Increased Sp1 phosphorylation as a mechanism of hepatocyte growth factor (HGF/SF)-induced vascular endothelial growth factor (VEGF/VPF) transcription

• Published in: Journal of cell science Vol. 116; no. Pt 2; pp. 225 - 238
• Main Authors: Reisinger, Kerstin, Kaufmann, Roland, Gille, Jens
• Format: Journal Article
• Language: English
• Published: England 15.01.2003
• Subjects: Animals; Cell Line; Endothelial Growth Factors - metabolism; Eukaryotic Cells - metabolism; Genes, Regulator - genetics; Hepatocyte Growth Factor - metabolism; Humans; Intercellular Signaling Peptides and Proteins - metabolism; Lymphokines - metabolism; MAP Kinase Kinase 1; Mitogen-Activated Protein Kinase Kinases - metabolism; Neovascularization, Pathologic - metabolism; Neovascularization, Pathologic - physiopathology; Neovascularization, Physiologic - physiology; Paracrine Communication - physiology; Phosphatidylinositol 3-Kinases - metabolism; Phosphorylation; Promoter Regions, Genetic - genetics; Protein Kinase C - metabolism; Protein-Serine-Threonine Kinases - metabolism; Signal Transduction - genetics; Sp1 Transcription Factor - metabolism; Transcription, Genetic - genetics; Transcriptional Activation - genetics; Up-Regulation - physiology; Vascular Endothelial Growth Factor A; Vascular Endothelial Growth Factors
• ISSN: 0021-9533; 1477-9137
• DOI: 10.1242/jcs.00237

Hepatocyte growth factor (HGF/SF)-induced expression of vascular endothelial growth factor (VEGF/VPF) has been implicated in paracrine amplification of angiogenesis, contributing to angiogenic responses during inflammation, wound healing, collateral formation and tumor growth. We have shown previously that HGF/SF-mediated VEGF/VPF expression by keratinocytes is primarily dependent on transcriptional activation, and we mapped the HGF/SF-responsive element to a GC-rich region between bp -88 and -65. Sp1-like factors bind to this element constitutively; however the VEGF/VPF promoter is transactivated by HGF/SF in the absence of induced binding activity. In experimental approaches to clarify molecular mechanisms of Sp1-dependent VEGF/VPF gene transcription, neither HGF/SF-dependent changes in nuclear expression nor in relative DNA binding activity of Sp family members to the indicated element were observed. Thus, HGF/SF was hypothesized to induce VEGF/VPF gene transcription via increased transactivation activity of Sp1 owing to biochemical modification. In immunoprecipitation studies, HGF/SF was found to increase the amount of serine-phosphorylated Sp1, revealing a likely mechanism of HGF/SF-induced VEGF/VPF expression, as phosphorylation may enhance the transcriptional activity of Sp1. The contribution of different signaling molecules to HGF/SF-induced VEGF/VPF transcription was demonstrated by the use of chemical inhibition, of expression of kinase-deficient signaling proteins, and by the use of antisense oligonucleotides. Herein, we provide evidence that PI 3-kinase, MEK1/2 and PKC-zeta play a significant role in HGF/SF-induced VEGF/VPF promoter activation. Together, our results elucidate a critical pathway of paracrine amplification of angiogenesis, suggesting that HGF/SF-induced Sp1 phosphorylation may activate VEGF/VPF promoter activity that requires the contribution of distinct signaling molecules.