Interleukin-1 receptor–associated kinase 4 (IRAK4)

Interleukin‑1 receptor–associated kinase 4 (IRAK4) is a serine/threonine protein kinase that plays an essential role in the signal transduction pathways initiated by Toll-like receptors (TLRs) and interleukin‑1 receptors (IL‑1Rs), which are critical components of the innate immune system. Upon activation by upstream signals such as pathogen recognition or cytokines, IRAK4 is recruited via adaptor proteins like MyD88 to the activated TLR/IL‑1R complex. It then phosphorylates downstream targets including other members of the IRAK family—most notably acting upstream of them—and triggers cascades leading to activation of transcription factors such as NF-kappaB and IRF5, resulting in expression of inflammatory mediators. Deficiency or loss-of-function mutations in IRAK4 result in severe impairment of innate immunity with increased susceptibility to recurrent pyogenic bacterial infections but resistance to certain endotoxin challenges. Overactivity or dysregulation has been implicated in chronic inflammation, autoimmunity, and some cancers—making it an attractive therapeutic target for drug development aimed at modulating excessive inflammation or oncogenic signaling pathways.

Other names

IRAK-4interleukin 1 receptor-associated kinase 4IL-1 receptor-associated kinase 4Pelle homolog (in reference to Drosophila)

Drugs targeting IRAK4 typically act as kinase inhibitors, blocking its serine/threonine phosphorylation activity to suppress downstream inflammatory signaling through TLRs/IL‑1Rs. This results in reduced activation of transcription factors like NF-kappaB and IRF5, leading to decreased production of pro-inflammatory cytokines.