IL23A (Interleukin 23 Subunit Alpha) encodes the p19 subunit of interleukin-23 (IL-23), a critical cytokine in the IL-23/Th17 axis that plays a central role in neuroinflammation and immune regulation in neurodegenerative diseases. IL-23 is a heterodimeric cytokine composed of the p19 subunit (encoded by IL23A) and the p40 subunit (encoded by IL12B), forming the functional IL-23 cytokine that drives Th17 cell differentiation and maintenance[1].
| Property | Value |
|---|---|
| Gene Symbol | IL23A |
| Full Name | Interleukin 23 Subunit Alpha |
| Chromosomal Location | 12q13.2 |
| NCBI Gene ID | 51561 |
| OMIM ID | 605502 |
| Ensembl ID | ENSG00000110944 |
| UniProt ID | Q9NPF7 |
| Encoded Protein | IL-23 subunit p19 |
| Protein Family | Interleukin-6 family cytokine |
| Molecular Weight | ~19 kDa |
The IL23A gene spans approximately 5.5 kb on chromosome 12q13.2 and consists of 6 exons. The gene encodes a 189-amino acid protein that forms the p19 subunit of IL-23. Unlike the IL-12 p40 subunit (IL12B), which is shared with IL-12, the p19 subunit is IL-23-specific and is not expressed constitutively in most tissues.
IL23A is expressed in various cell types:
IL23A expression is regulated by various transcription factors including:
Pro-inflammatory stimuli including LPS, TNF-α, and IL-1β can induce IL23A expression in immune cells.
IL-23 is essential for the differentiation, expansion, and maintenance of Th17 cells, which produce IL-17A, IL-17F, IL-21, and IL-22[3]. This axis has emerged as a critical pathway in neuroinflammation:
IL-17A (encoded by IL17A) is the primary effector cytokine of the Th17 pathway and has been implicated in multiple neurodegenerative conditions:
Alzheimer's Disease:
Parkinson's Disease:
Multiple Sclerosis:
Amyotrophic Lateral Sclerosis:
The IL-23/Th17 pathway has been increasingly implicated in Alzheimer's disease pathogenesis:
Genetic associations: IL23R (interleukin-23 receptor) polymorphisms are associated with AD in Han Chinese populations, suggesting IL23R may be a susceptibility gene for AD[10]
IL-12/IL-23 signaling: Recent research demonstrates that IL-12/IL-23 signaling drives AD pathology through disrupting neuronal and oligodendrocyte homeostasis[7:1]. IL-12 receptors are predominantly expressed in neurons and oligodendrocytes in AD-like mice.
Neuroinflammation: The IL-23/IL-17 axis contributes to chronic neuroinflammation in AD:
Aβ pathology: IL-17A affects amyloid-beta accumulation through astrocyte-mediated pathways[6:1]
Therapeutic implications: Targeting the IL-23/Th17 pathway represents a potential therapeutic strategy for AD
Th17 cell involvement: Parkinson's disease patients show increased Th17 cell frequencies and elevated IL-17 levels in peripheral blood and CSF
Dopaminergic neuron vulnerability: IL-17A can enhance microglial activation and create a toxic environment for dopaminergic neurons
Autoimmunity: The IL-23/Th17 axis may contribute to PD through autoimmune mechanisms, as suggested by the presence of autoreactive T cells
Gut-brain axis: The gut microbiome influences IL-17 production, connecting the intestinal environment to brain inflammation in PD
CSF biomarkers: Th17-related cytokines including IL-17 are elevated in ALS cerebrospinal fluid[9:1]
Disease progression: IL-17 levels correlate with disease progression in some studies
Microglial activation: IL-23/IL-17 signaling contributes to non-inflammatory microglial activation in ALS
The IL-23/Th17 pathway is well-established in MS pathogenesis:
Altered IL-23/IL-17 axis has been reported in serum of patients with autism spectrum disorders[12], suggesting potential neurodevelopmental implications.
The IL-23 receptor complex consists of:
Signaling pathways activated by IL-23:
Th17 cells produce multiple cytokines:
Several therapeutic strategies are being explored:
IL-23 blocking antibodies:
IL-17 blocking agents:
IL-23R antagonists: Small molecule inhibitors of IL-23R
IL23A shows specific expression patterns across brain regions:
| Region | Expression Level | Notes |
|---|---|---|
| Hippocampus | Moderate | Neuronal expression |
| Cortex | Moderate | Neuronal and glial |
| Substantia Nigra | Moderate | Dopaminergic region |
| Cerebellum | Low-Moderate | Limited expression |
| Spinal Cord | Low | Minimal expression |
IL23A is expressed in various peripheral tissues:
| Partner | Interaction Type | Functional Consequence |
|---|---|---|
| IL12B (p40) | Protein binding | Forms functional IL-23 |
| IL23R | Receptor | Signal transduction |
| JAK2 | Kinase | Signaling cascade |
| TYK2 | Kinase | Signaling cascade |
| STAT3 | Transcription factor | Gene activation |
| NF-κB | Transcription factor | Inflammatory response |
IL-23 signaling intersects with multiple pathways:
The IL-23/Th17 pathway shows biomarker potential:
Diagnostic Biomarkers:
Progression Biomarkers:
Therapeutic Biomarkers:
Current Status:
Trial Design Considerations:
Agonists vs. Antagonists:
Delivery Challenges:
AD Models:
PD Models:
MS Models (EAE):
IL23A encodes the p19 subunit of interleukin-23, a cytokine critical for Th17 cell differentiation and function. The IL-23/Th17 pathway has emerged as a key mediator of neuroinflammation in Alzheimer's disease, Parkinson's disease, ALS, and multiple sclerosis. Genetic associations, animal model data, and human studies support a role for this pathway in neurodegeneration. Targeting IL-23 and Th17-related cytokines represents a promising therapeutic strategy for neurodegenerative diseases, though CNS delivery and timing of intervention remain key challenges.
IL-23: a heterodimeric cytokine composed of p19 and p40 subunits. ↩︎
Expression of IL-23 and its receptors in primary cultured neurons. ↩︎
The IL-23/IL-17 axis in central nervous system inflammation. ↩︎
IL-17A disrupts neuronal plasticity and memory via decreasing neurotrophic factor. ↩︎
IL-17A promotes astrocyte-derived neurotrophic factor expression through TRIF-dependent signaling pathway. ↩︎
The gut microbiome controls reactive astrocytosis during Aβ amyloidosis via propionate-mediated regulation of IL-17. ↩︎ ↩︎
IL-12 signaling drives Alzheimer's disease pathology through disrupting neuronal and oligodendrocyte homeostasis. ↩︎ ↩︎
Cytokine profiles and IL-23/Th17 pathway in multiple sclerosis. ↩︎
Th17 cell-related cytokines in the cerebrospinal fluid of patients with amyotrophic lateral sclerosis. ↩︎ ↩︎
Interleukin-23 receptor polymorphisms are associated with Alzheimer's disease in Han Chinese. ↩︎
Fate-Mapping of GM-CSF Expression Identifies a Discrete Subset of Inflammation-Driving T Helper Cells. ↩︎
Altered IL-23/IL-17 axis in serum of patients with autism spectrum disorders. ↩︎