Adhesion to vascular cell adhesion molecule 1 and fibronectin. Comparison of alpha 4 beta 1 (VLA-4) and alpha 4 beta 7 on the human B cell line JY.
Most mononuclear leukocytes and cell lines express the integrin alpha 4 beta 1 (VLA-4) heterodimer. In this study we have used Northern blotting and immunoprecipitation experiments to demonstrate that a B lymphoblastoid cell line (JY) expressed the integrin beta 7 subunit in association with alpha 4. These alpha 4 beta 7-positive JY cells bound poorly or not at all to VLA-4 ligands (soluble form of vascular cell adhesion molecule 1 (sVCAM-1) and the CS1 region of fibronectin). In contrast, a beta 1-positive variant of JY cells (selected to express a mixture of alpha 4 beta 1 and alpha 4 beta 7) bound avidly to VLA-4 ligands, and this binding was completely inhibitable by anti-alpha 4 and anti-beta 1 monoclonal antibodies. Thus, beta 1 expression appears to be a critically important component of VLA-4-mediated binding to its ligands. After either JY or JY-beta 1 cells were stimulated for 15 min with the phorbol ester 12-O-tetradecanoylphorbol-13-acetate, the majority of adhesion to VCAM or fibronectin remained alpha 4- and beta 1-dependent, but a low amount of adhesion to sVCAM-1 or fibronectin became alpha 4-dependent, beta 1-independent, thus suggesting a role for alpha 4 beta 7. In summary, we have found (i) that alpha 4 beta 7 makes little or no contribution to fibronectin or VCAM-1 binding on unstimulated JY cells, (ii) that alpha 4 beta 7 perhaps makes a minor contribution to ligand binding on 12-O-tetradecanoyl-phorbol-13-acetate-stimulated cells, and (iii) that alpha 4 beta 1 is the functionally dominant VCAM-1 and fibronectin receptor even when expressed in relatively low amounts compared to alpha 4 beta 7.
Chan
B M
BM
Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts 02115.
Elices
M J
MJ
Murphy
E
E
Hemler
M E
ME
D000911:Antibodies, Monoclonal; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D015152:Blotting, Northern; D002448:Cell Adhesion; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D016023:Integrins / Q000276:immunology / Q000378:metabolism*; D011233:Precipitin Tests; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D015854:Up-Regulation; D019010:Vascular Cell Adhesion Molecule-1
D000911:Antibodies, Monoclonal; D015815:Cell Adhesion Molecules; D005353:Fibronectins; D016023:Integrins; D019010:Vascular Cell Adhesion Molecule-1; D013755:Tetradecanoylphorbol Acetate