To study the structural basis of ligand-induced receptor-mediated internalization of interleukin-2 (IL-2), a strategy has been developed to generate variant T cells that are deficient in internalization of this cytokine. IL-2 receptor (IL-2R) α- and β-bearing EL4 cells, that express high-affinity IL-2R and internalize IL-2, were treated with low doses of IL-2-Pseudomonas exotoxin chimeric protein (IL-2-PE40).This treatment resulted in isolation of a variant (CX1) that was unable to express high-affinity IL-2R or internalize IL-2. Transfection of CX1 with the IL-2Rβ cDNA led to surface expression of IL-2Rβ and high-affinity IL-2R as well as the ability to internalize IL-2. This finding indicates that the absence of the β subunit was the sole defect in CX1 responsible for its failure to internalize IL-2. By transfecting CX1 with mutated β cDNA, several CX1 transfectants were produced that expressed a β-subunit that lacked all amino acids of the intracytoplasmic region. These transfectants expressed high-affinity IL-2R and internalized IL-2 at a rate comparable to cells expressing wild-type β-chain. These results demonstrate that internalization of IL-2 is independent of any signals contained in the intracytoplasmic tail of the β subunit and raise the possibility that such signals may be entirely contained within the γ subunit.
- Interleukin-2 receptor
- Interleukin-2-pseudomonas exotoxin
ASJC Scopus subject areas