Interleukin-31 (IL31) signals via a heterodimeric receptor composed of Interleukin-31 receptor A (IL31RA) and the Oncostatin M receptor (OSMR). IL31 binds first to IL31RA (LeSaux et al. 2010). This initial binding is essential for subsequent binding to OSMR, possibly because binding induces a conformational change in IL31. The resulting IL31:IL31RA complex recruits OSMR, which increases the strength of IL31 binding and is essential for subsequent STAT signaling (Diveu et al. 2004, Maier et al. 2015). As the pre-association of IL31RA with JAK1 is unproven this event is represented as a black-box.
Le Saux, S,