The intracellular functions of alpha(6)beta(4) integrin are regulated by EGF

Upon ligand binding, the alpha(6) beta(4) integrin becomes phosphorylated on tyrosine residues and combines sequentially with the adaptor molecules She and Grb2, linking to the ras pathway, and with cytoskeletal elements of hemidesmosomes. Since alpha(6) beta(4) is expressed in a variety of tissues regulated by the EGF receptor (EGFR), we have examined the effects of EGF on the cytoskeletal and signaling functions of alpha(6) beta(4). Experiments of immunoblotting with anti-phosphotyrosine antibodies and immunoprecipitation followed by phosphoamino acid analysis and phosphopeptide mapping showed that activation of the EGFR causes phosphorylation of the beta(4) subunit at multiple tyrosine residues, and this event: requires ligation of the integrin by laminins or specific antibodies. Immunoprecipitation experiments indicated that stimulation with EGF does not result in association of alpha(6) beta(4) with Shc. In contrast, EGF can partially suppress the recruitment of She to ligated alpha(6) beta(4) Immunofluorescent analysis revealed that EGF treatment does not induce increased assembly of hemidesmosomes, but instead causes a deterioration of these adhesive structures. Finally, Boyden chamber assays indicated that exposure to EGF results in upregulation of alpha(6) beta(4)-mediated cell migration toward laminins. We conclude that EGF-dependent signals suppress the association of activated alpha(6) beta(4) with both signaling and cytoskeletal molecules, but upregulate alpha(6) beta(4)-dependent cell migration. The changes in alpha(6) beta(4) function induced by EGF may play a role during wound healing and tumorigenesis.