Glypican 4 (GPC4) is a cell surface heparan sulfate proteoglycans which composed of a membrane-associated protein core substituted with a variable number of heparan sulfate chains. Members of the glypican-related integral membrane proteoglycan family (GRIPS) contain a core protein anchored to the cytoplasmic membrane via a glycosyl phosphatidylinositol linkage. These proteins may play a role in the control of cell division and growth regulation. Besides, Fibroblast Growth Factor 2, Basic (FGF2) has been identified as an interactor of GPC4, thus a functional binding ELISA assay was conducted to detect the interaction of recombinant rat GPC4 and recombinant human FGF2. Briefly, GPC4 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate samples of 100 μl were then transferred to FGF2-coated microtiter wells and incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h with anti-GPC4 pAb, then aspirated and washed 3 times. After incubation with HRP labelled secondary antibody, wells were aspirated and washed 5 times. With the addition of substrate solution, wells were incubated 15-25 minutes at 37℃. Finally, add 50 μL stop solution to the wells and read at 450 nm immediately. The binding activity of recombinant rat GPC4 and recombinant human FGF2 was shown in Figure 1, the EC50?for this effect is 2.64 ug/mL.