Recruitment pharmacophore for interleukin 5 receptor α antagonism

Abstract

Interleukin-5 receptor alpha is a therapeutic target for hypereosinophilic diseases including allergic inflammations and asthma. The cyclic peptide AF17121 (Ac-VDE[CWRIIASHTWFC]AEE-CONH(2)) has been identified as a submicromolar inhibitor of interleukin 5 (IL5)-interleukin 5 receptor alpha (IL5Ralpha) interaction from a random peptide screen. However, this inhibitor has limitations as a drug lead because of its relatively large size. We used chemical synthesis of peptides with natural and non-natural amino acids along with kinetic binding and cell proliferation competition assays to expand definition of structural elements in the peptide that are important for receptor antagonism and to elucidate the underlying pharmacophore. We found that the specific steric array of hydrogen bonding groups in the Arg 6 guanido side chain is critical for receptor inhibition. We also investigated noncharged structural elements in AF17121. Screening a set of five hydrophobic residues showed that peptide function is strongly sensitive to variations in several of these residues, most prominently Ile 7 and Trp 13. We postulate that presentation of charged, hydrogen bonding and hydrophobic structural elements within the disulfide-constrained peptide drives IL5Ralpha recruitment by AF17121. We hypothesize from these results and previous receptor mutagenesis studies that Arg 6 recruitment of IL5Ralpha occurs through hydrogen bonding as well as charge-charge interactions with Asp 55 in site one of domain 1 of IL5Ralpha, and that this interaction is complemented by additional charged and hydrophobic interactions around the Asp 55 locus. Scaffolding a limited set of structural elements in the inhibitor pharmacophore may be useful for small molecule antagonist design inspired by the peptide.

The GM–CSF/IL‐3/IL‐5 cytokine receptor family: from ligand recognition to initiation of signaling

“…Site‐directed mutagenesis and functional analysis of C‐terminal truncation models have helped identify residues in helix B (H38, K39, and H41), the C–D turn (E88, E89, R90, and R91), and helix D (T109, E110, and W111) as the receptor binding elements in IL‐5 . The importance of positively charged residues on the C–D strand of IL‐5 for IL5Rα recruitment and receptor activation has been confirmed by phage‐based C–D strand randomization studies and functional studies on a peptide antagonist AF17121 . AF17121 is a selective and potent antagonist of IL5Rα that was discovered from screening a library of recombinant peptides.…”

Discovery of potent inhibitors for phosphodiesterase 5 by virtual screening and pharmacophore analysis

“…The receptor and ligands were analyzed the active site for hydrogen bond donors, acceptors, and hydrophobes. The results of the calculation were interaction maps [31,[33][34][35][36] .…”

“…In this study, sildenafil citrate (Viagra) and tadalafil (Cialis) were selected as the control set in this protocol ( Figure 1) [31] . We expected to discover some compounds from nature products that would have higher activities than that of Viagra and Cialis.…”

Structure-Based Rationale for Interleukin 5 Receptor Antagonism

“…In order to seek ideas about structural tendency, we performed molecular dynamics (MD) simulations on AF17121, using the GROMOS96 package of programs and the GROMOS96 43A1 force field [62,64]. Conformation of the major cluster obtained from MD simulation is shown in Fig.…”

“…Thus, a structure-activity relationship study was undertaken to elucidate the underlying pharmacophore. We used chemical synthesis of peptides with natural and non-natural amino acids to expand definition of structural elements in the cyclic peptide that are important for receptor antagonism [64]. The AF17121 central loop between cysteine residues at positions of 4 and 15 contains five hydrophobic side chains, including three that are aromatic, of ten total residues (Fig.…”