Deciphering the multifaceted role of double-stranded RNA sensor protein kinase R: pathophysiological function beyond the antiviral response.

Protein kinase R (PKR) is a serine/threonine kinase that recognizes double-stranded RNAs (dsRNAs) to initiate innate immune signalling during viral infection. PKR dimerizes on long dsRNAs and undergoes autophosphorylation. Phosphorylated/Activated PKR then catalyses the phosphorylation of numerous substrates to control global translation, inflammatory response, and cell signalling pathways. While primarily known for its antiviral role, emerging evidence suggests that PKR can play multifaceted roles in uninfected cells by interacting with cellular dsRNAs and protein regulators. The misactivation of PKR in uninfected cells is associated with many degenerative and inflammatory diseases. Even in healthy cells, PKR can affect gene expression by controlling mRNA splicing and gene-specific translation under stress. In addition, PKR can modulate cell cycle progression and promote cellular differentiation in several tissue types. This review explores PKR function in various pathological and physiological contexts in the absence of viral stimuli. By elucidating these diverse functions, we aim to highlight the perspectives in cellular dsRNA research and the therapeutic implications of targeting PKR, stimulating further research into this versatile and essential RNA-dependent kinase.