IL-3 Maintains Activation of the p90S6K/RPS6 Pathway and Increases Translation in Human Eosinophils.
IL-5 is a major therapeutic target to reduce eosinophilia. However, all of the eosinophil-activating cytokines, such as IL-5, IL-3, and GM-CSF, are typically present in atopic diseases, including allergic asthma. As a result of the functional redundancy of these three cytokines on eosinophils and the loss of IL-5R on airway eosinophils, it is important to take IL-3 and GM-CSF into account to efficiently reduce tissue eosinophil functions. Moreover, these three cytokines signal through a common β-chain receptor but yet differentially affect protein production in eosinophils. Notably, the increased ability of IL-3 to induce the production of proteins, such as semaphorin-7A, without affecting mRNA levels suggests a unique influence of IL-3 on translation. The purpose of this study was to identify the mechanisms by which IL-3 distinctively affects eosinophil function compared with IL-5 and GM-CSF, with a focus on protein translation. Peripheral blood eosinophils were used to study intracellular signaling and protein translation in cells activated with IL-3, GM-CSF, or IL-5. We establish that, unlike GM-CSF or IL-5, IL-3 triggers prolonged signaling through activation of ribosomal protein S6 (RPS6) and the upstream kinase 90-kDa ribosomal S6 kinase (p90S6K). Blockade of p90S6K activation inhibited phosphorylation of RPS6 and IL-3-enhanced semaphorin-7A translation. Furthermore, in an allergen-challenged environment, in vivo phosphorylation of RPS6 and p90S6K was enhanced in human airway compared with circulating eosinophils. Our findings provide new insights into the mechanisms underlying differential activation of eosinophils by IL-3, GM-CSF, and IL-5. These observations identify IL-3 and its downstream intracellular signals as novel targets that should be considered to modulate eosinophil functions.
Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792; sesnault@medicine.wisc.edu.
Stephane
S
Esnault
Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792;
Elizabeth A B
EA
Kelly
Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and.
Zhong-Jian
ZJ
Shen
Department of Biomolecular Chemistry, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792.
Mats W
MW
Johansson
Department of Pathology, University of Texas Southwestern Medical Center, Dallas, TX 75390; and.
James S
JS
Malter
Division of Allergy, Pulmonary, and Critical Care Medicine, Department of Medicine, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792;
Nizar N
NN
Jarjour
D001249:Asthma / Q000276:immunology; D002478:Cells, Cultured; D004789:Enzyme Activation; D004802:Eosinophilia / Q000276:immunology; D004804:Eosinophils / Q000166:cytology / Q000502:physiology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology; D006801:Humans; D006967:Hypersensitivity / Q000276:immunology; D007377:Interleukin-3 / Q000276:immunology*; D015848:Interleukin-5 / Q000276:immunology; D053666:Interleukin-5 Receptor alpha Subunit / Q000378:metabolism; D010766:Phosphorylation; D012333:RNA, Messenger / Q000096:biosynthesis; D038601:Ribosomal Protein S6 / Q000235:genetics / Q000378:metabolism*; D019893:Ribosomal Protein S6 Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D039961:Semaphorins / Q000096:biosynthesis / Q000235:genetics; D015398:Signal Transduction / Q000235:genetics
C508596:IL3 protein, human; C508599:IL5 protein, human; C485918:IL5RA protein, human; D007377:Interleukin-3; D015848:Interleukin-5; D053666:Interleukin-5 Receptor alpha Subunit; D012333:RNA, Messenger; D038601:Ribosomal Protein S6; D039961:Semaphorins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D019893:Ribosomal Protein S6 Kinases