Global proteomic analysis of advanced glycation end products in the Arabidopsis proteome provides evidence for age-related glycation hot spots

Abstract

Glycation is a post-translational modification resulting from the interaction of protein amino and guanidino groups with carbonyl compounds. Initially, amino groups react with reducing carbohydrates, yielding Amadori and Heyns compounds. Their further degradation results in formation of advanced glycation end products (AGEs), also originating from α-dicarbonyl products of monosaccharide autoxidation and primary metabolism. In mammals, AGEs are continuously formed during the life of the organism, accumulate in tissues, are well-known markers of aging, and impact age-related tissue stiffening and atherosclerotic changes. However, the role of AGEs in age-related molecular alterations in plants is still unknown. To fill this gap, we present here a comprehensive study of the age-related changes in the glycated proteome, including the proteins affected and specific glycation sites therein. We also consider the qualitative and quantitative changes in glycation patterns in terms of the general metabolic background, pathways of AGE formation, and the status of plant anti-oxidative/anti-glycative defense. Although the patterns of glycated proteins were only minimally influenced by plant age, the abundance of 96 AGE sites in 71 proteins was significantly affected in an age-dependent manner and clearly indicated the existence of age-related glycation hot spots in the plant proteome. Homology modeling revealed glutamyl and aspartyl residues in close proximity (less than 5 Å) to these sites in three aging-specific and eight differentially glycated proteins, four of which were modified in catalytic domains. Thus, the sites of glycation hot spots might be defined by protein structure that indicates, at least partly, site-specific character of glycation.

Does Protein Glycation Impact on the Drought-Related Changes in Metabolism and Nutritional Properties of Mature Pea (Pisum sativum L.) Seeds?

“…The characteristic fragment signals attributed to compounds of certain chemical classes were selected from predicted tandem mass-spectral library deposited in Human Metabolome Database (HMDB, http://www.hmdb.ca/). A search for specific diagnostic fragment ions, characteristic for different groups of metabolites revealed several chemical families, six of which could be identified-coumarine derivates (97), metabolites with phosphocholine group (527), oxylipins (26), metabolites conjugated with sugar moieties (2), fatty acid residues (63), metabolites with phosphate group (49), which could be visualized in PLS-DA and HCA models.…”

“…Thereby, in comparison to the mammalian proteins, plant polypeptides demonstrated much higher numbers of AGE sites, where modifications were formed mostly via oxidative glycosylation [25]. Moreover, a significant increase of glycation levels at specific protein residues was characteristic for ageing of Arabidopsis leaves [26] and pea root nodules [27]. Not less importantly, enhanced AGE formation accompanied environmental stress [28].…”

Reassessing plant glyoxalases: large family and expanding functions

“…Furthermore, MG-mediated loss of proteasomal activity or impaired proteostasis due to the formation of proteolysisresistant AGEs can also contribute to aging (Nigro et al, 2019). On similar lines, age-related changes have also been observed in the Arabidopsis glycated proteome (Bilova et al, 2017) and also during natural leaf senescence in winter wheat (Hav e et al, 2015), indicating the existence of age-related glycation hotspots. Together, glycation may reasonably be termed as a nonenzymatic post-translational modification marker guiding proteins to degradation and organs to senescence.…”

Drought-related Changes in the Metabolism and Nutritional Properties of Mature Pea (<em>Pisum sativum L.</em>) Seeds in the Context of Protein Glycation

“…The characteristic fragment signals attributed to compounds of certain chemical classes were selected from predicted tandem mass-spectra library deposited in Human Metabolome Database (HMDB, http://www.hmdb.ca/). A search for specific diagnostic fragment ions, characteristic for different groups of metabolites revealed several chemical families, six of which could be identified -coumarine derivates (97), metabolites with phosphocholine group (527), oxylipins (26), metabolites conjugated with sugar moieties (2), fatty acid residues (63), metabolites with phosphate group (49), which could be visualized in PLS-DA and HCA models. The results clearly indicated that metabolites, featured with a phosphocholine group (most probably phosphatidylcholines), and oxylipins are more represented in the seeds of the drought-treated plants in comparison to those from controls.…”