Insulin stimulates haptotactic migration of human epidermal keratinocytes through activation of NF-κB transcription factor

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Abstract
Insulin-mediated cell motility as well as the role of transcription factors in insulin-activated intracellular signal events have not been extensively studied. In this report we have examined whether insulin could mediate haptotactic migration of cultured human epidermal keratinocytes through activation of transcription factor NF-κB. Insulin caused a dose-dependent stimulation of keratinocyte migration that maximally reached 2-fold at 2×10−7 M hormone. This phenomenon was independent of the nature of the extracellular matrix component (collagen I or laminin5/nicein) on which the cells migrated, indicating that a specific integrin-ligand complex is not required. A 10−7 M insulin treatment of keratinocytes resulted in activation of a major κB DNA binding complex within 15 to 30 minutes, which was identified as the p65/p50 NF-κB heterodimer by electrophoretic mobility shift assays. The activation induced nuclear translocation of cytosolic pools of NF-κB factor. Pyrrolidine dithiocarbamate and N-acetylleucinyl-leucinyl-norleucinal H (two compounds that differentially inhibit IκBα degradation and, thus, NF-κB activation) reversed the insulin-stimulated keratinocyte haptotactic migration without affecting insulin receptor activation. These compounds inhibited the insulin-induced nuclear translocation of NF-κB as detected by confocal laser scanning microscopy. Taken together our experiments demonstrate that insulin stimulates haptotactic migration of human epidermal keratinocytes through activation of NF-κB transcription factor. They emphasize the ability of insulin to stimulate keratinocyte movement and provide a first clue to the mechanism of insulin-induced haptotactic signaling.