Inhibition of ubiquitin-specific processing proteases 10 and 13 modulates IL-10 and TNF-α production in response to LPS in murine macrophages

Abstract

Innate immune response is activated by pathogen-associated molecular patterns (PAMPs) through Toll-like receptors (TLRs). To maintain immune homeostasis, TLR signaling molecules are regulated by a dynamic interplay of various ubiquitination (Ub) and deubiquitylation (DUB) events. Specifically, Lys-63 (K63)-linked ubiquitination on TRAF6 is involved in phosphorylation and activation of downstream MAPKs and IkB kinases. While certain types of ubiquitin modifications lead to activation and stability of proteins, other types cause increased proteasomal degradation and hence deactivation. DUBs are a class of the family of proteases that remove ubiquitin or ubiquitin-like proteins from a variety of protein-substrates. The role of DUBs in regulating the TLR pathway has not been well studied. Through RNA sequencing, we identified that LPS activation of bone marrow derived murine macrophages (BMDMs) leads to significant increase of two DUBs: ubiquitin-specific protease (USP) 10 and 13. To further study their role, we used Spautin-1, an inhibitor of USP10 and USP13. Spautin-1 modulated the LPS-mediated cytokine production and led to upregulation of IL-10, reduction of TNF-α, and had no effect on IL-6 production. However, we found no changes in expression of TRAF-6 or downstream MAPKs, including ERK, JNK, and P38. Alternative pathways were also studied with no effect in pSTAT-1, pSTAT-3, or A20 expression. Altered expression of pro-inflammatory mediators in the presence of Spautin-1 may have clinical importance associated with processes such as acute or chronic inflammatory processes.