Interstitial collagenase (matrix metalloproteinase-1) expresses serpinase activity

Area of Science:

• Biochemistry
• Cell Biology
• Proteomics

Background:

• Plasma contains major serine proteinase inhibitors (Serpins), including alpha 1-proteinase inhibitor and alpha 1-antichymotrypsin.
• These Serpins regulate protease activity in physiological processes.
• Human endothelial cells can be stimulated to secrete metalloproteinases.

Purpose of the Study:

• To identify the metalloproteinase secreted by stimulated human endothelial cells.
• To determine the effect of this metalloproteinase on plasma Serpins.
• To elucidate the mechanism of Serpin inactivation.

Main Methods:

• Stimulation of human endothelial cells with interleukin-1 beta, tumor necrosis factor-alpha, or phorbol myristate acetate.
• Isolation and identification of the secreted metalloproteinase.
• Biochemical assays to assess the hydrolysis and inactivation of alpha 1-proteinase inhibitor and alpha 1-antichymotrypsin.
• NH2-terminal sequence analysis of cleaved Serpins.

Main Results:

• A metalloproteinase was secreted by stimulated endothelial cells.
• The secreted metalloproteinase was identified as human interstitial collagenase (matrix metalloproteinase-1, MMP-1).
• MMP-1 hydrolyzed and inactivated both alpha 1-proteinase inhibitor and alpha 1-antichymotrypsin.
• MMP-1 cleaved Serpins at unique sites, distinct from its collagenolytic activity.
• Cleavage sites were located near the reactive center of Serpins.

Conclusions:

• Matrix metalloproteinase-1 (MMP-1) possesses a broader substrate specificity than previously known.
• MMP-1 can inactivate major plasma Serpins, suggesting a novel function beyond extracellular matrix degradation.
• This discovery establishes a new link between connective tissue metabolism and the regulation of protease activity by Serpins.