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A region of the integrin VLA alpha 4 subunit involved in homotypic cell aggregation and in fibronectin but not vascular cell adhesion molecule-1 binding.
- Source :
-
The Journal of biological chemistry [J Biol Chem] 1996 Feb 02; Vol. 271 (5), pp. 2696-702. - Publication Year :
- 1996
-
Abstract
- The VLA-4 (alpha 4 beta 1) integrin is involved in the adhesion of cells to fibronectin and vascular cell adhesion molecule-1 (VCAM-1). In order to study alpha 4 structure-function relationships, we have expressed mutated alpha 4 subunit by transfection into VLA-4-negative K562 cells. Substitutions at alpha 4 residues Arg89-Asp90, which show the highest surface probability indexes inside the N-terminal alpha 4/80 fragment, resulted in a reduction in the reactivity of all anti-alpha 4 epitope A monoclonal antibodies (mAbs) tested, compared with the reactivity with anti-alpha 4 epitopes B1, B2, and C mAb, both by transfectant flow cytometry, and by immunoprecipitation and SDS-polyacrylamide gel electrophoresis analysis of transfectant surface-iodinated proteins. In contrast, substitutions at nearby residues, Gln101, Pro102, and Ile105 did not affect the reactivity of any anti-alpha 4 mAb representing the known alpha 4 epitopes. Homotypic cell aggregation triggered by anti-alpha 4 epitope A mAb was prevented in the transfectants expressing mutated alpha 4 Arg89-Asp90Asp residues, while cell aggregation was fully achieved with either anti-alpha 4 epitope B2 or anti-beta 1 mAb. Mutations at alpha 4 residues Gln101, Pro102, and Ile108 did not affect the homotypic cell aggregation of the transfectants expressing these mutations. In addition, the adhesion of mutant Arg89-Asp90 alpha 4 transfectants to the connecting segment-1-containing fibronectin-40 (FN-40) fragment of fibronectin was diminished compared to wild type alpha 4 transfectants, as well as to other mutant alpha 4 transfectants. This adhesion to FN-40 was restored when the activating anti-beta 1 TS2/16 mAb was present in the adhesion assays. In contrast, adhesion to VCAM-1 was not affected by mutations at Arg89-Asp90, nor at Gln101, Pro102, and Ile108 alpha 4 residues. Altogether, these results indicate that alpha 4 residues Arg89 and Asp90 are included in a region involved in homotypic cell aggregation, as well as in adhesion to FN-40, but not to VCAM-1.
- Subjects :
- Animals
Cell Adhesion
Cell Line
DNA, Complementary
Humans
Integrin alpha4beta1
Integrins chemistry
Integrins genetics
Mutagenesis, Site-Directed
Protein Binding
Receptors, Lymphocyte Homing chemistry
Receptors, Lymphocyte Homing genetics
Receptors, Very Late Antigen chemistry
Receptors, Very Late Antigen genetics
Fibronectins metabolism
Integrins metabolism
Receptors, Lymphocyte Homing metabolism
Receptors, Very Late Antigen metabolism
Vascular Cell Adhesion Molecule-1 metabolism
Subjects
Details
- Language :
- English
- ISSN :
- 0021-9258
- Volume :
- 271
- Issue :
- 5
- Database :
- MEDLINE
- Journal :
- The Journal of biological chemistry
- Publication Type :
- Academic Journal
- Accession number :
- 8576243
- Full Text :
- https://doi.org/10.1074/jbc.271.5.2696