Matrix metalloproteinase 2 releases active soluble ectodomain of fibroblast growth factor receptor 1.

Recent studies have demonstrated the existence of a soluble fibroblast growth factor (FGF) receptor type 1 (FGFR1) extracellular domain in the circulation and in vascular basement membranes. However, the process of FGFR1 ectodomain release from the plasma membrane is not known. Here we report that the 72-kDa gelatinase A (matrix metalloproteinase type 2, MMP2) can hydrolyze the Val368-Met369 peptide bond of the FGFR1 ectodomain, eight amino acids upstream of the transmembrane domain, thus releasing the entire extracellular domain. Similar results were obtained regardless of whether FGF was first bound to the receptor or not. The action of MMP2 abolished binding of FGF to an immobilized recombinant FGFR1 ectodomain fusion protein and to Chinese hamster ovary cells overexpressing FGFR1 The released recombinant FGFR1 ectodomain was able to bind FGF after MMP2 cleavage, suggesting that the cleaved soluble receptor maintained its FGF binding capacity. The activity of MMP2 could not be reproduced by the 92-kDa gelatinase B (MMP9) and was inhibited by tissue inhibitor of metalloproteinase type 2. These studies demonstrate that FGFR1 may be a specific target for MMP2 on the cell surface, yielding a soluble FGF receptor that may modulate the mitogenic and angiogenic activities of FGF.

Cloning and characterization of cDNAs for matrix metalloproteinases of regenerating newt limbs.

Matrix metalloproteinases (MMPs) of regenerating urodele limbs have been suggested to play crucial roles in the process of the dedifferentiation of cells in the damaged tissues and the ensuing blastema formation because the activation of MMPs is an early and conspicuous event occurring in the amputated limb. MMP cDNAs were cloned as products of the reverse transcription-PCR from cDNA libraries of newt limbs, and their structures were characterized. Three cDNAs encoding newt MMPs (2D-1, 2D-19, and 2D-24) have been cloned from second day postamputation regenerating limbs, and a cDNA (EB-1) was cloned from early bud-stage regenerating limbs. These cDNAs included the full-length coding regions. The deduced amino acid sequences of 2D-1, 2D-19, 2D-24, and EB-1 had a homology with mammalian MMP9, MMP3/10, MMP3/10, and MMP13, respectively. The basic motif of these newt MMP genes was similar to mammalian counterparts and contained regions encoding a putative signal sequence, a propeptide, an active site with three zinc-binding histidine residues, a calcium-binding domain, a hemopexin region, and three key cysteine residues. However, some unique molecular evolutionary features were also found in the newt MMPs. cDNAs of 2D-19 and 2D-24 contained a specific insertion and deletion, respectively. The insertion of 2D-19 is threonine-rich, similar to the threonine cluster found in the collagenase-like sea urchin hatching enzyme. Northern blot analysis showed that the expression levels of the newt MMPs were dramatically increased after amputation, suggesting that they play an important role(s) in tissue remodeling of the regenerating limb.