Presenilin-2 (PS2)
Gene	[PSEN2](/genes/psen2)
UniProt	O00287
PDB	4HO6, 5E2Z
Mol. Weight	50 kDa (full-length), ~20 kDa (C-terminal fragment)
Localization	Endoplasmic reticulum, Golgi apparatus, mitochondria
Family	Presenilin family, aspartyl proteases
Diseases	[Alzheimer's Disease](/diseases/alzheimers), [Familial Alzheimer's Disease](/diseases/familial-alzheimers)
Associated Diseases	ALS, ALZHEIMER, ALZHEIMER'S DISEASE, Aging, Als
KG Connections	508 edges

Presenilin-2 (PS2)

Introduction

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.

Overview

Presenilin-2 (PS2) is a multipass transmembrane aspartyl protease that plays a critical role in γ-secretase complex formation and amyloid precursor protein (APP) processing^{1The gamma-secretase complex: membrane-embedded proteolytic ensemble2016 · PMID 26821143Open reference}. Along with presenilin-1 (PS1), PS2 is responsible for generating amyloid-β (Aβ) peptides, the primary constituents of amyloid plaques in Alzheimer’s disease^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}.

Structure

Presenilin-2 is a ~467 amino acid protein with:

• Nine transmembrane domains: Spanning the membrane

• Aspartyl protease motif: Two conserved aspartate residues (D257, D263) in transmembrane domains 6 and 7

• Large hydrophilic loop: Between transmembrane domains 6 and 7

The active enzyme requires assembly into the γ-secretase complex with three other subunits:

• Nicastrin (NCT)

• Aph-1

• Pen-2

Function

γ-Secretase Activity

Presenilin-2, as part of the γ-secretase complex, catalyzes the intramembranous proteolysis of:

• Amyloid Precursor Protein (APP): Generates Aβ peptides

• Notch receptors: Essential for development

• E-cadherin: Cell adhesion

• **LDL receptor-related proteins

APP Processing

APP → α-secretase → sAPPα + C83 → γ-secretase → Aβ40
APP → β-secretase → sAPPβ + C99 → γ-secretase → Aβ42/Aβ43

PS2 tends to produce longer Aβ peptides (Aβ42, Aβ43) compared to PS1.

Cellular Functions

• Notch signaling: Essential for neurodevelopment

• Calcium homeostasis: Regulates ER calcium stores

• Protein trafficking: ER and Golgi function

• Mitochondrial function: Affects mitochondrial dynamics

Role in Alzheimer’s Disease

Familial AD Mutations

Over 40 PSEN2 mutations are linked to familial Alzheimer’s disease (FAD):

• N141I: Volga German families

• M239V: Other FAD families

• D439H: Late-onset AD risk

Pathogenic Mechanisms

• Increased Aβ42/43 production: More aggregation-prone peptides

• Altered γ-secretase activity: Reduced overall proteolysis

• Calcium dysregulation: ER calcium leak

• Mitochondrial dysfunction: Energy metabolism defects

• Autophagy impairment: Lysosomal dysfunction

Differences from PS1

• Later onset: PS2 mutations typically cause later-onset FAD

• Reduced penetrance: Some PS2 mutations have incomplete penetrance

• Less aggressive: Slower disease progression than PS1

Regulation

Expression

• Brain: Neurons and glia

• Upregulated during stress

• Transcriptional regulation by BACE1

Post-Translational

• Endoproteolysis: Cleavage into NTF/CTF

• Glycosylation: Maturation in ER/Golgi

• Phosphorylation: Affects γ-secretase activity

Therapeutic Implications

γ-Secretase Modulators

• NSAIDs: Modulators (not inhibitors) shift Aβ production

• Small molecule modulators: Reduce Aβ42 production

Challenges

• Notch side effects: Essential for development

• Broad substrate specificity

Key Publications

^{1The gamma-secretase complex: membrane-embedded proteolytic ensemble2016 · PMID 26821143Open reference}: Wolfe MS. The gamma-secretase complex: membrane-embedded proteolytic ensemble. J Neurochem. 2016;139 Suppl 2:39-52. ^{1The gamma-secretase complex: membrane-embedded proteolytic ensemble2016 · PMID 26821143Open reference}(https://pubmed.ncbi.nlm.nih.gov/26821143/)

^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}: Haass C, Selkoe DJ. Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide. Cell. 1993;73(6):1055-1058. ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}(https://pubmed.ncbi.nlm.nih.gov/8101482/)

^{3Presenilin-2: more than an epsilon-cleaving protease2015 · PMID 25925283Open reference}: Ryman NR, Lamb BT. Presenilin-2: more than an epsilon-cleaving protease. Mol Neurodegener. 2015;10(Suppl 1):S7. ^{3Presenilin-2: more than an epsilon-cleaving protease2015 · PMID 25925283Open reference}(https://pubmed.ncbi.nlm.nih.gov/25925283/)

Background

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.

External Links

• PubMed - Biomedical literature

• Alzheimer’s Disease Neuroimaging Initiative - Research data

• Allen Brain Atlas - Brain gene expression data

See Also

• PSEN2 Gene

• Presenilin-1

• APP Processing

• Amyloid Cascade

• Alzheimer’s Disease

• Familial Alzheimer’s Disease

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Additional Content (merged from /entities/presenilin-2)

Presenilin-2 (PS2)

Introduction

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. ^{1The gamma-secretase complex: membrane-embedded proteolytic ensemble2016 · PMID 26821143Open reference}

Overview

Presenilin-2 (PS2), encoded by the psen2 gene on chromosome 1q42.13, is a 448-amino acid multi-pass transmembrane protein that, like its homolog presenilin-1, serves as the catalytic subunit of the gamma-secretase complex. PS2-containing 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 amyloid-beta production profiles compared to PS1-containing complexes (Sannerud et al., 2016). ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}

Mutations in psen2 are a rare cause of familial alzheimers (FAD), accounting for fewer than 5% of autosomal dominant AD cases. Approximately 60 psen2 mutations have been identified — far fewer than the ~300 psen1 mutations — and they generally cause later-onset (50-70 years) disease with more variable penetrance compared to psen1 mutations. Recent research has revealed that PS2 has important functions in calcium homeostasis, autophagy, and endolysosomal function that are independent of, or only partially dependent on, gamma-secretase activity. ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}0

Structure and Gamma-Secretase Complex

Protein Topology

PS2 shares ~67% amino acid sequence identity with PS1 and has a similar nine-transmembrane domain topology: [^4]

• 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-Containing Gamma-Secretase

PS2 assembles with nicastrin, APH-1B (preferentially, rather than APH-1A used by PS1), and PEN-2. Key differences from PS1-containing complexes: [^5]

• Subcellular localization: PS2-gamma-secretase is enriched in late endosomes/lysosomes, while PS1-gamma-secretase predominates at the plasma membrane and early endosomes

• 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 activity in the brain

• Late endosomal processing: The endolysosomal localization of PS2-gamma-secretase means it generates intracellular amyloid-beta, which may seed intraneuronal amyloid aggregation

Normal Function

Gamma-Secretase Activity

PS2-containing gamma-secretase processes the same substrates as PS1-gamma-secretase, including 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. [^6]

Calcium Homeostasis

PS2 plays a significant role in ER-mitochondria calcium signaling: ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}1

• PS2 localizes to 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, 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

Role in Alzheimer’s Disease

Pathogenic Mutations

Approximately 60 psen2 mutations have been reported in FAD, with distinct characteristics from psen1: ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}2

• Variable penetrance: Unlike psen1 mutations (near 100% penetrance), some 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

• Variable clinical phenotype: Greater clinical heterogeneity, including atypical presentations

• Parkinsonism: Some psen2 mutations present with parkinsonian features and Lewy body pathology in addition to amyloid plaques and neurofibrillary tangles

Notable Mutations

| Mutation | Age of Onset | Notes |

|----------|-------------|-------| ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}3 | N141I (Volga German) | 45-85 | Most common psen2 mutation; large Volga German kindred; variable penetrance | ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}4 | M239V | 50-65 | Italian families | ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}5 | T122R | 50-60 | Associated with frontotemporal features | ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}6 | A85V | Variable | Debated pathogenicity | ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}7

Mechanisms of Disease

• Shifted amyloid-beta ratio: Like psen1 mutations, psen2 mutations increase the Aβ42/Aβ40 ratio through impaired processivity

• Calcium dyshomeostasis: Disrupted ER-mitochondria calcium transfer contributes to neuronal vulnerability

• autophagy dysfunction: Impaired autophagosome clearance leads to accumulation of toxic protein aggregates

• Endolysosomal impairment: Altered lysosomal function reduces clearance of 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)

PS2 vs. PS1 Comparison

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)

Calcium Dysregulation — A Gamma-Secretase-Independent Pathogenic Mechanism

PS2 has an important gamma-secretase-independent role in intracellular calcium homeostasis, which is increasingly recognized as a key pathogenic mechanism:

ER Calcium Leak

• 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)

Mitochondria-Associated ER Membranes (MAMs)

• PS2 is enriched at MAMs — specialized ER-mitochondria contact sites that regulate calcium transfer, lipid metabolism, and 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, opening of the permeability transition pore, and apoptosis

Downstream Effects on Autophagy

• FAD-PSEN2 mutations impair 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 amyloid-beta and tau/proteins/tau

IP3 Receptor-Mediated Calcium Release

• PS2 modulates IP3 receptor ([IP3R

IP3 Receptor-Mediated Calcium Release

• 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

Therapeutic Implications

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 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 enhancers: Compounds that enhance autophagic flux downstream of calcium dysregulation (e.g., trehalose, rapamycin analogs) may counteract PS2 mutation effects on protein clearance.

Brain Atlas Resources

• Allen Human Brain Atlas: Presenilin-2 expression search

• Allen Mouse Brain Atlas: Presenilin-2 search

• Allen Cell Type Atlas: Transcriptomic cell type reference

• BrainSpan Developmental Transcriptome: Presenilin-2 developmental expression

See Also

• Genes Index — All gene pages

• [Proteins Index — Protein pages

• [alzheimers — Neurodegenerative disease

External Links

• NCBI Gene — Gene database

• ^{2Cellular processing of beta-amyloid precursor protein and the genesis of amyloid beta-peptide1993 · PMID 8101482Open reference}8(https://www.uniprot.org) — Protein database

Background

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.