and tau]
- This mechanism is distinct from [PSEN1[/genes/[psen1[/genes/[psen1[/genes/[psen1[/genes/[psen1--TEMP--/genes)--FIX---mediated autophagy impairment (which involves v-ATPase targeting)
PSEN2 is enriched at MAMs:
- MAMs regulate calcium transfer from ER to mitochondria via IP3R-VDAC-MCU axis
- PSEN2 FAD mutations increase MAM function, enhancing ER-mitochondrial calcium transfer
- Excessive mitochondrial calcium causes [oxidative stress[/mechanisms/[oxidative-stress[/mechanisms/[oxidative-stress[/mechanisms/[oxidative-stress[/mechanisms/[oxidative-stress--TEMP--/mechanisms)--FIX-- and [apoptosis[/entities/[apoptosis[/entities/[apoptosis[/entities/[apoptosis[/entities/[apoptosis--TEMP--/entities)--FIX--
- MAM dysregulation may contribute to [mitochondrial dysfunction[/mechanisms/[mitochondrial-dysfunction[/mechanisms/[mitochondrial-dysfunction[/mechanisms/[mitochondrial-dysfunction[/mechanisms/[mitochondrial-dysfunction--TEMP--/mechanisms)--FIX-- seen in AD
- GSMs shift cleavage toward shorter [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- species (Aβ37, Aβ38) without inhibiting total [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- activity
- May be particularly relevant for PSEN2 mutations that increase Aβ42/43 ratios
- Avoid the toxicity of pan gamma (which failed in [clinical trials[/[clinical-trials[/[clinical-trials[/[clinical-trials[/[clinical-trials[/[clinical-trials[/[clinical-trials[/[clinical-trials[/clinical-trials due to Notch signaling disruption)
- PSEN2 mutation carriers are eligible for the Dominantly Inherited Alzheimer Network] Trials Unit ([DIAN] prevention trials
- Biomarker-driven prevention strategies can target carriers before symptom onset
- Understanding incomplete penetrance may identify protective factors applicable to sporadic AD
- Restoring ER calcium homeostasis could address PSEN2-specific pathogenic mechanisms
- Rycal compounds that stabilize RyR channels may counteract calcium leak
- Dantrolene and other RyR modulators show preclinical efficacy in PSEN-mutant models
¶ Genetic Testing and Counseling
- Recommended for individuals with early-onset AD (<65 years) and autosomal dominant family history
- Incomplete penetrance complicates predictive testing and risk communication
- Genetic counseling should address the wide range of onset ages and possibility of non-penetrance
- [Apolipoprotein E[/entities/[apoe[/entities/[apoe[/entities/[apoe[/entities/[apoe--TEMP--/entities)--FIX-- ([APOE
The study of Presenilin 2 (Psen2) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying [mechanisms of neurodegeneration[/[mechanisms[/[mechanisms[/[mechanisms[/[mechanisms[/[mechanisms[/[mechanisms[/[mechanisms[/mechanisms and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.
- [Jayadev S, et al. The N141I mutation in PSEN2: implications for the quintessential case of Alzheimer's Disease. Arch Neurol. 2010;67[1]
- [Levy-Lahad E, et al. Candidate gene for the chromosome 1 familial [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX-- locus. Science. 1995;269[2]
- [Bhalla A, et al. Altered expression of Presenilin2 impacts [5 endolysosomal homeostasis and synapse function in [Alzheimer's disease[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers[/diseases/[alzheimers--TEMP--/diseases)--FIX---relevant brain circuits. Nat Commun. 2024;15:10117. [DOI][3]
- [Fedeli C, et al. PSEN2 [4]
- [Tomita T, et al. The presenilin 2 mutation [5]
- [Walker ES, et al. Presenilin 2 familial Alzheimer's Disease mutations result in partial loss of function and dramatic changes in [Aβ[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta[/entities/[amyloid-beta--TEMP--/entities)--FIX-- 42/40 ratios. J Neurochem. 2005;92[6]
- [Filadi R, et al. Presenilin 2 modulates endoplasmic reticulum-mitochondria coupling by tuning the antagonistic effect of mitofusin 2. Cell Rep. 2016;15[7]
- [Wolfe MS. Structure and function of the [gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase[/entities/[gamma-secretase--TEMP--/entities)--FIX-- complex. Biochemistry. 2019;58[8]
- [Bird TD, et al. Wide range in age of onset for chromosome 1-related familial Alzheimer's Disease. Ann Neurol. 1996;40[9]
- [Area-Gomez E, et al. Presenilins are enriched in endoplasmic reticulum membranes associated with mitochondria. Am J Pathol. 2009;175[10]
- [Sherrington R, et al. Alzheimer's Disease associated with mutations in presenilin 2 is rare and variably penetrant. Hum Mol Genet. 1996;5[11]
- [Szaruga M, et al. Alzheimer's-causing mutations shift Aβ length by destabilizing γ-secretase-Aβn interactions. Cell. 2017;170[12]