IDENTIFICATION OF MESSENGER-RNAS ENCODING 2 DIFFERENT SOLUBLE FORMS OF THE HUMAN INTERFERON ALPHA-RECEPTOR

Transcripts of the human IFN alpha-receptor (IFNAR) gene, lacking the transmembrane (TM) domain were found in human myeloma U266(S) cells, i n addition to the transmembranal IFNAR cDNA. Two different cDNAs encod ing such soluble IFNAR forms were identified. Form 1 has a deletion ca using a frameshift toward the end of the extracellular (EC) domain pre dicting a tail of 7 amino acids. Form 2 has two in-frame deletions and conserves most of the intracytoplasmatic domain of IFNAR. The transcr ipts for the two soluble forms are still found in U266(R) cells which have lost the transmembranal IFNAR transcript. Human cells seem to hav e independent mechanisms to synthesize soluble IFN receptors, which ma y act as competitors outside the cells or carry IFN-mediated functions inside the cell.