Expression of human IL-2 receptor alpha- and beta-chains using the baculovirus expression system.

The genes encoding the alpha- and beta-chains of the human interleukin-2 receptor were expressed in lepidopteran insect cells using the baculovirus expression vector system. The corresponding genes were inserted under the polyhedrin promoter of the Autographa california nuclear polyhedrosis virus and expressed in the Spodoptera frugiperda insect cell line during viral infection. The recombinant receptor proteins were identified in the insect cell lysates by using protein dot blot and ELISA techniques. At 36 h post infection the corresponding proteins were clearly detected using anti-IL-2 alpha- and beta-receptor-specific antibodies. A large amount of the alpha-chain was also found in the supernatant culture media at 72 h post infection and metabolic labelling with [35S]-methionine indicated that it was proteolytically cleaved into a 32 kDa soluble form. A similar soluble or secreted form of the beta-chain was, however, not observed. Both receptor proteins were expressed on the surface of the insect cells as determined by flow cytometry analysis. Studies performed with the different IL-2 receptor forms (alpha- and beta-chains alone or in combination) in the presence or absence of rIL-2 suggest that the receptor proteins when expressed in infected insect cells are non-functional with respect to tyrosine phosphorylation.