- Ufd1 is a cofactor of gp78 and plays a key role in cholesterol metabolism by regulating the stability of HMG-CoA reductase. Cao, J., Wang, J., Qi, W., Miao, H.H., Wang, J., Ge, L., DeBose-Boyd, R.A., Tang, J.J., Li, B.L., Song, B.L. Cell Metab. (2007)