The cytokine interleukin-5 (IL-5) effects cotransport of its receptor subunits to the nucleus in vitro.
Interleukin (IL)-5 is central in regulating eosinophilia in allergic disease and parasitic infections. We have recently shown that human (h) IL-5 both possesses a functional nuclear localization signal capable of targeting a heterologous protein to the nucleus and localises to the nucleus of intact receptor-expressing cells. In this study, the extracellular domains of the hIL-5 alpha- and beta-receptor subunits were expressed in baculovirus, fluorescently labelled and assayed for nuclear targeting in vitro in the absence and presence of IL-5. The beta-subunit, which lacks IL-5 binding activity, only accumulated in the nucleus in the presence of both the hIL-5 binding alpha-subunit and hIL-5. The IL-5-binding alpha-subunit showed similar results. IL-5 thus effected nuclear transport of its alpha- and beta-receptor subunits apparently through a 'piggy back' mechanism, raising the possibility that IL-5's nuclear signalling role may be to cotarget its receptor subunits to the nucleus. This is the first demonstration of nuclear protein piggy back transport in vitro.
Jans
D A
DA
Division of Biochemistry and Molecular Biology, John Curtin School of Medical Research, Australian National University, Canberra.
Briggs
L J
LJ
Gustin
S E
SE
Jans
P
P
Ford
S
S
Young
I G
IG
D000818:Animals; D001692:Biological Transport; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D006801:Humans; D015848:Interleukin-5 / Q000235:genetics / Q000378:metabolism*; D018123:Receptors, Interleukin / Q000378:metabolism*; D053649:Receptors, Interleukin-5; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D018411:Spodoptera / Q000166:cytology
D015848:Interleukin-5; D018123:Receptors, Interleukin; D053649:Receptors, Interleukin-5; D011993:Recombinant Fusion Proteins