Required for MUC2 post-transcriptional synthesis and secretion. May play a role in the production of mucus by intestinal cells. Proto-oncogene that may play a role in cell migration, cell differentiation and cell growth (By similarity). Promotes cell adhesion (By similarity). Monomer and homodimer. Interacts with LYPD3 and DAG1 (alphaDAG1). Interacts with MUC2; disulfide-linked. Expressed in lung, skeletal muscle, testis, liver, stomach, colon, small intestine, the goblet cells of the intestine and the mucuous neck cells of the stomach. Expressed in embryo at 15 dpc onwards. Mice are viable but display altered production of mucus with loss of production of MUC2 despite expression of its mRNA. They also display an increase in mast cells in the intestine, an increased expression of inflammation-specific genes, and frequent rectal prolapse. This is associated with a higher susceptibility to colitis. Belongs to the AGR family.