Thermodynamic and structural description of allosterically regulated VEGFR-2 dimerization.
VEGFs activate 3 receptor tyrosine kinases, VEGFR-1, VEGFR-2, and VEGFR-3, promoting angiogenic and lymphangiogenic signaling. The extracellular receptor domain (ECD) consists of 7 Ig-homology domains; domains 2 and 3 (D23) represent the ligand-binding domain, whereas the function of D4-7 is unclear. Ligand binding promotes receptor dimerization and instigates transmembrane signaling and receptor kinase activation. In the present study, isothermal titration calorimetry showed that the Gibbs free energy of VEGF-A, VEGF-C, or VEGF-E binding to D23 or the full-length ECD of VEGFR-2 is dominated by favorable entropic contribution with enthalpic penalty. The free energy of VEGF binding to the ECD is 1.0-1.7 kcal/mol less favorable than for binding to D23. A model of the VEGF-E/VEGFR-2 ECD complex derived from small-angle scattering data provided evidence for homotypic interactions in D4-7. We also solved the crystal structures of complexes between VEGF-A or VEGF-E with D23, which revealed comparable binding surfaces and similar interactions between the ligands and the receptor, but showed variation in D23 twist angles. The energetically unfavorable homotypic interactions in D4-7 may be required for re-orientation of receptor monomers, and this mechanism might prevent ligand-independent activation of VEGFR-2 to evade the deleterious consequences for blood and lymph vessel homeostasis arising from inappropriate receptor activation.
Biomolecular Research, Molecular Cell Biology Paul Scherrer Institut, Villigen, Switzerland.
Maurice S
MS
Brozzo
Sasa
S
Bjelić
Kaisa
K
Kisko
Thomas
T
Schleier
Veli-Matti
VM
Leppänen
Kari
K
Alitalo
Fritz K
FK
Winkler
Kurt
K
Ballmer-Hofer
D000494:Allosteric Regulation; D000818:Animals; D002478:Cells, Cultured; D006801:Humans; D008024:Ligands; D008958:Models, Molecular; D010843:Pichia; D011485:Protein Binding; D055503:Protein Multimerization / Q000502:physiology*; D020836:Protein Structure, Quaternary; D018411:Spodoptera; D013816:Thermodynamics; D040281:Vascular Endothelial Growth Factor Receptor-1 / Q000737:chemistry / Q000378:metabolism; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000737:chemistry* / Q000378:metabolism*; D040321:Vascular Endothelial Growth Factor Receptor-3 / Q000737:chemistry / Q000378:metabolism
D008024:Ligands; D040281:Vascular Endothelial Growth Factor Receptor-1; D040301:Vascular Endothelial Growth Factor Receptor-2; D040321:Vascular Endothelial Growth Factor Receptor-3