Molecular anatomy of eosinophil activation by IL5 and IL33

IL5 and IL33 are major activating cytokines that cause circulating eosinophils to polarize, adhere, and release their granule contents. We correlated microscopic features of purified human blood eosinophils stimulated for 10 min with IL5 or IL33 with phosphoproteomic changes determined by multiplexed isobaric labeling. IL5 caused phosphorylation of sites implicated in JAK/STAT signaling and localization of pYSTAT3 to nuclear speckles whereas IL33 caused phosphorylation of sites implicated in NFκB signaling and localization of RELA to nuclear speckles. Phosphosites commonly impacted by IL5 and IL33 were involved in networks associated with cytoskeletal organization and eosinophil adhesion and migration. Many differentially regulated phosphosites were in a diverse set of large proteins—RAB44, a “large RAB” associated with crystalloid granules; NHSL2 and VIM that change localization along with the nucleus during polarization; TNFAIP3 vital for control of NFκB signaling, and SRRM2 and PML that localize, respectively, to nuclear speckles and PML bodies. Gene expression analysis demonstrated differential effects of IL5 and IL33 on IL18, CCL5, CSF1, and TNFSF14. Thus, common effects of IL5 and IL33 on the eosinophil phosphoproteome are important for positioning in tissues, degranulation, and initiation of new protein synthesis whereas specific effects on protein synthesis contribute to phenotypic heterogeneity. KEY POINTS IL33 and IL5 impact common pathways of eosinophil cytoskeletal reorganization, adhesion and migration. Each lobe of the human eosinophil nucleus has a specific anatomy poised for new onset of cytokine-specific transcription and splicing.