• DNA methylation regulates expression of VEGF-R2 (KDR) and VEGF-R3 (FLT4).

      Quentmeier, Hilmar; Eberth, Sonja; Romani, Julia; Weich, Herbert A; Zaborski, Margarete; Drexler, Hans G; Helmholtz Centre for infection research, Inhoffenstr. 7, 38124 Braunschweig, Germany. (2012-01-17)
      Vascular Endothelial Growth Factors (VEGFs) and their receptors (VEGF-Rs) are important regulators for angiogenesis and lymphangiogenesis. VEGFs and VEGF-Rs are not only expressed on endothelial cells but also on various subtypes of solid tumors and leukemias contributing to the growth of the malignant cells. This study was performed to examine whether VEGF-R2 (KDR) and VEGF-R3 (FLT4) are regulated by DNA methylation.
    • An episomally replicating vector binds to the nuclear matrix protein SAF-A in vivo.

      Jenke, Bok Hee C; Fetzer, Christian P; Stehle, Isa M; Jönsson, Franziska; Fackelmayer, Frank O; Conradt, Harald; Bode, Jürgen; Lipps, Hans J; Institute of Cell Biology, Stockumer Strasse 10, University of Witten/Herdecke, D-58448 Witten. (2002-04)
      pEPI-1, a vector in which a chromosomal scaffold/matrix-attached region (S/MAR) is linked to the simian virus 40 origin of replication, is propagated episomally in CHO cells in the absence of the virally encoded large T-antigen and is stably maintained in the absence of selection pressure. It has been suggested that mitotic stability is provided by a specific interaction of this vector with components of the nuclear matrix. We studied the interactions of pEPI-1 by crosslinking with cis-diamminedichloroplatinum II, after which it is found to copurify with the nuclear matrix. In a south-western analysis, the vector shows exclusive binding to hnRNP-U/SAF-A, a multifunctional scaffold/matrix specific factor. Immunoprecipitation of the crosslinked DNA-protein complex demonstrates that pEPI-1 is bound to this protein in vivo. These data provide the first experimental evidence for the binding of an artificial episome to a nuclear matrix protein in vivo and the basis for understanding the mitotic stability of this novel vector class.
    • The role of heterodimerization between VEGFR-1 and VEGFR-2 in the regulation of endothelial cell homeostasis.

      Cudmore, Melissa J; Hewett, Peter W; Ahmad, Shakil; Wang, Ke-Qing; Cai, Meng; Al-Ani, Bahjat; Fujisawa, Takeshi; Ma, Bin; Sissaoui, Samir; Ramma, Wenda; et al. (2012)
      VEGF-A activity is tightly regulated by ligand and receptor availability. Here we investigate the physiological function of heterodimers between VEGF receptor-1 (VEGFR-1; Flt-1) and VEGFR-2 (KDR; Flk-1) (VEGFR(1-2)) in endothelial cells with a synthetic ligand that binds specifically to VEGFR(1-2). The dimeric ligand comprises one VEGFR-2-specific monomer (VEGF-E) and a VEGFR-1-specific monomer (PlGF-1). Here we show that VEGFR(1-2) activation mediates VEGFR phosphorylation, endothelial cell migration, sustained in vitro tube formation and vasorelaxation via the nitric oxide pathway. VEGFR(1-2) activation does not mediate proliferation or elicit endothelial tissue factor production, confirming that these functions are controlled by VEGFR-2 homodimers. We further demonstrate that activation of VEGFR(1-2) inhibits VEGF-A-induced prostacyclin release, phosphorylation of ERK1/2 MAP kinase and mobilization of intracellular calcium from primary endothelial cells. These findings indicate that VEGFR-1 subunits modulate VEGF activity predominantly by forming heterodimer receptors with VEGFR-2 subunits and such heterodimers regulate endothelial cell homeostasis.