Publications

Complementary DNAs corresponding to the human receptor for interleukin 2 (IL-2) have been molecularly cloned, sequenced, and expressed in COS-1 cells. The human genome appears to contain a single structural gene for this receptor; however, when transcribed at least two messenger RNAs (mRNAs) are produced which vary in length due to the use of different polyadenylation signals. Sequence analysis of the cloned complementary DNAs indicates an alternate pathway of mRNA processing for this receptor. Splicing of a 216 base pairs segment contained within the protein coding region results in an mRNA unable to code for the IL-2 receptor. In contact complementary DNAs corresponding to unspliced mRNA encode membrane receptors which bind both IL-2 and anti-Tac (monoclonal anti-IL-2 receptor antibody). Analysis of the deduced amino acid sequence reveals that the receptor is composed of 272 amino acids including a signal peptide 21 amino acids in length. Hydrophobicity analysis suggests a single 19 amino acid transmembrane domain. A short intracytoplasmic domain composed of 13 amino acids is present at the carboxy terminus and contains three potential phosphate acceptor sites (serine and threonine but not tyrosine) and typical positively charged amino acids presumably involved in cytoplasmic anchoring. Two sites for N-linked glycosylation sites and numerous extracytoplasmic O-linked glycosylation sites are present.

We have used cDNAs for the human interleukin 2 (IL-2) receptor to study IL-2 receptor gene expression in normal activated T cells. Resting T cells do not contain detectable IL-2 receptor mRNA. Within 1 hr after stimulation with phytohemagglutinin (PHA), a large, presumably nuclear precursor RNA species is seen, which then gradually disappears. Mature IL-2 receptor mRNA forms appear within 8 hr after stimulation, reach peak levels between 8 and 24 hr, and then decline. Thus, in PHA-activated lymphocytes the rise and fall in IL-2 receptor mRNA levels precede by more than 24 hr the peak and decline of IL-2 receptor protein expression occurring at the cell surface. 4 beta-Phorbol 12-myristate 13-acetate (PMA) also stimulates IL-2 receptor mRNA and protein expression by T cells. Combinations of optimal concentrations of PHA and PMA produce an additive effect on IL-2 receptor mRNA levels, suggesting that PHA and PMA may induce IL-2 receptor gene expression through different, complementary mechanisms. Nuclease S1-protection assays indicate that IL-2 receptor mRNAs may differ in length due to the use of three different polyadenylylation signals. Further, these assays demonstrate the presence of transcripts that lack a 216-base segment within the protein-coding region and thus do not encode a functional IL-2 receptor. Nuclear transcription assays indicate that the increase in IL-2 receptor mRNA is reflected at the level of transcription. Thus, IL-2 receptor gene regulation controls IL-2 receptor expression at the cell surface and is intimately linked to the control of T-cell proliferation.