Defensin stimulates the binding of Lp(a) to purified fibronectin. (A) Solid-phase radioligand binding. Microtiter wells were coated with 5 μg/mL fibronectin (▩) or BSA (□), unreactive sites were blocked with 0.3% BSA, and the binding of125I-Lp(a) (10 nmol/L) alone or in the presence of the indicated concentrations of defensin was measured. The mean ± SD of 2 experiments performed in triplicate is shown. (B) Surface plasmon resonance. (B1) Immobilized apo(a) (960 RU) was incubated with fibronectin alone (10 and 50 nmol/L) or after preincubation of the chip with 5 μmol/L defensin. The surface was regenerated at 2,000 seconds, ie, between the 2 sets of incubation with fibronectin. (B2) Immobilized Lp(a) was preincubated with defensin (0, 312, 625, 1,250, and 2,500 nmol/L; sensorgrams 1 through 5, respectively), the chip was washed for 3 minutes, and fibronectin was injected at the indicated concentrations with the appropriate wash steps between injections. Binding of fibronectin to Lp(a) was not detected at concentrations of defensin below 0.625 μmol/L.
