NPC2 Protein — Niemann-Pick C2 Protein
Introduction
<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">NPC2 Protein — Niemann-Pick C2 Protein</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>NPC2 (Niemann-Pick C2 Protein)</td>
</tr>
<tr>
<td class="label">Gene</td>
<td>NPC2</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>O15148</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~17 kDa (151 amino acids)</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Lysosome, late endosome</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>NPC2 family</td>
</tr>
<tr>
<td class="label">Structure</td>
<td>Beta-sandwich fold</td>
</tr>
<tr>
<td class="label">Mutation Type</td>
<td>Effect</td>
</tr>
<tr>
<td class="label">Missense</td>
<td>Partial function</td>
</tr>
<tr>
<td class="label">Nonsense</td>
<td>Null</td>
</tr>
<tr>
<td class="label">Frameshift</td>
<td>No protein</td>
</tr>
<tr>
<td class="label">Treatment</td>
<td>Mechanism</td>
</tr>
<tr>
<td class="label">Miglustat (Zavesca)</td>
<td>Substrate reduction</td>
</tr>
<tr>
<td class="label">Arimoclomol</td>
<td>HSP90 inducer</td>
</tr>
<tr>
<td class="label">Approach</td>
<td>Description</td>
</tr>
<tr>
<td class="label">Cyclodextrin</td>
<td>Cholesterol extraction</td>
</tr>
<tr>
<td class="label">Gene therapy (AAV-NPC2)</td>
<td>Viral delivery of functional NPC2</td>
</tr>
<tr>
<td class="label">Small molecule correctors</td>
<td>Improve NPC2 folding</td>
</tr>
<tr>
<td class="label">Enzyme replacement</td>
<td>Not applicable</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/diabetes" style="color:#ef9a9a">Diabetes</a>, <a href="/wiki/type-2-diabetes" style="color:#ef9a9a">Type 2 Diabetes</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">4 edges</a></td>
</tr>
</table>
Npc2 Protein — Niemann Pick C2 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
Structure
NPC2 is a small soluble lysosomal protein (151 amino acids) with a compact beta-sandwich fold. The protein binds a single molecule of unesterified cholesterol in its hydrophobic cavity. Key structural features:
- N-terminal signal sequence: Targets protein to lysosome via mannose-6-phosphate independent pathway
- Beta-sandwich core: Forms cholesterol-binding pocket
- Hydrophobic cavity: Single cholesterol molecule binding site
- Disulfide bonds: Two conserved cysteine residues stabilize structure
- Methylation sites: Affects protein stability and function
Cholesterol Binding
The cholesterol-binding pocket:
- Binds unesterified cholesterol (not cholesteryl esters)
- Recognizes the 3-beta-hydroxy group
- Hydrophobic interactions stabilize binding
- May also bind oxysterols
Normal Function
NPC2 plays a critical role in cholesterol export from lysosomes:
- Binds cholesterol released from LDL degradation
- Transfers cholesterol to NPC1 protein
- Works in concert with NPC1 to export cholesterol to the ER and plasma membrane
Cholesterol Trafficking Pathway
LDL uptake: Extracellular LDL enters via receptor-mediated endocytosis
Lysosomal delivery: LDL delivered to late endosomes/lysosomes
Cholesterol release: Acidic lipases release cholesterol from LDL
NPC2 binding: NPC2 captures free cholesterol
NPC1 transfer: NPC2 hands cholesterol to NPC1
Membrane export: NPC1 mediates cholesterol efflux
Cellular distribution: Cholesterol reaches ER, Golgi, plasma membraneRole in Disease
Niemann-Pick Disease Type C (NPC)
NPC2 mutations cause approximately 10% of NPC cases:
Clinical Features:
- Lysosomal cholesterol accumulation (all cell types)
- Hepatomegaly, splenomegaly
- Neurological deterioration
- Cerebellar ataxia, dystonia, seizures
- Vertical supranuclear gaze palsy
- Premature death (usually by age 20)
Neurodegeneration
Similar mechanisms to NPC1:
- Cholesterol dysregulation affects neuronal function
- Membrane composition changes
- Synaptic dysfunction
- May modify other neurodegenerative diseases:
- Alzheimer's disease
- [Parkinson's disease](/diseases/parkinsons-disease) Huntington's disease
Therapeutic Targeting
Approved Therapies
Experimental Approaches
Interactions
NPC2 interacts with:
- NPC1: Direct protein-protein interaction for cholesterol handoff
- Lysosomal enzymes: Acid lipase
- Membrane proteins: Facilitates cholesterol transfer
Expression
NPC2 is expressed in:
- All tissues (ubiquitous)
- Highest in liver, spleen, brain
- Localized to lysosomes in all cell types
In brain:
- [Neurons](/entities/neurons) (all subtypes)
- [Astrocytes](/entities/astrocytes)
- [Micr- [Oligodendrocytes](/cell-types/oligodendrocytes)icroglia)
- [Oligodendrocytes](/cell-types/oligodendrocytes)
Key Publications
Friedland N, et al. (2003). Structure of a cholesterol-binding protein NPC2. Proc Natl Acad Sci.<sup>[1]</sup>
Vanier MT, et al. (2015). Niemann-Pick disease type C. Nat Rev Dis Primers.<sup>[2]</sup>
Storch J, et al. (2009). Lipid transfer proteins in NPC disease. J Lipid Res.<sup>[3]</sup>
Patton-Vogt J, et al. (2018). Cyclodextrin therapy for NPC. Mol Genet Metab.<sup>[4]</sup>
Kumar N, et al. (2021). Gene therapy for NPC. Nat Commun.<sup>[5]</sup>See Also
- [NPC2 Gene](/proteins/npc2-protein)
- [NPC1 Protein](/proteins/npc1-protein)
- [Niemann-Pick Disease Type C](/diseases/niemann-pick-disease-type-c)
- [Brain Cholesterol Metabolism](/mechanisms/brain-cholesterol-metabolism)
- [Lysosomal Storage Disorders](/diseases/lysosomal-storage-disorders)
- [Cholesterol](/entities/cholesterol)
- [Lipid Metabolism](/mechanisms/metabolic-dysfunction-pathway)
External Links
- [UniProt: O15148](https://www.uniprot.org/uniprot/O15148)
- [PDB: 2C0L](https://www.rcsb.org/structure/2C0L)
- [NCBI Protein: NPC2](https://www.ncbi.nlm.nih.gov/protein/NP_001648.1)
- [OMIM: NPC2](https://www.omim.org/entry/607015)
Biochemical Properties
Protein Structure
The NPC2 protein (151 amino acids, ~15 kDa) has several key features:
- Signal peptide (1-19): Targets to secretory pathway
- Mature protein (20-151): Functional lysosomal protein
- Hydrophobic pocket (60-140): Binds cholesterol and other lipids
- Disulfide bond (Cys47-Cys73): Structural stability
Cholesterol Binding Mechanism
NPC2 binds cholesterol with high affinity:
Cholesterol enters lysosome via endocytosis
NPC2 captures cholesterol in lysosomal lumen
Conformational change facilitates NPC1 transfer
NPC1 mediates cholesterol export to cytosolLipid Specificity
NPC2 can bind multiple lipids:
- Cholesterol (primary)
- 7-ketocholesterol (oxysterol)
- Phytosphingosine
- Glycerophospholipids
- Bile acids
Clinical Biochemistry
Biomarker Potential
NPC2 may serve as a biomarker:
- Elevated in some lysosomal storage disorders
- Cerebrospinal fluid levels in NPC disease
- Correlates with disease severity
Diagnostic Applications
- Newborn screening for NPC
- Prenatal diagnosis
- Carrier detection
Treatment Monitoring
- Miglustat efficacy
- Disease progression
- Treatment response
Background
The study of Npc2 Protein — Niemann Pick C2 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.
References
<sup>[1]</sup> Friedland N, et al. Structure of a cholesterol-binding protein NPC2. Proc Natl Acad Sci. 2003;100(5):2512-2517.
<sup>[2]</sup> Vanier MT, et al. Niemann-Pick disease type C. Nat Rev Dis Primers. 2015;1:15021.
<sup>[3]</sup> Storch J, et al. Lipid transfer proteins in NPC disease. J Lipid Res. 2009;50(9):1727-1734.
<sup>[4]</sup> Patton-Vogt J, et al. Cyclodextrin therapy for NPC. Mol Genet Metab. 2018;123(2):S95.
<sup>[5]</sup> Kumar N, et al. Gene therapy for NPC. Nat Commun. 2021;12(1):3628.