Extracellular cadherin repeat domains EC1 and EC5 of T-cadherin are essential for its ability to stimulate angiogenic behavior of endothelial cells.

T-cadherin (T-cad) promotes survival, proliferation, and migration of endothelial cells and induces angiogenesis. We aimed to identify domains of T-cad functionally relevant to its effects on endothelial cell behavior. To specifically target the functional properties of the 5 cadherin repeat domains (EC1-EC5) of T-cad, endothelial cells were transduced with lentivectors containing specific T-cad-domain-deletion mutant constructs (DeltaI, DeltaII, DeltaIII, DeltaIV, DeltaV). Empty (E) lentivector-transduced cells served as control. Similarly to overexpression of native T-cad, cells expressing DeltaII, DeltaIII, or DeltaIV displayed elevated levels of p-Akt and p-GSK3beta and increased proliferation rates (for DeltaII, DeltaIII) vs. E. DeltaI- and DeltaV-transduced cells exhibited reduced levels of p-Akt and p-GSK3beta and retarded growth rates vs. E. Stimulatory effects of native T-cad overexpression on Akt and GSK3beta phosphorylation were dose dependently inhibited by coexpression of DeltaI or DeltaV. Subsequent functional analyses compared only DeltaI-, DeltaII-, and DeltaV-mutant constructs with E as a negative control. Unlike DeltaII cells, DeltaI and DeltaV cells failed to exhibit homophilic ligation and deadhesion responses on a substratum of T-cad protein. In the wound assay, migration was increased for DeltaII cells but impaired for DeltaI and DeltaV cells. In endothelial cell-spheroid assay, angiogenic sprouting was augmented for DeltaII cells but inhibited for DeltaI and DeltaV cells. We conclude that EC1 and EC5 domains of T-cad are essential for its proangiogenic effects. DeltaI and DeltaV constructs may serve as dominant-negative mutants and as potential tools targeting excessive angiogenesis.