Ubiquitin-like protein MNSFß regulates TLR-2-mediated signal transduction.

ABSTRACT

Post-translational modification by monoclonal nonspecific suppressor factor ß (MNSFß) has been involved in the regulation of a variety of cellular processes. Previous studies have demonstrated that MNSFß covalently binds to the intracellular pro-apoptotic protein Bcl-G and regulates TLR-4-mediated signal transduction. Recently, we found that MNSFß also covalently conjugates to endophilin II, a member of the endophilin A family, and inhibits the signal pathway upstream of IKK activation, but not downstream of TLR-2 signaling. In this study, we further examined the mechanism of action of MNSFß in TLR-2-mediated signal transduction in macrophage-like cell line Raw264.7 cells. Although MNSFß siRNA enhanced Pam(3)CDK(4) (TLR-2-specific ligand)-stimulated TNFα production, Bcl-G siRNA did not affect. MNSFß cDNA inhibited the Pam(3)CDK(4)-stimulated TNFα production. High-molecular weight (130 kDa) MNSFß-adduct was induced in Pam(3)CDK(4)-stimulated Raw264.7 cells. This MNSFß-adduct was not induced by LPS, indicative of the specificity of TLR-2-mediated signal transduction. Similar observations were seen in BALB/c peritoneal macrophages. Interestingly, 40-kDa MNSFß-adduct was tyrosine phosphorylated by Pam(3)CDK(4) stimulation. Collectively, novel MNSFß-adducts may regulate TLR-2 signaling pathway in macrophages.