Oral Presentation The Australasian Society for Immunology 2017 Annual Scientific Meeting

A novel master adaptor for toll-like receptors tailors pro-inflammatory responses (#125)

Lin Luo 1 2 , Nilesh Bokil 1 2 , Adam Wall 1 2 , Ronan Kapetanovic 1 2 , Samuel Tong 1 2 , Margaret Hibbs 3 , Matt Sweet 1 2 , Jennifer Stow 1 2
  1. Institute for Molecular Bioscience (IMB), The University of Queensland, Brisbane, QLD, Australia
  2. IMB Centre for Inflammation and Disease Research, The University of Queensland, Brisbane, Qld, Australia
  3. Department of Immunology, Monash University, Melbourne, VIC, Australia

In innate immunity, danger signals such as Gram-negative bacterial lipopolysaccharide (LPS) initiate host inflammatory responses by engaging members of the Toll-like Receptor (TLR) family. TLR4 activates inflammatory responses through recruitment of a small number of TIR-domain containing adaptor proteins that shape signalling and transcriptional responses. We hypothesized that additional adaptors may be necessary to diversify cytokine outputs. Here, using GST pull-downs and mass spectrometry, we identified SCIMP as a novel binding partner for TLR41. SCIMP is a transmembrane adaptor and belongs to a member of the pTRAP family; it is a non-TIR domain containing protein but we identified that a specific region at C terminus of SCIMP binds to the TIR domain of TLR4 in an LPS-induced and novel manner. SCIMP and TLR4 are co-located in lipid raft domains on filopodia and surface ruffles of activated macrophages. SCIMP scaffolds Lyn kinase and is responsible for Lyn-dependent tyrosine phosphorylation of TLR4. SCIMP silencing or knockout and functional studies show that SCIMP induces pro-inflammatory signalling and a surprisingly specific output of pro-inflammatory cytokines, confined to IL-6 and IL-12p40. Phosphorylation deficient mutations in SCIMP that abrogate TLR4 binding also prevent LPS-inducible production of SCIMP-dependent cytokines. Using newly developed phosphorylation probes2 we can show that SCIMP is phosphorylated in response to multiple TLR ligands, via different effectors and with different kinetics; SCIMP binds to multiple TLRs suggesting it is a universal regulator for TLR responses. Our studies implicate SCIMP as the adaptor for TLR tyrosine phosphorylation and reveal SCIMP as a wholly new proximal adaptor that imparts remarkable specificity in downstream inflammatory cytokine responses.

  1. Luo L, et al. (2017) SCIMP is a transmembrane non-TIR TLR adaptor that promotes proinflammatory cytokine production from macrophages. Nat Commun 8:14133. 2. Luo L, et al. (2017) Development of SH2 probes and pull-down assays to detect pathogen-induced, site-specific tyrosine phosphorylation of the TLR adaptor SCIMP. Immunol Cell Biol.