A Sos proteomimetic as a pan-Ras inhibitor

Abstract

Aberrant Ras signaling is linked to a wide spectrum of hyperproliferative diseases, and components of the signaling pathway, including Ras, have been the subject of intense and ongoing drug discovery efforts. The cellular activity of Ras is modulated by its association with the guanine nucleotide exchange factor Son of sevenless (Sos), and the high-resolution crystal structure of the Ras–Sos complex provides a basis for the rational design of orthosteric Ras ligands. We constructed a synthetic Sos protein mimic that engages the wild-type and oncogenic forms of nucleotide-bound Ras and modulates downstream kinase signaling. The Sos mimic was designed to capture the conformation of the Sos helix–loop–helix motif that makes critical contacts with Ras in its switch region. Chemoproteomic studies illustrate that the proteomimetic engages Ras and other cellular GTPases. The synthetic proteomimetic resists proteolytic degradation and enters cells through macropinocytosis. As such, it is selectively toxic to cancer cells with up-regulated macropinocytosis, including those that feature oncogenic Ras mutations.

Protein Macrocyclization for Tertiary Structure Stabilization

“…The presented cyclic proteins have mainly found application as biocatalysts or ligands for cellular receptors. There is growing evidence that stabilized tertiary structures can also allow the inhibition of protein‐protein interactions[ 90 , 91 , 92 , 93 ] that are not addressable with classic peptidomimetic approaches. [ 94 , 95 ] Therefore, it can be expected that cyclic proteins will find more fields of application in the future.…”

Design and Synthesis of Crosslinked Helix Dimers as Protein Tertiary Structure Mimics

“…A cluster of two to three hotspot residues on each neighboring helix suggests that CHD mimics of these segments may prove to be potent inhibitors of PPIs mediated by helix dimers. Ras/Sos and NEMO/vFLIP complexes were chosen for CHD design based on these analyses (Hong et al., 2021; Sadek et al., 2020). The overall workflow for CHD design is illustrated in Figure 4.…”

“…Here we describe protocols for accessing crosslinked helix dimers (CHDs). CHDs can stabilize two independent peptide strands efficiently as dimers, and serve as orthosteric inhibitors of protein‐protein interactions (Hong et al., 2021). Depending on the desired functional group sequence tolerance and availability of reagents, CHDs can be designed with two different types of linkages (bis‐triazole or dibenzyl ether), as described in this article.…”

Discovery of a Bicyclic Peptidyl Pan-Ras Inhibitor

“…KS-58 inhibited the growth of PANC-1 xenografts in mice by 65% but required a high dose of 40 mg/kg. Finally, stapled and stabilized α-helical peptides have been designed to block the interaction between Ras and Son-of-Sevenless (SOS) and shown to reduce the viability of KRas-mutant cell lines. − Collectively, the above studies demonstrate that macrocyclic peptides can serve as potent and specific inhibitors of Ras proteins in vitro but require substantial improvement in cell permeability before being used as therapeutic agents against Ras-mutant cancers.…”