Presenilin 2 (Ps2) is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Presenilin-2 (PS2), encoded by the [PSEN2[/genes/psen2 gene on chromosome 1q42.13, is a 448-amino acid multi-pass transmembrane protein that, like its homolog [Presenilin-1 (PS1)[/proteins/presenilin-1, serves as the catalytic subunit of the [gamma-secretase[/proteins/gamma-secretase complex. PS2-containing [gamma-secretase[/entities/gamma-secretase processes [amyloid precursor protein (APP], Notch, and other type I transmembrane substrates through regulated intramembrane proteolysis. However, PS2-containing complexes are less abundant and display distinct subcellular localization, substrate preferences, and [Aβ[/entities/amyloid-beta production profiles compared to PS1-containing complexes (Sannerud et al., 2016).
Mutations in [PSEN2[/genes/psen2 are a rare cause of familial [Alzheimer's disease[/diseases/alzheimers (FAD), accounting for fewer than 5% of autosomal dominant AD cases. Approximately 60 [PSEN2[/genes/psen2 mutations have been identified — far fewer than the ~300 [PSEN1[/genes/psen1 mutations — and they generally cause later-onset (50-70 years) disease with more variable penetrance compared to [PSEN1[/genes/psen1 mutations. Recent research has revealed that PS2 has important functions in calcium homeostasis, [autophagy[/entities/autophagy, and endolysosomal function that are independent of, or only partially dependent on, [gamma-secretase[/entities/gamma-secretase activity.
¶ Structure and Gamma-Secretase Complex
PS2 shares ~67% amino acid sequence identity with PS1 and has a similar nine-transmembrane domain topology:
- Two catalytic aspartate residues (Asp263 and Asp366) in TMD6 and TMD7 form the active site
- A large cytoplasmic loop between TMD6 and TMD7 undergoes endoproteolysis during complex maturation
- N- and C-termini are cytoplasmic
PS2 assembles with nicastrin, APH-1B (preferentially, rather than APH-1A used by PS1), and PEN-2. Key differences from PS1-containing complexes:
- Subcellular localization: PS2-[gamma-secretase[/entities/gamma-secretase is enriched in late endosomes/lysosomes, while PS1-[gamma-secretase[/entities/gamma-secretase predominates at the plasma membrane and early endosomes
- [Aβ[/entities/amyloid-beta species: PS2 complexes produce proportionally more Aβ42 relative to Aβ40 compared to PS1 complexes
- Lower abundance: PS2 represents only ~20-30% of total [gamma-secretase[/entities/gamma-secretase activity in the brain
- Late endosomal processing: The endolysosomal localization of PS2-[gamma-secretase[/entities/gamma-secretase means it generates intracellular [Aβ[/entities/amyloid-beta, which may seed intraneuronal amyloid aggregation
PS2-containing [gamma-secretase[/entities/gamma-secretase processes the same substrates as PS1-[gamma-secretase[/entities/gamma-secretase, including [APP[/genes/app and Notch, but with different kinetics and in different subcellular compartments. PS2 knockout mice are viable with mild pulmonary fibrosis, indicating PS1 can largely compensate for PS2 loss in development and most adult functions.
PS2 plays a significant role in ER-mitochondria calcium signaling:
- PS2 localizes to [ER-mitochondria contact sites (MAMs)[/mechanisms/er-mitochondria-contact-sites, where it modulates IP3 receptor-mediated calcium transfer from ER to mitochondria
- FAD PS2 mutations increase ER-mitochondria calcium coupling, leading to mitochondrial calcium overload
- PS2 modulates ER calcium leak channel activity, and mutations reduce this function, increasing ER calcium stores
- Altered calcium signaling impacts [mitochondrial] bioenergetics, [ROS[/mechanisms/oxidative-stress production, and apoptotic threshold
¶ Autophagy and Endolysosomal Function
- PS2 mutations impair autophagosome-lysosome fusion, leading to accumulation of [autophagosomes]
- This autophagy impairment is independent of gamma-secretase activity and is mediated through disrupted ER-lysosome calcium signaling
- PS2 mutations alter endolysosomal pH and proteolytic capacity, affecting degradation of aggregation-prone proteins
Approximately 60 [PSEN2[/genes/psen2 mutations have been reported in FAD, with distinct characteristics from [PSEN1[/genes/psen1:
- Variable penetrance: Unlike [PSEN1[/genes/psen1 mutations (near 100% penetrance), some [PSEN2[/genes/psen2 mutations show reduced penetrance (80-95%), meaning some carriers escape disease
- Later onset: Average onset is 50-70 years, compared to 30-60 for [PSEN1[/genes/psen1
- Variable clinical phenotype: Greater clinical heterogeneity, including atypical presentations
- Parkinsonism: Some [PSEN2[/genes/psen2 mutations present with parkinsonian features and Lewy body pathology in addition to amyloid plaques and neurofibrillary tangles
| Mutation |
Age of Onset |
Notes |
| N141I (Volga German) |
45-85 |
Most common [PSEN2[/genes/psen2 mutation; large Volga German kindred; variable penetrance |
| M239V |
50-65 |
Italian families |
| T122R |
50-60 |
Associated with frontotemporal features |
| A85V |
Variable |
Debated pathogenicity |
- Shifted [Aβ[/entities/amyloid-beta ratio: Like [PSEN1[/genes/psen1 mutations, [PSEN2[/entities/psen2 mutations increase the Aβ42/Aβ40 ratio through impaired processivity
- Calcium dyshomeostasis: Disrupted ER-mitochondria calcium transfer contributes to neuronal vulnerability
- [autophagy[/entities/autophagy dysfunction: Impaired autophagosome clearance leads to accumulation of toxic protein aggregates
- Endolysosomal impairment: Altered lysosomal function reduces clearance of [amyloid-beta[/entities/amyloid-beta and tau]
- Synapse dysfunction: Recent research shows PS2 expression changes accelerate amyloid build-up, disrupt lysosomal function, and weaken synaptic connections (Bhatt et al., 2024)
| Feature |
PS1 ([PSEN1) |
PS2 (PSEN2) |
| Chromosome |
14q24.2 |
1q42.13 |
| Amino acids |
467 |
448 |
| Known FAD mutations |
~300 |
~60 |
| Penetrance |
~100% |
80-95% |
| Typical onset age |
30-60 |
50-70 |
| Gamma-secretase contribution |
~70-80% |
~20-30% |
| Primary localization |
Plasma membrane, early endosomes |
Late endosomes, lysosomes, MAMs |
| Preferred APH-1 subunit |
APH-1A |
APH-1B |
| Mouse knockout phenotype |
Lethal (skeletal defects) |
Viable (mild pulmonary fibrosis) |
PS2 has an important gamma-secretase-independent role in intracellular calcium homeostasis, which is increasingly recognized as a key pathogenic mechanism:
- PS2 (and PS1) can form calcium-permeable channels in the endoplasmic reticulum (ER) membrane, independently of their gamma-secretase activity
- FAD-PSEN2 mutations alter ER calcium content, generally reducing ER calcium stores through enhanced leak channel activity
- The M239I mutation specifically reduces calcium release from the ER, impairing calcium-dependent signaling cascades (Bhattacharyya & bhatt, 2020)
- PS2 is enriched at MAMs — specialized ER-mitochondria contact sites that regulate calcium transfer, lipid metabolism, and [autophagy[/entities/autophagy
- FAD-PSEN2 mutations increase MAM density and enhance ER-to-mitochondria calcium transfer, leading to mitochondrial calcium overload
- Excessive mitochondrial calcium uptake can trigger [mitochondrial dysfunction[/mechanisms/mitochondrial-dysfunction, opening of the permeability transition pore, and apoptosis
- FAD-PSEN2 mutations impair [autophagy[/entities/autophagy by blocking autophagosome-lysosome fusion, a step that is calcium-dependent
- The autophagy impairment is downstream of ER calcium depletion: restoring ER calcium content rescues the autophagic defect (Fedeli et al., 2019)
- This creates a vicious cycle where impaired autophagy leads to accumulation of aggregated proteins including [Aβ[/entities/amyloid-beta and tau[/proteins/tau
- PS2 modulates IP3 receptor ([IP3R](/proteins/tau
- PS2 modulates IP3 receptor (IP3R)-mediated calcium release from the ER
- FAD-PSEN2 mutations enhance IP3R-mediated calcium signaling, increasing the amplitude and frequency of calcium oscillations
- These calcium signaling abnormalities may precede amyloid pathology and represent an early cellular phenotype in PSEN2 mutation carriers
Currently, no therapies specifically target PSEN2 dysfunction. However, several approaches are relevant:
- Gamma-secretase modulators (GSMs): Unlike inhibitors that block all gamma-secretase activity (causing Notch-related toxicity), GSMs selectively shift the Aβ42/Aβ40 ratio without affecting total [Aβ[/entities/amyloid-beta production or Notch processing. GSMs may be particularly relevant for PS2-containing complexes given their preferential production of Aβ42.
- Calcium homeostasis restoration: Strategies to normalize ER calcium levels or block excessive ER-mitochondria calcium transfer could address PS2's gamma-secretase-independent pathogenic effects.
- MAM-targeted therapies: Modulation of ER-mitochondria contact sites to reduce pathological calcium transfer is an emerging therapeutic concept.
- [autophagy[/entities/autophagy enhancers: Compounds that enhance autophagic flux downstream of calcium dysregulation (e.g., trehalose, rapamycin analogs) may counteract PS2 mutation effects on protein clearance.
- [Genes Index[/genes — All gene pages
- [Proteins Index[/proteins — Protein pages
- [Alzheimer's disease[/diseases/alzheimers — Neurodegenerative disease
The study of Presenilin 2 (Ps2) has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration 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.
- [Sannerud R, et al. Restricted location of PSEN2/γ-secretase determines substrate specificity and generates an intracellular Aβ pool. Cell. 2016;166(1]:193-208. DOI
- [Levy-Lahad E, et al. Candidate gene for the chromosome 1 familial Alzheimer's Disease locus. Science. 1995;269(5226]:973-977. DOI
- [Jayadev S, et al. Alzheimer's Disease phenotypes and genotypes associated with mutations in presenilin 2. Brain. 2010;133(Pt 4]:1143-1154. DOI
- [Fedeli C, et al. PSEN2 (presenilin 2] mutants linked to familial Alzheimer's Disease impair autophagy by altering Ca2+ homeostasis. [autophagy[/entities/autophagy. 2019;15(10):1726-1741. DOI
- [Rogaev EI, et al. Familial Alzheimer's Disease in kindreds with missense mutations in a gene on chromosome 1 related to the Alzheimer's Disease type 3 gene. Nature. 1995;376(6543]:775-778. DOI
- [Cai Y, et al. Mutations in presenilin 2 and its implications in Alzheimer's Disease and other dementia-associated disorders. Clin Interv Aging. 2015;10:1163-1172. DOI
- [Bhattacharyya R, Bhatt P. Intracellular calcium dysregulation by the Alzheimer's Disease-linked protein presenilin 2. Redox Biol. 2020;29:101380. DOI
-
-
-
- [Gamma-Secretase Complex (γ-Secretase)[/proteins/gamma-secretase## External Links
-
-
-
-