Drosophila TAB2 is required for the immune activation of JNK and NF-kappaB.

The TAK1 plays a pivotal role in the innate immune response of Drosophila by controlling the activation of JNK and NF-kappaB. Activation of TAK1 in mammals is mediated by two TAK1-binding proteins, TAB1 and TAB2, but the role of the TAB proteins in the immune response of Drosophila has not yet been established. Here, we report the identification of a TAB2-like protein in Drosophila called dTAB2. dTAB2 can interact with dTAK1, and stimulate the activation of the JNK and NF-kB signaling pathway. Furthermore, we have found that silencing of dTAB2 expression by dsRNAi inhibits JNK activation by peptidoglycans (PGN), but not by NaCl or sorbitol. In addition, suppression of dTAB2 blocked PGN-induced expression of antibacterial peptide genes, a function normally mediated by the activation of NF-kappaB signaling pathway. No significant effect on p38 activation by dTAB2 was found. These results suggest that dTAB2 is specifically required for PGN-induced activation of JNK and NF-kappaB signaling pathways.