Erlin-1 (ERLIN1), also known as SPFH1 (Stomatin/Prohibitin/Flotillin/HflC/K), is an ER-resident protein that plays critical roles in lipid raft dynamics, cholesterol metabolism, and protein quality control. It forms characteristic ring-like structures in the ER membrane and is involved in the ER-associated degradation (ERAD) of misfolded proteins. Mutations in ERLIN1 are associated with hereditary spastic paraplegia (HSP), and the protein has been implicated in ALS and other neurodegenerative disorders.
- Length: 299 amino acids
- Molecular Weight: ~33,700 Da
- Type: Type III ER membrane protein (both N- and C-termini in cytoplasm)
¶ Domain Architecture
- SPFH Domain (Residues 22-184):
- Highly conserved stomatin/prohibitin/flotillin/HflC/K domain
- Forms oligomeric complexes
- Mediates protein-protein interactions
- Transmembrane Regions:
- Two hydrophobic segments
- Anchors protein in ER membrane
- C-terminal Region (Residues 185-299):
- Lipid-binding capacity
- Oligomerization interface
- Ring-like Complexes: ERLIN1/2 form ~400 kDa ring structures
- Hetero-oligomers: ERLIN1 typically forms heterooligomers with ERLIN2
- Stoichiometry: ~12-14 subunits per ring
- R67X: Hereditary spastic paraplegia (HSP), truncation
- G51R: HSP, loss of function
- A145T: ALS, reduced function
ERLIN1 is a key component of the ERAD machinery:
- Cholesterol Sensing: Detects cholesterol excess in ER membranes
- Lipid Raft Turnover: Regulates lipid raft composition
- Protein Quality Control: Targets misfolded proteins for degradation
- SREBP Cleavage: Regulates SREBP (sterol regulatory element-binding protein)
- HMG-CoA Reductase: Degrades HMGCR under high cholesterol
- ACAT2: Regulates acyl-CoA:cholesterol acyltransferase
- ERAD Substrate Recognition: Identifies misfolded proteins
- VCP/p97 Recruitment: Recruits ubiquitin-proteasome machinery
- Channel Formation: May form retro-translocation channels
- Cytoskeletal Organization: Links to actin cytoskeleton
- Cell Signaling: Modulates various signaling pathways
- Membrane Protein Trafficking: Regulates membrane protein levels
- Autosomal Recessive inheritance
- Primary Function Loss: Mutations cause loss of ERLIN1 function
- ER Stress: Impaired lipid homeostasis triggers ER stress
- Corticospinal Tract Degeneration: Upper motor neuron loss
- Aggregate Recruitment: Found in TDP-43 protein aggregates
- ER Stress: Contributes to chronic ER stress
- Lipid Dysregulation: Alters membrane lipid composition
- Motor Neuron Vulnerability: Impaired protein quality control
- Cholesterol Metabolism: Links to lipid hypothesis of AD
- Amyloid Processing: May influence APP processing
- Neuronal ER Stress: Contributes to AD pathology
- α-Synuclein Interaction: May affect α-synuclein clearance
- ER-Mitochondria Contacts: Modulates MAM function
- Dopaminergic Neuron Survival: Critical for neuronal health
- Loss of Function: Mutations impair lipid homeostasis
- ER Stress: Chronic unfolded protein response
- Lipid Raft Abnormalities: Altered membrane composition
- Protein Aggregate Susceptibility: Impaired clearance
- Mitochondrial Dysfunction: Altered calcium handling
| Approach | Target | Status |
|----------|--------|--------|
| ER Stress Modulators | UPR pathway | Preclinical |
| Cholesterol-lowering | Lipid metabolism | Approved (AD) |
| Proteostasis Enhancers | Protein quality control | Phase 1 |
| Lipid Raft Stabilizers | Membrane function | Discovery |
- AAV-ERLIN1: Gene replacement for HSP
- CRISPR Editing: Correct ERLIN1 mutations
- siRNA Knockdown: For gain-of-function studies
- Recombinant ERLIN1: Protein replacement
- Peptide Mimetics: Functional ERLIN1 fragments
| Partner |
Interaction Type |
Relevance |
| ERLIN2 |
Heterooligomer |
Functional complex |
| VCP/p97 |
Recruitment |
ERAD pathway |
| UBXN3B |
Co-factor |
Protein degradation |
| SREBP |
Cholesterol sensing |
Lipid metabolism |
| HMG-CoA Reductase |
Substrate |
Cholesterol regulation |
| TDP-43 |
Aggregate |
ALS pathology |
| Flotillin-1 |
Homolog |
Membrane domains |