FOXRED2, also known as ERFAD, is an endoplasmic reticulum (ER) luminal flavoprotein which may function in ER associated degradation (ERAD). It has been proposed to bind non-native proteins in the endoplasmic reticulum and target them to the ubiquitination machinery for subsequent degradation. Upon knockdown of FOXRED2, the degradation of the ERAD model substrate ribophorin 332 is delayed, and the overall level of polyubiquitinated cellular proteins is decreased. Defects in the related protein FOXRED1 are a cause of mitochondrial complex I deficiency (MT-C1D), suggesting the FOXRED2 may also play a role in MT-C1D.