P2RY12

P2RY12 is a purinergic G-protein coupled receptor that defines the core signature of homeostatic, surveillance-state microglia. It is exquisitely sensitive to extracellular ADP and ATP, which are instantly released by injured neurons or disrupted vasculature following a local micro-lesion.

Under physiological conditions, P2RY12 acts as the primary "steering wheel" for microglia. Within minutes of detecting an ATP gradient, P2RY12 signaling reorganizes the microglial actin cytoskeleton, directing their motile processes to rapidly extend toward and continuously survey the site of damage, sealing small vascular ruptures in the process.

Crucially, P2RY12 is sharply downregulated the moment microglia encounter chronic, severe pathology—such as amyloid plaques, tau tangles, or demyelinated lesions. Its expression serves as an inverse biomarker for disease severity: intact P2RY12 indicates healthy tissue, while its absence demarcates fully transitioned Disease-Associated Microglia (DAM). Consequently, recovering P2RY12 expression is often used as a benchmark for therapeutic interventions attempting to restore healthy microglial homeostasis.