Faculty Collaboration Database

Thrombospondin forms complexes with single-chain and two-chain forms of urokinase. J Biol Chem 1990 Jul 05;265(19):11289-94

Date

07/05/1990

Pubmed ID

2141608

Scopus ID

2-s2.0-0025331427 (requires institutional sign-in at Scopus site)   41 Citations

Abstract

Thrombospondin (TSP), an adhesive glycoprotein found in platelets and extracellular matrix, has been shown previously to interact with plasminogen and tissue plasminogen activator, resulting in efficient plasmin generation. We now demonstrate specific complex formation of TSP with both the single-chain and two-chain forms of urokinase (scuPA and uPA). Binding of uPA and scuPA to immobilized TSP was detected and quantified using colorimetric immunoassays and a functional amidolytic assay. Binding was time and concentration dependent with apparent affinity constants of 40-50 nM. Binding was not affected by serine protease inhibitors, EDTA, or epsilon-aminocaproic acid. scUPA and uPA bound to TSP retained functional activity. Using a sensitive amidolytic assay we found that TSP. scuPA complexes were efficiently converted to TSP. uPA by catalytic plasmin concentrations. Additionally, TSP.uPA complexes were found to have plasminogen-activating activity equivalent to fluid-phase uPA and to be protected from inhibition by plasminogen activator inhibitor type 1, the major plasma and matrix plasminogen activator inhibitor. Using immunohistochemical techniques, we also demonstrated co-distribution of TSP and uPA in normal and malignant breast tissue. Complex formation of TSP with uPA may serve to localize, concentrate, and protect these enzymes on cell surfaces and within the extracellular matrix, thereby providing a reservoir of plasminogen activator activity.

Author List

Silverstein RL, Nachman RL, Pannell R, Gurewich V, Harpel PC

Author

Roy L. Silverstein MD Professor in the Medicine department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Amino Acid Sequence
Blood Platelets
Breast
Breast Neoplasms
Colorimetry
Enzyme-Linked Immunosorbent Assay
Extracellular Matrix
Fibrinolysin
Humans
Immunohistochemistry
Kinetics
Membrane Glycoproteins
Molecular Sequence Data
Plasminogen
Plasminogen Activators
Thrombospondins
Tissue Distribution
Urokinase-Type Plasminogen Activator