Abstract
One third of total proteins are co-translationally translocated to endoplasmic reticulum. Proteins are assembled and folded in ER, and native proteins are released from ER and transported through secretory pathway to extracellular space, other organelles, and plasma membrane. Truncated, misfolded or unassembled subunits of oligomeric protein are susceptible to aggregation. Failure to clear aggregated proteins is a common pathogenic event in human diseases including neurodegenerative diseases and diabetes. The misfolded or unfolded proteins in ER are exported across ER membrane into the cytosol and degraded by proteasome. This particular protein quality control pathway is called ER-associated degradation (ERAD). Through ER-associated degradation (ERAD), these proteins are retrotranslocated from ER to cytosol, ubiquitinated by ER-localized E3s and degraded by 26S proteosome. ERAD is essential for cell coping for stress and quality control. In this study, we have identified several novel ER-localized E3 ligases. Their expression upon ER-stress was found not to be regulated significantly by ER-stress. Moreover, a homolog of Herp1 called Herp2 was also studied for its cellular localization. Its expression is also not regulated by ER-stress. The information would be useful for further functional studies of these proteins.