title: Stabilizing the eIF4G1 α-helix increases its binding affinity with eIF4E: implications for peptidomimetic design strategies.
abstract: Eukaryotic initiation factor (eIF)4E is overexpressed in many types of cancer such as breast, head and neck, and lung. A consequence of increased levels of eIF4E is the preferential translation of pro-tumorigenic proteins such as c-Myc, cyclin D1, and vascular endothelial growth factor. Inhibition of eIF4E is therefore a potential therapeutic target for human cancers. A novel peptide based on the eIF4E-binding peptide eIF4G1, where the α-helix was stabilized by the inclusion of α-helix inducers as shown by CD measurements, was synthesized. The helically stabilized peptide binds with an apparent K(d) of 9.43±2.57 nM, which is ∼15.7-fold more potent than the template peptide from which it is designed. The helically stabilized peptide showed significant biological activity at a concentration of 400 μM, unlike the naturally occurring eIFG1 peptide when measured in cell-based cap-dependent translational reporter and WST-1 (4-[3-(4-iodophenyl)-2-(4-nitrophenyl)-2H-5-tetrazolio]-1,3-benzene disulfonate) assays. Fusion of the template peptide and the stabilized peptide to the cell-penetrating peptide TAT produced more active but equally potent inhibitors of cap-dependent translation in cell lines. They also equally disrupted cell metabolism as measured in a WST-1 assay. Propidium iodide staining revealed that the TAT-fused, helically stabilized peptide caused more cell death than the TAT-fused eIF4G1 template peptide with substantial decreases in the G1 and G2 cell populations. Annexin-staining experiments also indicated that the TAT-fused eIF4G1 derivative peptides caused cell death by apoptosis. The results presented should offer further insight into peptidomimetics development for eIF4E.
authors.affiliation: p53 Lab (p53Lab), 8A Biomedical Grove, #06-06, Immunos, Singapore 138648. cjbrown@p53lab.a-star.edu.sg
authors.forename: C J
authors.initials: CJ
authors.lastname: Brown
authors.forename: J J
authors.initials: JJ
authors.lastname: Lim
authors.forename: T
authors.initials: T
authors.lastname: Leonard
authors.forename: H C A
authors.initials: HC
authors.lastname: Lim
authors.forename: C S B
authors.initials: CS
authors.lastname: Chia
authors.forename: C S
authors.initials: CS
authors.lastname: Verma
authors.forename: D P
authors.initials: DP
authors.lastname: Lane
mesh_terms: D000595:Amino Acid Sequence; D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism; D017209:Apoptosis; D045744:Cell Line, Tumor; D015195:Drug Design; D039561:Eukaryotic Initiation Factor-4E / Q000737:chemistry* / Q000235:genetics; D039603:Eukaryotic Initiation Factor-4G / Q000737:chemistry* / Q000235:genetics; D015696:Gene Products, tat / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008969:Molecular Sequence Data; D057786:Peptidomimetics / Q000737:chemistry* / Q000378:metabolism; D011485:Protein Binding; D014176:Protein Biosynthesis / Q000187:drug effects; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; C113920:EIF4G1 protein, human; D039561:Eukaryotic Initiation Factor-4E; D039603:Eukaryotic Initiation Factor-4G; D015696:Gene Products, tat; D057786:Peptidomimetics; D011993:Recombinant Fusion Proteins