The Insulin Receptor (INSR) is a receptor tyrosine kinase that plays central roles in metabolic regulation and has been increasingly implicated in neurodegenerative , particularly Alzheimer's disease (type 3 diabetes hypothesis).
INSR (Insulin Receptor) is a receptor tyrosine kinase that binds insulin and mediates metabolic and growth effects. INSR exists as two isoforms (IR-A and IR-B) with distinct signaling properties. In the brain, INSR is widely expressed and regulates neuronal survival, synaptic function, and cognitive processes. Insulin resistance is a key feature of type 2 diabetes and is strongly linked to Alzheimer's disease pathogenesis.
INSR is a tetrameric receptor tyrosine kinase:
- Alpha subunits (2x): Extracellular ligand-binding domains (~730 aa each)
- Beta subunits (2x): Transmembrane + tyrosine kinase domains (~620 aa each)
- Disulfide bonds: Link alpha and beta subunits, and two half-receptors
Alternative splicing produces IR-A (embryonic/neural) and IR-B (adult/metabolic) isoforms.
INSR mediates insulin signaling:
- Glucose homeostasis: Regulates glucose uptake via GLUT4 translocation
- Lipid metabolism: Controls fatty acid synthesis and storage
- Protein synthesis: Activates mTOR pathway
- Gene transcription: Modulates nuclear transcription factors
- Neuronal function: Regulates neuronal survival, plasticity, metabolism
- Synaptic plasticity: Important for learning and memory
Major pathways: PI3K/Akt, MAPK/ERK.
- Brain insulin resistance is a hallmark of AD
- INSR signaling impairment in AD brains
- Amyloid-β disrupts INSR signaling
- Tau pathology affects insulin signaling
- Contributing to cognitive decline
- Insulin resistance in PD patients
- INSR signaling affects dopaminergic neuron survival
- May contribute to disease progression
- Insulin therapy being explored
- Altered insulin/INSR signaling
- May affect motor neuron metabolism
- Energy homeostasis disruption
- Insulin signaling affects ischemic injury
- Post-stroke insulin sensitivity changes
- Hyperglycemia worsens outcomes
- Chronic insulin resistance damages neurons
- Cognitive impairment link
- Vascular contributions
INSR-based therapies:
- Intranasal insulin: Direct brain delivery
- Insulin sensitizers: Thiazolidinediones
- INSR agonists: Novel peptides
- Lifestyle interventions: Diet, exercise