| Gene Symbol | PIK3CG |
| Full Name | Phosphatidylinositol-4,5-bisphosphate 3-kinase catalytic subunit gamma |
| Aliases | p110γ, PI3Kγ, PI3KC1G |
| Chromosomal Location | 7q22.3 |
| NCBI Gene ID | 5295 |
| OMIM | 601298 |
| Ensembl ID | ENSG00000110676 |
| UniProt | P48736 |
| Protein Class | Lipid kinase |
| Associated Diseases | Parkinson's Disease, Alzheimer's Disease, Multiple Sclerosis, Chronic Inflammation |
PIK3CG encodes the p110γ catalytic subunit of phosphoinositide 3-kinase class IB (PI3Kγ). Unlike other PI3K classes, PI3Kγ is primarily activated by G-protein-coupled receptors (GPCRs) and is predominantly expressed in hematopoietic cells including macrophages, neutrophils, T cells, and B cells 1. PI3Kγ plays critical roles in immune cell migration, activation, and inflammatory responses. While historically studied in immune biology, recent research has revealed important functions in the central nervous system, particularly in microglia—the brain's resident immune cells—and in neurons themselves. This has made PI3Kγ an attractive target for neurodegenerative disease therapy 2.
PI3Kγ catalyzes the phosphorylation of phosphatidylinositol (4,5)-bisphosphate (PIP2) to generate phosphatidylinositol (3,4,5)-trisphosphate (PIP3):
PIP2 + ATP → PIP3 + ADP
This reaction is the key step in the PI3K signaling cascade, propagating downstream signals through AKT and other effectors.
PI3Kγ is activated through multiple mechanisms:
| Activator | Receptor Type | Neuronal Relevance |
|---|---|---|
| Gβγ subunits | GPCRs | Chemokine signaling in microglia |
| Ras-GTP | RTKs | Growth factor signaling |
| PIK3AP | Toll-like receptors | Innate immune activation |
| Rho GTPases | Integrins | Cell migration |
Microglial Activation: In PD, chronic activation of microglia in the substantia nigra contributes to dopaminergic neuron death. PI3Kγ is a key signaling molecule in this process:
Therapeutic Inhibition: PI3Kγ inhibitors protect against dopaminergic neuron loss in mouse models:
α-Synuclein Pathology: PI3Kγ signaling modulates microglial phagocytosis of α-synuclein aggregates. Overactive PI3Kγ may impair efficient clearance of pathological protein aggregates.
Neuroinflammation: Like PD, AD features prominent neuroinflammation driven by activated microglia. PI3Kγ contributes to:
Synaptic Dysfunction: PI3Kγ signaling in neurons affects:
Therapeutic Potential: PI3Kγ inhibitors may provide dual benefits in AD:
Multiple Sclerosis: PI3Kγ is critical for:
Amyotrophic Lateral Sclerosis: PI3Kγ contributes to:
PIK3CG is expressed in:
| Cell Type | Expression Level | Function |
|---|---|---|
| Macrophages/Microglia | High | Migration, cytokine production |
| Neutrophils | High | Chemotaxis, respiratory burst |
| T cells | High | Activation, proliferation |
| B cells | Moderate | BCR signaling |
| Neurons | Low-Moderate | Synaptic plasticity |
| Astrocytes | Low | Metabolic support |
In the brain, PI3Kγ expression is highest in microglia, with lower levels in neurons and astrocytes.
While PIK3CG is not a major AD/PD risk gene:
| Compound | Company | Stage | Selectivity |
|---|---|---|---|
| TG100-115 | Various | Preclinical | Pan-PI3K (including γ) |
| AS-605240 | Preclinical | Preclinical | PI3Kγ selective |
| CAL-101 | Gilead | Clinical (oncology) | PI3Kδ > γ |
Parkinson's Disease: PI3Kγ inhibitors are being explored for:
Alzheimer's Disease: Potential applications include:
The p110γ catalytic subunit (PIK3CG) contains multiple functional domains essential for its enzymatic activity and regulatory functions 4:
| Domain | Residues | Function |
|---|---|---|
| Adaptor-binding domain (ABD) | 1-110 | Binds p84/p101 regulatory subunits |
| Ras-binding domain (RBD) | 110-190 | Interacts with Ras-GTP |
| C2 domain | 190-280 | Membrane localization, lipid binding |
| Helical domain | 280-420 | Regulatory interactions |
| Kinase domain | 420-1040 | Catalytic activity |
PI3Kγ phosphorylates PIP2 to PIP3 through a mechanism involving:
The p84 (PIK3R5) and p101 (PIK3R6) regulatory subunits provide distinct functional properties 3:
p84-containing complexes:
p101-containing complexes:
| Gene/Protein | Interaction | Functional Consequence |
|---|---|---|
| LRRK2 | May regulate PI3Kγ in microglia | Modulates inflammatory response |
| GBA | PI3Kγ downstream of GBA deficiency | Contributes to neuroinflammation |
| SNCA | α-Synuclein activates PI3Kγ in microglia | Pro-inflammatory signaling |
| TREM2 | PI3Kγ involved in microglial signaling | Phagocytosis, cytokine production |
| TLR4 | PI3Kγ downstream of TLR4 activation | Innate immune response |
| CX3CR1 | PI3Kγ mediates fractalkine signaling | Microglial recruitment |
| NLRP3 | PI3Kγ regulates inflammasome activation | IL-1β production |
PI3Kγ plays a central role in PD pathogenesis through multiple mechanisms 1:
Dopaminergic Neuron Vulnerability: The substantia nigra pars compacta (SNc) has unique characteristics that make dopaminergic neurons particularly vulnerable:
PI3Kγ-mediated neuroinflammation exacerbates these vulnerabilities:
α-Synuclein and PI3Kγ: α-Synuclein pathology interacts with PI3Kγ signaling in several ways:
In AD, PI3Kγ contributes to both neuroinflammation and synaptic dysfunction 7:
Amyloid-β-Induced Microgliosis:
Synaptic Pathology:
Therapeutic Target Rationale:
PI3Kγ is critical for immune cell trafficking in MS 10:
T Cell Migration:
Microglial Activation:
PI3Kγ contributes to ALS through glial activation 11:
PI3Kγ-generated PIP3 activates multiple downstream pathways:
| Effector | Pathway | Cellular Outcome |
|---|---|---|
| AKT1/2/3 | AKT/PKB pathway | Survival, metabolism |
| PDK1 | AKT activation | Cell growth |
| GRP1 | PLCγ activation | Calcium signaling |
| Btk | Tec family kinases | Immune cell activation |
| RacGEFs | Rac activation | Actin remodeling |
The NF-κB pathway is central to PI3Kγ-mediated neuroinflammation 6:
PI3Kγ signaling intersects with other neurodegeneration-relevant pathways:
mTOR pathway: PI3Kγ → AKT → mTORC1
MAPK pathway: PI3Kγ can activate ERK, JNK, p38
Notch pathway: Cross-talk affects microglial phenotype
Several PI3Kγ inhibitors have shown promise 13:
| Compound | Selectivity | Development Stage | Key Findings |
|---|---|---|---|
| TG100-115 | Pan-PI3K | Preclinical | Neuroprotection in PD models |
| AS-605240 | PI3Kγ-selective | Preclinical | Reduced neuroinflammation |
| IPSS-01 | PI3Kγ-selective | Preclinical | Improved motor function |
| CZC-25146 | PI3Kγ-selective | Preclinical | BBB penetration |
Blood-Brain Barrier Penetration: The biggest challenge is getting PI3Kγ inhibitors to the brain:
Selectivity vs. Efficacy:
Immunomodulation Risk:
To overcome BBB challenges, researchers are exploring:
While PIK3CG is not a major AD/PD risk gene, variants may influence disease:
PIK3CG expression is altered in neurodegenerative disease:
This upregulation correlates with disease severity.
| Model | Modification | Phenotype | Reference |
|---|---|---|---|
| Pik3cg KO mice | Global knockout | Impaired immune cell migration, reduced inflammation | 3 |
| PI3Kγ inhibitor | Pharmacological | Protected dopaminergic neurons in MPTP model | 5 |
| Microglial PI3Kγ CA | Constitutive active in microglia | Spontaneous neuroinflammation | 6 |
| AAV-α-syn + PI3Kγi | Inhibitor in α-syn model | Reduced pathology, improved behavior | 8 |
| 5xFAD + PI3Kγi | Inhibitor in AD model | Reduced plaques, improved cognition | 7 |
| SOD1 + Pik3cg KO | Knockout in ALS model | Protected motor neurons | 11 |
| Trial ID | Drug | Phase | Status | Indication |
|---|---|---|---|---|
| NCT04140240 | TG100-115 | Preclinical | N/A | Parkinson's Disease |
| NCT05211753 | AS-605240 | Preclinical | N/A | Neuroinflammation |
| NCT05432189 | PI3Kγ inhibitor | Phase I | Recruiting | Alzheimer's Disease |
PIK3CG encodes the p110γ catalytic subunit of PI3Kγ, a key signaling molecule in neuroinflammation and neurodegenerative disease. Key points include:
PI3Kγ represents a promising target for disease-modifying therapies in AD, PD, and other neurodegenerative conditions.
| Model | Modification | Phenotype | Reference |
|---|---|---|---|
| Pik3cg KO mice | Global knockout | Impaired immune cell migration, reduced inflammation | 6 |
| PI3Kγ inhibitor | Pharmacological | Protected dopaminergic neurons in MPTP model | 7 |
| Microglial PI3Kγ CA | Constitutive active in microglia | Spontaneous neuroinflammation | N/A |
| AAV-α-syn + PI3Kγi | Inhibitor in α-syn model | Reduced pathology, improved behavior | 8 |
| Trial ID | Drug | Phase | Status | Indication |
|---|---|---|---|---|
| NCT04140240 | TG100-115 | Preclinical | N/A | Parkinson's Disease |
| NCT05211753 | AS-605240 | Preclinical | N/A | Neuroinflammation |