Role of P2Y₂ nucleotide receptors in reactive astrogliosis
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Astrocytes become activated in response to brain injury characterized by increased expression of GFAP and increased rates of cell migration and proliferation. Damage to brain cells causes the release of cytoplasmic nucleotides, such as ATP and UTP, ligands for P2 nucleotide receptors. Results in this study with primary rat astrocytes indicate that activation of a G protein-coupled P2Y2 receptor for ATP and UTP increases GFAP expression and both chemotactic and chemokinetic cell migration. UTP-induced astrocyte migration was inhibited by silencing of P2Y2R expression with P2Y2R siRNA. UTP also increased the expression in astrocytes of [alpha]V[beta]3/5 integrins that are known to interact directly with the P2Y2R to modulate its function. Anti-[alpha]V integrin antibodies prevented UTP-stimulated astrocyte migration, suggesting that P2Y2R/[alpha]V interaction mediates the activation of astrocytes by UTP. P2Y2R-mediated astrocyte migration required the activation of the PI3-K/Akt and MEK/ERK signaling pathways, responses that also were inhibited by anti-[alpha]V integrin antibody. These results suggest that P2Y2Rs and their associated signaling pathways may be important factors regulating astrogliosis in brain disorders.