Pellino isoforms -1, 2 and 3 have been shown to interact with IRAK1 and IRAK4 (Jiang et al. 2003, Strellow et al. 2003, Butler et al. 2005, 2007). It has been also reported that Pellino-1 forms a complex with TRAF6, but not TAK1 or IL1R (Jiang et al. 2003), suggesting that Pellino-1 function as intermediate complex with IRAK1 in the propagation of signal from the activated receptor to activation of TAK1.
All Pellino isoforms function as E3 ubiquitin ligases in conjunction with several different E2-conjugating enzymes - Ubc13-Uev1a, UbcH4, or UbcH5a/5b.(Schauvliege R et al. 2006, Butler MP et al. 2007, Ordureau A et al. 2008). Their C-terminus contains a RING-like domain which is responsible for IL1-induced Lys63-linked polyubiquitination of IRAK1 in vitro.