Additifs supramoléculaires de cristallisation des transporteurs ABC de résistance à de multiples agents chimiothérapeutiques – AddX

The structure-based design of highly efficient and selective, therapeutic inhibitors, requires the knowledge of their protein targets at the atomic level, if possible in several conformations, that will reflect the different catalytic steps of a given process. This is a particularly difficult task concerning membrane proteins for which 3D-structure data are very challenging to obtain. Notwithstanding this inherent difficulty, it is critical to succeed in the endeavour because membrane proteins represent the main class of therapeutic targets. Among them, the ABC transporters on which this project is focused are the object of intense studies as they are responsible for cell resistance to chemotherapeutic treatments. A critical point for crystallization of membrane proteins is to increase protein-protein contacts, which are reduced by the crown of detergent surrounding their lipophilic region. To circumvent this, we propose to develop innovative tools, based on promising preliminary results and a long-term investment in this field. We will develop a strategy focused on the crystallization trials of three selected multidrug resistance ABC transporters as targets, from human (Breast Cancer Resistance Protein) and bacteria (BmrA and YheI/YheH), for which we have developed efficient expression systems. We will design crystallization agents, based on (i) calix[4, 6 or 8]arene derivatives for which we have recently observed that they promote a rapid crystallization of BmrA, one of our protein targets, enabling to obtain diffracting crystals, (ii) saponins and (iii) lanthanide chelator-like tris dipicolinates. We will also screen a library of selected modulators of multidrug ABC transporters, such as flavonoids, an approach based on the fact that we previously observed that BmrA crystallizes in the presence of transported drugs such as the anticancer doxorubicin and rhodamine. This suggests that these types of substrates should be screened more systematically because we are still lacking a structure with a bound substrate, and this step is mandatory if one wants to envisage drug design. Reaching these ambitious goals requires skills from Biology, Physics and Chemistry, strongly organised to gain in efficacy: we have thus gathered two tandems of Biochemists and Crystallographers, at IBCP (Lyon) and IBS (Grenoble), in order to optimize the research, and these two groups are coupled to a team of Chemists.