Ganglioside GM3 Mediates Glucose-Induced Suppression of IGF-1 Receptor-Rac1 Activation to Inhibit Keratinocyte Motility

Activation of insulin-like growth factor-1 (IGF-1) receptor (IGF1R) signaling induces keratinocyte migration, but little is known about its regulation, including in diabetic wounds. GM3, a lipid raft ganglioside synthesized by GM3 synthase (GM3S), regulates receptor signaling. In diabetic mice, knockout or topically applied nanoconstruct-mediated knockdown of GM3S promotes wound edge IGF1R phosphorylation and re-epithelialization. Through modulating GM3 expression, we explored the role of GM3 in regulating human keratinocyte IGF1R signaling. Increases in GM3 and GM3S expression, including by exposure to high glucose, inhibit keratinocyte migration and IGF-1einduced chemotaxis in association with inhibition of IGF1R phosphorylation, suppression of Rac1 signaling, and activation of RhoA signaling. In contrast, GM3 depletion accelerates cell migration; increases cell velocity, displacement, and persistence; and activates IGF1R-Rac1 signaling. These data implicate GM3 in mediating glucose-induced suppression of IGF1R-Rac1 signaling. Furthermore, our findings provide evidence of a pivotal role for GM3-induced insulin resistance in impairing keratinocyte migration and reinforce the previously published studies in diabetic mice supporting GM3-depleting strategies as an approach for accelerating the healing of human diabetic wounds.