Casein kinase 2 complex: a master regulator of multiple pathobiological signaling pathways in Cryptococcus neoformans 

Casein kinase 2 complex: a master regulator of multiple pathobiological signaling pathways in Cryptococcus neoformans 

Yeseul Choi1, Seong-Ryong Yu1, Ann-Yae Na2, Ran Seo3, Anna F. Averette4, Han-Seung Lee3, Jong-Seung Lee3, Sangkyu Lee2, Joseph Heitman4, and Yong-Sun Bahn1*

1Department of Biotechnology, College of Life Science and Biotechnology, Yonsei University, Seoul, Republic of Korea

2 Research Institute of Pharmaceutical Sciences, College of Pharmacy, Kyungpook National University, Daegu, Republic of Korea

3AmtixBio Co., Ltd., Hanam-si, Gyeonggi-do, Republic of Korea

4Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, North Carolina, USA

*Corresponding to Y-S Bahn (ysbahn@yonsei.ac.kr)

Cryptococcus neoformans, a basidiomycete fungal pathogen, causes fatal meningoencephalitis in both immunocompromised and immunocompetent individuals. However, the therapeutic options for cryptococcosis are limited. In a previous study, we demonstrated Cka1, a serine/threonine kinase and the catalytic subunit of the casein kinase 2 (CK2) complex, as crucial for controlling the growth, morphology, and virulence of C. neoformans. This current study aims to further characterize the function and regulatory mechanisms of the entire CK2 complex in C. neoformans. The CK2 complex comprises a catalytic subunit (Cka1) and two regulatory subunits (Ckb1 and Ckb2). We found that the ckb1Δ, ckb2Δ, and ckb1Δ ckb2Δ mutants exhibited increased susceptibility to antifungal agents, oxidative stress, and DNA damaging agents, indicating the accessary role of Ckb1 and Ckb2 for Cka1. However, the ckb1Δ ckb2Δ cka1Δ triple mutant showed more severe growth defects and stress sensitivity, suggesting Ckb1 and Ckb2 might have Cka1-independent functions. Co-immunoprecipitation assays revealed physical interactions between Cka1, Ckb1, and Ckb2, implying a heterotetrameric structure (Cka1-Ckb1-Ckb2-Cka1) for the CK2 complex. Furthermore, downstream effector genes and proteins were identified through RNAseq-based transcriptomics and mass spectrometry-based proteomics analyses. Notably, Cka1 was found to regulate the Hog1 MAPK pathway, cell wall integrity Mpk1 pathway, and calcineurin pathway, indicating its significant role in various signaling pathways and fungal pathogenicity regulation. Targeting the CK2 complex, particularly Cka1, represents a promising approach for developing antifungal treatments and combating life-threatening cryptococcosis, by gaining insights into the molecular pathways and virulence mechanisms associated with the infection.

*The presenting author: yeseul7052@hotmail.com