Alternative glycosylation modulates function of IgG and other proteins — Implications on evolution and disease

BackgroundNearly all membrane and secreted proteins, as well as numerous intracellular proteins are glycosylated. However, contrary to proteins which are defined by their individual genetic templates, glycans are encoded in a complex dynamic network of hundreds of genes which participate in the complex biosynthetic pathway of protein glycosylation.Scope of reviewThis review summarizes present knowledge about the importance of alternative glycosylation of IgG and other proteins.Major conclusionsNumerous proteins depend on correct glycosylation for proper function. Very good example for this is the alternative glycosylation of IgG whose effector functions can be completely changed by the addition or removal of a single monosaccharide residue from its glycans.General significanceThe change in the structure of a protein requires mutations in DNA and subsequent selection in the next generation, while even slight alterations in activity or intracellular localization of one or more biosynthetic enzymes are sufficient for the creation of novel glycan structures, which can then perform new functions. Glycome composition varies significantly between individuals, which makes them slightly or even significantly different in their ability to execute specific molecular pathways with numerous implications for development and progression of various diseases. This article is part of a Special Issue entitled Glycoproteomics.

► Glycans are encoded in a complex dynamic network of hundreds of genes.
► Glycome composition varies significantly between individuals.
► Alternative glycosylation modulates function of numerous proteins.