Abstract
Ligand-induced macromolecular protein complex formation has emerged as a common means by which the innate immune system activates signal transduction pathways essential for host defense. Despite their structural divergence, key signaling molecules in diverse innate immune pathways mediate signal transduction by assembling higher-order protein complexes at specific subcellular locations in a stimulus-dependent manner. These protein complexes are collectively known as the supramolecular organizing centers (SMOCs), which link active receptors to a variety of downstream cellular responses. In the Toll-like receptor (TLR) pathway, the signaling adaptor MyD88 is the core of a SMOC called the myddosome, which is composed of the sorting adaptor TIRAP and the IRAK family kinases. Depending on the microbial ligands encountered, the myddosome can be assembled at the plasma membrane or endosomes, thereby leading to NF-ĸB and AP-1 activation, and the subsequent expression of pro-inflammatory cytokines. Herein, we provide a detailed protocol for studying myddosome assembly in murine bone marrow-derived macrophages (BMDMs).