• High-resolution mass spectrometric analysis of the secretome from mouse lung endothelial progenitor cells.

      Hemmen, Katherina; Reinl, Tobias; Buttler, Kerstin; Behler, Friederike; Dieken, Hauke; Jänsch, Lothar; Wilting, Jörg; Weich, Herbert A; Department of Gene Regulation, HZI, Build. D, Inhoffenstr. 7, 38124, Braunschweig, Germany. katharina.hemmen@ewetel.net (2011-05)
      Recently, we isolated and characterized resident endothelial progenitor cells from the lungs of adult mice. These cells have a high proliferation potential, are not transformed and can differentiate into blood- and lymph-vascular endothelial cells under in vitro and in vivo conditions. Here we studied the secretome of these cells by nanoflow liquid chromatographic mass spectrometry (LC-MS). For analysis, 3-day conditioned serum-free media were used. We found 133 proteins belonging to the categories of membrane-bound or secreted proteins. Thereby, several of the membrane-bound proteins also existed as released variants. Thirty-five proteins from this group are well known as endothelial cell- or angiogenesis-related proteins. The MS analysis of the secretome was supplemented and confirmed by fluorescence activated cell sorting analyses, ELISA measurements and immunocytological studies of selected proteins. The secretome data presented in this study provides a platform for the in-depth analysis of endothelial progenitor cells and characterizes potential cellular markers and signaling components in hem- and lymphangiogenesis.
    • 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.