The receptor tyrosine kinase macrophage stimulating 1 receptor (MST1R, aka recepteur d'origine nantais, RON) is the cell surface receptor for macrophage stimulating protein 1 (MST1, aka MSP) (Wang et al. 1997). Like their ligands, MST1R (and MET) is a cleaved disulfide-linked heterodimer, the mature receptor consisting of alpha and beta chains. The MST1/MST1R pathway is involved in several important biological processes, including macrophage activity, wound healing, and epithelial cell behaviour (Kretschmann et al. 2010). MST1 binding to MST1R promotes receptor dimerisation followed by receptor autophosphorylation.