Bhattacharya Madhushree, Pillalamari Udaya, Sarkhel Sanjay, Ishino Tetsuya, Urbina Cecilia, Jameson Bradford, Chaiken Irwin
Department of Biochemistry and Molecular Biology, Drexel University College of Medicine, Philadelphia, PA, 19102, USA.
Biopolymers. 2007;88(1):83-93. doi: 10.1002/bip.20612.
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.
白细胞介素-5受体α是包括过敏性炎症和哮喘在内的嗜酸性粒细胞增多性疾病的治疗靶点。环肽AF17121（Ac-VDE[CWRIIASHTWFC]AEE-CONH₂）已从随机肽筛选中被鉴定为白细胞介素5（IL5）-白细胞介素5受体α（IL5Rα）相互作用的亚微摩尔抑制剂。然而，由于其相对较大的尺寸，这种抑制剂作为药物先导物存在局限性。我们使用天然和非天然氨基酸的肽化学合成以及动力学结合和细胞增殖竞争试验，以扩展对肽中对受体拮抗重要的结构元件的定义，并阐明潜在的药效团。我们发现精氨酸6胍基侧链中氢键基团的特定空间排列对受体抑制至关重要。我们还研究了AF17121中的非带电结构元件。对一组五个疏水残基的筛选表明，肽功能对其中几个残基的变化非常敏感，最显著的是异亮氨酸7和色氨酸13。我们推测，在二硫键约束的肽中呈现带电、氢键和疏水结构元件可驱动AF17121招募IL5Rα。根据这些结果和先前的受体诱变研究，我们假设IL5Rα的精氨酸6招募是通过氢键以及与IL5Rα结构域1位点一中的天冬氨酸55的电荷-电荷相互作用发生的，并且这种相互作用由天冬氨酸55位点周围的额外带电和疏水相互作用补充。在抑制剂药效团中构建有限的一组结构元件可能有助于受该肽启发的小分子拮抗剂设计。
