Interleukin 6 and liver regeneration

Abstract

Apart from the cytokine itself, the IL-6 family comprises IL-11, ciliary neurotrophic factor (CNTF), cardiotropin (CT-1), oncostatin M (OSM), leukaemia inhibitory factor (LIF), and the novel neurotrophin 1/B cell stimulating factor 3 (NNT-1/BSF-3), which all share the common signal transducer gp130 as part of their receptors. Except for CNTFR, the IL-6-type cytokine signalling receptors are type I membrane proteins (extracellular N terminus, one transmembrane domain). This receptor family is defined by the presence of at least one cytokine binding molecule (CBM), a set of four conserved tyrosine residues, and a tryptophan-serine-X-tryptophan-serine (W-S-X-S-W) motif, located outside the transmembrane domain. Signal transduction after ligand binding is elicited by homodimerisation of gp130 in the case of IL-6 and IL-11, by heterodimerisation of gp130 and LIFR in the case of LIF, CNTF and CT-1, or by heterodimerisation of gp130 and OSMR in the case of OSM.1 Thus the molecular mechanism of redundancy between the family members can be explained because all members use at least one gp130 molecule for signal transduction.