SEPTIN8 is a member of the septin family of GTP-binding proteins that play critical roles in cytoskeletal organization, membrane dynamics, and synaptic function. In the brain, SEPTIN8 is predominantly expressed in [neurons](/entities/neurons) and is enriched at synaptic terminals where it participates in synaptic vesicle trafficking and neurotransmitter release[@hall2015]. Research has implicated SEPTIN8 in the pathogenesis of neurodegenerative diseases, particularly through its interaction with alpha-synuclein in Parkinson's disease models[@tsoi2018][@liu2020].
<div class="infobox infobox-gene">
| Property | Value |
|----------|-------|
| Gene Symbol | SEPTIN8 |
| Gene Name | Septin 8 |
| Chromosomal Location | 5q31.1 |
| NCBI Gene ID | [23176](https://www.ncbi.nlm.nih.gov/gene/23176) |
| OMIM | [607410](https://www.omim.org/entry/607410) |
| UniProt | [Q9UQD8](https://www.uniprot.org/uniprot/Q9UQD8) |
| Ensembl | [ENSG00000141504](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000141504) |
| Aliases | SEP8, SEPT8 |
</div>
SEPTIN8 is a member of the septin family, a group of GTP-binding proteins that form hetero-oligomeric complexes and assemble into filamentous structures at the membrane [cortex](/brain-regions/cortex)[@mostowy2012]. Unlike most GTP-binding proteins, septins exhibit slow GTP hydrolysis and exchange rates, allowing them to function as scaffolds and diffusion barriers rather than molecular switches[@sirajuddin2007].
SEPTIN8 is a member of the septin family of GTP-binding proteins that play critical roles in cytoskeletal organization, membrane dynamics, and synaptic function. In the brain, SEPTIN8 is predominantly expressed in [neurons](/entities/neurons) and is enriched at synaptic terminals where it participates in synaptic vesicle trafficking and neurotransmitter release[@hall2015]. Research has implicated SEPTIN8 in the pathogenesis of neurodegenerative diseases, particularly through its interaction with alpha-synuclein in Parkinson's disease models[@tsoi2018][@liu2020].
<div class="infobox infobox-gene">
| Property | Value |
|----------|-------|
| Gene Symbol | SEPTIN8 |
| Gene Name | Septin 8 |
| Chromosomal Location | 5q31.1 |
| NCBI Gene ID | [23176](https://www.ncbi.nlm.nih.gov/gene/23176) |
| OMIM | [607410](https://www.omim.org/entry/607410) |
| UniProt | [Q9UQD8](https://www.uniprot.org/uniprot/Q9UQD8) |
| Ensembl | [ENSG00000141504](https://www.ensembl.org/Homo_sapiens/Gene/Summary?g=ENSG00000141504) |
| Aliases | SEP8, SEPT8 |
</div>
SEPTIN8 is a member of the septin family, a group of GTP-binding proteins that form hetero-oligomeric complexes and assemble into filamentous structures at the membrane [cortex](/brain-regions/cortex)[@mostowy2012]. Unlike most GTP-binding proteins, septins exhibit slow GTP hydrolysis and exchange rates, allowing them to function as scaffolds and diffusion barriers rather than molecular switches[@sirajuddin2007].
SEPTIN8 contains several conserved domains:
SEPTIN8 typically forms heterooligomeric complexes with other septin family members, including SEPTIN6 and SEPTIN7. These complexes assemble into higher-order structures such as filaments and rings that serve as diffusion barriers at the synapse[@martinez2005]. The SEPTIN8-SEPTIN6-SEPTIN7 complex is particularly abundant in neuronal tissues and is thought to regulate synaptic vesicle pools at presynaptic terminals[@xie2009].
SEPTIN8 exhibits high expression in the brain, with particular enrichment in:
SEPTIN8 plays multiple roles in synaptic physiology:
SEPTIN8 localizes to presynaptic terminals where it associates with synaptic vesicles and regulates their cycling[@tsang2008]. Studies using electron microscopy have demonstrated that SEPTIN8 forms ring-like structures around synaptic vesicle clusters, suggesting a role in organizing vesicle pools and potentially regulating vesicle release sites[@hsu2008].
SEPTIN8 has been implicated in both [long-term potentiation](/mechanisms/long-term-potentiation) (LTP) and long-term depression (LTD). Knockdown of SEPTIN8 in hippocampal neurons reduces dendritic spine density and impairs LTP induction[@li2011]. The mechanism involves SEPTIN8 interaction with the actin cytoskeleton and regulation of AMPA receptor trafficking.
Functional studies have shown that SEPTIN8 modulates neurotransmitter release probability. Overexpression of SEPTIN8 enhances evoked excitatory postsynaptic currents, while knockdown reduces release probability[@fujita2013]. This may relate to SEPTIN8's role in organizing the active zone protein complex.
One of the most significant findings regarding SEPTIN8 in neurodegeneration is its physical interaction with alpha-synuclein[@tsoi2018a][@chen2020]. Alpha-synuclein is the primary component of Lewy bodies, the characteristic protein aggregates found in Parkinson's disease brains. SEPTIN8 has been shown to:
The interaction between SEPTIN8 and alpha-synuclein appears to occur through multiple mechanisms:
In rodent models of Parkinson's disease:
The SEPTIN8-alpha-synuclein interaction represents a potential therapeutic target:
While less well-characterized than in Parkinson's disease, SEPTIN8 has also been implicated in Alzheimer's disease pathogenesis:
SEPTIN8 polymorphisms have been associated with epilepsy susceptibility in genome-wide studies. Functional characterization suggests altered SEPTIN8 expression may affect neuronal excitability through modulation of GABAergic signaling[@chen2017].
Several GWAS studies have identified SEPTIN8 variants as associated with schizophrenia risk. The biological mechanism may involve SEPTIN8's role in synaptic function and dopamine signaling[@ripke2013].
Preliminary evidence suggests SEPTIN8 may be involved in ALS pathogenesis. SEPTIN8 aggregates have been observed in motor neurons from ALS patients, and SEPTIN8 interacts with [TDP-43](/mechanisms/tdp-43-proteinopathy), another key ALS protein aggregate[@sasaki2020].
While SEPTIN8 is not a primary disease-causing gene, certain variants may modify neurodegeneration risk:
| Variant | Location | Potential Effect |
|---------|----------|-----------------|
| rs2304138 | 5' UTR | Altered expression |
| rs3794567 | Intron | Splicing modifier |
| rs13182883 | 3' UTR | miRNA binding |
SEPTIN8 shows moderate evolutionary conservation across mammals. Population genetic analyses indicate purifying selection on this gene, suggesting essential neuronal functions[@pan2009].
SEPTIN8 represents an emerging therapeutic target for neurodegenerative diseases:
No SEPTIN8-specific inhibitors are currently in clinical use, but several compounds have shown activity in preclinical models:
SEPTIN8 in cerebrospinal fluid (CSF) has been explored as a biomarker:
Key questions remaining about SEPTIN8 in neurodegeneration:
SEPTIN8 is a synaptic septin GTPase that plays important roles in neuronal function and has emerged as a significant player in neurodegenerative disease pathogenesis. Its direct interaction with alpha-synuclein makes it a compelling therapeutic target for Parkinson's disease, while emerging evidence suggests roles in Alzheimer's disease and other neurological conditions. Further research is needed to translate these findings into disease-modifying therapies.