Small‐Molecule Stabilization of the 14‐3‐3/Gab2 Protein–Protein Interaction (PPI) Interface

Abstract

Small-molecule modulation of protein-protein interactions (PPIs) is one of the most promising new areas in drug discovery. In the vast majority of cases only inhibition or disruption of PPIs is realized, whereas the complementary strategy of targeted stabilization of PPIs is clearly under-represented. Here, we report the example of a semi-synthetic natural product derivative--ISIR-005--that stabilizes the cancer-relevant interaction of the adaptor protein 14-3-3 and Gab2. The crystal structure of ISIR-005 in complex with 14-3-3 and the binding motif of Gab2 comprising two phosphorylation sites (Gab2pS210pT391) showed how the stabilizing molecule binds to the rim-of-the-interface of the protein complex. Only in the direct vicinity of 14-3-3/Gab2pT391 site is a pre-formed pocket occupied by ISIR-005; binding of the Gab2pS210 motif to 14-3-3 does not create an interface pocket suitable for the molecule. Accordingly, ISIR-005 only stabilizes the binding of the Gab2pT391 but not the Gab2pS210 site. This study represents structural and biochemical proof of the druggability of the 14-3-3/Gab2 PPI interface with important implications for the development of PPI stabilizers.

Modulators of Protein–Protein Interactions

“…150 More recently, C-12 dehydroxy derivative 24 ( Figure 14) was shown to be an analogue well-suited for the stabilization of 14-3-3 interactions with partner proteins bearing internal (or "mode I or II") binding motifs. 151 Biophysical and cellular experiments showed 24 to stabilize the 14-3-3 − Gab2 PPI by a factor of 5.3 and the crystal structure of the ternary complex provided further structural insight. 151 The potential of fusicoccane semisynthetics is not limited to the search for potent stabilizers.…”

“…151 Biophysical and cellular experiments showed 24 to stabilize the 14-3-3 − Gab2 PPI by a factor of 5.3 and the crystal structure of the ternary complex provided further structural insight. 151 The potential of fusicoccane semisynthetics is not limited to the search for potent stabilizers. Ohkanda, Kato, and co-workers elegantly demonstrated the power of intracellular oxime ligation to generate a fusicoccane−peptide hybrid (25) that induced cell death, presumably through inhibition of 14-3-3 PPIs ( Figure 14).…”

Molecular insight into specific 14-3-3 modulators: Inhibitors and stabilisers of protein–protein interactions of 14-3-3

“…This turn is not observed in Gab2pS210, which leads to the postulation by the authors that the difference of one or two amino acids in the 14-3-3 recognition motifs of Gab2 could be used to design PPI-target-specific stabilisers. [58] Figure 25. Stabiliser 28, which stabilises the complex of Gab2pT391 peptide and 14-3-3(ζ).…”

“…[58] It was shown that, in the pT391 motif, Leu392 of Gab2 can be best accommodated in the hydrophobic contact surface of Leu172, Ile217 and Leu220 of 14-3-3(ζ). Gab2 motifs are anchored through the phosphonic acid in the binding triad of Arg56, Arg127 and Tyr128, as is frequently observed and described in this review.…”

“…Stabiliser 28, which stabilises the complex of Gab2pT391 peptide and 14-3-3(ζ). [58] M A N U S C R I P T…”