E3 ubiquitin ligase – disease-relevant neo-substrate complex (E3-substrate complex)

The E3 ubiquitin ligase – disease-relevant neo-substrate complex is a transient ternary assembly that serves as the functional unit for targeted protein degradation (TPD) therapies. This complex is typically composed of an E3 ubiquitin ligase (such as Cereblon or Von Hippel-Lindau), a small-molecule degrader (molecular glue or PROTAC), and a specific disease-linked protein known as a neo-substrate (Nature Reviews Drug Discovery, 2022). Under normal conditions, the E3 ligase does not recognize the neo-substrate; however, the degrader molecule acts as a chemical bridge or inducer that stabilizes their interaction, effectively 'reprogramming' the ligase's specificity (Science, 2014). Once the complex is formed, the E3 ligase facilitates the transfer of ubiquitin molecules to the neo-substrate, marking it for destruction by the 26S proteasome (Chemical Reviews, 2017). This mechanism is highly potent because it allows for the elimination of proteins previously considered 'undruggable,' such as transcription factors and non-enzymatic scaffolding proteins, by removing the protein entirely rather than just inhibiting its active site. Clinically, this approach is most prominently used in the treatment of hematological malignancies like multiple myeloma through immunomodulatory drugs (IMiDs) and is being rapidly expanded into solid tumors and inflammatory conditions (Cell, 2018).

Other names

Ternary complexE3 ligase-degrader-target complexMolecular glue complexPROTAC-induced complexInduced proximity complex

Targeted protein degradation (TPD) via the formation of a ternary complex that recruits an E3 ubiquitin ligase to a specific neo-substrate, leading to its polyubiquitination and subsequent degradation by the 26S proteasome.