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Glucose on the sugar side chains of proteins keeps unfolded proteins in the ER. Mannoses on sugar side chains act as a timer for protein folding. Unfolded proteins in the ER are threaded through a retrotranslocon into the cytosol where they are ubiquitylated and digested. IRE1, ATF6 and PERK sense the amount of unfolded protein and generates several responses to reduce the effects and amount of unfolded protein.
Quora User, B.S. Proteins bound for a variety of locations (ER, Golgi, lysosomes, plasma membrane, secretion...) are translated by ribosomes in the cytoplasm but need to get into the ER. The signal required for their transport into the ER is a short signal sequence at the beginning of the protein.