CLONING AND EXPRESSION OF AN ALTERNATIVELY SPLICED MESSENGER-RNA ENCODING A SOLUBLE FORM OF THE HUMAN INTERLEUKIN-6 SIGNAL TRANSDUCER GP130

The membrane-bound gp130 glycoprotein acts as an affinity converting a nd signal transducing receptor (R) for interleukin-6 and several other cytokines. In this work, we RT-PCR amplified gp130 cDNA using primers flanking the sequence encoding the transmembrane domain of gp130, We observed in blood mononuclear cells, in addition to the expected 333-b p length fragment, a second major band of 418 bp, Sequencing of the 41 8-bp fragment and its genomic counterpart showed a new 85-bp exon loca ted in the sequence encoding the extracellular region of the gp130 pro tein, This exon is most likely due to alternative splicing and leads t o a frame-shift resulting in a stop-codon I bp before the transmembran e coding region, Correspondingly, supernatants from chinese hamster ov ary cells transfected with this cDNA contained 4-5 times more soluble (s) gp130 than supernatants from cells transfected with a cDNA encodin g the membrane-bound gp130 protein, Both gp130 and alternatively splic ed sgp130 were also transcribed by the myeloma cell lines XG-1, XG-2, XG-4, XG-4CNTF XG-6, XG-7, XG-9, XG-10, U266 and RPMI 8226, However, X G-4A cells derived from XG-4 cells, but growing independently of exoge nous IL-6, did not transcribe sgp130 mRNA, A possible interference wit h intracrine stimulatory factors by alternatively spliced sgp130 needs to be further investigated. (C) 1997 Federation of European Biochemic al Societies.