A comprehensive proteomics-based interaction screen that links DYRK1A to RNF169 and to the DNA damage response.

Dysregulation of the DYRK1A protein kinase has been associated with human disease. On the one hand, its overexpression in trisomy 21 has been linked to certain pathological traits of Down syndrome, while on the other, inactivating mutations in just one allele are responsible for a distinct yet rare clinical syndrome, DYRK1A haploinsufficiency. Moreover, altered expression of this kinase may also provoke other human pathologies, including cancer and diabetes. Although a few DYRK1A substrates have been described, its upstream regulators and downstream targets are still poorly understood, an information that could shed light on the functions of DYRK1A in the cell. Here, we carried out a proteomic screen using antibody-based affinity purification coupled to mass spectrometry to identify proteins that directly or indirectly bind to endogenous DYRK1A. We show that the use of a cell line not expressing DYRK1A, generated by CRISPR/Cas9 technology, was needed in order to discriminate between true positives and non-specific interactions. Most of the proteins identified in the screen are novel candidate DYRK1A interactors linked to a variety of activities in the cell. The in-depth characterization of DYRK1A's functional interaction with one of them, the E3 ubiquitin ligase RNF169, revealed a role for this kinase in the DNA damage response. We found that RNF169 is a DYRK1A substrate and we identified several of its phosphorylation sites. In particular, one of these sites appears to modify the ability of RNF169 to displace 53BP1 from sites of DNA damage. Indeed, DYRK1A depletion increases cell sensitivity to ionizing irradiation. Therefore, our unbiased proteomic screen has revealed a novel activity of DYRK1A, expanding the complex role of this kinase in controlling cell homeostasis.

DYRK1A Kinase Positively Regulates Angiogenic Responses in Endothelial Cells.

Angiogenesis is a highly regulated process essential for organ development and maintenance, and its deregulation contributes to inflammation, cardiac disorders, and cancer. The Ca2+/nuclear factor of activated T cells (NFAT) signaling pathway is central to endothelial cell angiogenic responses, and it is activated by stimuli like vascular endothelial growth factor (VEGF) A. NFAT phosphorylation by dual-specificity tyrosine phosphorylation-regulated kinases (DYRKs) is thought to be an inactivating event. Contrary to expectations, we show that the DYRK family member DYRK1A positively regulates VEGF-dependent NFAT transcriptional responses in primary endothelial cells. DYRK1A silencing reduces intracellular Ca2+ influx in response to VEGF, which dampens NFAT activation. The effect is exerted at the level of VEGFR2 accumulation leading to impairment in PLCγ1 activation. Notably, Dyrk1a heterozygous mice show defects in developmental retinal vascularization. Our data establish a regulatory circuit, DYRK1A/ Ca2+/NFAT, to fine-tune endothelial cell proliferation and angiogenesis.