LGR5 and inflammatory bowel disease: Moreover, IBD-relevant ER stress signaling interferes with Wnt signaling and leads to a loss of Lgr5+ ISCs (Heijmans et al., 2013; van Lidth de Jeude et al., 2017), and ER dysfunction might impair Wnt factor maturation in general, as newly synthesized Wnt proteins need to be lipid-modified in the ER by the acyltransferase Porcupine (Takada et al., 2006).