The RAF kinases play a fundamental role in the regulation of cells and are frequently mutated in cancer, particularly in malignant melanomas. Dimerization is a key step in oncogenic activation of RAF and the main contributing cause of paradoxical transactivation of RAF kinase function by kinase drugs in experimental and clinical settings. Common oncogenic mutations act by destabilizing the inactive conformation and through allosteric effects that promote dimerization. There has been substantial effort to understand RAF kinase regulation using structural and functional studies, but the link between allosteric effects and activation is yet to be established to guide rational design of kinase drugs. Through multiscale simulations and NMR spectroscopy we study how allosteric communication  drives the activation of RAF kinases and the inhibitor-induced paradoxical activation of BRAF dimers  that lead to  the emergence of drug resistance. Computational network analysis of BRAF crystal structures in the monomeric and dimer forms reveal at the molecular level how oncogenic BRAF mutations function by bypassing the requirement for BRAF dimerization. We discuss structure-based design studies of conformation-specific BRAF modulators that can sequester a dormant state by affecting conformation of the regulatory αC-helix and precluding side-to-side dimerization that limits the utility of existing drugs. Oncogenic kinases can adopt different mechanisms to alleviate negative regulatory processes associated with their intrinsic conformational instability. One of them is the recruitment to the Hsp90 chaperone that protects kinases that are abnormally activated by mutations in cancer cells. We modeled allosteric regulatory mechanisms by which oncogenic BRAF mutants rely on the Hsp90 dependence for the accumulation of the constitutively active form. By integrating computational systems biology analysis of Hsp90-BRAF binding and biophysical experiments, we analyze how allosteric modulators of Hsp90 and BRAF kinase may act synergistically by antagonizing the Hsp90-BRAF interactions and depriving the client kinase of access to the molecular chaperone.

Computational studies of allosteric regulation of BRAF kinases: Combining multiscale modeling and network analysis in design of conformation-specific and allosteric modulators targeting oncogenic BRAF mutants

251st National Meeting (2016)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.