Mechanism of c-Cbl Transition from Autoinhibited to Partially Open State via Substrate Binding

Cellular Casitas B-lineage lymphoma (c-Cbl), a RING-type E3 ligase, regulates the degradation of diverse proteins, whose dysregulation is implicated in solid tumors and hematological malignancies. The conformational change of c-Cbl with substrate binding plays a critical role in the activation of c-Cbl, which facilitates the opening of the RING domain and exposes c-Cbl's ubiquitin-conjugating enzyme (E2) recognition sites to promote E2 binding and following ubiquitin transfer. However, the molecular mechanism of this conformational transition that is essential for c-Cbl-targeted drug discovery remains unclear. Here, by performing NEB (nudged elastic band) calculations, molecular dynamics (MD) simulations, and Markov state model (MSM), we revealed the molecular mechanism of c-Cbl transformation from autoinhibited to partially open conformation upon substrate binding at the molecular level and identified the key metastable states of c-Cbl during this process, which are beneficial for discovery and development of small molecules targeting c-Cbl.