Extracellular matrix tenascin-X in combination with vascular endothelial growth factor B enhances endothelial cell proliferation.
BACKGROUND
An extracellular matrix tenascin-X (TNX) is highly expressed in muscular tissues, especially heart and skeletal muscle, and is also prominent around blood vessels. The precise in vivo role of TNX remains to be elucidated. To identify proteins that interact with TNX in the extracellular environment, we searched for TNX-binding proteins using a yeast two-hybrid system.


RESULTS
We used mouse TNX-specific fibronectin type III repeats (mTNX/FNIII13-25) as a bait for the screening. We found that vascular endothelial growth factor B (VEGF-B) binds to mTNX/FNIII13-25. This interaction was confirmed by pull-down assays and co-immunoprecipitation assays. The full-length mTNX, as well as mTNX/FNIII13-25, interacted with both alternative splice isoforms VEGF-B186 and VEGF-B167. Furthermore, the full-length mTNX also bound to VEGF-A. The minimal region of TNX that interacts with VEGF-B was mapped to the FNIII repeats (FNIII13-25) but not to the other characteristic domains of TNX. The TNX-binding site of VEGF-B was located in the N-terminal 115-amino acid region. mTNX/FNIII13-25 did not prevent the interaction of VEGF-B with VEGFR-1 (VEGF receptor 1), and VEGF-B could simultaneously bind to both mTNX/FNIII13-25 and VEGFR-1. A conditioned medium from transfected 293T cells coexpressing full-length TNX and VEGF-B could promote DNA synthesis in bovine endothelial cells in which VEGFR-1 were expressed. VEGFR-1 phosphorylation triggered by VEGF-B186 were increased in cells plated with mTNX/FNIII13-25 or full-length mTNX, compared with cells plated with VEGF-B186 alone.


CONCLUSIONS
TNX interacts with VEGF-B and enhances the ability of VEGF-B to stimulate cell proliferation. This enhanced mitogenecity is caused by increased signals mediated by the VEGFR-1 receptor. This finding suggests a role for TNX in the regulation of the development of blood vessels such as vasculogenesis and angiogenesis.
Ikuta
T
T
Department of Molecular Biology, Graduate School of Pharmaceutical Sciences, Hokkaido University, Sapporo, Japan.
Ariga
H
H
Matsumoto
K
K
D017398:Alternative Splicing / Q000235:genetics; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D002417:Cattle; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004357:Drug Synergism; D016228:Endothelial Growth Factors / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D005109:Extracellular Matrix / Q000378:metabolism*; D005353:Fibronectins / Q000235:genetics; D006801:Humans; D051379:Mice; D010766:Phosphorylation / Q000187:drug effects; D011233:Precipitin Tests; D011485:Protein Binding / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000494:pharmacology; D019063:Tenascin / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D020798:Two-Hybrid System Techniques; D042461:Vascular Endothelial Growth Factor A; D042561:Vascular Endothelial Growth Factor B; D040281:Vascular Endothelial Growth Factor Receptor-1
D017077:Culture Media, Conditioned; D016228:Endothelial Growth Factors; D005353:Fibronectins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D019063:Tenascin; D042461:Vascular Endothelial Growth Factor A; D042561:Vascular Endothelial Growth Factor B; C081865:tenascin X; D020794:Receptor Protein-Tyrosine Kinases; D040281:Vascular Endothelial Growth Factor Receptor-1