ALS4 Protein (Alsin)

📖 Wiki Page

protein1328 wordssynced 2026-04-02

ALS4 Protein (Alsin)

Overview

...

ALS4 Protein (Alsin)

Overview

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">ALS4 Protein (Alsin)</th>
</tr>
<tr>
<td class="label">Protein Name</td>
<td>Alsin</td>
</tr>
<tr>
<td class="label">Gene Symbol</td>
<td>ALS4</td>
</tr>
<tr>
<td class="label">Alternative Names</td>
<td>ALS4 protein, IGHMBP2</td>
</tr>
<tr>
<td class="label">Chromosomal Location</td>
<td>11q13.2</td>
</tr>
<tr>
<td class="label">NCBI Gene ID</td>
<td>7080</td>
</tr>
<tr>
<td class="label">UniProt ID</td>
<td>Q9UQB8</td>
</tr>
<tr>
<td class="label">Protein Length</td>
<td>1,648 amino acids</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~185 kDa</td>
</tr>
<tr>
<td class="label">Expression</td>
<td>Highest in motor neurons, brain, spinal cord</td>
</tr>
<tr>
<td class="label">Protein Domains</td>
<td>Mitochondrial localization domain, Rab5 GEF domain, transcription activation domain</td>
</tr>
<tr>
<td class="label">Tissue</td>
<td>Expression Level</td>
</tr>
<tr>
<td class="label">Motor neurons</td>
<td>Highest</td>
</tr>
<tr>
<td class="label">Spinal cord</td>
<td>High</td>
</tr>
<tr>
<td class="label">Brain</td>
<td>High</td>
</tr>
<tr>
<td class="label">Heart</td>
<td>Moderate</td>
</tr>
<tr>
<td class="label">Liver</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Kidney</td>
<td>Low</td>
</tr>
<tr>
<td class="label">Protein/Entity</td>
<td>Interaction Type</td>
</tr>
<tr>
<td class="label">Rab5</td>
<td>GEF substrate</td>
</tr>
<tr>
<td class="label">VCP/p97</td>
<td>Co-localization</td>
</tr>
<tr>
<td class="label">[TDP-43](/mechanisms/tdp-43-proteinopathy)</td>
<td>Binding</td>
</tr>
<tr>
<td class="label">SOD1</td>
<td>Interaction</td>
</tr>
<tr>
<td class="label">Mitochondria</td>
<td>Localization</td>
</tr>
<tr>
<td class="label">Autophagy machinery</td>
<td>Regulation</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">ALS</a>, <a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/amyotrophic-lateral-sclerosis" style="color:#ef9a9a">Amyotrophic Lateral Sclerosis</a>, <a href="/wiki/ataxia" style="color:#ef9a9a">Ataxia</a>, <a href="/wiki/dementia" style="color:#ef9a9a">Dementia</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">120 edges</a></td>
</tr>
</table>

The ALS4 gene (Alsin) encodes the Alsin protein, a multifunctional Rab5 guanine nucleotide exchange factor (GEF) critical for endosomal trafficking, mitochondrial function, and neuronal survival. Alsin is predominantly expressed in motor [neurons](/entities/neurons) and is essential for proper neuronal function and survival. Biallelic loss-of-function mutations in ALS4 cause juvenile-onset amyotrophic lateral sclerosis (ALS4), an autosomal recessive form of ALS characterized by distal muscle weakness, atrophy, and slow progression. Additionally, ALS4 variants have been implicated in other neurodegenerative conditions including Charcot-Marie-Tooth disease type 2A2 (CMT2A2) and mitochondrial disorders. Understanding Alsin function provides insights into motor neuron biology and therapeutic strategies for ALS.

Introduction

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by progressive loss of upper and lower motor neurons, leading to muscle weakness, paralysis, and ultimately death[@chen2021]. While most ALS cases are sporadic, approximately 10% are familial with identified genetic causes[@renton2014]. ALS4 is a rare, autosomal recessive form caused by mutations in the ALS4 gene (also known as ALS4 or IGHMBP2) that typically presents in adolescence or young adulthood with a slower disease course compared to classic ALS[@chance1998][@liew2000]. The ALS4-encoded protein Alsin is a 1648 amino acid protein that functions as a Rab5 GEF, regulating endosomal trafficking and mitochondrial dynamics[@hadano2006][@otomo2008].

This comprehensive analysis covers ALS4/Alsin structure, function, disease associations, therapeutic implications, and current research.

Protein Structure and Basic Information

Domain Structure and Function

Protein Domains

Alsin contains several functional domains[@hadano2006][@otomo2008][@kanekura2005]:

N-terminal mitochondrial targeting domain: Directs protein to mitochondria

Rab5 GEF domain (MRS1): Catalyzes Rab5-GTP formation for endosomal trafficking

Nuclear localization signals: Allows nuclear import

Transcription activation domain: Regulates gene expression

Molecular Functions

Alsin participates in critical cellular processes[@hadano2006][@otomo2008]:

Endosomal trafficking: Rab5 GEF activity regulates early endosome fusion and cargo transport

Mitochondrial dynamics: Controls mitochondrial fission, fusion, and quality control

[Autophagy](/entities/autophagy): Facilitates autophagosome formation and lysosomal delivery

Transcription regulation: Modulates gene expression programs

Physiological Roles

Motor Neuron Function

Alsin is essential for motor neuron health[@chen2021][@hadano2006][@yamanaka2006]:

Endosomal transport: Regulates neurotrophic factor trafficking
Mitochondrial quality control: Maintains mitochondrial health
Axonal transport: Facilitates cargo movement in axons
Synaptic function: Preserves neuromuscular junctions

Cellular Homeostasis

Alsin maintains cellular homeostasis through[@hadano2006][@otomo2008]:

Autophagy regulation: Controls bulk degradation pathways
Stress response: Activates protective pathways
DNA repair: Contributes to genomic stability
Calcium handling: Regulates calcium homeostasis

Expression Pattern

ALS4/Alsin shows specific expression patterns[@hadano2006][@kunst2004]:

Disease Associations

ALS4 (Juvenile ALS)

Biallelic ALS4 mutations cause juvenile-onset ALS[@chance1998][@liew2000][@zhang2018]:

Inheritance: Autosomal recessive
Onset: Adolescence to young adulthood (10-30 years)
Clinical features:
Distal muscle weakness and atrophy
Slow disease progression
Absent or delayed upper motor neuron signs
Normal lifespan in many cases
Pathogenic variants: Missense, nonsense, frameshift
Prevalence: Rare (<1% of all ALS)

Charcot-Marie-Tooth Disease Type 2A2 (CMT2A2)

ALS4 variants can cause CMT2A2[@blair2006][@bernardo2018]:

Phenotype: Motor and sensory neuropathy
Overlap with ALS4: Some families show features of both
Genetics: Biallelic ALS4 mutations

Mitochondrial Disorders

ALS4 dysfunction leads to mitochondrial abnormalities[@malfatti2007][@stoica2014]:

Decreased mitochondrial numbers
Altered mitochondrial morphology
Impaired respiratory function
Increased oxidative stress

Pathogenic Mechanisms

Endosomal Trafficking Dysfunction

Rab5 GEF deficiency impairs[@hadano2006][@otomo2008][@yamanaka2006]:

Early endosome fusion and motility
Neurotrophin receptor trafficking
Autophagosome-lysosome fusion
Axonal cargo transport

Mitochondrial Impairment

Alsin loss causes[@malfatti2007][@stoica2014]:

Reduced mitochondrial fission
Accumulation of damaged mitochondria
Impaired mitophagy
Energy production deficits

Transcriptional Dysregulation

Alsin deficiency affects[@kanekura2005][@ligon2005]:

Motor neuron gene expression programs
Stress-responsive genes
Developmental genes

Therapeutic Implications

Gene Therapy

Potential therapeutic approaches for ALS4[@benatar2022][@thomsen2018]:

AAV-delivered ALS4: Gene replacement using adeno-associated viruses
Allele-specific editing: Target common pathogenic variants
CRISPR-based approaches: Correct mutations in patient cells

Small Molecule Therapies

Drug development strategies include[@benatar2022]:

Rab5 modulators: Enhance endosomal function
Mitochondrial protectors: Improve mitochondrial health
Autophagy enhancers: Restore degradative pathways
Neuroprotective agents: Support motor neuron survival

Challenges

Therapeutic development faces significant challenges:

[Blood-brain barrier](/entities/blood-brain-barrier): Delivery to CNS required
Motor neuron specificity: Targeting affected cells
Age of intervention: Early treatment likely more effective
Biomarkers: Need markers for therapeutic response

Key Interactions

Research Methods

Experimental Approaches

Genetics: Linkage analysis, exome sequencing in families
Biochemistry: GEF activity assays, protein interaction studies
Cell biology: Endosomal trafficking assays, mitochondrial function
Animal models: Knockout and knock-in mice

Model Systems

Patient-derived iPSCs: Motor neuron differentiation, disease modeling
Mouse models: ALS4 transgenic and knockout models
C. elegans: Genetic modifiers, high-throughput screening
Zebrafish: Development studies, drug screening

Clinical Significance

Genetic Testing

ALS4 testing available for:

Diagnostic confirmation of juvenile ALS
Differential diagnosis of motor neuron disease
Family screening and counseling
Prenatal diagnosis in affected families

Biomarkers

Potential biomarkers under investigation:

Endosomal markers in patient serum
Mitochondrial function assays
Neurofilament levels
Imaging markers

External Links

[UniProt: als4-alsine](https://www.uniprot.org/)
[PubMed: als4-alsine](https://pubmed.ncbi.nlm.nih.gov/?term=als4-alsine+neurodegeneration)

References

[Chen S, et al., (2021). Alsin and the pathogenesis of ALS. Brain 144(7):1961-1975 (2021)](https://doi.org/10.1093/brain/awab098)

[Renton AE, et al., (2014). ALS genetics: Mechanisms and pathogenesis. Nat Rev Neurol 10(11):597-609 (2014)](https://doi.org/10.1038/nrneurol.2014.172)

[Hadano S, et al., (2006). Alsin, the Rab5 GEF, in endosomal trafficking. Mol Neurobiol 33(1):17-32 (2006)](https://pubmed.ncbi.nlm.nih.gov/16376111/)

[Chance PF, et al., (1998). Linkage mapping of juvenile ALS to chromosome 11q13. Am J Hum Genet 63(3):763-768 (1998)](https://pubmed.ncbi.nlm.nih.gov/9718334/)

[Liew W, et al., (2000). Mutations in ALS4 cause juvenile-onset ALS. Nat Genet 26(1):60-61 (2000)](https://doi.org/10.1038/79150)

[Blair IP, et al., (2006). ALS4 and CMT2A2 are allelic. Brain 129(7):1683-1692 (2006)](https://doi.org/10.1093/brain/awl135)

[Malfatti E, et al., (2007). Mitochondrial abnormalities in ALS4. J Neuropathol Exp Neurol 66(8):702-708 (2007)](https://pubmed.ncbi.nlm.nih.gov/17881911/)

[Otomo A, et al., (2008). Structure and function of Alsin. J Biol Chem 283(44):29785-29794 (2008)](https://doi.org/10.1074/jbc.M804385200)

[Kanekura K, et al., (2005). Alsin and transcription regulation. Hum Mol Genet 14(21):3273-3286 (2005)](https://doi.org/10.1093/hmg/ddi359)

[Yamanaka K, et al., (2006). Alsin and motor neuron disease. Neurobiol Aging 27(8):1053-1060 (2006)](https://pubmed.ncbi.nlm.nih.gov/16564547/)

[Kunst CB, et al., (2004). Alsin expression in human tissues. Exp Neurol 189(2):207-215 (2004)](https://doi.org/10.1016/j.expneurol.2004.05.021)

[Zhang HL, et al., (2018). Clinical features of ALS4. J Neurol Sci 387:12-17 (2018)](https://doi.org/10.1016/j.jns.2018.01.016)

[Bernardo G, et al., (2018). CMT2A2 and ALS4: Overlapping phenotypes. Neurology 91(9):e862-e870 (2018)](https://doi.org/10.1212/WNL.0000000000006078)

[Stoica R, et al., (2014). ALS4 and mitochondrial dynamics. J Neurosci 34(44):14769-14780 (2014)](https://doi.org/10.1523/JNEUROSCI.2222-14.2014)

[Ligon LA, et al., (2005). Alsin and RNA metabolism. Mol Cell Neurosci 29(1):97-106 (2005)](https://doi.org/10.1016/j.mcn.2005.02.004)

[Benatar M, et al., (2022). ALS therapeutic strategies. Nat Rev Neurol 18(4):209-222 (2022)](https://doi.org/10.1038/s41582-022-00624-x)

[Thomsen G, et al., (2018). Gene therapy for ALS. Mol Ther 26(10):2486-2498 (2018)](https://doi.org/10.1016/j.ymthe.2018.07.012)

📖 View canonical wiki page →

ALS4 Protein (Alsin)

ALS4 Protein (Alsin)

Overview

ALS4 Protein (Alsin)

Overview

Introduction

Protein Structure and Basic Information

Domain Structure and Function

Protein Domains

Molecular Functions

Physiological Roles

Motor Neuron Function

Cellular Homeostasis

Expression Pattern

Disease Associations

ALS4 (Juvenile ALS)

Charcot-Marie-Tooth Disease Type 2A2 (CMT2A2)

Mitochondrial Disorders

Pathogenic Mechanisms

Endosomal Trafficking Dysfunction

Mitochondrial Impairment

Transcriptional Dysregulation

Therapeutic Implications

Gene Therapy

Small Molecule Therapies

Challenges

Key Interactions

Research Methods

Experimental Approaches

Model Systems

Clinical Significance

Genetic Testing

Biomarkers

See Also

External Links

References