Faculty Collaboration Database

Activation of rat alveolar macrophage-derived latent transforming growth factor beta-1 by plasmin requires interaction with thrombospondin-1 and its cell surface receptor, CD36. Am J Pathol 1999 Sep;155(3):841-51

Date

09/17/1999

Pubmed ID

10487979

Pubmed Central ID

PMC1866879

DOI

10.1016/s0002-9440(10)65183-8

Scopus ID

2-s2.0-0032886794 (requires institutional sign-in at Scopus site)   157 Citations

Abstract

Transforming growth factor-beta-1 (TGF-beta1) is secreted by cells in a latent form (L-TGF-beta1) noncovalently bound to a latency-associated peptide. Activated alveolar macrophages obtained from rat lungs after bleomycin-induced pulmonary injury released increased amounts of active TGF-beta1 as well as plasmin, a protease, and thrombospondin-1 (TSP-1), a trimeric glycoprotein. Previously we had demonstrated that plasmin was critical to the activation of L-TGF- beta1. In the present study we demonstrated that TSP-1 is also important for the activation of L-TGF- beta1 because the activation can be inhibited by anti-TSP-1 monoclonal antibody. Proteins obtained from alveolar macrophage cell lysates immunoprecipitated with antibodies specific for TSP-1 were identified on immunoblots as LAP and TGF-beta1, indicating that TSP-1/L-TGF-beta1 complexes are present on alveolar macrophages. However, in the presence of plasmin both latency-associated peptide and TGF-beta1 were decreased in the same cell lysates, indicating that L-TGF-beta1 associated with TSP-1 is released by plasmin. Using immunofluorescence and antibodies to TGF-beta1 and CD36, a receptor for TSP-1, there was colocalization of TGF-beta1 with CD36. Because TSP-1 but not TGF-beta1 is a natural ligand for CD36, these findings suggest that the L-TGF-beta1 in a complex with TSP-1 localizes to the macrophage cell surface when TSP-1 interacts with its receptor, CD36. Furthermore, the association of TSP-1/L-TGF-beta1 complex with CD36 is necessary to the activation of L-TGF-beta1 because antibodies to CD36 prevent the colocalization of TGF-beta1 with CD36 as observed by immunofluorescence and inhibit activation of the L-TGF-beta1 by explanted alveolar macrophages. These findings suggest that activation of L-TGF-beta1 by plasmin occurs at the cell surface of activated alveolar macrophages and requires a TSP-1/CD36 interaction.

Author List

Yehualaeshet T, O'Connor R, Green-Johnson J, Mai S, Silverstein R, Murphy-Ullrich JE, Khalil N

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

Animals
Antibodies, Monoclonal
Antimetabolites, Antineoplastic
Bleomycin
Blotting, Western
CD36 Antigens
Cells, Cultured
Enzyme-Linked Immunosorbent Assay
Female
Fibrinolysin
Fluorescent Antibody Technique, Indirect
Macrophages, Alveolar
Precipitin Tests
Proteins
Rats
Rats, Sprague-Dawley
TNF Receptor-Associated Factor 3
Thrombospondin 1
Transforming Growth Factor beta