Gq-coupled Purinergic Receptors Inhibit Insulin-like Growth Factor-I/Phosphoinositide 3-Kinase Pathway-dependent Keratinocyte Migration

Insulin-like growth factor-I (IGF-I) activation of phosphoinositol 3-kinase (PI3K) is an essential pathway for keratinocyte migration that is required for epidermis wound healing. We have previously reported that activation of G alpha((q/11))-coupled-P2Y(2) purinergic receptors by extracellular nucleotides delays keratinocyte wound closure. Here, we report that activation of P2Y(2) receptors by extracellular UTP inhibits the IGF-I-induced p110 alpha-PI3K activation. Using siRNA and pharmacological inhibitors, we demonstrate that the UTP antagonistic effects on PI3K pathway are mediated by G alpha((q/11))-and not G((i/o))-independently of phospholipase C beta. Purinergic signaling does not affect the formation of the IGF-I receptor/insulin receptor substrate-I/p85 complex, but blocks the activity of a membrane-targeted active p110 alpha mutant, indicating that UTP acts downstream of PI3K membrane recruitment. UTP was also found to efficiently attenuate, within few minutes, the IGF-I-induced PI3K-controlled translocation of the actin-nucleating protein cortactin to the plasma membrane. This supports the UTP ability to alter later migratory events. Indeed, UTP inhibits keratinocyte spreading and migration promoted by either IGF-I or a membrane-targeted active p110 alpha mutant, in a G alpha(q/11)-dependent manner both. These findings provide new insight into the signaling cross-talk between receptor tyrosine kinase and G alpha((q/11))-coupled receptors, which mediate opposite effects on p110 alpha-PI3K activity and keratinocyte migration.