Signal Transduction by Integrins: Increased Protein Tyrosine Phosphorylation Caused by Clustering of β1Integrins

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 88; no. 19; pp. 8392 - 8396
• Main Authors: Kornberg, Lori J., Earp, H. Shelton, Turner, Christopher E., Prockop, Carol, Juliano, R. L.
• Format: Journal Article
• Language: English
• Published: Washington, DC National Academy of Sciences of the United States of America 01-10-1991
• Subjects: Antibodies; Biological and medical sciences; Cell physiology; Cells; Fundamental and applied biological sciences. Psychology; Ice; Integrins; KB cells; Molecular and cellular biology; Monoclonal antibodies; Phosphatases; Phosphorylation; Receptors; Signal transduction; Vanadates; Proteins; Signal transduction; Immunoprecipitation reaction; Phosphorylation; Integrin; KB cell line; Cluster; Cell cell interaction; Glycoproteins; Monoclonal antibody; Mechanism of action; Biological receptor
• ISSN: 0027-8424; 1091-6490

The integrin family of cell adhesion receptors mediates many of the interactions between cells and the extracellular matrix. Because the extracellular matrix has profound influences on cell behavior, it seems likely that integrins transduce biochemical signals across the cell membrane. The nature of these putative signals has, thus far, remained elusive. Antibody-mediated clustering of integrin receptors was used to mimic the integrin clustering process that occurs during formation of adhesive contacts. Human epidermal carcinoma (KB) cells were incubated with an anti-β1integrin monoclonal antibody for 30 min on ice followed by incubation at 37⚬with anti-rat IgG. This treatment, which induced integrin clustering, stimulated the phosphorylation on tyrosine residues of a 115- to 130-kDa complex of proteins termed pp130. When integrins were clustered in the presence of the phosphatase inhibitor sodium orthovanadate, pp130 showed a substantial increase in phosphorylation compared to the case in which integrins were clustered in the absence of vanadate. Maximal pp130 phosphorylation was observed 10-20 min after initiation of integrin clustering in the absence of vanadate or after 5-10 min in its presence. These time courses roughly parallel the formation of integrin clusters on the cell surface as observed by fluorescence microscopy. pp130 phosphorylation depended on the amount of anti-integrin antibody present. Additionally, the tyrosine phosphorylation of pp130 showed specificity since it was stimulated by antibodies to the integrin α3and β1subunits but not by antibodies to other integrin α subunits or to nonintegrin cell surface proteins. Immunoprecipitation experiments clearly demonstrated that pp130 is not itself a β1integrin. It is postulated, therefore, that the integrin-stimulated tyrosine phosphorylation of pp130 may reflect part of an important signal transduction process between the extracellular matrix and the cell interior.