Latent transforming growth factor-beta-binding protein 2 is an adhesion protein for melanoma cells.
Of the four latent transforming growth factor (TGF)-beta-binding proteins (LTBPs), LTBP-2 is different in the respect that it does not bind small latent forms of TGF-beta. LTBP-2 is therefore likely to have other roles in the extracellular matrix. LTBP-2 contains an RGD putative integrin recognition site, suggesting a role in cell adhesion. We carried out a study on cell attachment to LTBP-2. Purified recombinant LTBP-2 was used as substratum in cell adhesion and migration studies. We found that, unlike most adherent cell lines, all of the melanoma cell lines tested adhered to LTBP-2 very efficiently and in a concentration-dependent manner. Bowes melanoma cells bound most efficiently to LTBP-2 and were used for further characterization. Cell adhesion assays with recombinant LTBP-2 fragments indicated that the adhesive site is located in an N-terminal region of LTBP-2. The attachment of melanoma cells to LTBP-2 was prevented with monoclonal antibody against beta1 integrin in a concentration-dependent manner, suggesting an important role for beta1 integrin in the process. Antibodies against integrin subunits alpha3 and alpha6 decreased melanoma cell adhesion as well. The beta1 and alpha3 integrins were localized on the cell surface, especially in lamellipodia, as observed by immunofluorescence. In addition to integrin antagonists, heparin also markedly decreased melanoma cell adhesion. LTBP-2 also supported Bowes cell migration in modified Boyden chamber assays in a manner similar to the migration on fibronectin. Current data indicate that LTBP-2 can play a role in melanoma cell adhesion.
Vehviläinen
Piia
P
Department of Pathology, Haartman Institute, University of Helsinki, Finland.
Hyytiäinen
Marko
M
Keski-Oja
Jorma
J
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002448:Cell Adhesion / Q000235:genetics; D002465:Cell Movement / Q000235:genetics; D006801:Humans; D053779:Latent TGF-beta Binding Proteins; D008545:Melanoma / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D014407:Tumor Cells, Cultured
D048868:Adaptor Proteins, Signal Transducing; D002352:Carrier Proteins; C509035:LTBP2 protein, human; D053779:Latent TGF-beta Binding Proteins