Proteolysis of insulin-like growth factor binding protein-3 during rat pregnancy: a role for matrix metalloproteinases.
Insulin-like growth factor binding protein-3 (IGFBP-3) is degraded by a cation-dependent protease(s) present in the serum of late gestation rats. Proteolysis of IGFBP-3 results in an increase in IGF-I clearance and possibly in IGF bioavailability. Based on our previous findings that matrix metalloproteinases (MMPs) degrade IGFBP-3 in fibroblast conditioned media, we hypothesized that MMPs might be involved in the degradation of IGFBP-3 by rat pregnancy serum. In the present study, we demonstrate that tissue inhibitor of metalloproteinases (TIMP-1), a specific inhibitor of all MMPs, inhibited significantly the degradation of 125I-rhIGFBP-3 by both rat pregnancy serum and rat placental extracts. Purified human MMPs (principally MMP-1 and MMP-3) degraded IGFBP-3 in solution; MMP-3 produced a pattern of IGFBP-3 degradation products identical in size to the fragments produced by pregnancy serum. Furthermore, the combined addition of antihuman MMP-1 IgG and anti-human MMP-3 IgG to rat pregnancy serum blocked almost completely the degradation of 125I-rhIGFBP-3, suggesting that these two MMPs are the principal MMPs involved in IGFBP-3 degradation in rat pregnancy serum. Together, these data suggest that MMPs function as IGFBP-3-degrading proteases in the serum of late gestational pregnant rats.
Fowlkes
J L
JL
Department of Pediatrics, Duke University Medical Center, Durham, North Carolina 27710.
Suzuki
K
K
Nagase
H
H
Thrailkill
K M
KM
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D005109:Extracellular Matrix / Q000201:enzymology*; D005260:Female; D006023:Glycoproteins / Q000494:pharmacology; D018969:Insulin-Like Growth Factor Binding Proteins; D008666:Metalloendopeptidases / Q000037:antagonists & inhibitors / Q000502:physiology*; D010447:Peptide Hydrolases / Q000378:metabolism*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins; D013002:Somatomedins / Q000378:metabolism; D019714:Tissue Inhibitor of Metalloproteinases
D002352:Carrier Proteins; D006023:Glycoproteins; D018969:Insulin-Like Growth Factor Binding Proteins; D011994:Recombinant Proteins; D013002:Somatomedins; D019714:Tissue Inhibitor of Metalloproteinases; D010447:Peptide Hydrolases; D008666:Metalloendopeptidases