Advanced glycation endproducts and polysialylation affect the turnover of the neural cell adhesion molecule (NCAM) and the receptor for advanced glycation endproducts (RAGE)

Abstract

The balance between protein synthesis and degradation regulates the amount of expressed proteins. This protein turnover is usually quantified as the protein half-life time. Several studies suggest that protein degradation decreases with age and leads to increased deposits of damaged and non-functional proteins. Glycation is an age-dependent, non-enzymatic process leading to posttranslational modifications, so-called advanced glycation endproducts (AGE), which usually damage proteins and lead to protein aggregation. AGE are formed by the Maillard reaction, where carbonyls of carbohydrates or metabolites react with amino groups of proteins. In this study, we quantified the half-life time of two important receptors of the immunoglobulin superfamily, the neural cell adhesion molecule (NCAM) and the receptor for advanced glycation end products (RAGE) before and after glycation. We found, that in two rat PC12 cell lines glycation leads to increased turnover, meaning that glycated, AGE-modified proteins are degraded faster than non-glycated proteins. NCAM is the most prominent carrier of a unique enzymatic posttranslational modification, the polysialylation. Using two PC12 cell lines (a non-polysialylated and a polysialylated one), we could additionally demonstrate, that polysialylation of NCAM has an impact on its turnover and that it significantly increases its half-life time.

Sialic Acid Metabolic Engineering of Breast Cancer Cells Interferes with Adhesion and Migration

“…However, engineering with ManNHex displayed only a 20% reduction in cell surface expressed NCAM. This reduction in NCAM expression after glycoengineering could be explained by the turnover as well as the half-life of NCAM, since these are dependent on polysialylation [23]. Furthermore, we recently observed reduced NCAM expression after treatment of cells with fluorescent CMP-Neu5Ac mimetics, which interfere with sialyltransferases and also reduce polysialylation of NCAM [24].…”

Glycaemic patterns in healthy elderly individuals and in those with impaired glucose metabolism – exploring the relationship with nonglycaemic variables

“…an advanced glycation end product. Glycation affects the interactions of proteins with specific receptors [1,2], (auto-)antibodies [3], protein half-lives, senescence [4] and protein folding [5,6]. Oligosaccharide glycan is covalently attached to polypeptide side chains.…”