Structural views of glycoprotein-fate determination in cells

Processing of the N-glycans is coupled with the fates of glycoproteins in cells. A series of processing intermediates of high-mannose-type glycans are generated by specific glycosidases and thereby express biological signals recognized by intracellular lectins operating as molecular chaperones, cargo receptors, and ubiquitin ligases. Consequently, these lectins govern the intracellular processes of folding, transport, and degradation of the carrier polypeptides. To understand the underlying mechanisms of glycoprotein-fate determination, structural information on modes of molecular recognition by these lectins and enzymes is undoubtedly important. This article overviews our current knowledge of the structural basis for quality control of glycoproteins in cells.