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 (ΔI, ΔII, ΔIII, ΔIV, ΔV). Empty (E) lentivector-transduced cells served as control. Similarly to overexpression of native T-cad, cells expressing ΔII, ΔIII, or ΔIV displayed elevated levels of p-Akt and p-GSK3β and increased proliferation rates (for ΔII, ΔIII) vs. E. ΔI- and ΔV-transduced cells exhibited reduced levels of p-Akt and p-GSK3β and retarded growth rates vs. E. Stimulatory effects of native T-cad overexpression on Akt and GSK3β phosphorylation were dose dependently inhibited by coexpression of ΔI or ΔV. Subsequent functional analyses compared only ΔI-, ΔII-, and ΔV-mutant constructs with E as a negative control. Unlike ΔII cells, ΔI and ΔV cells failed to exhibit homophilic ligation and deadhesion responses on a substratum of T-cad protein. In the wound assay, migration was increased for ΔII cells but impaired for ΔI and ΔV cells. In endothelial cell-spheroid assay, angiogenic sprouting was augmented for ΔII cells but inhibited for ΔI and ΔV cells. We conclude that EC1 and EC5 domains of T-cad are essential for its proangiogenic effects. ΔI and ΔV constructs may serve as dominant-negative mutants and as potential tools targeting excessive angiogenesis.