Histidine N(τ)-cyclized macrocycles as a new genre of polo-like kinase 1 polo-box domain-binding inhibitors

Abstract

Transition toward peptide mimetics of reduced size is an important objective of peptide macrocyclization. We have previously shown that PLHSpT (2a) (where H indicates the presence of a -(CH)Ph group at the N(π) position and pT indicates phosphothreonine) is an extremely high affinity ligand of the polo-like kinase 1 (Plk1) polo-box domain (PBD). Herein we report that C-terminal macrocyclization of 2a employing N(π),N(τ)-bis-alkylated His residues as ring junctions can be achieved in a very direct fashion. The resulting macrocycles are highly potent in biochemical assays and maintain good target selectivity for the Plk1 PBD versus the PBDs of Plk2 and Plk3. Importantly, as exemplified by 5d, our current approach permits deletion of the N-terminal "Pro-Leu" motif to yield tripeptide ligands with decreased molecular weight, which retain high affinity and show improved target selectivity. These findings could fundamentally impact the future development of peptide macrocycles in general and Plk1 PBD-binding peptide mimetics in particular.

Design and synthesis of a new orthogonally protected glutamic acid analog and its use in the preparation of high affinity polo-like kinase 1 polo-box domain – binding peptide macrocycles

“…The complex was formed and crystals were grown using the same methods and under similar conditions to the complex with a related macrocycle. 58 Briefly, frozen PBD stock at 37 mg mL −1 was thawed and diluted to 10 mg mL −1 . A stock solution of the macrocycle at 100 mM in DMSO was added directly to the diluted protein to a final concentration of 1 mM, then 4 M ammonium acetate was added to a final 0.4 M concentration.…”

Insights on the Synthesis of N-Heterocycles Containing Macrocycles and Their Complexion and Biological Properties

“…Hymel et al [ 19 ] reported the synthesis of tripeptide ligands with decreased molecular weight 11 – 14 ( Figure 4 ). This was conducted by C -terminal macrocyclisation, employing N(π),N(τ)-bis-alkylated residues as ring junctions and showing improved target selectivity for the polo-box domain of polo-like kinase 1 (Plk1 PBD) versus the PBDs of Plk2 and Plk3.…”

Regulation of the SIAH2-HIF-1 Axis by Protein Kinases and Its Implication in Cancer Therapy

“…Among them, GW843682 has the closest IC 50 level toward PLK3 compared to that of PLK1 (9.1 nM for PLK3 vs. 2.2 nM for PLK1) ( Murugan et al, 2011 ; Liu, 2015 ). Attempts to enhance the specificity toward PLKs over other kinases or PLK1 over other PLKs have been made to inhibit its PBD using small molecules, phosphopeptides, or using siRNA ( Kumar and Kim, 2015 ; Hymel et al, 2018 ; Alverez et al, 2020 ). For instance, small chemicals Poloxin and poloxipan inhibit the polo box of PLKs with the IC 50 ranging from 1.17 μM to 53.9 μM toward PLK 1/2/3.…”