Unraveling the Binding Mode of TSC2-Rheb through Protein Docking and Simulations.

Proteasome inhibitors (PIs) constitute the first line of therapy for multiple myeloma (MM). Despite the impressive clinical efficacy, MM remains fatal due to the development of drug resistance over time. During MM progression, stress responses to hypoxia and PIs suppress mammalian target of rapamycin complex 1 (mTORC1) activity by releasing tuberous sclerosis complex 2 (TSC2), which deactivates Ras homologue enriched in brain (Rheb), a crucial regulator of mTORC1. The efficacy of PIs targeting MM is enhanced when mTORC1 is hyperactivated. We thus propose that the inhibition of TSC2 will improve the efficacy of PIs targeting MM. To the best of our knowledge, no cocrystallized structure of the TSC2-Rheb complex has been reported. We therefore developed a representative model using the individual structures of TSC2 (PDB: 7DL2) and Rheb (PDB: 1XTS). Computational modeling involving an extensive protein-protein docking consensus approach was performed to determine the putative binding mode of TSC2-Rheb. The proposed docking poses were refined, clustered, and evaluated by MD simulations to explore the conformational dynamics and protein mobility, particularly at the drug-binding interface of TSC2-Rheb. Our results agree with the suggested binding mode of TSC2-Rheb previously reported in the literature. The results reported herein establish a basis for the development of new inhibitors blocking the binding of TSC2 and Rheb, aiming to reinstate mTORC1 activation and facilitate improved efficacy of PIs against multiple myeloma.