Insulin-like growth factor-binding protein 3, also known as IGFBP3 is one of six
IGF binding proteins (IGFBP1 to IGFBP6) that have highly conserved structures
and bind the insulin-like growth factors IGF-1 and IGF-2 with high affinity. Within
tissues, IGFBP3 can bind IGF1 and IGF2 released by many cell types, and block
their access to the IGF-1 receptor (IGF1R), which is activated by both IGFs.
IGFBP3 also interacts with cell-surface proteins, affecting cell signaling from
outside the cell or after internalization, and also enters the cell nucleus where it
binds to nuclear hormone receptors and other ligands. Besides, Fibronectin (FN)
has been identified as an interactor of IGFBP3, thus a binding ELISA assay was
conducted to detect the interaction of recombinant human IGFBP3 and
recombinant human FN.
Briefly, IGFBP3 were diluted serially in PBS, with 0.01% BSA (pH 7.4). Duplicate
samples of 100ul were then transferred to FN-coated microtiter wells and
incubated for 1h at 37℃. Wells were washed with PBST and incubated for 1h
with anti-IGFBP3 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 50µL stop solution to the wells and read at 450nm immediately.
The binding activity of IGFBP3 and FN was shown in Figure 1, the EC50 was 78
ng/ml.