JNK kinase regulates phosphorylation of HCoV-229E nucleocapsid protein.

Identifying common host factors essential for the replication cycles of human coronaviruses (HCoV) could help uncover potential therapeutic targets. Mitogen-activated protein kinases (MAPKs) regulate critical cellular signaling pathways. Among them, c-Jun N-terminal kinases (JNK) are activated in response to diverse environmental stresses, including viral infections. However, the relevance of the JNK pathway for host responses and replication of HCoV infections has remained elusive. Using live-cell microscopy, quantitative immunofluorescence and immunoblotting, we found that JNK is specifically activated in cells infected with HCoV-229E and plays a crucial role in mediating the phosphorylation of the viral nucleocapsid (N) protein, an essential step required during the viral replication cycle. Consequently, pharmacological inhibition of JNK kinase activity impeded HCoV-229E as well as SARS-CoV-2 infection. Given the conservation of phosphorylation sites within the nucleocapsid protein across coronaviruses, inhibitors targeting these N protein kinases, such as JNK, may hold therapeutic promise as broad-spectrum CoV antivirals.