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Pseudokinase domain of Interleukin-1 Receptor Associated Kinase 3 The pseudokinase domain shows similarity to protein kinases but lacks crucial residues for catalytic activity. IRAKs are involved in Toll-like receptor (TLR) and interleukin-1 (IL-1) signalling pathways, and are thus critical in regulating innate immune responses and inflammation. IRAKs contain an N-terminal Death domain (DD), a proST region (rich in serines, prolines, and threonines), a central kinase domain (a pseudokinase in the case of IRAK3), and a C-terminal domain; IRAK-4 lacks the C-terminal domain. Vertebrates contain four IRAKs (IRAK-1, -2, -3 (or -M), and -4) that display distinct functions and patterns of expression and subcellular distribution, and can differentially mediate TLR signaling. IRAK3 (or IRAK-M) is the only IRAK that does not show kinase activity. It is found only in monocytes and macrophages in humans, and functions as a negative regulator of TLR signaling including TLR-2 induced p38 activation. It also negatively regulates the alternative NFkB pathway in a TLR-2 specific manner. IRAK3 is downregulated in the monocytes of obese people, and is associated with high SOD2, a marker of mitochondrial oxidative stress. It is an important inhibitor of inflammation in association with obesity and metabolic syndrome. The IRAK3 subfamily is part of a larger superfamily that includes the catalytic domains of other protein serine/threonine kinases, protein tyrosine kinases, RIO kinases, aminoglycoside phosphotransferase, choline kinase, and phosphoinositide 3-kinase. |
Jiyao W et al.(2023). "The conserved domain database in 2023.",