Macrocyclization in the Design of Non-Phosphorus-Containing Grb2 SH2 Domain-Binding Ligands

Abstract

Macrocyclization from the phosphotyrosyl (pTyr) mimetic's beta-position has previously been shown to enhance Grb2 SH2 domain-binding affinity of phosphonate-based analogues. The current study examined the effects of such macrocyclization using a dicarboxymethyl-based pTyr mimetic. In extracellular assays affinity was enhanced approximately 5-fold relative to an open-chain congener. Enhancement was also observed in whole-cell assays examining blockade of Grb2 binding to the erbB-2 protein-tyrosine kinase.

Crystal Structures of a High-affinity Macrocyclic Peptide Mimetic in Complex with the Grb2 SH2 Domain

“…16,21 This type of ring closure has advantages over traditional head-to-tail cyclization by reducing the degrees of rotational freedom at both ring junctures. However, a certain degree of flexibility remains in both the macrocycle skeleton and the side-chains (Figure 4(c)).…”

“…This inhibitor is remarkable not only for its binding potency, but also for its ability to block the association of Grb2 with activated cytoplasmic growth factor receptor PTK when administered to whole cells at sub-micromolar concentrations without the aid of prodrug derivatization or the use of artificial carrier techniques. 16 Unlike most SH2 domains, which bind pTyrcontaining peptides in extended conformations, ligands bind to Grb2 SH2 domains in type I b-turns with the pTyr and specificity-determining Asn residues being located at the i and iC2 positions, respectively. 11 This unique mode of 0022-2836/$ -see front matter Published by Elsevier Ltd.…”

“…22 More recently, structure 3 was modified by replacement of its pTyr mimetic phosphonate group with a 2-malonyl moiety to yield macrocycle S1s. 16 This modification was predicated on the high Grb2 SH2 domain-binding affinity obtained when the phosphonomethylphenylalanyl (Pmp) residue of peptide 2 was replaced with p-malonylphenylalanine (Pmf). 23 S1s is remarkable for its high Grb2 SH2 domainbinding affinity in extracellular assays and its potency in whole cells.…”

Involvement of Targeting and Scaffolding Proteins in the Regulation of the EGFR/Ras/MAPK Pathway in Oncogenesis

“…These compounds either represent small tripeptides or cyclic peptides (e.g. CGP78850, compound 1, compound 2) which efficiently block EGFR-GRB2 and Shc-GRB2 interaction, thereby inhibiting anchorage-independent growth and reducing cell proliferation in cancer cells [195][196][197][198].…”

Structural Examination of Ring-Closing Metathesis-Derived 15-Member Macrocycles as Grb2 SH2 Domain-Binding Tetrapeptide Mimetics

“…A unique feature of our approach has been the joining of C-terminal alkenyl subsituents onto vinyl-and allyl-functionality appended to the β-methylene of N-terminal pTyr mimetics. [10][11][12][13] The open-chain peptide 1 (K D = 5.6 μM) 14 represents a low micromolar affinity starting point for exploring the application of RCM macrocyclization within a unified family of Grb2 SH2 domain-binding inhibitors ( Figure 1). Earlier we reported 2a (K D = 23 nM) and 2b (K D = 55 nM) as the first members of this genre of analogues.…”