Part III: Exploring the inhibition of Alk2 kinase and dimerization of EGFR kinase

One of the most common pathologically relevant mutated variants of ALK-2 (activin receptor-like kinase-2) has a point mutation (R206H) in its Ser/Thr kinase domain that promotes uncontrolled signaling in rare diseases, namely Fibrodysplasia Ossificans Progressiva (FOP) and Diffuse Intrinsic Pontine Glioma (DIPG). Currently, there are no FDA approved drugs available for ALK-2 inhibition in these diseases. A computational platform has been developed for de novo design of similar dual inhibitors that can simultaneously engage other key targets – similarly augmented by protein-protein interactions. Employing this strategy and iterative modifications, a mutant-selective inhibitor for ALK-2 (R206H) has recently been identified that may have promise for the treatment of FOP and DIPG.
Eukaryotic protein kinases are induced to drive phosphorylation-initiated signal transduction via allosteric self-assembly. They explore a continuum of conformations that includes ensembles of ‘active state’ and ‘inactive state’ conformers. In the absence of a signaling stimulus, inactive state conformers dominate the continuum. When a signaling event is triggered by ligand binding (initiating self-assembly by homo- or hetero-oligomerization of kinase domains) or by recruitment of adapter proteins, the shift in the monomer/dimer equilibrium favors the active state conformers. We investigate the quantitative effects of patient-derived activating mutations on kinase domain dimerization strength (driving EGFR activation ‘from the inside’), activity of the kinase domain monomer and dimer, as well as structural dynamics of EGFR kinase domain activation and possible novel modes of disrupting this self assembly. Understanding the dynamics of constitutive allosteric activation in EGFR mutants seen in lung cancer patients, and how the mutations shift the equilibrium towards the active form of enzyme, are key steps in appreciating and combatting the origins of inhibitor resistance.