p38 dependent IL-33 responses define a conserved inflammatory programme in mast cells
Interleukin-33 (IL-33) is a key cytokine in mast cell mediated immunity, promoting inflammatory cytokine production without inducing degranulation. Here, we compared IL-33 induced proteomic responses across three mast cell culture systems, Foetal Liver derived Mast Cells (FLMCs), Bone Marrow derived Mast Cells (BMMCs), and Peritoneal Mast Cells (PMCs), using quantitative data-independent acquisition mass spectrometry. Although baseline proteomes were largely conserved across all mast cell types, clear differences were observed between culture systems. PMCs exhibited a more mature phenotype, characterised by higher abundance of granule-associated proteins and lower levels of proteins involved in metabolism and translation. In contrast, FLMCs and BMMCs displayed higher levels of biosynthetic and metabolic machinery, consistent with a less differentiated state. IL-33 stimulation induced a conserved proteomic programme across all mast cell types, enriched for inflammatory signalling pathways, cytokine production, and enzymes involved in prostaglandin and biogenic amine biosynthesis. Pathway analysis demonstrated robust activation of nuclear factor {kappa}B (NF{kappa}B) associated signalling, with a relative enrichment of components linked to non-canonical NF{kappa}B signalling and tumour necrosis factor (TNF) receptor associated pathways. Mechanistically, IL-33 driven proteomic remodelling was strongly regulated by mitogen-activated protein kinase (MAPK) signalling. p38 MAPK emerged as the dominant regulator of the IL-33 response, with ERK1/2 contributing to a subset of induced proteins. These pathways differentially regulated key effector outputs, including IL-6, IL-9, IL-1 family cytokines, and enzymes required for prostaglandin, serotonin, and histamine biosynthesis. Together, these data define conserved IL-33 dependent inflammatory programmes across mast cell differentiation states and demonstrate how MAPK signalling pathways shape the composition of mast cell effector responses.