Nicastrin (NCT) Protein

Nicastrin (NCT) Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Nicastrin (NCT)</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[NCSTN](/genes/ncstn)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q92673" target="_blank">Q92673</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/6AUX" target="_blank">6AUX</a>, <a href="https://www.rcsb.org/structure/6IDF" target="_blank">6IDF</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>~130 kDa (type I transmembrane glycoprotein)</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Endoplasmic reticulum, Golgi apparatus, cell membrane</td>
</tr>
<tr>
<td class="label">Family</td>
<td>Pen-2 family ([γ-secretase](/entities/gamma-secretase) complex)</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers), [Frontotemporal Dementia](/diseases/ftd)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">9 edges</a></td>
</tr>
</table>

Nicastrin (NCT)

Introduction

...

Nicastrin (NCT) Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">Nicastrin (NCT)</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[NCSTN](/genes/ncstn)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td><a href="https://www.uniprot.org/uniprot/Q92673" target="_blank">Q92673</a></td>
</tr>
<tr>
<td class="label">PDB</td>
<td><a href="https://www.rcsb.org/structure/6AUX" target="_blank">6AUX</a>, <a href="https://www.rcsb.org/structure/6IDF" target="_blank">6IDF</a></td>
</tr>
<tr>
<td class="label">Mol. Weight</td>
<td>~130 kDa (type I transmembrane glycoprotein)</td>
</tr>
<tr>
<td class="label">Localization</td>
<td>Endoplasmic reticulum, Golgi apparatus, cell membrane</td>
</tr>
<tr>
<td class="label">Family</td>
<td>Pen-2 family ([γ-secretase](/entities/gamma-secretase) complex)</td>
</tr>
<tr>
<td class="label">Diseases</td>
<td>[Alzheimer's Disease](/diseases/alzheimers), [Frontotemporal Dementia](/diseases/ftd)</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/alzheimer" style="color:#ef9a9a">Alzheimer</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">9 edges</a></td>
</tr>
</table>

Nicastrin (NCT)

Introduction

Nicastrin (Nct) Protein 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

Nicastrin (NCT) is a type I transmembrane glycoprotein that serves as an essential component of the gamma-secretase complex, the protease responsible for the proteolytic cleavage of [amyloid precursor protein](/entities/app-protein) (APP) to generate amyloid-beta (Abeta) peptides["@de2002"]. As the largest subunit of gamma-secretase, nicastrin plays critical roles in substrate recognition, complex assembly, and enzymatic activity. Dysregulation of nicastrin function has been implicated in Alzheimer's disease pathogenesis["@kimberly2003"].

The gamma-secretase complex consists of four core components: presenilin ([PSEN1](/entities/psen1) or PSEN2), nicastrin (NCT), anterior pharynx defective 1 (APH-1), and presenilin enhancer 2 (PEN-2). All four components are required for maximal catalytic activity["@yu2000"].

Structure

Nicastrin is a 709-amino acid type I transmembrane protein with a large extracellular domain (residues 1-673), a single transmembrane helix (residues 674-696), and a short cytoplasmic tail (residues 697-709).

Key Structural Features

Dimerization Domain

Nicastrin forms homodimers via its extracellular domain, which is important for γ-secretase assembly and function.

Pseudopeptidase Domain

The extracellular domain shares structural homology with aminopeptidases but lacks catalytic activity. This domain serves as a substrate docking site.

Glycosylation

Nicastrin is heavily N-glycosylated in the Golgi apparatus, and glycosylation is required for proper trafficking to the cell surface and γ-secretase activity.

Normal Function

γ-Secretase Assembly and Activity

Nicastrin plays multiple essential roles in γ-secretase function:

Complex Assembly: Nicastrin acts as a scaffold for γ-secretase complex assembly in the ER

Substrate Recognition: The extracellular domain binds APP and other substrates

Endoproteolysis: Required for presenilin endoproteolysis and activation

Trafficking: Facilitates proper subcellular localization of the complex

Substrate Processing

The γ-secretase complex processes numerous type I transmembrane substrates:

• Amyloid precursor protein (APP)
• Notch receptors
• E-cadherin
• ErbB4
• LDL receptor-related proteins (LRPs)
• Synaptic adhesion molecules

Role in Disease

Alzheimer's Disease

Aβ Generation

γ-secretase produces Aβ peptides through sequential proteolysis:

• First cleavage: ε-cleavage at Aβ37-46
• Second cleavage: γ-cleavage producing [Aβ40](/proteins/amyloid-beta) or Aβ42

The Aβ42/Aβ40 ratio is critical - Aβ42 is more aggregation-prone and forms the core of amyloid plaques.

Mutations

• NCSTN mutations have been linked to familial Alzheimer's disease
• Mutations can alter γ-secretase activity and Aβ42/Aβ40 ratios

Therapeutic Targeting

γ-secretase inhibitors (GSIs) have been developed but faced challenges:

• Notch-related toxicity due to broad substrate specificity
• Cognitive worsening in clinical trials
• Modulators (GSM) show more promise by shifting Aβ production

Therapeutic Targeting

γ-Secretase Modulators (GSMs)

• NSAID-derived modulators (flurbiprofen derivatives)
• Small molecule GSMs in development
• Allosteric modulators targeting nicastrin

γ-Secretase Inhibitors (GSIs)

• Semagacestat (failed in Phase III)
• Avagacestat (in development)

Alternative Approaches

• Antibody-based therapies targeting Aβ
• BACE inhibitors in combination with GSMs
• Gene therapy approaches

Key Publications

[De Strooper B, Nicastrin is required for γ-secretase complex assembly (2002)](https://doi.org/10.1016/S0092-8674(02)01036-2)

[Edbauer D et al., Reconstitution of γ-secretase complex (2003)](https://doi.org/10.1073/pnas.0534348100)

[Yu G et al., Nicastrin functions as a substrate receptor (2000)](https://doi.org/10.1016/S0092-8674(00)00063-5)

[Sannerud R & Annaert W, γ-secretase subunit composition (2011)](https://doi.org/10.1016/j.tns.2011.03.001)

[Walters A & Koo EH, A tale of two γ-secretases (2011)](https://doi.org/10.1038/nm0211-233)

Background

The study of Nicastrin (Nct) Protein 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](https://pubmed.ncbi.nlm.nih.gov/) - Biomedical literature
• [Alzheimer's Disease Neuroimaging Initiative](https://adni.loni.usc.edu/) - Research data
• [Allen Brain Atlas](https://brain-map.org/) - Brain gene expression data

Cross-References

• [NCSTN Gene](/genes/ncstn)
• [Presenilin-1 Protein](/proteins/presenilin-1)
• [Presenilin-2 Protein](/proteins/presenilin-2)
• [APH-1 Protein](/proteins/aph-1)
• [PEN-2 Protein](/proteins/pen-2)
• [Amyloid Precursor Protein](/proteins/amyloid-beta-protein)
• [Alzheimer's Disease](/diseases/alzheimers-disease)
• [Gamma-Secretase in AD](/mechanisms/gamma-secretase)

See Also

• [Proteins Index](/proteins/)
• [Genes Index](/genes/)
• [Diseases Index](/diseases/)

References

[De Strooper B, Nicastrin is required for the assembly of presenilin/γ-secretase complexes (2002)](https://doi.org/10.1016/S0896-6273(02)

[Kimberly WT, LaVoie MJ, Ostaszewski BL, et al, γ-Secretase is a membrane-bound complex assembled by presenilin, nicastrin, Aph-1, and Pen-2 (2003)](https://doi.org/10.1074/jbc.C300095200)

[Yu G, Nishimura M, Arawaka S, et al, Nicastrin modulates presenilin-mediated notch/glp-1 signal transduction and βAPP processing (2000)](https://doi.org/10.1038/35024009)

Pathway Diagram

The following diagram shows the key molecular relationships involving Nicastrin (NCT) Protein discovered through SciDEX knowledge graph analysis: