Uncovering the Structural Logic of Grb7: From Domain Mutagenesis to Therapeutic Implications in Cancer Signaling

Grb7 is a member of the Grb7 protein family, which also includes Grb10 and Grb14. These adaptor proteins function mainly as scaffolds in phosphorylation-dependent signaling pathways. The family is known to interact with receptor tyrosine kinases and other signaling molecules, and their activity is influenced by protein-protein interactions within their conserved five-domain structure. Grb7 has also been linked to cancer progression and is thought to form dimers and undergo intramolecular interactions that may regulate its signaling functions. In this study, we focused on understanding how the SH2 domain of Grb7 interacts with its RA-PH (RAPH) region, which may partially regulate its overall structure and activity. We introduced five single-site mutations (V45A, R46A, R46K, E47D, S48A) into the SH2 domain and studied their effects using biochemical, biophysical, and computational methods. Circular dichroism (CD) spectroscopy showed that all mutants maintained the overall fold of the SH2 domain. However, the introduction of mutations enhanced the thermal instability of SH2 from 59°C to a range of 56°C-47°C. Surface plasmon resonance (SPR) analysis revealed that mutations at R46 resulted in approximately 1.5-6 times weaker binding to the RAPH region. AlphaFold and ClusPro models and matrices scores supported the biophysical experimental findings. Docking and size exclusion experiments confirmed the RA and PH domains form a stable unit. Truncating the distorted poly-proline region of Grb7 improved its model quality. Collectively, the results provide additional insight into the regulatory mechanisms of Grb7 and may aid in the development of Grb7-signaling dependent cancer therapeutics.