Matrix-bound sixth Ig-like domain of cell adhesion molecule L1 acts as an angiogenic factor by ligating alphavbeta3-integrin and activating VEGF-R2.
Angiogenic signals can be matrix attached or freely diffusible. Here, the sixth Ig-like domain of L1 (L1Ig6), a ligand for alphavbeta3-integrin, was investigated. This domain was expressed as a fusion protein having a substrate sequence for factor XIII to enable covalent binding into three-dimensional fibrin matrices. Matrix-bound L1Ig6 induced endothelial cell (EC) process extension in vitro, which was associated with ligation and phosphorylation of alphavbeta3-integrin. VEGF-R2 and alphavbeta3 were observed to co-associate after stimulation with either L1Ig6 or VEGF-A165, whereas no co-association with bFGF-R was observed. Furthermore, VEGF-R2 was tyrosine phosphorylated after stimulation with L1Ig6, even in the absence of exogenous VEGF-A165, indicating close cooperation between VEGF-R2 and alphavbeta3. Angiogenesis was investigated in vivo by stimulating chicken chorioallantoic membranes (CAMs) with L1Ig6-modified matrices with or without co-incorporation of VEGF-A165 or bFGF. Matrix-immobilized L1Ig6 induced angiogenesis to a similar degree as VEGF-A165; co-stimulation with bFGF increased vascular branching, whereas VEGF-A165 did not. Matrix-immobilized L1Ig6 induced up-regulation of alphav in CAMs by a similar degree as stimulation with VEGF-A165, and this up-regulation was increased further by co-stimulation with matrix-bound L1Ig6 and VEGF-A165. alpha5 and beta1 levels were not increased. The similarity of action of matrix-bound L1Ig6 and soluble VEGF-A165 indicate a close link between specific ligation of alphavbeta3-integrin and VEGF-R2 and suggest the possible use of matrix-bound L1Ig6 in local therapeutic angiogenesis.
Hall
Heike
H
Institute for Biomedical Engineering and Department of Materials, Federal Institute of Technology and University of Zurich, Zurich, Switzerland. heike.hall@met.ethz.ch
Hubbell
Jeffrey A
JA
D043925:Angiogenesis Inducing Agents / Q000737:chemistry; D000818:Animals; D002478:Cells, Cultured; D002645:Chickens; D049033:Chorioallantoic Membrane / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006133:Growth Substances; D015151:Immunoblotting; D007136:Immunoglobulins / Q000737:chemistry; D047468:Immunoprecipitation; D039302:Integrin alphaVbeta3 / Q000378:metabolism*; D008024:Ligands; D009389:Neovascularization, Pathologic; D039842:Neural Cell Adhesion Molecule L1 / Q000737:chemistry*; D010766:Phosphorylation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014443:Tyrosine / Q000737:chemistry; D015854:Up-Regulation; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000737:chemistry* / Q000378:metabolism
D043925:Angiogenesis Inducing Agents; D006133:Growth Substances; D007136:Immunoglobulins; D039302:Integrin alphaVbeta3; D008024:Ligands; D039842:Neural Cell Adhesion Molecule L1; D014443:Tyrosine; D040301:Vascular Endothelial Growth Factor Receptor-2