Abstract 5145: A new discovering motif on SOS1 PR domain clues Grb2-SOS1 association

Abstract

Grb2 is an adaptor protein that recruits Ras-specific guanine nucleotide exchange factor (GEF), such as Son of sevenless 1 (SOS1), to the plasma membrane. SOS1 exchanges GDP by GTP, activating Ras. Grb2 consists of an SH2 domain in the middle and flanks nSH3/cSH3 domains at both ends. Both nSH3/cSH3 domains bind to SOS1’s C-terminal proline rich (PR) domain and have the preference for interacting with the PXXPXR motif. Our NMR data suggest that the arginine residue, followed by prolines in the PXXPXR motif, is responsible for the SH3-SOS1 association, yielding large chemical shift perturbations (CSPs) on the binding interface of SH3. The SOS1’s PR motif, PVPPPVPPRRRP, exhibits the strongest binding affinity to both SH3 domains. Using comprehensive techniques involving molecular dynamics (MD) simulation and NMR measurement, we uncover a new SOS1’s PR motifs, PKLPPKTYKREH, which shows strong binding to cSH3 but exhibits very weak affinity to nSH3. Unlike the arginine residue in the PXXPXR motif, the lysine residue in the PXXPPKXXKR motif induces weak interaction with cSH3. However, high affinity interaction is mainly derived from the hydrophobic interaction between the PXXP motif and cSH3, indicating the different binding modes of interaction. Our results suggest that Grb2 nSH3/cSH3 bind to SOS1 at distinct locations and provide atomic detailed models of Grb2-SOS1 association. Recent Grb2 targeted therapy reveals that peptide inhibitors, which interrupt Grb2-SOS1 interaction, effectively prevent the migration of breast cancer cell. The mechanism of Grb2-SOS1 interaction may enlighten the promising drug treatment development. Citation Format: Tsung-Jen Liao, Hyunbum Jang, Ruth Nussinov, David Fushman. A new discovering motif on SOS1 PR domain clues Grb2-SOS1 association [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5145.