Stefano Annunziato, Chao Quan, Etienne J. Donckèle, Ilaria Lamberto, R.D. Bunker, Mary Zlotosch, Laura Schwander, Anastasia C. Murthy, L. Wiedmer, Camille Staehly, Michelle Matysik, Samuel Gilberto, Despina Kapsitidou, Daric Wible, Gian Marco De Donatis, Peter Trenh, Rohitha Sriramaratnam, Vaïk Strande, Raphael Lieberherr, David Lyon, Danielle Rocio de Souza Arns Steiner, Joao Silva, Reinaldo Almeida, Elena Dolgikh, Bradley DeMarco, Jennifer Tsai, Amine Sadok, Vladislav Zarayskiy, Magnus W. Walter, Ralph Tiedt, Kevin J. Lumb, Débora Bonenfant, Bernhard Fasching, John C. Castle, Sharon A. Townson, Pablo Gaínza, Georg Petzold
Molecular glue degraders (MGDs) are small-molecule compounds that divert E3 ligases to degrade nonnatural substrates called neosubstrates. Clinically effective MGDs bind cereblon (CRBN), a substrate receptor of the Cullin 4–RING E3 ubiquitin ligase (CRL4CRBN), and recruit neosubstrates to an MGD-induced neosurface on the CRBN CULT domain through molecular mimicry of a natural CRBN degron. Here, we identify G3BP2 (Ras–GAP SH3 domain-binding protein 2), a neosubstrate that bypasses canonical interactions with CRBN by engaging an unconventional binding site on the CRBN LON domain. The ternary complex interface does not resemble known interactions with CRBN. Instead, CRBN leverages a preexisting protein–protein interaction (PPI) hotspot on the target protein by mimicking an endogenous binding partner of G3BP2. Our findings suggest that composite neosurfaces that mimic and stabilize the footprint of natural PPIs (in short, ‘glueprints’) could become a viable strategy for the rational expansion of the MGD target repertoire. Annunziato, Quan and Donckele et al. identify G3BP2 (Ras–GAP SH3 domain-binding protein 2) as a molecular glue-induced neosubstrate of the CRL4CRBN E3 ubiquitin ligase. The CRBN–glue neosurface uses a molecular surface mimicry mechanism to recruit and degrade G3BP2 in a compound-dependent manner.