Signal-transducing molecule (PubMed:1602143). The receptor systems for IL6, LIF, OSM, CNTF, IL11, CTF1 and BSF3 can utilize IL6ST for initiating signal transmission. Binding of IL6 to IL6R induces IL6ST homodimerization and formation of a high-affinity receptor complex, which activate the intracellular JAK-MAPK and JAK-STAT3 signaling pathways (PubMed:1602143, PubMed:10661409). That causes phosphorylation of IL6ST tyrosine residues which in turn activates STAT3 (PubMed:10661409). In parallel, the IL6 signaling pathway induces the expression of two cytokine receptor signaling inhibitors, SOCS1 and SOCS3, which inhibit JAK and terminate the activity of the IL6 signaling pathway as a negative feedback loop (PubMed:9202125). Also activates the yes-associated protein 1 (YAP) and NOTCH pathways to control inflammation-induced epithelial regeneration, independently of STAT3 (PubMed:25731159). Mediates signals which regulate immune response, hematopoiesis, pain control and bone metabolism (PubMed:10661409, PubMed:26255596, PubMed:25057188, PubMed:8552649). Has a role in embryonic development (PubMed:10661409). Essential for survival of motor and sensory neurons and for differentiation of astrocytes (PubMed:10377352). Required for expression of TRPA1 in nociceptive neurons (PubMed:25057188). Required for the maintenance of PTH1R expression in the osteoblast lineage and for the stimulation of PTH-induced osteoblast differentiation (PubMed:25228504). Required for normal trabecular bone mass and cortical bone composition (PubMed:24339143, PubMed:9348227, PubMed:26255596).