Mouse soluble isoform of Interleukin-27 receptor alpha subunit (Il27ra or sWSX-1)can be produced by two mechanism. There is experimental evidence of expression of soluble Il27ra in primary cortical neurons(PCNs) after replacing of Exon 8 in Il27ra by a neomycin-resistant gene (forming Il27ra-E8 or WSX-1-E8) (Hashimoto et al. 2010). This mechanism is an alternatively spliced mRNA or proteolytic cleavage of the membrane-anchored receptor.

Anyway this fact does not discard the possibility of other mechanism which could involve the production of this soluble isoform, which is proteolitic cleavage of the membrane anchored receptor.

A human soluble form of Interleukin-27 receptor alpha subunit (IL27RA) is produced by activated CD4(+) and CD8(+) T cells, B cells, myeloid cells and various cell lines.

Soluble IL27RA is released as two N-glycosylated variants of around 90 and 70 kDa. Production of this soluble IL27RA is inhibited by the metalloprotease inhibitors broad-spectrum matrix metalloproteinase inhibitor(GM6001 or galardin or ilomastat) and Tumor necrosis factor-alpha processing inhibitor-0 (TAPI-0). The soluble IL27RA is a natural antagonist of Interleukin-27 heterodimer (Dietrich et al. 2014)
Since there is no evicence of the exact mechanism of the origin of the soluble isoform of this protein, this reaction is a black box event.