Optimization of protein kinase CK2 inhibitors derived from 4,5,6,7-tetrabromobenzimidazole
Mario A Pagano1, Mariola Andrzejewska, Maria Ruzzene
1Dipartimento di Chimica Biologica, Università di Padova, Padova, Italy.
Abstract:
Casein kinase 2 (CK2) is a ubiquitous, essential, and highly pleiotropic protein kinase whose abnormally high constitutive activity is suspected to underlie its pathogenic potential in neoplasia and infective diseases. Thus, CK2 inhibitors designed to dissect the signaling pathways affected by this kinase, in perspective, may give rise to pharmacological tools. One of the most successful CK2 inhibitors is TBB (4,5,6,7-tetrabromobenzotriazole). Here we show that its inhibitory properties can be markedly improved by generating adducts in which N(2) is replaced by a carbon atom bound to a variety of polar functions. The most efficient inhibitor is 4,5,6,7-tetrabromo-2-(dimethylamino)benzimidazole (2c) followed by the methylsulfanyl (8), isopropylamino (2e), and amino (2a) congeners. All these compounds display K(i) values <100 nM (40 nM in the case of 2c). 2c induces apoptosis of Jurkat cells more readily than TBB (DC(50) value 2.7 vs 17 microM) and, unlike TBB, it does not display any side effect on mitochondria polarization up to 10 microM concentration. Molecular modeling of the CK2-2c complex, based on the crystal structure of the CK2-TBB complex suggests that a number of additional apolar contacts between its two methyl groups and hydrophobic residues nearby could account for its superior inhibitory properties. Consequently, 2c is even more susceptible than TBB to mutations of the unique hydrophobic residues V66 and/or I174 to alanine. We propose to adopt 2c as first choice CK2 inhibitor instead of TBB, especially for in cell studies.
Insights
A novel casein kinase 2 (CK2) inhibitor, 2c, demonstrates superior efficacy and reduced side effects compared to the established TBB inhibitor. This advancement offers a promising new tool for research into CK2-related diseases.
Area of Science:
- Biochemistry
- Molecular Biology
- Pharmacology
Background:
- Casein kinase 2 (CK2) is a crucial protein kinase implicated in various diseases, including cancer.
- CK2 inhibitors are valuable tools for studying its signaling pathways and developing therapeutics.
- 4,5,6,7-tetrabromobenzotriazole (TBB) is a well-established CK2 inhibitor.
Purpose of the Study:
- To develop improved CK2 inhibitors with enhanced efficacy and reduced side effects compared to TBB.
- To evaluate novel benzimidazole-based CK2 inhibitors.
- To investigate the molecular mechanisms underlying the improved inhibition.
Main Methods:
- Synthesis of novel CK2 inhibitors based on TBB structure with modifications at the N(2) position.
- Enzyme inhibition assays to determine inhibition constants (K(i)).
- Cell-based assays to assess apoptosis induction and mitochondrial polarization.
- Molecular modeling to elucidate binding interactions.
Main Results:
- A series of novel CK2 inhibitors were synthesized, with 4,5,6,7-tetrabromo-2-(dimethylamino)benzimidazole (2c) showing the highest potency (K(i) = 40 nM).
- Compound 2c demonstrated significantly stronger induction of apoptosis in Jurkat cells compared to TBB (DC(50) 2.7 vs 17 microM).
- Unlike TBB, 2c did not affect mitochondrial polarization at effective concentrations, suggesting improved specificity.
Conclusions:
- The novel benzimidazole derivative 2c represents a superior CK2 inhibitor compared to TBB.
- 2c exhibits enhanced potency, improved cellular activity, and a better safety profile.
- 2c is recommended as a preferred inhibitor for in-cell studies and future therapeutic development targeting CK2.
