Abstract 272: Direct binding of neuregulin-1 to integrins is involved in neuregulin-1/ErbB signaling

Abstract

Abstract Crosstalk between growth factor receptors and integrins play a role in growth factor signaling. In current models of NRG/ErbB signaling, integrins and ErbB receptors transduce signals independently upon binding to their ligands (e.g., extracellular matrix and NRGs, respectively) and their signals are merged inside the cells. We discovered that the EGF-like domain of NRG1 binds directly to integrins αvβ3 and α6β4. Docking simulation predicted that three Lys residues at the amino terminus of NRG1 are involved in integrin binding. We mutated these residues to Glu (designated the 3KE mutant). Indeed the 3KE mutation markedly reduced the NRG1 binding to integrins, while the 3KE mutation did not affect the NRG1 binding to ErbB3. This is consistent with the prediction that the Lys residues critical for integrin binding are not involved in ErbB binding. We studied the effect of the 3KE mutation on NRG1/ErbB signaling in MCF-7 and T47D human breast cancer cells. The 3KE mutation markedly reduced the levels of ErbB3 phosphorylation, AKT and Erk1/2 activation, suggesting that direct integrin binding to NRG1 is critical for NRG1/ErbB signaling. Furthermore, stimulation of cells with WT NRG1 induced co-precipitation of ErbB3 with integrin α6β4. This suggests that WT NRG1 induces integrin-NRG1-ErbB3 ternary complex formation. WT NRG1 induced co-precipitation of ErbB3 with integrin αvβ3 to a less extent than with integrin α6β4. This probably reflects low levels of integrin αvβ3 expression compared to integrin α6β4 in these cells. In contrast, the 3KE mutation markedly reduced the levels of ternary complex formation, suggesting that this process depends on the ability of NRG1 to bind to integrins. Notably, the 3KE mutant acted as an antagonist to ErbB/NRG1 signaling in vitro and effectively suppressed proliferation of breast cancer cells in vivo. These results suggest that 1) NRG1-integrin interaction mediates crosstalk of integrins with ErbB receptors, 2) integrin α6β4 plays a major role in ErbB/NRG signaling in the cancer cells tested, and 3) the 3KE mutant has potential as a therapeutic in cancer. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 272.