PTP1B in Calpain Dependent Feedback Regulation of VEGFR2 in Endothelial Cells: Implication in VEGF‐Dependent Angiogenesis and Diabetic Wound Healing

Abstract

The VEGF/VEGFR2/Akt/eNOS/NO pathway is essential to VEGF‐induced angiogenesis. We have previously discovered a novel role of calpain in mediating VEGF‐induced PI3K/AMPK/Akt/eNOS activation through Ezrin. Here, we sought to identify possible feedback regulation of VEGFR2 by calpain via cleavage and activation of its substrate protein phosphotyrosine phosphatase 1B (PTP1B), and the relevance of this pathway to VEGF‐induced angiogenesis, especially in diabetic wound healing. Over‐expression of PTP1B inhibited VEGF‐induced VEGFR2 and Akt phosphorylation in bovine aortic endothelial cells (BAECs), while PTP1B siRNA increased both VEGFR2 and Akt phosphorylation in response to VEGF stimulation. Calpain inhibitor induced VEGFR2 activation can be completely blocked by PTP1B over‐expression. These data implicate calpain/PTP1B feedback regulation of VEGFR2. We next examined a potential role of PTP1B in VEGF‐induced angiogenesis. Endothelial cells transfected with PTP1B siRNA showed faster wound closure in response to VEGF. Aortic discs isolated from PTP1B siRNA transfected mice also had augmented endothelial outgrowth. To further define the role of PTP1B in physiological angiogenesis in vivo, wound healing assay in diabetic mice was carried out. Furthermore, we found that PTP1B over‐expression or calpain inhibition significantly deteriorated wound healing in STZ‐induced diabetic mice. In conclusion, our data for the first time demonstrate a calpain/PTP1B/VEGFR2 negative feedback loop. A critical role of PTP1B as a negative regulator in VEGF‐induced angiogenesis is revealed. Modulation of local calpain and PTP1B activities may prove beneficial in the treatment of defective wound healing in diabetes.Support or Funding InformationThis study has been supported by National Heart, Lung and Blood Institute (HL088975).