Function studies of Grb2 through nuclear magnetic resonance and fluorescence: correlating dynamics and structure

Abstract

Cell metabolism is mediated by signaling pathways that are up regulated through enzymatic amino acids side chain phosphorylation dependent. So Protein Tyrosine Kinases (PTKs) play pivotal role on gene expression, cellular growth, division and differentiation, among others. Once phosphorylated, PTKs recruits protein partners such as Grb2, Shc, Ras, etc. to build up early signaling complexes that will activate specific signaling pathways inside cell. In many cases kinases and phosphatases go through these processes together. FGFRs are key PTKs in many signaling process where the aberrant activity causes several human diseases, including cancer. The adaptor protein Grb2 (Growth-factor receptor bound protein 2) is an important regulator of FGFR2 and Shp2 by preventing kinase and phosphatase activity respectively before extra-cellular stimuli. Phosphorylation of Grb2 by FGFR2 abrogates its binding to the receptor, resulting in up-regulation of both FGFR2's kinase and Shp2's phosphatase activity. On the other hand, dephosphorylation of Grb2 by Shp2 rescues the FGFR2-Grb2 complex. Other study reports that Grb2 is a regulator of MAPK pathway activity. This study states that only monomeric Grb2 is capable of interacting to SOS that will result in an upregulation of MAPK signaling while the dimeric form of Grb2 is inhibitory to this process. Then, Grb2 is a global regulator of these mutually dependent reactions, which turn this protein in an important biological target to be studied and tested within anti-tumor molecules. Grb2's versatility on executing biological functions other than adaptor protein is probably related to its flexibility which is inherent to multi-domain and intrinsically disordered proteins so we intend to use NMR-based techniques to characterize Grb2's molecular dynamics, conformational changes induced by phosphorylation and/or binding and access intermediated folding states that could be related to cell proliferation. (AU)