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).