SEPTIN5 (Septin 5) encodes a member of the septin family of GTP-binding proteins essential for cytoskeleton organization, cell division, and membrane dynamics. Septins form hetero-oligomeric complexes that assemble into filaments and rings, functioning as scaffolds for protein localization and barriers in membrane trafficking. SEPTIN5 is predominantly expressed in the nervous system and is particularly important for synaptic vesicle organization, neurotransmitter release, and neuronal survival.
SEPTIN5 is a 367-amino acid GTP-binding protein with:
GTP-binding domain with P-loop motif (residues 73-80) that hydrolyzes GTP to GDP
Septin unique element (SUE) — a conserved 30-amino acid insert unique to septins
Central helix for protein-protein interactions
C-terminal filament assembly domain for polymerization
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SEPTIN5 — Septin 5
Overview
SEPTIN5 (Septin 5) encodes a member of the septin family of GTP-binding proteins essential for cytoskeleton organization, cell division, and membrane dynamics. Septins form hetero-oligomeric complexes that assemble into filaments and rings, functioning as scaffolds for protein localization and barriers in membrane trafficking. SEPTIN5 is predominantly expressed in the nervous system and is particularly important for synaptic vesicle organization, neurotransmitter release, and neuronal survival.
SEPTIN5 is a 367-amino acid GTP-binding protein with:
GTP-binding domain with P-loop motif (residues 73-80) that hydrolyzes GTP to GDP
Septin unique element (SUE) — a conserved 30-amino acid insert unique to septins
Central helix for protein-protein interactions
C-terminal filament assembly domain for polymerization
SEPTIN5 forms hetero-oligomeric complexes with [SEPTIN2](/proteins/septin2-protein), [SEPTIN6](/proteins/septin6-protein), and [SEPTIN7](/proteins/septin7-protein), creating higher-order structures essential for cellular functions.
Key Functions
Synaptic Vesicle Clustering — SEPTIN5 localizes to presynaptic terminals where it organizes synaptic vesicles into functional pools, enabling efficient neurotransmitter release [1].
Neurotransmitter Release Regulation — Through interactions with SNARE complex proteins, SEPTIN5 modulates exocytosis and synaptic plasticity [2].
Cytokinesis in Dividing Neurons — During neurogenesis, SEPTIN5 contributes to cell division machinery in neural progenitor cells.
Mitochondrial Dynamics — Recent research demonstrates SEPTIN5 involvement in mitochondrial fission and trafficking along axons [3].
Membrane Trafficking — SEPTIN5 acts as a barrier at the plasma membrane, regulating vesicle trafficking and endocytosis [4].
Expression and Localization
Brain Expression Patterns
High expression in:
Cerebral cortex — Layer V pyramidal neurons (corticospinal motor neurons)
Hippocampus — CA3 pyramidal cells and dentate gyrus granule cells
Growth cones — Guides axonal pathfinding during development
Mitochondria — Associates with mitochondrial outer membranes
Golgi apparatus — Involved in vesicular trafficking
Expression Across Development
SEPTIN5 expression increases during postnatal brain development, peaking in early adulthood and remaining elevated in aged brains, with particular vulnerability in regions affected by neurodegeneration.
Role in Neurodegeneration
Parkinson's Disease
SEPTIN5 plays a critical role in [Parkinson's disease](/diseases/parkinsons-disease) pathogenesis through multiple mechanisms:
Alpha-Synuclein Aggregation — SEPTIN5 directly interacts with [alpha-synuclein](/genes/snca), co-localizing in Lewy bodies. This interaction accelerates aggregation and stabilizes toxic oligomers [5].
Dopaminergic Neuron Vulnerability — SEPTIN5 is highly expressed in substantia nigra pars compacta neurons, which are selectively vulnerable in PD. Loss of SEPTIN5 function exacerbates dopaminergic degeneration [6].
Synaptic Vesicle Dysfunction — PD-linked mutations in SEPTIN5 impair synaptic vesicle clustering, disrupting neurotransmitter release and leading to synaptic failure [7].
Genetic Associations — Polymorphisms in the SEPTIN5 gene locus (22q11.21) have been associated with increased PD risk in genome-wide association studies [8].
Alzheimer's Disease
In [Alzheimer's disease](/diseases/alzheimers-disease), SEPTIN5 contributes to:
Tau Pathology — SEPTIN5 interacts with hyperphosphorylated tau, potentially affecting microtubule stability and axonal transport [10].
Excitotoxicity — Septin cytoskeleton alterations contribute to dysregulated calcium homeostasis and excitotoxic cell death.
Lewy Body Dementia
SEPTIN5 is a component of [Lewy body](/diseases/lewy-body-dementia) pathology, where it co-aggregates with alpha-synuclein and may influence the progression of synucleinopathies.