Cell surface binding of TIMP-2 and pro-MMP-2/TIMP-2 complex

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Tissue inhibitor of metalloproteinases-2 (TIMP-2) is a proteinase inhibitor.
• TIMP-2 inhibits activated matrix metalloproteinases (MMPs).
• TIMP-2 exists freely or complexed with pro-matrix metalloproteinase-2 (pro-MMP-2).

Purpose of the Study:

• To investigate the binding characteristics of recombinant TIMP-2 (rTIMP-2) to HT-1080 and MCF-7 cell lines.
• To determine if TIMP-2 binds directly to cell surfaces.
• To assess TIMP-2's role in localizing MMP-2 to the cell surface.

Main Methods:

• Radiolabeling of recombinant TIMP-2 with iodine-125 ([125I]rTIMP-2).
• Incubation of [125I]rTIMP-2 with suspended HT-1080 cells and MCF-7 cell monolayers.
• Measurement of binding affinity (Kd) and receptor site density.
• Competition assays using TIMP-1 and pro-MMP-2/TIMP-2 complex.

Main Results:

• HT-1080 cells bound [125I]rTIMP-2 with a Kd of 2.5 nM (30,000 sites/cell).
• MCF-7 cells bound [125I]rTIMP-2 with a Kd of 1.6 nM (25,000 sites/cell).
• Pro-MMP-2/TIMP-2 complex bound to HT-1080 cells in a TIMP-2-dependent manner, while MMP-2 alone did not.
• TIMP-1 did not compete for rTIMP-2 binding.

Conclusions:

• Recombinant TIMP-2 directly binds to the cell surfaces of HT-1080 and MCF-7 cells.
• TIMP-2 possesses specific binding sites on these cell lines.
• TIMP-2 mediates the localization of MMP-2 to the cell surface through these interactions.