| Property |
Value |
| Protein Name |
Cellular Prion Protein |
| Gene |
PRNP |
| UniProt ID |
P04156 |
| PDB ID |
1QLX, 1QM0, 2W9D, 4DGI |
| Molecular Weight |
~33-35 kDa (membrane-bound form) |
| Subcellular Localization |
Cell membrane (GPI-anchored), cytoplasm |
| Protein Family |
Prion protein family |
The cellular prion protein (PrPC) is a GPI-anchored glycoprotein expressed predominantly in the central nervous system. While its physiological function remains incompletely understood, PrPC is best known for its central role in prion diseases—fatal neurodegenerative disorders caused by conformational conversion to the disease-associated isoform PrPSc (scrapie prion protein). This page covers PrP structure, normal neurological functions, disease mechanisms, and therapeutic approaches.
The prion protein is a 253-amino acid GPI-anchored protein with a distinctive domain organization:
¶ Domain Organization
- Signal peptide (residues 1-23): N-terminal signal sequence for ER targeting
- Flexible N-terminal domain (residues 23-120): Unstructured, copper-binding region
- C-terminal globular domain (residues 121-231): Ordered, globular, contains three alpha-helices and two beta-strands
- GPI anchor signal (residues 232-253): Glycosylphosphatidylinositol anchor for membrane attachment
- Alpha-helices: Three alpha-helices (A: 144-154, B: 173-194, C: 200-228)
- Beta-strands: Two beta-strands (B1: 128-131, B2: 161-164) form a small beta-sheet
- Disulfide bond (Cys179-Cys214): Stabilizes the C-terminal domain
- Glycosylation sites: Two N-linked glycosylation sites (Asn181, Asn197)
- Copper binding: Octarepeat region (residues 51-91) binds Cu2+ ions
The disease-associated PrPSc isoform differs dramatically in:
- Beta-sheet content: Increased from ~10% to ~40-50%
- Protease resistance: C-terminal fragment (residues ~81-231) becomes proteinase K-resistant
- Aggregation propensity: Forms amyloid fibrils and plaques
- Glycosylation pattern: Distinct glycoform ratios compared to PrPC
- Antioxidant activity: Copper-bound PrPC exhibits SOD-like activity
- Cellular stress response: Upregulated under oxidative stress conditions
- Anti-apoptotic signaling: Activates PI3K/Akt and MAPK pathways
- Synaptic maintenance: Essential for synaptic structure and function
- Neurotransmission: Modulates GABAergic and glutamatergic signaling
- Synaptic plasticity: Involved in long-term potentiation (LTP)
- Copper binding: The octarepeat region binds up to 4 Cu2+ ions
- Copper uptake: May function as a copper influx transporter
- Copper metabolism: Regulates neuronal copper balance
- Membrane microdomains: Enriched in lipid rafts for signaling
- Protein interactions: Binds to various ligands including Cu2+, A-beta, and laminin
- Neuroprotective complexes: Forms complexes with A-beta to potentially neutralize its toxicity
- Neuronal differentiation: Involved in neural progenitor cell function
- Myelin maintenance: Important for oligodendrocyte survival
- Axonal guidance: May participate in axonal pathfinding
Prion diseases, also called transmissible spongiform encephalopathies (TSEs), are caused by conversion of PrPC to PrPSc:
-
Creutzfeldt-Jakob Disease (CJD)
- Most common human prion disease
- Sporadic (sCJD), genetic (gCJD), and iatrogenic (iCJD) forms
- Rapidly progressive dementia, ataxia, myoclonus
- Typical survival: months to 2 years
-
Fatal Familial Insomnia (FFI)
- Caused by D178N mutation with methionine at codon 129
- Progressive insomnia, autonomic dysfunction, cognitive decline
- Selective thalamic degeneration
-
Gerstmann-Sträussler-Scheinker Syndrome (GSS)
- Autosomal dominant prion disease
- Cerebellar ataxia, slowly progressive dementia
- Younger onset than CJD (40-60 years)
-
Kuru
- Historical prion disease in Papua New Guinea
- Transmitted through ritualistic cannibalism
- Cerebellar ataxia, tremors
- Scrapie: Sheep and goat prion disease
- Bovine Spongiform Encephalopathy (BSE): "Mad cow disease"
- Chronic Wasting Disease (CWD): Deer, elk, and moose
-
Nucleation-dependent polymerization
- PrPSc seeds template-driven conversion of PrPC
- Exponential amplification of PrPSc aggregates
- Seeding threshold determines disease incubation period
-
Strain diversity
- Different PrPSc conformations encode strain properties
- Strains differ in incubation periods, neuropathology, and species barrier
- Glycoform ratios (PrPSc di-, mono-, non-glycosylated) characterize strains
-
Loss of function
- Conversion depletes functional PrPC
- Loss of neuroprotective signaling
- Synaptic dysfunction
-
Gain of toxic function
- PrPSc aggregates are directly neurotoxic
- Membrane disruption by oligomeric species
- Activation of apoptotic pathways
-
Cellular dysfunction
- Endoplasmic reticulum stress: UPR activation
- Mitochondrial dysfunction: Complex I inhibition, ROS production
- Calcium dysregulation: Impaired calcium homeostasis
- Autophagy impairment: Accumulation of autophagic vacuoles
- Synaptic failure: Loss of synaptic proteins and function
-
Neuroinflammation
- Microglial activation
- Cytokine release (IL-1β, IL-6, TNF-α)
- Complement system activation
PrPC interacts with amyloid-beta (Aβ) peptide:
- Aβ binding: PrPC binds to Aβ oligomers with high affinity
- Toxicity mediation: PrPC may mediate Aβ-induced synaptic dysfunction
- Memory deficits: Aβ-PrPC interaction contributes to memory impairment in AD models
The PRNP gene (chromosome 20p13) shows polymorphism at codon 129:
- Methionine (M) or Valine (V): Homozygosity (M/M or V/V) increases sporadic CJD risk
- D178N mutation: Causes FFI when coupled with M129
- P102L mutation: Most common GSS mutation
- E200K mutation: Most common genetic CJD mutation (worldwide)
- Blood-brain barrier: Limits drug delivery to CNS
- Conformational conversion: Difficult to target with traditional inhibitors
- Strain diversity: Different PrPSc conformations require broad-spectrum approaches
- Monoclonal antibodies: Target PrPC or PrPSc epitopes
- Intrabodies: Intracellular antibodies to neutralize intracellular PrP
- Passive immunization: Antibody delivery to clear PrPSc
- Copper chelators: Disrupt metal-mediated aggregation
- Polyphenol derivatives: (e.g., epigallocatechin gallate) inhibit conversion
- Phenylbenzamides: Bind to PrP and prevent aggregation
- Aniline derivatives: PrPSc formation inhibitors
- RNAi: Knockdown of PRNP expression
- Antisense oligonucleotides (ASOs): Reduce PrPC levels
- CRISPR/Cas9: Gene editing approaches (preclinical)
- Microglial modulation: Reduce neuroinflammation
- Complement inhibition: Block complement-mediated damage
- Dominant-negative PrP: Mutant PrP that prevents conversion
- Decoy peptides: Compete with endogenous PrP for conversion
- Antisense oligonucleotides: Trials ongoing for genetic prion disease
- Antibody therapies: Several in preclinical development
- Copper-based therapies: Limited clinical benefit observed
- Prusiner, S.B. et al. (1993) Molecular structure of the prion protein (Cold Spring Harbor Laboratory Press)
- Prusiner, S.B. (1997) Prion diseases and the BSE crisis (Science)
- Brown, D.R. et al. (1997) The cellular prion protein binds copper in vivo (Nature)
- Colby, D.W. & Prusiner, S.B. (2011) Prions (Cold Spring Harbor Perspectives in Biology)
- Lauren, J. et al. (2009) Cellular prion protein as a receptor for amyloid-beta (Nature)
- White, A.R. et al. (2003) Monoclonal antibodies against prion protein (Journal of Neurochemistry)