RESUMO
During angiogenesis, cell adhesion molecules expressed on the endothelial cell surface promote the growth and survival of newly forming vessels. Hence, elucidation of the signaling pathways activated by cell-to-matrix adhesion may assist in the discovery of new targets to be used in antiangiogenic therapy. In proliferating endothelial cells, the single-pass transmembrane glycoprotein CD93 has recently emerged as an important endothelial cell adhesion molecule regulating vascular maturation. In this study, we unveil a signaling pathway triggered by CD93 that regulates actin cytoskeletal dynamics responsible of endothelial cell adhesion. We show that the Src-dependent phosphorylation of CD93 and the adaptor protein Cbl leads to the recruitment of Crk, which works as a downstream integrator in the CD93-mediated signaling. Moreover, confocal microscopy analysis of FRET-based biosensors shows that CD93 drives the coordinated activation of Rac1 and RhoA at the cell edge of spreading cells, thus promoting the establishment of cell polarity and adhesion required for cell motility.
Assuntos
Citoesqueleto de Actina/metabolismo , Moléculas de Adesão Celular/metabolismo , Movimento Celular/genética , Células Endoteliais da Veia Umbilical Humana/metabolismo , Glicoproteínas de Membrana/metabolismo , Receptores de Complemento/metabolismo , Transdução de Sinais/genética , Proteína rhoA de Ligação ao GTP/metabolismo , Adesão Celular/genética , Moléculas de Adesão Celular/genética , Polaridade Celular/genética , Células Cultivadas , Humanos , Glicoproteínas de Membrana/genética , Fosforilação/genética , Proteínas Proto-Oncogênicas c-cbl/metabolismo , Proteínas Proto-Oncogênicas c-crk/metabolismo , Interferência de RNA , Receptores de Complemento/genética , Proteína cdc42 de Ligação ao GTP/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Quinases da Família src/metabolismoRESUMO
Blocking the signaling activated by the plasma membrane receptor CD93 has recently been demonstrated a useful tool in antiangiogenic treatment and oncotherapy. In the proliferating endothelium, CD93 regulates cell adhesion, migration, and vascular maturation, yet it is unclear how CD93 interacts with the extracellular matrix activating signaling pathways involved in the vascular remodeling. Here for the first time we show that in endothelial cells CD93 is structured as a dimer and that this oligomeric form is physiologically instrumental for the binding of CD93 to its ligand Multimerin-2. Crystallographic X-ray analysis of recombinant CD93 reveals the crucial role played by the C-type lectin-like and sushi-like domains in arranging as an antiparallel dimer to achieve a functional binding state, providing key information for the future design of new drugs able to hamper CD93 function in neovascular pathologies.