Nicastrin (encoded by the NCSTN gene is an essential subunit of the γ-secretase complex that cleaves amyloid precursor protein (APP) and Notch receptors. As a gatekeeper for γ-secretase substrate access, nicastrin is central to amyloid-β production in Alzheimer's disease.
Nicastrin is a type I transmembrane glycoprotein of ~130 kDa that serves as the substrate receptor of the γ-secretase complex[1]. The γ-secretase complex — composed of presenilin-1 or presenilin-2 (catalytic subunit), nicastrin, APH-1, and PEN-2 — is an intramembrane aspartyl protease essential for processing over 90 type I transmembrane substrates[2]. Nicastrin recognizes the N-terminus of substrate ectodomains after ectodomain shedding, gating substrate access to the presenilin active site. [1]
| | | [2]
|---|---| [3]
| Protein Name | Nicastrin |
| Gene | NCSTN |
| UniProt ID | Q92542 |
| Molecular Weight | ~78 kDa (predicted), ~130 kDa (mature, glycosylated) |
| Length | 709 amino acids |
| Subcellular Localization | Plasma membrane, endosomes, Golgi |
| Function | γ-secretase substrate receptor |
Nicastrin has a large ectodomain and a single transmembrane pass[3]:
The four subunits assemble in a defined order in the ER[2]:
Nicastrin's ectodomain functions as the substrate receptor for γ-secretase[1]:
| Substrate | Sheddase | γ-Secretase Product | Disease Relevance |
|---|---|---|---|
| APP | β-secretase (BACE1 | Aβ40/Aβ42 | Alzheimer's disease |
| APP | α-secretase (ADAM10 | p3 (non-amyloidogenic) | Non-pathogenic |
| Notch1-4 | ADAM10/TACE | NICD (transcription factor) | Development, cancer |
| N-cadherin | ADAM10 | CTF2 | Synaptic signaling |
| ErbB4 | ADAM17 | ICD | Neuregulin signaling |
Nicastrin is required for γ-secretase cleavage of APP into Aβ peptides[4]:
Nicastrin modulates AD pathogenesis through its role in Aβ production[4]:
Heterozygous loss-of-function NCSTN mutations cause familial acne inversa[5]:
| Interactor | Type | Function |
|---|---|---|
| Presenilin-1 | Complex subunit | Catalytic subunit of γ-secretase |
| Presenilin-2 | Complex subunit | Alternative catalytic subunit |
| APH-1A/1B | Complex subunit | Scaffolding subunit |
| PEN-2 | Complex subunit | Presenilin endoproteolysis trigger |
| APP C99 | Substrate | Amyloid precursor protein C-terminal fragment |
| Notch receptors | Substrate | Developmental signaling receptors |
[De Strooper B, Aph-1, Pen-2, and Nicastrin with Presenilin generate an active gamma-secretase complex (2003)](https://doi.org/10.1016/S0896-6273(03). 2003. ↩︎
Selkoe DJ & Hardy J, The amyloid hypothesis of Alzheimer's disease at 25 years (2016). 2016. ↩︎
Wang B et al. Gamma-secretase gene mutations in familial acne inversa (2010). 2010. ↩︎