Tyr86, Tyr106 and Tyr187 were identified as possible phosphorylation sites (Gray P et al. 2006). An additional study has shown that Tyr86, Tyr106, and Tyr159 are important residues, as mutagenesis of these residues impaired TIRAP (MAL) phosphorylation, affected its interaction with BTK and also impaired downstream signaling (Piao W et al. 2008). Structural insights further confirm that BTK phosphorylates TIRAP at positions Tyr86 and Tyr106 (Paracha RZ et al. 2014). BTK-mediated phosphorylation of TIRAP leads to recruitment of suppressor of cytokine signaling 1 (SOCS1), which assembles K48-linked polyubiquitin chains resulting in TIRAP's proteosomal degradation, disrupting the TLR complex, and terminating signaling (Mansell A et al. 2006). TIRAP function is also regulated by the cysteine protease caspase-1, which cleaves the protein in a region of the molecule that interacts with MyD88 and TLR4 (Ulrichts P et al. 2010).
Muhammad, SA, Ahmad, J, Ali, A, Niazi, U, Hussain, R, Paracha, RZ
Walch, E, Wietek, C, O'Neill, LA, Brunner, C, Brint, E, Doyle, S, Wirth, T, Dunne, A, Jefferies, CA
Chen, H, Piao, W, Fitzgerald, KA, O'Neill, LA, Wahl, LM, Medvedev, AE, Song, C
Brikos, C, O'Neill, LA, Gray, P, Doyle, SL, Jefferies, CA, Dunne, A
protein tyrosine kinase activity of TIRAP:PI(4,5)P2:BTK:activated TLR2/4 [plasma membrane]
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