Generation of 'truncated' interleukin-6 receptor (IL-6R) mRNA by alternative splicing; a possible source of soluble IL-6R

Receptors for interleukin-6 (IL-6) occur in body fluids in soluble form, as well. This is an approx. 50 kDa protein with the ability to bind IL-6. The soluble IL-6 receptor (sIL-6R)/IL-6 complex can attach to membrane anchore d gp130, a molecule associated with the signal transduction induced by IL-6 and by other related cytokines. Earlier we described the appearance of sIL -6R in various body fluids of autoimmune patients. In this study using reve rse transcriptase polymerase chain reaction (RT-PCR) we isolated and charac terised a truncated form of amplified cDNA reverse-transcribed from IL-6 re ceptor mRNA both from human hepatoma cell line HepG2 and mononuclear cells from inflammatory bowel disease (IBD) patients. Using digestion by Pvu II r estriction endonuclease and direct nucleotide sequencing we conclude that a lternative splicing is likely involved in generation of sIL-6R. Our further experiments suggest that IL-6 and recombinant sIL-6R themselves do not inf luence the alternative splicing of IL-6 receptor gene. (C) 1999 Elsevier Sc ience B.V. All rights reserved.