Why Are Misfolded Glycoproteins?

Glycoproteins, such as cytokines, hormones, or antibodies, play important roles in several biological events. During their biosynthetic pathways, correctly folded glycoproteins are transported to cell surfaces, secreted, or retained in intracellular compartments. By contrast, terminally misfolded glycoproteins are delivered to cytosol and eliminated by a degradation process called ER-associated degradation (ERAD). This mechanism is essential in maintaining the vitality of living systems, by maximizing the production of active proteins as well as by avoiding the accumulation of a misfolded glycoprotein, which is inactive and often toxic.
Processing of asparagine (Asn)-linked (N-linked) glycans creates a variety of glycoforms which play important