| FLT3 |
|---|
| Protein Name | FMS-like Tyrosine Kinase 3 |
| Gene | FLT3 |
| UniProt ID | P36888 |
| Protein Family | Receptor tyrosine kinase, PDGFR family |
| Molecular Weight | ~143 kDa |
| Expression | Hematopoietic cells, brain ([neurons](/entities/neurons), microglia) |
| Ligands | FLT3 ligand (FL) |
FLT3 (FMS-like Tyrosine Kinase 3) is a class III receptor tyrosine kinase expressed primarily in hematopoietic progenitor cells. While best characterized in acute myeloid leukemia (AML), FLT3 is also expressed in the central nervous system, where it plays important roles in neuronal development, survival, and immune function. Emerging research suggests FLT3 signaling may be relevant to neurodegenerative diseases, particularly Alzheimer's disease and Parkinson's disease, through effects on microglia and neuroinflammation [1].
¶ Structure and Signaling
FLT3 is a type I transmembrane receptor consisting of:
- Extracellular domain: 5 immunoglobulin-like domains for ligand binding
- Transmembrane helix: Single pass through the membrane
- Juxtamembrane domain: Contains regulatory motifs
- Kinase domain: Intracellular tyrosine kinase activity
- C-terminal tail: Contains tyrosine residues for signaling
FLT3 signaling involves:
- Ligand binding: FLT3 ligand (FL) binds extracellular domain
- Dimerization: Receptor dimerization activates kinase
- Autophosphorylation: Intracellular tyrosine residues phosphorylated
- Adaptor recruitment: Grb2, Shc, PLCγ bind phosphorylated residues
- Signal transduction: PI3K/Akt, MAPK/ERK, JAK/STAT pathways activated
In the nervous system, FLT3 is expressed in:
- Microglia: Primary immune cells of the brain
- Neurons: Developmental expression, lower in adults
- Neural progenitor cells: During neurogenesis
- Endothelial cells: Blood-brain barrier component
FLT3 signaling in the brain regulates:
- Microglial activation: Modulates inflammatory responses
- Neuronal survival: Neurotrophic effects during development
- Synaptic plasticity: Activity-dependent modifications
- Blood-brain barrier: Endothelial function
FLT3 contributes to Alzheimer's disease pathogenesis through microglial pathways:
Microglial FLT3 signaling promotes inflammatory responses:
- Increased pro-inflammatory cytokine production
- Enhanced phagocytic activity
- Potential effects on amyloid clearance
Evidence for FLT3-amyloid interactions:
- FLT3 expression increases in AD microglia
- Amyloid may act as a FLT3 ligand
- Dysregulated inflammation in AD brains
In Parkinson's disease, FLT3 may play roles in:
- Microglial activation: Chronic neuroinflammation
- Dopaminergic neuron survival: Developmental effects
- Alpha-synuclein pathology: Interaction with microglial responses
- Therapeutic targeting: FLT3 inhibitors in development
FLT3 as a therapeutic target for neuroinflammation:
- FLT3 inhibitors reduce microglial activation
- Potential for disease modification
- Selective targeting in the CNS
During brain development, FLT3:
- Promotes neuronal progenitor proliferation
- Supports differentiation
- Regulates migration
- Influences synapse formation
Understanding FLT3 in development suggests:
- Developmental disorder treatments
- Regenerative medicine approaches
- Stem cell therapy enhancement
FDA-approved FLT3 inhibitors (primarily for AML) include:
- Midostaurin
- Gilteritinib
- Quizartinib
Potential CNS applications:
- Reduce neuroinflammation
- Modulate microglial function
- Combined with other therapies
FLT3 expression may serve as:
- Marker of microglial activation
- Biomarker for disease progression
- Therapeutic response indicator
FLT3 is a receptor tyrosine kinase expressed in microglia and neurons in the central nervous system. While extensively studied in hematological malignancies, FLT3 signaling in the brain influences neuroinflammation, microglial function, and neuronal survival. Dysregulated FLT3 activity contributes to the pathogenesis of Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders through effects on inflammatory processes. FLT3 represents a potential therapeutic target for modulating neuroinflammation in these conditions.