TRANSFORMING GROWTH FACTOR-ALPHA-INDUCED TRANSCRIPTIONAL ACTIVATION OF THE VASCULAR-PERMEABILITY FACTOR (VPF VEGF) GENE REQUIRES AP-2-DEPENDENT DNA-BINDING AND TRANSACTIVATION/

The endothelial cell-specific mitogen vascular permeability factor/vas cular endothelial growth factor (VPF/ VEGF) represents a central regul ator of cutaneous angiogenesis, Increased VPF/VEGF expression has rece ntly been reported in psoriatic skin and healing wounds, both conditio ns in which transforming growth factor-alpha (TGF alpha) and its ligan d, the epidermal growth factor receptor, are markedly up-regulated. Si nce TGF alpha strongly induces VPF/VEGF synthesis in keratinocytes, TG F alpha-mediated VPF/VEGF expression is likely to play a significant r ole in the initiation and maintenance of increased vascular hyperperme ability and hyperproliferation in skin biology. The objectives of the present studies were to determine the molecular mechanisms responsible for TGF alpha-induced transcriptional activation of the VPF/VEGF gene , We have identified a GC-rich TGF alpha-responsive region between -88 bp and -65 bp of the VPF/VEGF promoter that is necessary for constitu tive and TGF alpha-inducible transcriptional activation, In electropho retic mobility shift assays, this region binds Spl-dependent protein c omplexes constitutively and an additional TGF alpha-inducible protein complex that is distinct from Sp1 protein. Both AP-2 and Egr-1 transcr iption factors were detected as components of the TGF alpha-inducible protein complex in supershift EMSA studies, In co-transfection studies , an AP-2 but not an Egr-1 expression vector activated VPF/ VEGF trans cription, thus indicating that AP-2 protein is functionally important in TGF alpha-induced VPF/VEGF gene expression, By clarifying regulator y mechanisms that are critical for angiogenic processes in the skin, t hese studies may form the basis for new therapeutic strategies to modu late VPF/VEGF expression in cutaneous inflammation and wound healing.