Fig. 1.

Nrp1 binds TGF-β1 components. (A) LAP-TGF-β1, LAP (β1), TGF-β1, and VEGF bound to Nrp1-Fc (but not control Fc) and were retained on protein G-sepharose beads. Bound proteins were recovered and immunoblots performed with specific antibodies. Molecular weight markers are indicated. (B) To demonstrate binding by ELISA, Nrp1-Fc-coated plates were incubated with increasing concentrations of the ligands. LAP (alone but not in the presence of 2 μg/ml heparin) and LAP-TGF-β1 bound at high affinity to Nrp1-Fc (see text). Several control proteins, including IFN-γ and IL-2, did not bind (not shown). (C) Active TGF-β1 bound to immobilized Nrp1-Fc. (D) Soluble Nrp1-Fc bound to plate-bound LAP, and this was inhibited by an anti-LAP antibody. The data in A–D are representative of three or more independent experiments.