Science Bite (3 minute oral presentation with PPT in live session with pre-recorded e-poster) Lorne Infection and Immunity 2021

The transmembrane TLR adaptor SCIMP scaffolds Erk1/2 to drive macrophage pro-inflammatory responses (#112)

Richard M Lucas 1 , James EB Curson 1 , Yvette Koh 1 , Liping Liu 1 , Matt J Sweet 1 , Jennifer L Stow 1 , Lin Luo 1
  1. Institute for Molecular Bioscience and Centre for Inflammatory Disease and Research, University of Queensland, St Lucia, QLD, Australia

Innate immune and inflammatory responses are triggered by pathogen or damage activation of Toll-like (TLR) receptors. We have previously shown that the immune-specific transmembrane adaptor SCIMP is a regulator of TLR signalling and pro-inflammatory responses in macrophages1,2. SCIMP directly binds TLRs through a non-canonical, TIR-non-TIR interaction, scaffolding the Src family kinase, Lyn, for TLR activation and driving the selective production of IL-6 and IL-12p40, but the mechanism for the selectivity of these cytokine outputs was not known. Using mass spectrometry, affinity pull downs and co-immunoprecipitation in macrophage lysates we identify Erk1/2 as a novel binding partner of SCIMP. BMMs from SCIMP KO mice show the requirement for SCIMP in Erk-mediated production of pro-inflammatory IL-1b, IL-2 and TNF but not for anti-inflammatory cytokines or chemokines. High-resolution live imaging shows that SCIMP recruits Erk to signalling domains on cell surface ruffles in an LPS-inducible manner. SCIMP-scaffolded Erk1/2 enhances nuclear translocation of c-Fos for transcriptional activation. Thus, we identify a mechanism by which SCIMP recruits Erk1/2 for c-Fos activation in pro-inflammatory TLR signalling in macrophages. From this, SCIMP emerges as a novel, immune specific scaffold for Erk1/2 kinase with important roles in inflammation and infection. SCIMP is genetically associated with human autoimmune and chronic inflammatory diseases including SLE and Alzheimer’s disease, highlighting the SCIMP/Erk/c-Fos axis as a possible therapeutic target. 

  1. Luo, L. et al. SCIMP is a transmembrane non-TIR TLR adaptor that promotes proinflammatory cytokine production from macrophages. Nature Communications 8, 1–14 (2017).
  2. Luo, L. et al. SCIMP is a universal Toll-like receptor adaptor in macrophages. J. Leukoc. Biol. (2019) doi:10.1002/JLB.2MA0819-138RR.