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Structural analysis of fungal pathogenicity-related casein kinase α subunit, Cka1, in the human fungal pathogen
Belinda X Ong1, Youngki Yoo1, Myeong Gil Han2,3
1Department of Systems Biology, College of Life Science and Biotechnology, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul, 03722, Republic of Korea.
Abstract:
CK2α is a constitutively active and highly conserved serine/threonine protein kinase that is involved in the regulation of key cellular metabolic pathways and associated with a variety of tumours and cancers. The most well-known CK2α inhibitor is the human clinical trial candidate CX-4945, which has recently shown to exhibit not only anti-cancer, but also anti-fungal properties. This prompted us to work on the CK2α orthologue, Cka1, from the pathogenic fungus Cryptococcus neoformans, which causes life-threatening systemic cryptococcosis and meningoencephalitis mainly in immunocompromised individuals. At present, treatment of cryptococcosis remains a challenge due to limited anti-cryptococcal therapeutic strategies. Hence, expanding therapeutic options for the treatment of the disease is highly clinically relevant. Herein, we report the structures of Cka1-AMPPNP-Mg2+ (2.40 Å) and Cka1-CX-4945 (2.09 Å). Structural comparisons of Cka1-AMPPNP-Mg2+ with other orthologues revealed the dynamic architecture of the N-lobe across species. This may explain for the difference in binding affinities and deviations in protein-inhibitor interactions between Cka1-CX-4945 and human CK2α-CX-4945. Supporting it, in vitro kinase assay demonstrated that CX-4945 inhibited human CK2α much more efficiently than Cka1. Our results provide structural insights into the design of more selective inhibitors against Cka1.
Insights
The protein kinase CK2α inhibitor CX-4945 shows anti-fungal properties. Structural analysis of the fungal Cka1 protein reveals differences from human CK2α, suggesting a need for more selective inhibitors against Cka1 for treating fungal infections.
Area of Science:
- Biochemistry
- Structural Biology
- Mycology
Background:
- Protein kinase CK2α (CK2α) is a conserved enzyme regulating cellular metabolism and implicated in various cancers.
- The CK2α inhibitor CX-4945 exhibits anti-cancer and anti-fungal activities.
- Cryptococcus neoformans causes life-threatening cryptococcosis, with limited treatment options.
Purpose of the Study:
- To investigate the structure of Cka1, a CK2α orthologue from Cryptococcus neoformans.
- To understand the structural basis for differential inhibition of Cka1 and human CK2α by CX-4945.
- To provide insights for designing selective Cka1 inhibitors for cryptococcosis treatment.
Main Methods:
- X-ray crystallography was used to determine the structures of Cka1-AMPPNP-Mg2+ and Cka1-CX-4945.
- Structural comparisons were made between Cka1 and other CK2α orthologues.
- In vitro kinase assays were performed to assess the inhibitory activity of CX-4945.
Main Results:
- The crystal structures of Cka1-AMPPNP-Mg2+ (2.40 Å) and Cka1-CX-4945 (2.09 Å) were determined.
- Structural comparisons highlighted the dynamic N-lobe architecture of Cka1 across species.
- CX-4945 demonstrated significantly lower inhibition of Cka1 compared to human CK2α in vitro.
Conclusions:
- Structural differences, particularly in the N-lobe, may explain the varying binding affinities and inhibitor interactions between Cka1 and human CK2α.
- CX-4945 is less effective against Cka1 than human CK2α.
- These findings are crucial for developing targeted inhibitors against Cka1 for cryptococcosis therapy.
