Overview of glycans in disease: plant lectins as sensitive tools to decode glycosylation changes

Glycomic events could be the cause of the onset of many pathologies, some of them with imprecise diagnostics. Glycosylation is a post-translational modification of proteins where the resulting products, O-glycans and N-glycans located in the cell membrane (part of the cell glycome), as well as all the enzymatic machinery necessary for their processing, over- and under-expression (glycosyltransferases and glycosidases), constitute markers of a possible glycomic anomaly. The O- and N-glycan modifications are dependent on the specificity of the expressed enzymes involved in their biosynthesis and could result in loss of glycans, generation of truncated glycans or insertion of specific carbohydrates (fucose, sialic acid, galactose, mannose, lactose and others), increasing branching, which alters the cell glycomic profile. These insertions create different identities in the identification of diseases, such as cancer, diabetes, immunological, metabolic, and neurodegenerative diseases. Different diseases can express different glycosylated biomarkers. Ideally, they should be detected early. Early detection of glycan biomarkers requires highly accurate analytical methodologies, to establish an early diagnosis, which may mean a more favourable prognosis. Plant lectins are attractive proteins for use as molecular tools, as they exhibit unique specificities for glycans, and can detect alterations in the cell glycome that could be used to detected biomarkers of diseases.