ER Endogenous Protein Complexed with Lectin Chaperones Calnexin/Calreticulin

Glycoprotein quality control in the endoplasmic reticulum is achieved by multiple molecular chaperones, glycosyltransferases, and glycosidases. Calnexin and calreticulin, which are lectin-type molecular chaperones, play important roles in glycoprotein folding. These chaperones interact with nascent proteins modified with the Glc1Man9GlcNAc2 (G1M9) glycan, leading to the formation of a correct structure. ERp57, a disulfide isomerase family protein, complexes with these chaperones and assists in the formation of disulfide bonds. In recent years, it has been shown that proteins other than ERp57 also complex with chaperones, suggesting that there may be multiple chaperone-binding partner molecules. This review discusses partner proteins interacting with calnexin and calreticulin and their functions. It also recommends further studying the formation of the intracellular complex of CNX/CRT with peptidyl-prolyl cis-trans isomerases and protein disulfide isomerase family proteins in order to understand the involvement of these proteins in glycoprotein quality control mechanism.