Characterization of the integrin alpha v beta 6 as a fibronectin-binding protein.

Abstract

Integrins are a complex family of divalent cation-dependent cell adhesion receptors composed of one alpha and one beta subunit noncovalently bound to one another. A subset of integrins contains the alpha v subunit in association with one of several beta subunits (e.g. beta 3, beta 5, beta 1). We have recently identified a novel integrin beta subunit, beta 6, that is present in a number of epithelial cell lines. Using a polyclonal antibody raised against the carboxyl-terminal peptide of beta 6, we have now identified the integrin heterodimer, alpha v beta 6, on the surface of two human carcinoma cell lines. Using affinity chromatography of lysates from the pancreatic carcinoma cell line, FG-2, we demonstrate that alpha v beta 6 binds to fibronectin, but not to vitronectin or collagen I. In contrast, the alpha v beta 5 integrin, which is also expressed on FG-2 cells, binds exclusively to vitronectin. Immobilized collagen I does not interact with alpha v integrins, but binds beta 1-containing integrins. Both alpha v beta 6 and alpha v beta 5 are eluted from their respective immobilized ligands by a hexa-peptide containing the sequence Arg-Gly-Asp (RGD). RGD is highly effective in the presence of Ca2+, somewhat less effective in Mg2+, and virtually inactive in Mn2+. These results suggest that alpha v beta 6 functions as an RGD-dependent fibronectin receptor in FG-2 carcinoma cells. In agreement with this notion, cell adhesion assays show that FG-2 cell attachment to fibronectin is only partially inhibited by anti-beta 1 integrin antibodies, implying that other fibronectin receptors may be involved. Taken together with recent reports on the vitronectin receptor function of alpha v beta 5, our results suggest that the previously described carcinoma cell integrin, alpha v beta x (Cheresh, D. A., Smith, J. W., Cooper, H. M., and Quaranta, V. (1989) Cell 57, 59-69), is a mixture of at least two different receptors: alpha v beta 5, mediating adhesion to vitronectin, and alpha v beta 6, mediating adhesion to fibronectin.

• Authors: M Busk, R Pytela, D Sheppard
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 267 Issue 9 Pg. 5790-6 (Mar 25 1992) ISSN: 0021-9258 [Print] United States
• PMID: 1532572 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antigens, Neoplasm
• Fibronectins
• Integrins
• Macromolecular Substances
• Receptors, Fibronectin
• Receptors, Immunologic
• integrin alphavbeta6

Topics

• Amino Acid Sequence
• Antigens, Neoplasm
• Cell Line
• Cell Membrane (metabolism)
• Chromatography, Affinity
• Electrophoresis, Polyacrylamide Gel
• Fibronectins (metabolism)
• Humans
• Integrins (isolation & purification, metabolism)
• Kinetics
• Lung Neoplasms
• Macromolecular Substances
• Molecular Sequence Data
• Pancreatic Neoplasms
• Receptors, Fibronectin
• Receptors, Immunologic (isolation & purification, metabolism)
• Substrate Specificity