A functional bipartite nuclear localisation signal in the cytokine interleukin-5

Interleukin (IL)-5 is central in regulating eosinophilia in allergic disease and parasitic infections, We have identified a bipartite nuclear localisation signal (NLS) within amino acids 95-111 of human IL-5 (hIL-5), also present in mouse IL-5 (mIL-5), hIL-5 and mIL-5 were labelled fluorescently, and nuclear uptake subsequent to membrane binding and internalisation by intact receptor expressing cells visualised and quantified using confocal laser scanning microscopy, hIL-5 and mIL-5 were shown to be transported to the nucleus in in vivo and in vitro nuclear protein import assays, The hIL-5 NLS was able to target a heterologous protein to the nucleus both in vivo and in vitro, Mutations within the proximal arm of the NLS abrogated nuclear targeting activity, confirming its bipartite nature, The results imply a nuclear signalling role for IL-5 additional to pathways linked to the membrane receptor system. (C) 1997 Federation of European Biochemical Societies.