Activation of cell-survival transcription factor NFκB in L1Ig6-stimulated endothelial cells

Ligation of the integrin α_vβ₃ in endothelial cells has been shown to be important for their survival. Such ligation induces signalling events merging into the Raf-Ras-ERK cascade that eventually induces activation of nuclear factor kappa B (NFκB), leading to its phosphorylation and nuclear translocation and thus inhibiting apoptosis. Here, the recombinant sixth immunoglobulin-like domain of cell adhesion molecules L1 (L1Ig6), a ligand for integrin α_vβ ₃, was explored as a component of vascular implant surfaces to initiate the NFκB-cell survival pathway. This supposition was supported. Specifically, NFκB-p65 was expressed in human umbilical vein endothelial cells (HUVECs) and when stimulated on L1Ig6, the phosphorylated form was found in the nucleus in over 60% of the cells. NFκB was not translocated into the nucleus on a number of other extracellular matrix substrates examined or when fibroblasts were cultured on L1Ig6. NFκB phosphorylation and nuclear translocation could be inhibited by blocking ligation of α _vβ₃ by L1Ig6 with an antibody recognizing α_vβ₃, with a cyclic RGD peptide, and with soluble L1Ig6. Moreover, blocking of α_vβ₃ interaction with L1Ig6 was correlated with induction of apoptosis. Thus, these experiments demonstrate that L1Ig6 may be useful as α_vβ ₃ ligand for the induction of endothelial survival pathways mediated by NFκB-p65.