Characterization of a 60-kDa cell surface-associated transforming growth factor-beta binding protein that can interfere with transforming growth factor-beta receptor binding.
We have characterized a 60-kDa transforming growth factor-beta (TGF-beta) binding protein that was originally identified on LNCaP adenocarcinoma prostate cells by affinity cross-linking of cell surface proteins by using 125I-TGF-beta 1. Binding of 125I-TGF-beta 1 to the 60-kDa protein was competed by an excess of unlabeled TGF-beta 1 but not by TGF-beta 2, TGF-beta 3, activin, or osteogenic protein-1 (OP-1), also termed bone morphogenetic protein-7 (BMP-7). In addition, no binding of 125I-TGF-beta 2 and 125I-TGF-beta 3 to the 60-kDa binding protein on LNCaP cells could be demonstrated by using affinity labeling techniques. The 60-kDa TGF-beta binding protein showed no immunoreactivity with antibodies against the known type I and type II receptors for members of the TGF-beta superfamily. Treatment of LNCaP cells with 0.25 M NaCl, 1 microgram/ml heparin, or 10% glycerol caused a release of the 60-kDa protein from the cell surface. In addition, we found that the previously described TGF-beta type IV receptor on GH3 cells, which does not form a heterometric complex with TGF-beta receptors, could be released from the cell surface by these same treatments. This suggests that the 60-kDa protein and the similarly sized TGF-beta type IV receptor are related proteins. The eluted 60-kDa LNCaP protein was shown to interfere with the binding of TGF-beta to the TGF-beta receptors. Thus, the cell surface-associated 60-kDa TGF-beta binding protein may play a role in regulating TGF-beta binding to TGF-beta receptors.
Piek
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Department of Cell Biology, University of Nijmegen, The Netherlands. esterp@sci.kun.nl
Franzén
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Heldin
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ten Dijke
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D048868:Adaptor Proteins, Signal Transducing; D000230:Adenocarcinoma; D001665:Binding Sites; D002352:Carrier Proteins / Q000302:isolation & purification / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002462:Cell Membrane / Q000378:metabolism; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D007700:Kinetics; D053779:Latent TGF-beta Binding Proteins; D008024:Ligands; D008297:Male; D008970:Molecular Weight; D011471:Prostatic Neoplasms; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; D047908:Intracellular Signaling Peptides and Proteins; D053779:Latent TGF-beta Binding Proteins; D008024:Ligands; D016212:Transforming Growth Factor beta