Presenilin 1 (Ps1) 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-1 (PS1), encoded by the [PSEN1[/genes/psen1 gene on chromosome 14q24.2, is a 467-amino acid multi-pass transmembrane protein that serves as the catalytic subunit of the [gamma-secretase[/entities/gamma-secretase complex. This aspartyl protease complex cleaves over 100 type I transmembrane substrates, most notably [amyloid precursor protein[/genes/app ([APP[/genes/app to generate [amyloid-beta[/entities/amyloid-beta ([Aβ) peptides, and Notch receptors, which are essential for cell fate determination during development.[1]
Mutations in [PSEN1[/genes/psen1 are the most common cause of early-onset familial [Alzheimer's disease[/diseases/alzheimers (FAD), accounting for approximately 70% of autosomal dominant AD cases. Over 450
pathogenic [PSEN1[/genes/psen1 variants have been identified — more than in any other gene associated with AD — with disease onset typically between ages 25–60, often decades earlier than
sporadic AD.[8] The vast majority of these mutations
cause a loss of [gamma-secretase[/entities/gamma-secretase's precision cleavage (processivity), shifting [Aβ[/entities/amyloid-beta production toward longer, more aggregation-prone Aβ42/43 peptides relative to shorter Aβ38/40
species.[2]
PS1 is a polytopic membrane protein with nine transmembrane domains (TMDs) and a large cytoplasmic loop between TMD6 and TMD7:
- The N-terminus and C-terminus reside in the cytoplasm
- TMD6 and TMD7 harbor the two catalytic aspartate residues (Asp257 and Asp385) that form the active site of the [gamma-secretase[/entities/gamma-secretase aspartyl protease
- The large intracellular loop (~110 amino acids) undergoes regulated endoproteolysis during [gamma-secretase[/entities/gamma-secretase complex maturation
- TMD1–6 and TMD7–9 form two structural halves that create a water-filled intramembrane cavity for substrate access
PS1 functions within a heterotetrameric complex consisting of:
- Presenilin-1 (or [Presenilin-2): Catalytic subunit — provides the aspartyl protease activity
- Nicastrin: Substrate recognition and gating — its ectodomain acts as a steric gatekeeper, admitting only substrates whose ectodomains have been previously shed
- APH-1 (anterior pharynx-defective 1): Scaffolding and stabilization during complex assembly
- PEN-2 (presenilin enhancer 2): Triggers PS1 endoproteolysis and activation; required for catalytic maturation
Cryo-EM structures of the [gamma-secretase[/entities/gamma-secretase complex (resolved to ~2.6 Å with substrate bound) have revealed how the complex accommodates substrates within a water-filled intramembrane chamber and how FAD mutations distort the substrate binding channel.[3]
¶ Endoproteolysis and Activation
During [gamma-secretase[/entities/gamma-secretase assembly, PS1 undergoes autocatalytic endoproteolysis within the large cytoplasmic loop (between TMD6 and TMD7), generating a ~28 kDa N-terminal fragment (NTF) and ~18 kDa C-terminal fragment (CTF). These fragments remain tightly associated as a heterodimer within the active complex. Only endoproteolyzed PS1 is catalytically active. The stoichiometry of the mature complex is 1:1:1:1 (PS1-NTF/CTF:Nicastrin:APH-1:PEN-2).
PS1-containing [gamma-secretase[/entities/gamma-secretase performs regulated intramembrane proteolysis (RIP) of type I transmembrane proteins. The cleavage of [APP[/genes/app proceeds through a well-defined sequence:[2]
- ε-cleavage (initial endopeptidase cut): Occurs at the membrane-cytoplasm boundary at Aβ48 or Aβ49 position, releasing the [APP[/genes/app intracellular domain (AICD)
- ζ-cleavage (first tripeptide trimming): Aβ49→46 or Aβ48→45
- γ-cleavage (successive tripeptide trimming): Continues as Aβ46→43→40 or Aβ45→42→38, with each step releasing a tri- or tetrapeptide
- The final released [Aβ[/entities/amyloid-beta species depends on the efficiency of this processivity — FAD mutations reduce processivity, causing premature substrate release at longer (more pathogenic) species
Two major product lines exist:
- Aβ49 → 46 → 43 → 40 → 37 (the predominant pathway, producing shorter, less pathogenic species)
- Aβ48 → 45 → 42 → 38 (produces Aβ42, the more aggregation-prone species)
- [APP[/genes/app: Generates [Aβ[/entities/amyloid-beta peptides of varying lengths (Aβ37–43)
- Notch: Cleavage releases the Notch intracellular domain (NICD), which translocates to the nucleus to regulate transcription of HES/HEY target genes — essential for neural development, adult neurogenesis, and immune cell differentiation
- E-cadherin: Cell adhesion molecule; cleavage modulates cell-cell contacts
- ErbB4: Receptor tyrosine kinase; cleavage releases signaling domain
- [LRP1[/entities/lrp1, CD44, N-cadherin, DCC, p75-NTR, and >90 other substrates
PS1 also has functions independent of its role in [gamma-secretase[/entities/gamma-secretase:[6]
- ER calcium regulation: PS1 functions as an ER calcium leak channel; FAD mutations reduce this function, increasing ER calcium stores and sensitizing [neurons[/entities/neurons to calcium-dependent excitotoxicity
- Wnt/β-catenin signaling: PS1 interacts with β-catenin and [GSK-3β[/entities/gsk3-beta, modulating Wnt signaling independently of Notch processing
- [autophagy[/entities/autophagy/lysosomal function: PS1 is required for proper acidification of lysosomes and autophagosomes via its role in targeting the v-ATPase proton pump; FAD mutations impair lysosomal pH regulation and autophagic flux[9]
- Protein trafficking: Facilitates transport of proteins through the ER-Golgi secretory pathway
Over 450 [PSEN1[/genes/psen1 mutations have been identified in FAD families worldwide. Key features:5,8
- Predominantly missense mutations: Single amino acid substitutions affecting [gamma-secretase[/entities/gamma-secretase processivity
- Loss-of-processivity mechanism: Rather than increasing total [Aβ[/entities/amyloid-beta, most mutations reduce the efficiency of sequential tripeptide trimming, leading to premature release of longer Aβ42/43 before it can be trimmed to Aβ38/40[2]
- Elevated Aβ42/40 ratio: The ratio of Aβ42 to Aβ40 is the key pathogenic metric; even modest increases (1.5–2 fold) dramatically accelerate amyloid nucleation and plaque formation
- Complete penetrance: Virtually all carriers develop AD, with predictable age of onset for specific mutations
- Variable onset age: Different mutations cause onset from age 24 (L166P) to age 65 (some partial loss-of-function variants), correlating inversely with the degree of gamma
Stalled enzyme-substrate complexes: A 2025 study revealed that FAD mutations lead to stabilized gamma-secretase/substrate complexes that accumulate at synapses and trigger synaptic loss independently of [Aβ[/entities/amyloid-beta production, representing a novel pathogenic mechanism beyond the canonical amyloid hypothesis.[14]
| Mutation |
Age of Onset |
Prevalence |
Notes |
| E280A |
~49 years |
Largest FAD kindred (~6000 carriers, Antioquia, Colombia) |
[DIAN] and Alzheimer's Prevention Initiative trial target |
| A431E |
25–35 years |
Mexican families |
Among the most aggressive PSEN1 mutations |
| H163R |
45–55 years |
European families |
Common in Scandinavian populations |
| M146L/V |
38–48 years |
Multiple ethnicities |
Well-characterized biochemical effects |
| L166P |
24–35 years |
European |
Near-complete loss of processivity; among earliest onset known |
| A246E |
50–60 years |
Multiple families |
Founder mutation in some populations |
While the primary phenotype is Alzheimer's dementia, some PSEN1 mutations cause atypical presentations:[12]
- Spastic paraparesis: Seen with mutations causing cotton wool plaques (e.g., Δexon 9 deletion)
- Frontotemporal Dementia-like presentation: Some mutations mimic behavioral variant FTD
- Lewy body pathology: Co-occurring [alpha-synuclein[/proteins/alpha-synuclein pathology with some mutations
- Cerebellar ataxia: Particularly with mutations near TMD1 and TMD2
- Seizures: Myoclonus and generalized tonic-clonic seizures, particularly with early-onset mutations
- PS1-M146V knock-in mice: Show increased Aβ42/40 ratio, enhanced ER calcium release, and accelerated amyloid pathology when crossed with [APP[/genes/app transgenics
- 5xFAD mice ([APP[/genes/app/PS1 double transgenic): Carry 3 [APP[/genes/app and 2 PSEN1 mutations; develop aggressive amyloid pathology by 2 months; widely used for preclinical drug testing
- PS1 knockout mice: Lethal perinatally due to Notch signaling failure; demonstrate essential developmental role
- Conditional PS1/PS2 double knockout mice: Develop progressive neurodegeneration and memory impairment without amyloid pathology, supporting PS1 loss-of-function as independently pathogenic
- Semagacestat: Failed Phase III trial (2010) — caused cognitive worsening, skin cancer, and GI toxicity due to Notch inhibition
- Avagacestat: Also failed — similar Notch-mediated toxicity and paradoxical worsening
- The failure of GSIs established that non-selective gamma-secretase inhibition is not viable for AD treatment
GSMs shift Aβ production from longer species (Aβ42) toward shorter species (Aβ38/37) without affecting total Aβ levels or Notch processing. This approach directly addresses the processivity defect caused by PSEN1 mutations:[10]
- E2012: First-generation GSM; demonstrated proof-of-concept Aβ42 lowering
- BPN-15606: Potent second-generation GSM in clinical development
- NSAIDs (ibuprofen, sulindac sulfide): Original GSMs discovered incidentally; weak but validated the mechanism
A 2024 proof-of-concept study demonstrated that AAV9-mediated delivery of wild-type human PSEN1 can rescue gamma-secretase function in four different lines of Psen-mutant mice, reducing Aβ42/40 ratios and improving synaptic function — establishing gene replacement as a potential therapeutic strategy for FAD carriers.[13]
- [lecanemab[/treatments/lecanemab and [donanemab[/treatments/donanemab target downstream Aβ pathology and are being evaluated in FAD carriers
- The [DIAN-TU] ([Dominantly Inherited Alzheimer Network[/entities/dian-study — Trials Unit) tests therapies specifically in PSEN1/[PSEN2[/genes/psen2/APP mutation carriers
- [Researchers Index[/researchers — All researchers
- [Diseases Index[/diseases — Disease overview pages
The study of Presenilin 1 (Ps1) 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.
- [De Strooper B (2003). Aph-1, Pen-2, and nicastrin with presenilin generate an active gamma-secretase complex. [Neuron[/entities/neurons, 38(1):9-12. DOI:10.1016/S0896-6273(03
- [Szaruga M, Munteanu B, Lisber S, et al. (2017). Alzheimer's-causing mutations shift Aβ length by destabilizing γ-secretase-Aβn interactions. Cell, 170(3):443-456. DOI
- [Bai XC, Yan C, Yang G, et al. (2015). An atomic structure of human γ-secretase. Nature, 525(7568):212-217. DOI
- [Bentahir M, Nyabi O, Bhatt D, et al. (2006). Presenilin clinical mutations can affect gamma-secretase activity by different mechanisms. Journal of Neurochemistry, 96(3):732-742. DOI
- [Sun L, Zhou R, Yang G, et al. (2017). Analysis of 138 pathogenic mutations in [presenilin-1[/genes/psen1 on the in vitro production of Aβ42 and Aβ40 peptides by γ-secretase. PNAS, 114(4):E476-E485. DOI
- [Tu H, Nelson O, Bhatt A, et al. (2006). Presenilins form ER Ca2+ leak channels, a function disrupted by familial Alzheimer's Disease-linked mutations. Cell, 126(5):981-993. DOI
- [Lee JH, Yu WH, Kumar A, et al. (2010). Lysosomal proteolysis and autophagy require presenilin 1 and are disrupted by Alzheimer-related PS1 mutations. Cell, 141(7):1146-1158. DOI
- [Sherrington R, Rogaev EI, Liang Y, et al. (1995). Cloning of a gene bearing missense mutations in early-onset familial Alzheimer's Disease. Nature, 375(6534):754-760. DOI
- [Coen K, Flannagan RS, Baron S, et al. (2012). Lysosomal calcium homeostasis defects, not proton pump defects, cause endo-lysosomal dysfunction in PSEN-deficient cells. Journal of Cell Biology, 198(1):23-35. DOI
- [Kretner B, et al. (2016). Generation and deposition of Aβ43 by the virtually inactive [presenilin-1[/entities/psen1 L435F mutant contradicts the presenilin loss-of-function hypothesis of Alzheimer's Disease. EMBO Molecular Medicine, 8(5):458-465. DOI
- Alzforum PSEN1 database. PSEN1 Mutations — Alzforumhttps://www.alzforum.org/mutations/psen-1
- [Romero-Molina C, et al. (2023). Presenilin-1 mutations: clinical phenotypes beyond Alzheimer's Disease. International Journal of Molecular Sciences, 24(9):8417. DOI: 10.3390/ijms24098417)
- Bhatt A, et al. (2024). Proof-of-concept presenilin-based gene therapy targets early-onset Alzheimer's Disease carrying PSEN mutations. Brigham and Women's Hospital/Harvard Medical School. Summary
- [Bhatt A, et al. (2025). Presenilin-1 familial Alzheimer mutations impair γ-secretase cleavage of [APP[/genes/app through stabilized enzyme-substrate complex formation. Biomolecules, 15(7):955. DOI: 10.3390/biom15070955)
- Veugelen S, et al. (2025). Identification of presenilin mutations that have sufficient gamma-secretase proteolytic activity to mediate Notch signaling but disrupt organelle and neuronal health. PMC. PMC: 12184874## See Also
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- [Alzheimer's disease[/diseases/alzheimers — Primary disease caused by PSEN1 mutations
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- [gamma-secretase[/entities/gamma-secretase — Protease complex containing PS1
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- [presenilin-2[/genes/psen2 — Homologous catalytic subunit
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- [APP[/genes/app — Major gamma-secretase substrate
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- [BACE1[/entities/bace1 — Beta-secretase; upstream APP cleavage
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- [DIAN Study[/entities/dian-study — Clinical trials in PSEN mutation carriers
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- [Amyloid Cascade Hypothesis] — Theoretical framework## External Links
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