PENK and cholestasis: MRGPRX1 could play a role in cholestatic itch as well, both genes for MRGPRC11 (rodent analog of MRGPRX1) and proenkephalin, the precursor of the endogenous MRGPRX1-ligand bovine adrenal medulla peptide 8-22 (BAM8-22), are upregulated in a cholestasis mouse model (Sanjel et al., 2019).