Limited Cleavage of Cellular Fibronectin by Plasminogen Activator Purified from Transformed Cells

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 84; no. 9; pp. 2776 - 2780
• Main Authors: Quigley, James P., Gold, Leslie I., Schwimmer, Randi, Sullivan, Lee M.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-05-1987; National Acad Sciences
• Subjects: Animals; Avian Sarcoma Viruses - genetics; Biological and medical sciences; Cell physiology; Cell transformation and carcinogenesis. Action of oncogenes and antioncogenes; Cell Transformation, Neoplastic; Cells; Chick Embryo; Chickens; Enzymes; Extracellular matrix; fibroblasts; Fibroblasts - enzymology; fibronectin; Fibronectins - metabolism; Fundamental and applied biological sciences. Psychology; Gels; Humans; Molecular and cellular biology; Molecular weight; Molecules; Monoclonal antibodies; plasminogen activator; Plasminogen activators; Plasminogen Activators - isolation & purification; Plasminogen Activators - metabolism; Substrate Specificity; Thrombin - metabolism; Urokinase-Type Plasminogen Activator - metabolism; Embryo; Purification; Transformed cell; Migration; Plasminogen activator; Fibronectin; Characterization; Vertebrata; Extracellular matrix; Substrate attachment; Chicken; Aves; Mechanism of action
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.84.9.2776

The substrate specificity and direct catalytic activity of plasminogen activator (PA) was examined under conditions where its natural substrate, plasminogen, was missing or inhibited. PA, purified from cultures of transformed chicken fibroblasts, was incubated with purified preparations of potential substrates. The adhesive glycoprotein fibronectin, isolated from normal chicken fibroblast extracellular matrix, underwent limited but specific cleavage by PA in the absence of plasminogen. Analysis of the cleavage products by polyacrylamide gels under both reducing and nonreducing conditions indicated that PA-mediated cleavage occurred near the carboxyl terminus of fibronectin but on the amino-terminal side of the interchain disulfide bridge, thus disrupting the native dimeric fibronectin molecule. Under the identical conditions, chicken ovalbumin was not cleaved while the established substrate, chicken plasminogen, was extensively converted to plasmin. A monoclonal antibody, directed against avian PA and shown to inhibit plasminogen-free, cell-mediated matrix degradation, specifically inhibited the fibronectin cleavage. A human PA, urokinase, also cleaved fibronectin under plasminogen-free conditions yielding a limited number of high molecular weight cleavage products.