Thrombospondin-1 induces tyrosine phosphorylation of adherens junction proteins and regulates an endothelial paracellular pathway

Academic Article


  • Thrombospondin-1 (TSP) induces endothelial cell (EC) actin reorganization and focal adhesion disassembly and influences multiple EC functions. To determine whether TSP might regulate EC-EC interactions, we studied the effect of exogenous TSP on the movement of albumin across postconfluent EC monolayers. TSP increased transendothelial albumin flux in a dose-dependent manner at concentrations ≥1 μg/ml (2.2 nM). Increases in albumin flux were observed as early as 1 h after exposure to 30 μg/ml (71 nM) TSP. Inhibition of tyrosine kinases with herbimycin A or genistein protected against the TSP-induced barrier dysfunction by >80% and >50%, respectively. TSP-exposed monolayers exhibited actin reorganization and intercellular gap formation, whereas pretreatment with herbimycin A protected against this effect. Increased staining of phosphotyrosine-containing proteins was observed in plaque-like structures and at the intercellular boundaries of TSP-treated cells. In the presence of protein tyrosine phosphatase inhibition, TSP induced dose- and time-dependent increments in levels of phosphotyrosine-containing proteins; these TSP dose and time requirements were compatible with those defined for EC barrier dysfunction. Phosphoproteins that were identified include the adherens junction proteins focal adhesion kinase, paxillin, γ-catenin, and p120(Cas). These combined data indicate that TSP can modulate endothelial barrier function, in part, through tyrosine phosphorylation of EC proteins.
  • Published In

    Digital Object Identifier (doi)

    Author List

  • Goldblum SE; Young BA; Wang P; Murphy-Ullrich JE
  • Start Page

  • 1537
  • End Page

  • 1551
  • Volume

  • 10
  • Issue

  • 5