MAPPING THE INTERACTION BETWEEN THE CANCER RELATED PROTEINS CAGA AND ASPP2: A BASIS FOR DRUG DESIGN

The ASPP2 protein stimulates apoptosis and is frequently downregulated in human cancers. The Helicobacter Pylori CagA protein is one of the most important factors that link infection with H. Pylori to the development of gastric cancer. ASPP2 interacts with CagA in vivo. Following this interaction, ASPP2 still recruits its natural target protein p53 but its function is altered to inhibition of apoptosis. Understanding this interaction at the molecular level will contribute to the understanding of the increased risk of gastric cancer in patients infected with H. pylori CagA strains. Some of the interactions between the different domains of ASPP2 and CagA have been studied. The structure of CagA (Domain I) with ASPP2 derived peptide (716-765) has been solved, and also several more interactions between ASPP2 disordered region and CagA NTD have been found. However, only little is known so far. In our research we will focus on the ASPP2 Ank-SH3 domain which mediates its protein interactions with several apoptosis related proteins. Our research goal is to map the interaction between the cancer related proteins CagA and ASPP2 to understand the interaction at the molecular level and as a basis for developing anti-cancer compounds that inhibit the interactions between them. First, we optimized the protocols for expression and purification of the ASPP2 Ank-SH3 domain. Once we had a pure protein we focused on identifying the binding interface between ASPP2 and CagA. Using peptide array screening, we found that CagA bound peptides derived from the entire ASPP2 sequence, including the Ank-SH3 and Pro domains. These results reveal new binding sites for CagA in ASPP2, in addition to the known ASPP2 330-861 site that partly overlaps ASPP2 Pro.