Acetoxymethyl Ester of Tetrabromobenzimidazole–Peptoid Conjugate for Inhibition of Protein Kinase CK2 in Living Cells

• Published in: Bioconjugate chemistry 2015-12, Vol.26 (12), p.2324-2335
• Main Authors: Viht, Kaido, Saaver, Siiri, Vahter, Jürgen, Enkvist, Erki, Lavogina, Darja, Sinijärv, Hedi, Raidaru, Gerda, Guerra, Barbara, Issinger, Olaf-Georg, Uri, Asko
• Format: Article
• Language: English
• Subjects: Benzimidazoles - chemistry; Benzimidazoles - pharmacokinetics; Benzimidazoles - pharmacology; Biochemistry; Casein Kinase II - antagonists & inhibitors; Casein Kinase II - metabolism; Cell Survival - drug effects; Cells; Esterification; HeLa Cells; Humans; Inhibitors; Kinases; Models, Molecular; Peptoids - chemistry; Peptoids - pharmacokinetics; Peptoids - pharmacology; Permeability; Phosphorylation; Protein Kinase Inhibitors - chemistry; Protein Kinase Inhibitors - pharmacokinetics; Protein Kinase Inhibitors - pharmacology; Proteins
• ISSN: 1043-1802; 1520-4812
• DOI: 10.1021/acs.bioconjchem.5b00383

CK2 is a ubiquitous serine/threonine protein kinase, which has the potential to catalyze the generation of a large proportion of the human phosphoproteome. Due to its role in numerous cellular functions and general anti-apoptotic activity, CK2 is an important target of research with therapeutic potential. This emphasizes the need for cell-permeable highly potent and selective inhibitors and photoluminescence probes of CK2 for investigating the protein phosphorylation networks in living cells. Previously, we had developed bisubstrate inhibitors for CK2 (CK2-targeted ARCs) that showed remarkable affinity (K D < 1 nM) and selectivity, but lacked proteolytic stability and plasma membrane permeability. In this report, the structures of CK2-targeted ARCs were modified for the application in live cells. Based on structure–activity studies, proteolytically stable achiral oligoanionic peptoid conjugates of 4,5,6,7-tetrabromo-1H-benzimidazole (TBBz) were constructed. Affinity of the conjugates toward CK2 reached subnanomolar range. Acetoxymethyl (AM) prodrug strategy was applied for loading TBBz–peptoid conjugates into living cells. The uptake of inhibitors was visualized by live cell imaging and the reduction of the phosphorylation levels of two CK2-related phosphosites, Cdc37 pSer13 and NFκB pSer529, was demonstrated by Western blot analysis.