RAGE phosphorylation by CK2 in human epithelial cell model: Modulation of connexin 43 expression

The receptor for advanced glycation end products (RAGE) is a membrane protein involved in many diseases linked to epithelial dysfunction. Its activation mechanism remains unclear because RAGE lacks intrinsic kinase activity depending on other kinases for phosphorylation. Using an epithelial amniotic cell model (FL cells), researchers combined mass spectrometry, phosphorylation assays, microscale thermophoresis to show that RAGE intracellular domain binds to the α subunit of protein kinase CK2, leading to the phosphorylation of RAGE at serine 400. Ser400Ala mutation preserves CK2α binding but disrupts downstream signaling, altering phosphorylation of the transcription factors CREB (Ser133) and c-Jun (Ser63) after AGE ligands stimulation. In silico analyses identify binding sites for these two transcription factors in the connexin 43 promoter/UTR, a known RAGE target, associated with the overexpression of its mRNA. Overall, these findings highlight that phosphorylation at serine 400 is essential for RAGE signaling and transcriptional regulation in response to AGE ligands.