May play a role in regulating membrane trafficking of cargo proteins. Together with ATP9A and MON2, regulates SNX3 retromer-mediated endosomal sorting of WLS away from lysosomal degradation. Homooligomer. Heterotrimer with ATP9A and MON2; this interaction is retromer-independent. Interacts with SNX3. Expressed in liver, heart and brain. Highly expressed in developing nervous system. Belongs to the dopey family.