DYRKP kinase:
The role of DYRKP and its regulatory mechanism in microalgae
The dual-specificity tyrosine-regulated kinase (DYRK) is a well-conserved protein kinase family in eukaryotic cells. This kinase family consists of DYRK1, DYRK2, YAK1, pre-mRNA processing factor4 kinase (PRP4K), homeodomain interacting protein kinase (HIPK), and plant-specific DYRK (DYRKP). When the tyrosine residue of DYRK is autophosphorylated, the kinase becomes activated and is ready to phosphorylate serine and threonine residues of other kinase protein substrates. The DYRK family is known to be an important regulator of cell growth, cell cycle, and development.
Among them, we are interested in DYRKP, whose function and regulation are largely unknown. In 2016, the DYRKP knockout mutant of model microalga Chlamydomonas reinhardtii accumulated significant starch and TAG under nitrogen starvation conditions in an autotrophic culture, and proposed that DYRKP acts as a negative regulator of the sink capacity of photosynthetic cells that integrates nutrient and energy signals (Schulz-Raffelt M. et al., Biotechnology for Biofuels (2016)). In 2018, the DYRKP knockout mutants of Euglena gracilis grew slower but had a higher content of wax ester and paramylon than wild-type under anaerobic conditions (Kimura M. & Ishikawa T., Journal of Applied Phycology (2018)). In addition, the study using moss Marchantia polymorpha proposed that DYRKP may be important for tissue morphogenesis (Furuya T. et al., Journal of Plant Research (2021)).
* Image sources: Schulz-Raffelt M. et al., Biotechnology for biofuels (2016) / Furuya T. et al., Journal of Plant Research (2021)
Generally, protein kinases play a part in many cell processes via phosphorylation of downstream substrates (i.e., kinase cascade). Thus, it is very likely that DYRKP has multiple roles in cell metabolism, as an upstream regulator. Recently, Dr. Kim and the French research group (Dr. Yonghua Li-Beisson, BIAM, CEA Cadarache) discovered a new role of DYRKP in C. reinhardtii: ‘Regulation of cell wall glycoprotein degradation’. Although the C. reinhardtii DYRKP knockout mutant was observed to form multicellular structures, their reason was unknown at the time due to the lack of available technology. We discovered that these multicellular structures are related to the degradation of the cell wall, especially glycoproteins, through gene editing using CRISPR-Cas9 and comparative transcriptome and proteome analysis (Kim M. et al., The Plant Cell (2024)). These findings further strengthen our belief that DYRKP is involved in various metabolic pathways. Now, our team is currently working to elucidate the cellular metabolic processes involved in DYRKP and its regulatory mechanisms.
* Image source: Kim M. et al., The Plant Cell (2024)
