Negative regulation of EGFR signalling through integrin-α1β1-mediated activation of protein tyrosine phosphatase TCPTP

Integrin-mediated cell adhesion regulates a multitude of cellular responses, including proliferation, survival and crosstalk between different cellular signalling pathways(1). So far, integrins have been mainly shown to convey permissive signals enabling anchorage-dependent receptor tyrosine kinase signalling(2-4). Here we show that a collagen-binding integrin alpha(1)beta(1) functions as a negative regulator of epidermal growth factor receptor (EGFR) signalling through the activation of a protein tyrosine phosphatase. The cytoplasmic tail of a 1 integrin selectively interacts with a ubiquitously expressed protein tyrosine phosphatase TCPTP (T-cell protein tyrosine phosphatase) and activates it after cell adhesion to collagen. The activation results in reduced EGFR phosphorylation after EGF stimulation. Introduction of the a 1 cytoplasmic domain peptide into cells induces phosphatase activation and inhibits EGF-induced cell proliferation and anchorage-independent growth of malignant cells. These data are the first demonstration of the regulation of TCPTP activity in vivo and represent a new molecular paradigm of integrin-mediated negative regulation of receptor tyrosine kinase signalling.