The intracellular signal transduction mechanism of interleukin 5 in eosinophils: The involvement of lyn tyrosine kinase and the ras-raf-1-MEK-microtubule-associated protein kinase pathway

Konrad Pazdrak, Douglas Schreiber, Patricia Forsythe, Louis Justement, Rafeul Alam

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    148 Scopus citations

    Abstract

    Interleukin 5 (IL-5) regulates the growth and function of eosinophils. The objective of this study was to investigate the intraceUular signal transduction mechanism of IL-5 in eosinophils. Purified eosinophils were stimulated with IL-5, and the involvement of various kinases was investigated by immunoblotting, immune complex kinase assay, and in situ denatured/renatured kinase assay. We found that IL-5 induced tyrosine phosphorylation and activation of a number of kinases. Two species of lyn kinases (53 and 56 kD) were present in eosinophils. Both forms were Tyrphosphorylated and activated rapidly within 1 min. Further, lyn kinase was physically associated with the IL-5β receptor in eosinophils. Ras was studied by immunoprecipitation followed by thin-layer chromatography. Ras bound higher quantities of [α-32p]guanosine 5′-triphosphate upon stimulation with IL-5. Raf-1 kinase showed increased Tyr phosphorylation on immunoblotting and increased activity in the immune complex kinase assay. Two species of MEK (MAP or Erk kinase) (41 and 45 kD) were identified in eosinophils, which underwent autophosphorylation upon stimulation. Microtubule-associated protein (MAP) kinase (p44) was Tyr-phosphorylated on immunoblotting and had increased activity in the immune-complex kinase assay. MAP kinases were also studied after metabolic radiolabeling of the cells with [32p]orthophosphates. IL-5 stimulated phosphorylation of MAP kinases in situ. Thus, we have delineated major components of an important signaling pathway in eosinophils. We believe that one of the signals generated by IL-5 receptor activation is propagated through the lyn-Ras-Raf-I-MEK-MAP kinase pathway.

    Original languageEnglish (US)
    Pages (from-to)1827-1834
    Number of pages8
    JournalJournal of Experimental Medicine
    Volume181
    Issue number5
    DOIs
    StatePublished - May 1 1995

    ASJC Scopus subject areas

    • Immunology and Allergy
    • Immunology

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