Latent transforming growth factor-beta 1 associates to fibroblast extracellular matrix via latent TGF-beta binding protein.
The role of latent transforming growth factor-beta (TGF-beta) binding protein (LTBP) in the association of TGF-beta 1 to the extracellular matrix of cultured fibroblasts and HT-1080 fibrosarcoma cells was studied by immunochemical methods. The matrices were isolated from the cells, and the levels of LTBP and TGF-beta 1 were estimated by immunoblotting and immunoprecipitation. LTBP, TGF-beta 1, and its propeptide (latency-associated peptide, LAP) were found to associate to the extracellular matrix. Immunoblotting analysis indicated that treatment of the cells with plasmin resulted in a concomitant time and dose dependent release of both LTBP and TGF-beta 1 from the extracellular matrix to the supernatant. Comparison of molecular weights suggested that plasmin treatment resulted in the cleavage of LTBP from the high molecular weight fibroblast form to a form resembling the low molecular weight LTBP found in platelets. Pulse-chase and immunoprecipitation analysis indicated that both the free form of LTBP and LTBP complexed to latent TGF-beta were efficiently incorporated in the extracellular matrix, from where both complexes were slowly released to the culture medium. Addition of plasmin to the chase solution resulted, however, in a rapid release of LTBP from the matrix. Fibroblast derived LTBP was found to associate to the matrix of HT-1080 cells in a plasmin sensitive manner as shown by immunoprecipitation analysis. These results suggest that the latent form of TGF-beta 1 associates with the extracellular matrix via LTBP, and that the release of latent TGF-beta 1 from the matrix is a consequence of proteolytic cleavage(s) of LTBP.
Taipale
J
J
Department of Virology, University of Helsinki, Finland.
Miyazono
K
K
Heldin
C H
CH
Keski-Oja
J
J
D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D005109:Extracellular Matrix / Q000378:metabolism*; D005341:Fibrinolysin / Q000378:metabolism; D005347:Fibroblasts; D005354:Fibrosarcoma / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D008970:Molecular Weight; D011485:Protein Binding; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D014407:Tumor Cells, Cultured
D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D016212:Transforming Growth Factor beta; D005341:Fibrinolysin