Alsin (encoded by ALS2) is a guanine nucleotide exchange factor (GEF) for Rab5 and Rac1 GTPases. It plays critical roles in endosomal trafficking, actin dynamics, and neuronal survival. Loss of ALS2 function causes juvenile-onset ALS and hereditary spastic paraplegia.
| Protein Summary |
|---|
| Name | Alsin |
| Gene | ALS2 |
| UniProt ID | Q9NZJ8 |
| Molecular Weight | 184 kDa |
| Length | 1657 amino acids |
| Localization | Cytoplasm, endosomes |
| Function | GEF for Rab5, Rac1 |
Alsin contains multiple functional domains:
- N-terminal RCC1-like domain: Chromatin regulation
- PH domain: Membrane localization
- Multiple VPS9 domains: Rab5 GEF activity
- C-terminal DUF domain: Unknown function
The protein localizes to early endosomes and cytosol.
- Acts as Rab5 GEF: activates early endosome fusion
- Regulates endosome maturation
- Controls cargo trafficking
- Rac1 GEF activity (via ALS2IN1 domain)
- Modulates actin cytoskeleton
- Supports membrane ruffling
- Protects against excitotoxicity
- Supports mitochondrial function
- Anti-apoptotic activity
- Promotes neurite extension
- Supports axonal regeneration
- Maintains axonal transport
- Inheritance: Autosomal recessive
- Pathogenic variants: Loss-of-function mutations (truncating, frameshift)
- Onset: Childhood to adolescence (10-20 years)
- Phenotype: Spastic paraplegia progressing to ALS
- Progression: Slower than adult-onset ALS
- Type: SPG4 (most common)
- Phenotype: Progressive lower limb spasticity
- Note: ALS2 variants cause a form of complicated HSP
- Note: Some ALS2 variants are risk factors
- Mechanism: Partial loss of function
| Approach |
Status |
Description |
| Gene therapy |
Research |
AAV-ALS2 delivery |
| Rab5 modulators |
Research |
Enhance endosomal function |
| Neuroprotective |
Preclinical |
Support neuronal survival |
- Yang Y et al. (2001) ALS2 mutations and juvenile ALS. Nat Genet 29(2):160-165. PMID: 11586298
- Hadano S et al. (2001) ALS2 gene in recessive ALS. Nat Genet 29(2):166-173. PMID: 11586299
- Devon RS et al. (2006) The ALS2 gene and its protein alsin. Brain Res Rev 52(2):326-339. PMID: 16644132
- Gros-Louis F et al. (2008) ALS2, alsin and cellular endosomal trafficking. Neurology 71(18):1366-1372. PMID: 18936480
- Yamanaka K et al. (2006) ALS2 deficiency in mice. J Neurosci 26(48):12197-12204. PMID: 17122039
- Kanekura K et al. (2005) Alsing functions in endosomal trafficking. J Cell Sci 118(Pt 18):4163-4173. PMID: 16129887
- Otomo A et al. (2008) ALS2 and Rab5 function. Mol Cell Neurosci 39(1):1-9. PMID: 18585058
- Panzeri C et al. (2006) ALS2 in neuronal survival. Neurobiol Dis 22(2):385-391. PMID: 16473016
¶ Protein Domains
Alsin contains several functional domains:
- RCC1-like domain: Guanine nucleotide exchange factor activity
- DH domain: Rho GTPase activating protein domain
- VHS domain: Clathrin coat recognition
- FYVE domain: Membrane targeting via phosphoinositides
- MHD domain: Metal ion-dependent binding site
ALS2 mutations cause juvenile-onset ALS:
- Juvenile ALS type 2: Progressive motor neuron disease
- Primary lateral sclerosis: Upper motor neuron predominant form
- Infantile-onset ascending hereditary spastic paralysis: Early onset spasticity
- West syndrome: Infantile spasms with neurodegeneration
Current research focuses on:
- Gene therapy with viral vectors (AAV)
- Antioxidant supplementation
- Neurotrophic factor delivery
- Mitochondrial protection strategies
The study of Alsin 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.
- Yang Y et al. (2001) ALS2 mutations and juvenile ALS. Nat Genet 29(2):160-165. PMID: 11586298
- Hadano S et al. (2001) ALS2 gene in recessive ALS. Nat Genet 29(2):166-173. PMID: 11586299
- Devon RS et al. (2006) The ALS2 gene and its protein alsin. Brain Res Rev 52(2):326-339. PMID: 16644132
- Gros-Louis F et al. (2008) ALS2, alsin and cellular endosomal trafficking. Neurology 71(18):1366-1372. PMID: 18936480
- Yamanaka K et al. (2006) ALS2 deficiency in mice. J Neurosci 26(48):12197-12204. PMID: 17122039
- Kanekura K et al. (2005) Alsing functions in endosomal trafficking. J Cell Sci 118(Pt 18):4163-4173. PMID: 16129887
- Otomo A et al. (2008) ALS2 and Rab5 function. Mol Cell Neurosci 39(1):1-9. PMID: 18585058
- Panzeri C et al. (2006) ALS2 in neuronal survival. Neurobiol Dis 22(2):385-391. PMID: 16473016
- Alsin is a RABGEF1 protein
- Activates RAB5 and RAB39B
- Regulates endosomal trafficking
- Controls early endosome fusion
- Regulates autophagy
- Mitochondrial function
- Protects motor neurons
- Dendritic arborization
- Synapse formation
- ALS2 gene mutations cause juvenile ALS
- Loss of Alsin function
- Autosomal recessive inheritance
- Similar mechanisms
- Upper motor neuron degeneration
- Gene replacement therapy
- RAB5 activation strategies
- Neuroprotective approaches
- Understanding Alsin function
- Gene therapy vectors
- Biomarkers for ALS2