SVEP1 binds to integrin α4β1 and α9β1
SVEP1 is a known ligand for integrin α9β1, but whether SVEP1 can bind to the closely related integrin α4β122 has not been reported. Using immunoprecipitation we found SVEP1 to bind to integrin α4 (Fig. 1A), and confirmed the ligation of SVEP1 to integrin α9 (Fig. 1B). In addition to demonstrating the direct ligation of SVEP1 to integrin α4, we investigated how SVEP1 interacts with α4 using a cell adhesion assay. SVEP1 binds to integrin α9β1 through its CCP21 domain9. We coated tissue culture plastic with 100nM manose-binding protein (MBP), MBP-tagged CCP21 or CCP22 domain peptides. HEK293 cells overexpressing the integrin α4 subunit bound to the CCP21 peptide significantly greater than either MBP (P <0.01) or CCP22 (P <0.05) control proteins (Fig. 1C). Similar results were seen for HEK293 cells overexpressing the integrin α9 subunit, with cells binding to the CCP21 domain significantly higher than MBP (P <0.01) or CCP22 (P <0.05) control proteins (Fig. 1D).