Gas6-Axl receptor signaling is regulated by glucose in vascular smooth muscle cells

Objective-The receptor tyrosine kinase Axl and its ligand Gas6 are involved in the development of renal diabetic disease. In vascular smooth muscle cells (VSMCs) Axl is activated by reactive oxygen species and stimulates migration and cell survival, suggesting a role for Axl in the vascular complications of diabetes. Methods and Results-We investigated the effect of varying glucose concentration on Axl signaling in VSMCs. Glucose exerted powerful effects on Gas6-Axl signaling with greater activation of Akt and mTOR in low glucose, and greater activation of ERK1/2 in high glucose. Plasma membrane distribution and tyrosine phosphorylation of Axl were not affected by glucose. However, coimmunoprecipitation studies demonstrated that glucose changed the interaction of Axl with its binding partners. Specifically, binding of Axl to the p85 subunit of PI3-kinase was increased in low glucose, whereas binding to SHP-2 was increased in high glucose. Furthermore, Gas6-Axl induced migration was increased in high glucose, whereas Gas6-Axl mediated inhibition of apoptosis was greater in low glucose. Conclusion-This study demonstrates a role for glucose in altering Axl signaling through coupling to binding partners and suggests a mechanism by which Axl contributes to VSMC dysfunction in diabetes.