Exploring the proteomic landscape of THP-1 monocytes through two-challenge LPS induction.
Proteome remodelling is central to the regulation of innate immune activation, yet the temporal organisation of protein networks engaged during repeated lipopolysaccharide (LPS) stimulation remains incompletely defined. In the present study, label-free quantitative mass spectrometry-based proteomics was used to characterise protein abundance changes in THP-1 monocytes at early (30 min) and later (2 h) time points following a second LPS challenge. This analysis was complemented by an independent co-immunoprecipitation proteomics experiment designed to identify candidate proteins associated with the regulatory pseudo-kinase IRAK3 during early TLR4 signalling. At 30 min, differentially abundant proteins were enriched in pathways associated with pattern-recognition receptor signalling, NF-κB activity, RNA processing, phosphorylation, and ribonucleoprotein complex organisation. By 2 h, the proteomic response broadened to include oxidative phosphorylation, antigen processing and presentation, vesicle-mediated transport, protein folding, and cytokine-regulatory pathways. These findings indicate that repeated LPS stimulation is accompanied by progressive remodelling of inflammatory, metabolic, translational, and proteostatic programmes rather than major changes in protein identity. Co-immunoprecipitation identified established TLR/IRAK3-associated components together with candidate IRAK3-associated proteins linked to RNA regulation, kinase signalling, ubiquitin-mediated processes, redox control, cytoskeletal remodelling, and damage-associated molecular pattern responses. Collectively, these findings define a temporal framework of proteomic adaptation during repeated inflammatory stimulation and expand the range of candidate proteins potentially contributing to IRAK3-centred regulation of innate immune signalling.