TY - JOUR T1 - Structural and mechanistic insights into VEGF receptor 3 ligand binding and activation JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2013 A1 - Leppänen, Veli-Matti A1 - Tvorogov, Denis A1 - Kisko, Kaisa A1 - Prota, Andrea E A1 - Jeltsch, Michael A1 - Anisimov, Andrey A1 - Markovic-Mueller, Sandra A1 - Stuttfeld, Edward A1 - Goldie, Kenneth N A1 - Ballmer-Hofer, Kurt A1 - Alitalo, Kari KW - Amino Acid Sequence KW - Binding Sites KW - Binding, Competitive KW - Crystallography, X-Ray KW - Electrophoresis, Polyacrylamide Gel KW - Humans KW - Ligands KW - Microscopy, Electron KW - Models, Molecular KW - Molecular Sequence Data KW - Multiprotein Complexes KW - Mutation KW - Protein Binding KW - Protein Multimerization KW - Protein Structure, Tertiary KW - Scattering, Small Angle KW - Sequence Homology, Amino Acid KW - Thermodynamics KW - Vascular Endothelial Growth Factor C KW - Vascular Endothelial Growth Factor Receptor-3 KW - X-Ray Diffraction AB - Vascular endothelial growth factors (VEGFs) and their receptors (VEGFRs) are key drivers of blood and lymph vessel formation in development, but also in several pathological processes. VEGF-C signaling through VEGFR-3 promotes lymphangiogenesis, which is a clinically relevant target for treating lymphatic insufficiency and for blocking tumor angiogenesis and metastasis. The extracellular domain of VEGFRs consists of seven Ig homology domains; domains 1-3 (D1-3) are responsible for ligand binding, and the membrane-proximal domains 4-7 (D4-7) are involved in structural rearrangements essential for receptor dimerization and activation. Here we analyzed the crystal structures of VEGF-C in complex with VEGFR-3 domains D1-2 and of the VEGFR-3 D4-5 homodimer. The structures revealed a conserved ligand-binding interface in D2 and a unique mechanism for VEGFR dimerization and activation, with homotypic interactions in D5. Mutation of the conserved residues mediating the D5 interaction (Thr446 and Lys516) and the D7 interaction (Arg737) compromised VEGF-C induced VEGFR-3 activation. A thermodynamic analysis of VEGFR-3 deletion mutants showed that D3, D4-5, and D6-7 all contribute to ligand binding. A structural model of the VEGF-C/VEGFR-3 D1-7 complex derived from small-angle X-ray scattering data is consistent with the homotypic interactions in D5 and D7. Taken together, our data show that ligand-dependent homotypic interactions in D5 and D7 are essential for VEGFR activation, opening promising possibilities for the design of VEGFR-specific drugs. VL - 110 SN - 1091-6490 UR - http://www.pnas.org/content/110/32/12960.long IS - 32 JO - Proc. Natl. Acad. Sci. U.S.A. ER - TY - JOUR T1 - Structural determinants of vascular endothelial growth factor-D receptor binding and specificity JF - Blood Y1 - 2011 A1 - Leppänen, Veli-Matti A1 - Jeltsch, Michael A1 - Anisimov, Andrey A1 - Tvorogov, Denis A1 - Aho, Kukka A1 - Kalkkinen, Nisse A1 - Toivanen, Pyry A1 - Ylä-Herttuala, Seppo A1 - Ballmer-Hofer, Kurt A1 - Alitalo, Kari AB - Vascular endothelial growth factors (VEGFs) and their tyrosine kinase receptors (VEGFR-1-3) are central mediators of angiogenesis and lymphangiogenesis. VEGFR-3 ligands VEGF-C and VEGF-D are produced as precursor proteins with long N- and C-terminal propeptides and show enhanced VEGFR-2 and VEGFR-3 binding on proteolytic removal of the propeptides. Two different proteolytic cleavage sites have been reported in the VEGF-D N-terminus. We report here the crystal structure of the human VEGF-D Cys117Ala mutant at 2.9 Å resolution. Comparison of the VEGF-D and VEGF-C structures shows similar extended N-terminal helices, conserved overall folds, and VEGFR-2 interacting residues. Consistent with this, the affinity and the thermodynamic parameters for VEGFR-2 binding are very similar. In comparison with VEGF-C structures, however, the VEGF-D N-terminal helix was extended by 2 more turns because of a better resolution. Both receptor binding and functional assays of N-terminally truncated VEGF-D polypeptides indicated that the residues between the reported proteolytic cleavage sites are important for VEGF-D binding and activation of VEGFR-3, but not of VEGFR-2. Thus, we define here a VEGFR-2-specific form of VEGF-D that is angiogenic but not lymphangiogenic. These results provide important new insights into VEGF-D structure and function. VL - 117 UR - http://view.ncbi.nlm.nih.gov/pubmed/21148085 IS - 5 JO - Blood ER - TY - JOUR T1 - Structural determinants of growth factor binding and specificity by VEGF receptor 2 JF - Proceedings of the National Academy of Sciences of the United States of America Y1 - 2010 A1 - Leppänen, Veli-Matti A1 - Prota, Andrea E A1 - Jeltsch, Michael A1 - Anisimov, Andrey A1 - Kalkkinen, Nisse A1 - Strandin, Tomas A1 - Lankinen, Hilkka A1 - Goldman, Adrian A1 - Ballmer-Hofer, Kurt A1 - Alitalo, Kari AB - Vascular endothelial growth factors (VEGFs) regulate blood and lymph vessel formation through activation of three receptor tyrosine kinases, VEGFR-1, -2, and -3. The extracellular domain of VEGF receptors consists of seven immunoglobulin homology domains, which, upon ligand binding, promote receptor dimerization. Dimerization initiates transmembrane signaling, which activates the intracellular tyrosine kinase domain of the receptor. VEGF-C stimulates lymphangiogenesis and contributes to pathological angiogenesis via VEGFR-3. However, proteolytically processed VEGF-C also stimulates VEGFR-2, the predominant transducer of signals required for physiological and pathological angiogenesis. Here we present the crystal structure of VEGF-C bound to the VEGFR-2 high-affinity-binding site, which consists of immunoglobulin homology domains D2 and D3. This structure reveals a symmetrical 22 complex, in which left-handed twisted receptor domains wrap around the 2-fold axis of VEGF-C. In the VEGFs, receptor specificity is determined by an N-terminal alpha helix and three peptide loops. Our structure shows that two of these loops in VEGF-C bind to VEGFR-2 subdomains D2 and D3, while one interacts primarily with D3. Additionally, the N-terminal helix of VEGF-C interacts with D2, and the groove separating the two VEGF-C monomers binds to the D2/D3 linker. VEGF-C, unlike VEGF-A, does not bind VEGFR-1. We therefore created VEGFR-1/VEGFR-2 chimeric proteins to further study receptor specificity. This biochemical analysis, together with our structural data, defined VEGFR-2 residues critical for the binding of VEGF-A and VEGF-C. Our results provide significant insights into the structural features that determine the high affinity and specificity of VEGF/VEGFR interactions. VL - 107 UR - http://view.ncbi.nlm.nih.gov/pubmed/20145116 IS - 6 ER -