摘要
NF-κB signaling regulates diverse processes such as cell death,inflammation,immunity,and cancer.The activity of NF-κB is controlled by methionine 1-linked linear polyubiquitin,which is assembled by the linear ubiquitin chain assembly complex(LUBAC)and the ubiquitin-conjugating enzyme UBE2L3.Recent studies found that the deubiquitinase OTULIN breaks the linear ubiquitin chain,thus inhibiting NF-κB signaling.Despite the essential role of OTULIN in NF-κB signaling has been established,the regulatory mechanism for OTULIN is not well elucidated.To discover the potential regulators of OTULIN,we analyzed the OTULIN protein complex by proteomics and revealed several OTULIN-binding proteins,including LUBAC and tripartite motif-containing protein 32(TRIM32).TRIM32 is known to activate NF-κB signaling,but the mechanism is not dear.Genetic complement experiments found that TRIM32 is upstream of OTULIN and TRIM32-mediated NF-κB activation is dependent on OTULIN.Mutagenesis of the E3 ligase domain showed that the E3 ligase activity is essential for TRIM32-mediated NF-κB activation.Further experiments found that TRIM32 conjugates polyubiquitin onto OTULIN and the polyubiquitin blocks the interaction between HOIP and OTULIN,thereby activating NF-κB signaling.Taken together,we report a novel regulatory mechanism by which TRIM32-mediated non-proteolytic ubiquitination of OTULIN impedes the access of OTULIN to the LUBAC and promotes NF-κB activation.
基金
supported by the National Institutes of Health(R15AI126360,R21AI137750,R01AI141399,and P20GM103648 to S.L.
R01AI121288 to M.E.D.)
the Research Advisory Committee Fund(to L.W.)
the Oklahoma Center for the Advancement of Science and Technology(HR17-045 to S.L.).
