Structural biology of HER2/ERBB2 dimerization: mechanistic insights and differential roles in healthy versus cancerous cells

Aim: Present study was done to understand the dimerization of HER2/ERBB2 in normal and cancer cells using in-silico study. Methods: Pathway analysis was done using Reactome. Structure of HER2/ERBB2 protein was obtained from PDB database, and using Schrödinger software protein structure was analysed and dimerization was done. Results: In normal cells, HER2/ERBB2 is present at low levels and forms a stable complex with HSP90 (heat shock protein 90), CDC37 (cell division cycle 37), and ERBIN (an adaptor protein of the HER2/ERBB2 receptor). HER2/ERBB2 lacks a ligand-binding site, so it cannot bind ligands to activate HER2/ERBB2 signaling directly. Instead, it heterodimerizes with other EGFR family members, using their ligand-binding sites to activate cell proliferation signaling cascades. In cancer, overexpression of HER2/ERBB2 leads to ligand-independent activation of signaling through dimerization. During this process, HER2/ERBB2 dissociates from the HSP90 complex. Normally, HSP90 helps to correct misfolded and aggregated proteins, but it fails to correct mutated HER2/ERBB2 in cancer cells. Conclusions: This discussion focuses on the structural changes that HER2/ERBB2 undergoes, particularly in the form of homodimers, under normal and cancerous conditions. This analysis highlights the mutated state of HER2/ERBB2 and the role of HSP90 in this context. Notably, a single-point mutation outside a protein’s active site can significantly alter its structure. This is a critical consideration in drug discovery, underscoring the need to evaluate the entire protein conformation during simulations.